United States Department of Agriculture

Forest 

Service

Pacific Southwest 

Research Station

General Technical Report

PSW-GTR-248 August 

2016

Foothill Yellow-Legged Frog

Conservation Assessment 

in California 
In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil 

rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating 

based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived 

from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights 

activity, in any program or activity conducted or funded by USDA (not all bases apply to all 

programs). Remedies and complaint filing deadlines vary by program or incident. 

Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, American Sign Language, etc.) should contact the 

responsible Agency or USDA’s TARGET Center at (202) 720-2600 (voice and TTY) or contact 

USDA through the Federal Relay Service at (800) 877-8339. Additionally, program information may be made available in languages other than English. 

To file a program discrimination complaint, complete the USDA Program Discrimination 

Complaint Form, AD-3027, found online at http://www.ascr.usda.gov/complaint_filing_cust.

html and at any USDA office or write a letter addressed to USDA and provide in the letter all 

of the information requested in the form. To request a copy of the complaint form, call (866) 

632-9992. Submit your completed form or letter to USDA by: (1) mail: U.S. Department of 

Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, 

SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program.intake@

usda.gov. 

USDA is an equal opportunity provider, employer, and lender.

Technical Coordinators 

Marc P. Hayes is a senior research scientist, Washington Department of Fish 

and Wildlife, 600 Capitol Way North, Olympia, WA 98501; Clara A. Wheeler is 

an ecologist, U.S. Department of Agriculture, Forest Service, Pacific Southwest 

Research Station, 1700 Bayview Dr., Arcata, CA 95521; Amy J. Lind is a wildlife biologist, U.S. Department of Agriculture, Forest Service, Pacific Southwest 

Research Station, 1731 Research Park Drive, Davis, CA 95618, currently located 

at U.S. Department of Agriculture, Forest Service, Pacific Southwest Region, 631 

Coyote St., Nevada City, CA 95959; Gregory A. Green is a wildlife ecologist, Tetra 

Tech EC, 19803 North Creek Parkway, Bothell, WA 98011, currently located at Owl 

Ridge Natural Resource Consultants, Inc., 22116 45th Ave. SE, Bothell, WA 98021; 

and Diane C. Macfarlane is a wildlife biologist, U.S. Department of Agriculture, 

Forest Service, Pacific Southwest Region, 1323 Club Drive, Vallejo, CA 94592. 

Cover photo: Foothill yellow-legged frog (Rana boylii), by Ryan Peek. 
Abstract
 

Hayes, Marc P.; Wheeler, Clara A.; Lind, Amy J.; Green, Gregory A.; 

Macfarlane, Diane C., tech. coords. 2016. Foothill yellow-legged frog 

conservation assessment in California. Gen. Tech. Rep. PSW-GTR-248. Albany, 

CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research 

Station. 193 p. 

The foothill yellow-legged frog (Rana boylii) is a stream-breeding amphibian that has experienced significant population declines over a large portion of 

its historical range. This frog is nearing extirpation in much of the Sierra Nevada 

region where existing populations are sparse. Water development and diversions 

are likely to be the primary cause of population declines and are currently a 

prominent risk factor because they result in hydrological changes that chronically 

affect several aspects of the species’ life history. Other primary risk factors include 

climate change, mining and suction-dredging, introduced species, and habitat loss. 

Conservation approaches could include restoration of hydrologic attributes such as 

flow and thermal regimes on regulated rivers, restoration of associated uplands and 

connecting riparian corridors, and management of flow regimes to retain or restore 

favorable habitat conditions. 

Keywords: Rana boylii, Sierra Nevada, risk factors, water development 

and diversions. 
Executive Summary 

The foothill yellow-legged frog (Rana boylii) is associated with lower elevation 

streams draining the Pacific slope from west-central Oregon to northwestern Baja 

California. This assessment focuses on what is known about the natural history of 

this frog rangewide, with special focus on risks and management issues that pertain 

to the Sierra Nevada region at the heart of the species’ range. Historically common 

throughout its geographic distribution, the foothill yellow-legged frog now appears 

to be near extirpation over at least two-thirds of its range. The area over which this 

frog nears extirpation includes the Sierra Nevada, an area that comprises the eastern portion, or roughly one-quarter of the historical distribution. In areas where the 

species persists in the Sierra Nevada, populations are sparse. This pattern suggests 

that the species is at risk of extirpation regionally and the regional risk contributes 

to a broader risk of extinction. Therefore, the U.S. Forest Service initiated a multiagency effort to develop a conservation assessment focused on attenuating causative 

factors. This assessment has three parts: (1) a synopsis of foothill yellow-legged 

frog ecology designed to identify areas of vulnerability, (2) a review of foothill 

yellow-legged frog status across the national forests and national parks in California 

and specifically in the Sierra Nevada, and (3) an evaluation of current and future 

risk factors likely to impinge on the foothill yellow-legged frog and its habitat. This 

assessment is intended to form the basis for a conservation strategy for the species. 

Foothill yellow-legged frogs are currently recognized as one taxonomic unit, 

but genetic data reveal substantial genetic variability across their geographic range 

that may conceal unrecognized taxa. Foothill yellow-legged frogs occupy a diverse 

range of ephemeral and permanent streams, rivers, and adjacent moist terrestrial 

habitats over the course of their complex life history. Small streams often have 

dense canopies that limit the light needed by algae, the food resource of tadpoles. 

Adults can migrate down the drainage network to channels that are broad and more 

sunlit. Occupied streams are often partly shaded, low gradient, and dominated by 

coarse, unconsolidated rocky substrates. Seasonal variation in streamflow has a 

strong influence on life history and movement. To avoid disturbance and optimize 

feeding by tadpoles, adults breed and tadpoles develop in slow water velocity 

habitats. Reproduction occurs in synchrony with the transition from winter and 

spring snowmelt freshets to summer drought. The period of fastest tadpole growth 

and development coincides with blooms of algae and diatoms and warm water temperatures; tadpoles do not overwinter. Mortality is high through the juvenile stage 

because of abiotic factors such as stranding and scouring of egg masses as well as 

losses to predators. Early life stages, as prey items, are likely important to trophic 
transfer within stream food webs. Fall rains trigger movement of recently metamorphosed juveniles upstream and away from the active channel. Postmetamorphic 

stages occupy terrestrial stream-margin habitats as well as springs and seeps at 

varying distances from breeding and rearing sites. Radiotelemetry demonstrates 

that foothill yellow-legged frogs travel distances far enough to allow movement 

between breeding sites along a watercourse, but gene flow between breeding populations is impaired in river systems in which stream reaches have been fragmented 

by reservoirs. 

Historical records document species presence for every major Pacific-slope 

Sierra watershed between the upper Sacramento River and the Tehachapi Mountains, at elevations ranging from the Central Valley floor to around 2000 m; however, Central Valley records are sparse and may not reveal the presence of effective 

breeding populations. In California, a little over 30 percent of the historical range of 

foothill yellow-legged frogs is on national forest lands. The remainder is on private, 

state, and other federal lands. Occupancy surveys that covered historical sites and 

potentially suitable habitat suggest that the species is much less widespread than 

it was historically in the Sierra Nevada. Fewer than 10 recent records from the 

Cosumnes River southward suggest near-extirpation in the southern portion of 

their Sierran range. Records from the 1960s and 1970s imply that populations were 

robust until that time, but lack of monitoring prevents precisely identifying when 

declines began. A similar geographic pattern of extirpation exists within California 

in general, with few populations remaining south of San Francisco Bay. 

The most robust data implicate water development and diversions as the 

primary cause of declines in foothill yellow-legged frogs. Water development and 

diversions are a prominent risk because they result in hydrological changes that 

chronically affect several aspects of the frog’s life history. Recent studies from both 

regulated and unregulated rivers have demonstrated that small-scale changes in 

local habitat conditions, such as water velocities, depths, and temperatures, which 

often result from water management activities and landscape-scale changes, can 

lead to (1) inconsistent environmental cues for breeding, (2) lower growth rates 

for tadpoles, (3) scouring or stranding of egg masses and tadpoles, (4) reductions 

of overall habitat suitability for breeding and rearing, (5) barriers to gene flow 

around reservoirs, and (6) establishment of nonnative predators in reservoirs that 

then spread into the rivers. Other primary risk factors that may affect persistence of 

populations include mining and suction-dredging, climate change, introduced species, and habitat loss. Risk factors that were deemed less critical for consideration 

in development of a conservation strategy, but many of which remain unstudied, 
include airborne contaminants, acid deposition, disease, fire management and 

suppression, livestock grazing, locally applied pesticides, recreational activities, 

research activities, restoration activities, roads, UV-B radiation, and vegetation and 

fuels management. 

Generally, restoration of the key hydrologic attributes mechanistically linked 

to birth and death rates is crucial for population persistence on regulated rivers in 

the Sierra Nevada. Of particular importance is establishment of flow schedules and 

thermal regimes that mimic unimpaired patterns of seasonal and diurnal variation. 

Sound management of associated uplands and connecting riparian corridors is also 

essential. Notable information gaps exist regarding whether maintaining current 

levels of management for activities that affect stream and upland habitat, such as 

mining, livestock grazing, vegetation, and fuels and fire management, is adequate 

for species protection. Research to investigate information gaps is needed to 

assess the level of risk for several potential factors that are discussed but presently 

unstudied. 
 

 

 

 

 

 

 

 

Contents
 

1 Introduction 

1 Purpose of This Conservation Assessment 

2 Geographic Scope of This Assessment 

2 Document Organization 

3 Ecology 

3 Systematics and Taxonomy 

4 Description 

5 Habitat Requirements 

13 Life History 

17 Population Dynamics 

21 Movement 

21 Feeding 

22 Mortality 

24 Summary of the Ecology 

25 Status 

25 Rangewide Overview 

26 California 

29 Sierra Nevada 

30 Summary of Status 

30 Risk Factors Affecting the Status of the Species 

37 Water Development and Diversion 

45 Climate Change 

47 Habitat Loss, Urbanization, and Fragmentation 

49 Introduced Species 

52 Mining 

55 Summary of Risk Factors 

58 Future Conservation and Management 

58 Waterflow Management 

58 Stream Habitat and Nonnative Species Management 

59 Watershed Scale Management 

59 Population and Habitat Monitoring 
59 Future Research Priorities 

60 Acknowledgments 

60 English Equivalents 

60 Literature Cited 

96 Appendix 1: Agency Direction 

96 USDA Forest Service 

99 National Park Service 

100 California Department of Fish and Wildlife 

102 U.S. Fish and Wildlife Service 

104 Appendix 2: Museum Standard Symbolic Codes 

104 Literature Cited 

105 Appendix 3: Status: Federal Administrative Units 

105 Six Rivers National Forest 

107 Shasta-Trinity National Forest 

112 Lassen National Forest 

115 Plumas National Forest 

120 Mendocino National Forest 

124 Tahoe National Forest 

127 Eldorado National Forest 

129 Stanislaus National Forest 

134 Yosemite National Park 

135 Sierra National Forest 

136 Sequoia and Kings Canyon National Parks 

136 Sequoia National Forest 

141 Los Padres National Forest 

141 Angeles National Forest 

142 Literature Cited 

147 Appendix 4: Other Risk Factors 

147 Airborne Contaminants Including Pesticides 

148 Acid Deposition 

149 Disease 
151 Fire Management and Suppression 

153 Livestock Grazing 

156 Locally Applied Pesticides 

158 Recreational Activities 

160 Research Activities 

162 Restoration Activities 

163 Roads 

165 UV-B Radiation 

167 Vegetation and Fuels Management 

169 Literature Cited 

188 Appendix 5: Foothill Yellow-Legged Frog Working Group 
1 

Foothill Yellow-Legged Frog Conservation Assessment

Introduction 

Purpose of This Conservation Assessment 

Since about 1970, foothill yellow-legged frogs (Rana boylii) have disappeared from 

significant areas in California and Oregon, including parts of the Sierra Nevada 

(Borisenko 2000, Borisenko and Hayes 1999, Fellers and Drost 1993, Jennings 

1996, Jennings and Hayes 1994, Lind 2005, Sweet 1983). The foothill yellow-legged 

frog is currently on the U.S. Department of Agriculture (USDA) Forest Service 

Pacific Southwest Region (Region 5) Sensitive Species List (USDA FS 1998, 2004). 

The state of California considers the foothill yellow-legged frog to be a “Species of 

Special Concern.” On July 11, 2012, the foothill yellow-legged frog was petitioned 

for Federal Listing under the Endangered Species Act, 16 U.S.C. § 1533(b); Section 553(e) of the Administrative Procedure Act, 5 U.S.C. § 553(e); and 50 C.F.R. § 

424.14 (Adkins Giese et al. 2012). 

The Sierra Nevada Forest Plan Amendment (SNFPA) Record of Decision 

(ROD) commits the USDA Forest Service to completing a conservation assessment 

for the foothill yellow-legged frog in cooperation with other federal agencies, state 

agencies, universities, and research scientists (USDA FS 2001). The assessment is 

envisioned as the first of a three-phase process that also includes a conservation 

strategy and a conservation agreement. The conservation assessment synthesizes 

available data on life history, habitat associations, distribution and abundance data, 

and risk factors, providing the foundation for the conservation strategy. The conservation strategy will delineate specific conservation actions and lead to an agreement among various agencies and partners to implement the strategy. Following 

approval of the SNFPA ROD, a working group of biologists from the USDA Forest 

Service, U.S. Department of the Interior National Park Service (NPS) and Fish and 

Wildlife Service (USFWS), California Department of Fish and Wildlife (CDFW; 

formerly the California Department of Fish and Game), and academic and independent research scientists was established to develop this assessment and future 

strategy. This conservation assessment was developed to guide future conservation 

strategy and recovery planning for the Sierra Nevada populations of the foothill 

yellow-legged frog (Blankenship et al. 2001). Conservation assessments document 

all conservation- or management-pertinent information about a species, including 

its ecology, habitat needs, population levels, and management risks. Conservation 

assessments also provide management recommendations based on available knowledge. Agencies committed to this assessment include CDFW; the Pacific Southwest 

and Intermountain Regions of the Forest Service; Sequoia, Kings Canyon, and 

Yosemite National Parks; and the USFWS. Each agency has specific directives 
2 

GENERAL TECHNICAL REPORT PSW-GTR-248

and guidelines that direct their actions in relation to management and protection of 

native at-risk species. These directives and guides for each participating agency are 

explained in appendix 1. 

Geographic Scope of This Assessment 

The foothill yellow-legged frog occurs along the Pacific slope, from west-central 

Oregon to northwestern Baja California. This conservation assessment focuses 

on the species’ range in California; however, the information gathered here is 

applicable to the entire range of this frog. 

Document Organization 

The three main sections of this document address the ecology, status, and factors 

potentially presenting risks to the foothill yellow-legged frog’s persistence. The 

ecology section details the key interactions of frogs with the abiotic and biotic 

environment for survival and successful reproduction. This body of knowledge is 

necessary to develop a successful strategy for recovery of this species. The status 

section provides the latest information on foothill yellow-legged frog distribution 

and population status, with particular focus on each of the national forests and 

national parks within the Sierra Nevada planning area, and how these populations 

have changed pre- and post-1980. The risk factor section identifies, describes, and 

evaluates the relative importance of primary risk factors for the species, as supported by research and expert knowledge. Primary risk factors include management 

activities (water development and diversion, mining, introduced species, habitat 

loss) and environmental factors (climate change), each of which may have played a 

role in current foothill yellow-legged frog population trends. Additional risk factors 

that were deemed a lesser threat to the conservation of the species are described in 

appendix 4. These sections provide the conceptual and scientific foundation for the 

subsequent conservation strategy. 

Nomenclature for North American amphibians and reptiles follows Crother et 

al. (2008). However, because some of the name changes in this recent publication 

are very new and even controversial, the previous name is also provided in brackets 

for the first appearance of each species name. In addition, some of the new names 

result from geographic “splitting” of taxa. In those cases, names are presented as 

old name/new name, because determining the original geographic location from 

the literature for a given species, and hence the appropriate “new” name, was not 

always possible. For example, Rana catesbeiana is presented as Lithobates [Rana] 

catesbeianus and Rana muscosa is presented as Rana muscosa/sierrae. 
3 

Foothill Yellow-Legged Frog Conservation Assessment

Ecology 

Systematics and Taxonomy 

The foothill yellow-legged frog is a member of the true frog family Ranidae (fig. 1) 

(Jennings 2003). It is recognized as a distinct species; however, there is variation 

in color pattern and morphology between southern Sierra Nevada and north coast 

populations (Zweifel 1955), and recent studies demonstrate within-species genetic 

variation. In a mitochondrial DNA analysis, Lind (2005) and Lind et al. (2011) 

identified significant genetic partitioning between coastal and Sierra Nevada 

foothill yellow-legged frog populations as well as two distinct, more northerly 

groupings. Moreover, within the Sierra Nevada, a single sample from the southern 

Sierra showed significant differentiation from 10 samples from the central and 

northern Sierra, a pattern congruent with that of other species widespread across 

the Sierra (e.g., Macey et al. 2001). Conclusions about evolutionary relationships 

did not involve formal taxonomic description for any of these groups in either of 

these studies, but Lind (2005) and Lind et al. (2011) emphasized that such groupings 

would be critically important to consider in conservation planning, and some may 

ultimately be regarded as deserving formal taxonomic recognition. 

Kevin Wiseman 

Figure 1—Adult female foothill yellow-legged frog under water in the North Fork Feather River, 

Plumas National Forest, Butte County, California. 
4 

GENERAL TECHNICAL REPORT PSW-GTR-248

Description 

Adult foothill yellow-legged frogs are moderate-sized (37 to 82 mm snout-urostyle 

length [SUL]) ranid frogs with indistinct dorsolateral folds, fully webbed feet (i.e., 

from toetip to toetip) with slightly expanded toe tips (fig. 2), and rather thick, rough 

pebbly skin (Stebbins 1951, 2003; Zweifel 1955). Dorsal color is highly variable 

and is usually light and dark mottled gray, olive, or brown, but variable amounts of 

brick red are often present, and a pale triangle is often located between the eyes and 

the snout (Jones et al. 2005, Nussbaum et al. 1983, Zweifel 1955). The undersurfaces 

of the posterior abdomen and ventral surfaces of the rear legs are varying shades of 

yellow, which fades to white anteriorly on the belly (Stebbins 1951, Zweifel 1955). 

Females attain larger sizes than males (Jennings and Hayes 1994). Mature males 

have a dark swollen bump or nuptial pad on the dorso-medial surface of each thumb 

that becomes darker, slightly larger, and rougher to the touch during the breeding 

season. Males also have proportionally larger forearm muscles and narrower waists 

than females. 

Juvenile foothill yellow-legged frogs look similar to adults except for their 

smaller size (14 to 36 mm SUL), more contrasting dorsal coloration, and lack of 

significant yellow on their undersurfaces (Jones et al. 2005, Nussbaum et al. 1983, 

Stebbins 1951, Zweifel 1955). Undersurfaces of the youngest juveniles are cream 

or flesh colored and the yellow color makes its first appearance on the calves and 

thighs, expanding anteriorly and posteriorly as juveniles grow in size (M. Hayes, 

personal observation, 1994–1995). 

Newly hatched tadpoles are dark brown to black and typically measure 7 to 8 

mm in total length (Storer 1925, Zweifel 1955). As tadpoles grow, their coloration 

turns an olive color with coarse brown mottling dorsally. The ventral surface of 

the body is silvery and nearly opaque, and the coiled intestine is barely visible. The 

body is more flattened, and the tail fin, tallest at its mid-portion, has a relatively 

broad musculature (fig. 3) (Zweifel 1955). When viewed from above, the eyes of 

foothill yellow-legged frog tadpoles are dorsally positioned so they are located 

within the outline of the head in bird’s eye view (fig. 3). Foothill yellow-legged frog 

Figure 2—Hind foot webbing of adult foothill 

yellow-legged frog. Adapted from Zweifel (1955). 
5 

Foothill Yellow-Legged Frog Conservation Assessment

Figure 3—Appearance of foothill yellow-legged frog larva about 1 month old. Adapted from Zweifel 

(1955). 

tadpoles have a large, downward-oriented, almost suction-like mouth (fig. 3; lateral 

view) with several rows of denticles or labial teeth with the number of rows increasing with development (fig. 4). 

Egg masses contain from about 100 to more than 3,000 eggs, depending on the 

size of the female and geographic variation among populations (Kupferberg et al. 

2009b). Upon deposition, the mass is compact and the jelly is highly transparent 

and has a hyaline blue tint. Within 6 hours, the egg mass absorbs water, loses the 

bluish tint, expands to a long-axis diameter of 45 to 90 mm, and resembles a cluster 

of grapes. Each ovum is dark brown to black in appearance and surrounded by 

three jelly envelopes (fig. 5). Individual eggs range from 1.0 to 2.3 mm in diameter, 

and the outermost of the three jelly envelopes ranges from 3.9 to more than 6 mm in 

diameter (Storer 1925, Zweifel 1955). 

Habitat Requirements 

Foothill yellow-legged frogs occur in streams flowing through a variety of vegetation types, including valley-foothill hardwood, valley-foothill hardwood-conifer, 

valley-foothill riparian, ponderosa pine, mixed conifer, mixed chaparral, and wet 

meadows (associations characterized in Sawyer and Keeler-Wolf 1995). Frogs 

seem to favor channels with at least some shading (>20 percent) cast by riparian 

vegetation (Hayes and Jennings 1988). However, when canopy closure is too great 

(>90 percent), foothill yellow-legged frogs are rarely found (Fitch 1936, Hayes 

and Jennings 1988, Moyle 1973, Van Wagner 1996). Lack of suitable breeding and 

basking sites, and reduced levels of appropriate food, are two possible explanations 

for frog avoidance of streams with dense canopy cover. In a recent landscape-scale 

habitat analysis of frogs in Oregon, Olsen and Davis (2009) found that stream order, 

minimum temperatures, precipitation frequency, stream gradient, and elevation 

were important variables in predicting species presence. 

Breeding site selection occurs at two scales; populations congregate at suitable 

breeding habitat along streams and rivers, and females select specific oviposition 

sites within these breeding habitats (Wheeler and Welsh 2008). Site selection is 

not independent across these two scales. Breeding and rearing habitat is generally 

located in gently flowing, low-gradient stream sections with variable substrates 
6 

GENERAL TECHNICAL REPORT PSW-GTR-248

Figure 4—Tadpole tooth patterns for 8, 12, and 17 days from hatching. Figure 5—Ovum 

Drawings from Zweifel (1955). encased in three jelly 

envelopes. Adapted from 

Zweifel (1955). 

predominated by cobble and boulder (Bondi et al. 2013, Kupferberg 1996a, 

Van Wagner 1996, Wheeler and Welsh 2008, Yarnell 2005). Foothill yellow-legged 

frogs breed at locations that provide suitable velocities and depths over a relatively 

broad range of discharge volumes, ranging from small tributaries to large rivers 

(Kupferberg 1996a, Lind 2005, Yarnell 2008). In larger channels, breeding sites are 

often at point bars or depositional environments near the tail-end of pools, and in 

proximity to tributary confluences (Fuller and Lind 1992; Kupferberg 1996a, 1996b; 

Peek 2010). These sites have reduced chance of scour, seem to have some degree of 

spatial stability on a local scale (Mount 1995), and are consequently used annually 

(Fuller and Lind 1992; Kupferberg 1996a, 1996b; Wheeler and Welsh 2008) over 

many years. In smaller streams, egg masses are located in depositional areas with 

cobble and boulder substrates such as runs, or the tails and outlets of pools (Van 

Wagner 1996). Breeding sites appear to require some degree of insolation. Removal 

of alders that had encroached on cobble bars in the Trinity River appeared to have a 

positive effect on breeding site use; within 1 year of “bank feathering” alder-removal 

restoration projects, 10 of 24 (42 percent) egg masses found during surveys were 

found at restoration sites (Lind et al. 1996). Lack of pretreatment data on restoration 

sites makes the significance of this response difficult to interpret, but breeding is 

rarely observed in well-shaded sites (Van Wagner 1996, Zweifel 1955). 

Egg masses are typically attached to cobbles or boulders located near river 

margins in shallow and relatively slow (i.e., <5 cm sec-1) moving water (table 1, 

fig. 6). Placement of egg masses on the lee (i.e., flow-protected) side of substrates or 

under overhanging rocks ensures that flow velocities at the eggs will be consistently 

lower than ambient stream velocities (Kupferberg 1996a, 1996b). In a habitat suitability study, suitability for oviposition was high for shallow, low-velocity habitat 

and cobble and boulder substrates (Bondi et al. 2013). Site preparation behavior of 

scraping the oviposition substrate likely occurs to ensure proper adhesion of egg 

masses to the substrate (Rombough and Hayes 2005a, Wheeler et al. 2003). Females 
7 

Foothill Yellow-Legged Frog Conservation Assessment

Table 1—Variation in physical conditions at Rana boylii oviposition 

Water 

Data source Location Elevation temperature Depth Velocity 

Meters °C Centimeters Meters/second 

H. Eddingera 

L. Conwayb 

L. Conwayb 

Jose Creek (Sierra National Forest) 

Rose Creek (Stanislaus National Forest) 

North Fork Tuolumne River (Stanislaus 

National Forest) 

604 

463–475 

686 

12–15 

16 

17–19 

Van Wagner (1996) Clear Creek (Nevada County) 701 15 6–28 0–0.03 

C. Seltenrichc Stanislaus River (Tuolumne County) 350–930 ~15 <10 “Slack water” 

Mokelumne River (Calaveras County) 

Pit River (Shasta County) 

Bondi et al. (2013) North Fork and Middle Fork Feather 

River (Butte and Plumas Counties) 

Middle Fork Yuba River (Nevada 

County) 

North Fork, South Fork, and North 

Fork/Middle Fork American River 

(El Dorado, Placer, and Sacramento 

Counties) 

NA 14–67 0–0.15 

Rubicon River (El Dorado and Placer 

Counties) 

Clavey River (Tuolumne County) 

Kupferberg (1996a) South Fork Eel River (Mendocino 

County) 

363–418 11.5– 

12.0 

4–43 0.01–0.14 

Fuller and Lind (1992), 

Wheeler et al. (2006) 

Hurdygurdy Creek (Del Norte County) 

A. Lind and H. Welshd Various coastal watersheds 

Mean = 12.4 

(range 

10–15) 

7–22 

1–40 

0–0.6 

Data from coastal sites are in bold face. Water temperature data from Kupferberg (1996a) are a range of means, not actual values from several 

different oviposition sites. Data from Bondi et al. (2013) represent the range of water depths and velocities that were deemed “suitable” in a habitat 

suitability criteria analysis. 

a Eddinger, H. [N.d.]. Unpublished data. On file with: U.S. Department of Agriculture, Forest Service, Sierra National Forest, 1600 

Tollhouse Rd., Clovis, CA 93611. 

b Conway, L. [N.d.]. Unpublished data. On file with: U.S. Department of Agriculture, Forest Service, Stanislaus National Forest, 19777 

Greenley Rd., Sonora, CA 95370. 

c Seltenrich, C. Personal communication. Practice manager, DUDEK, 605 Third Street, Encinitas, CA 92024. 

d Lind. A; Welsh, H. [N.d.]. Unpublished data. On file with: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research 

Station, 1700 Bayview Dr., Arcata, CA 95521. 
8 

GENERAL TECHNICAL REPORT PSW-GTR-248

Figure 6—Sensitivity of stage height and velocity to discharge fluctuation at Rana boylii breeding (and early 

rearing) sites with different channel shapes. Frogs (not drawn to scale) are ovipositing at equal depths at discharge 

Q1

 = 3 m3 sec-1 in (A) a low-survival breeding site on the South Fork Eel River, and (B) a high survival site. At 

subsequent times (t) discharge can decrease (Q2

 = 1.5 m3 sec-1) or increase (Q3 = 4.5 m3 sec-1). Changes in stage 

(s) and velocity (v) were predicted using an HEC-1 model. Channel cross-sections are drawn with a 1:10 vertical 

exaggeration. Adapted from Kupferberg (1996a). 

may visit and “test” rub multiple oviposition locations; females may also choose 

sites based on the suitability of the substrate surface for oviposition (Rombough 

and Hayes 2005a). In a study to assess critical velocities and water depths on the 

Pit River during test flows, 8 of 15 egg masses survived high water velocities (up 

to 52 cm sec-1 maximum mean column velocity) (Spring Rivers Ecological Sciences 2003); however, at mean column velocities >10 cm sec-1, the flow threshold at 

which egg masses will be scoured depends on factors such as water depth and the 

amount of sheltering provided by the egg mass attachment substrate (Yarnell 2014). 

Sustained high-flow events (i.e., over several days) will shear egg masses from their 

substrates (Kupferberg 1996a, 1996b; Lind et al. 1996; Van Wagner 1996; Wheeler 

et al. 2013) and risk of scour increases with age of the egg mass (Spring Rivers 
9 

Foothill Yellow-Legged Frog Conservation Assessment

Ecological Sciences 2003). Further studies are necessary to quantify the critical 

velocities and other conditions that result in separation of egg masses from their 

points of attachment under different conditions. Critical velocities are expected to 

decline with the age of egg mass because of the progressive disintegration of egg 

mass jelly. To survive to hatching, eggs must remain inundated as well as attached 

to substrates despite fluctuating water levels. Stage height and near-bank velocities are less sensitive to changes in discharge in wide, shallow channels than in 

deeper, more confined channels (fig. 6) (Kupferberg 1996a, 1996b; Yarnell et al. 

2012). Channels with greater width:depth ratios generally facilitate greater hatching 

success than channels with lesser width:depth ratios, except when water levels drop 

and strand eggs. 

Tadpole rearing sites, which are in the same or proximate habitat as egg masses, 

appear to also require some degree of protection from unpredictable scouring 

flows. Lower water velocity and shallower water depth habitats are more suitable 

for tadpole rearing sites (Bondi et al. 2013). Low flows are particularly important 

immediately after hatching, when hatchling tadpoles are not yet able to feed, are 

heavy with yolk, and have only modest swimming ability (Kupferberg 1996b; 

Kupferberg et al. 2008, 2011b). As tadpoles become exposed to higher velocities 

during elevated streamflows, they become less active and remain in refugia in the 

substrate (Kupferberg et al. 2008, 2011b). In a flume experiment, critical velocities 

(at which foothill yellow-legged frog tadpoles were flushed out of a microhabitat 

and swept downstream) varied with developmental stage, body size, population of 

origin, and individual activity level, but consistently fell within a range of 20 to 

40 cm sec-1 (Kupferberg et al. 2008, 2011b). Vulnerability increased as tadpoles 

approached metamorphosis; critical velocities at which tadpoles were flushed 

decreased with increasing body size and developmental stage (Kupferberg et al. 

2008, 2011b). When foothill yellow-legged frog tadpoles were experimentally 

relocated from low-velocity (0 to 3 cm sec-1) to higher-velocity (10 to 15 cm sec-1) 

habitat patches, fewer than 50 percent of tadpoles were able to either find a refuge 

in the substrate or swim cross-current to a lower velocity patch (Kupferberg et al. 

2008, 2011b). Experimental work also showed that small foothill yellow-legged frog 

tadpoles were more vulnerable to predators and larger tadpoles experienced reduced 

growth at elevated velocities (Kupferberg et al. 2008, 2011b). The degree to which 

the substrate was embedded did not change the short-term behavioral response of 

foothill yellow-legged frog tadpoles to increasing velocity (Kupferberg et al. 2008, 

2011b); this lack of response may place tadpoles at risk in more sediment-embedded 

streams, presumably because fewer refugia from high-velocity conditions exist. 
10 

GENERAL TECHNICAL REPORT PSW-GTR-248

The accumulation of sediment is postulated to reduce refugia for other streamassociated amphibians (Welsh and Ollivier 1998) but is unexamined for larval 

foothill yellow-legged frogs. 

Nonbreeding active-season habitat for postmetamorphic foothill yellow-legged 

frogs consists of adjacent terrestrial riparian and aquatic habitats. The range of 

aquatic habitats in which foothill yellow-legged frogs have been found is diverse; 

frogs have been observed in permanent and intermittent streams with low to 

relatively high gradients, alluvial and bedrock channels (Leidy et al. 2009), streamassociated backwaters and isolated pools (Hayes and Jennings 1988), and slow-moving rivers with mud substrates (Fitch 1938). However, these frogs primarily inhabit 

relatively shallow low-gradient channels with riffles that have an unconsolidated 

coarse substrate (Fitch 1938; Hayes and Jennings 1988; Kupferberg 1996a, 1996b; 

Leidy et al. 2009; Lind et al. 1996; Moyle 1973, Storer 1925; Van Wagner 1996; 

Zweifel 1955). In a habitat-association study, 18 habitat variables were examined, 

but only the percentage of area in riffles was significantly positively correlated with 

foothill yellow-legged frog abundance (Hayes and Jennings 1988, Moyle 1973). The 

typical escape behavior of these shoreline-sitting and foraging frogs is to dive into 

water upon approach by a human (or presumably other predator) (Zweifel 1955). 

Turbulent water in riffles may reduce visibility and provide important refuge habitat for postmetamorphic foothill yellow-legged frogs (Hayes and Jennings 1988). In 

a study examining the distribution of foothill yellow-legged frogs relative to sediment movement, Yarnell (2000) revealed that the highest overall frog abundances 

occurred at sites with intermediate sediment supply rates, where enough transport 

occurred so that large boulders and cobbles were not buried in finer sediments, 

and enough deposition occurred to maintain distinct bedforms (pools, riffles, and 

bars). Subsequent studies by Yarnell (2005, 2008) showed that stream reaches with 

high aquatic and riparian habitat heterogeneity had the highest abundances of all 

life stages. Reaches with higher heterogeneity provide all the habitats required by 

each life stage in a shorter river distance and therefore less movement is required by 

frogs to meet life-history requirements (Yarnell 2005, 2008). Whether this heterogeneity affects overall fitness of individuals is not known. In the Coyote Creek 

watershed (Santa Clara County), Gonsolin (2010) documented a counterintuitive 

pattern. Females who traveled hundreds to thousands of meters between tributaries 

and mainstems to breed were larger and had better body condition than females that 

resided and bred within a heterogeneous stream reach. 
11 

Foothill Yellow-Legged Frog Conservation Assessment

Several studies have revealed age- and sex-specific use of habitat outside of the 

breeding season (Gonsolin 2010; Haggarty 2006; Van Wagner 1996; Yarnell 2000, 

2005, 2008). Van Wagner (1996) encountered adult females most frequently in 

pools during the nonbreeding season; pools were also used as winter refugia. In the 

fall, juveniles were most commonly found in riffles (Van Wagner 1996). Haggarty 

(2006) found that adults and subadults (juveniles) showed preference for pools 

and riffles, whereas metamorphs (young-of-the-year) preferred glides and runs. In 

fall, Yarnell (2000) observed higher young-of-the-year abundance in areas with a 

more stable bed (i.e., low mobility) and coarse-textured substrate (low q*, points 

above lines in fig. 7). For adult frogs, patterns implied that preferences in channel 

type and surface texture varied seasonally, but females tend to travel farther than 

males and occupy habitats more distant from the breeding areas, such as tributaries, where predators like garter snakes are less common (Gonsolin 2010). Of all the 

microhabitat factors commonly measured (e.g., depth, velocity, substrate, canopy 

cover, aspect, presence of fish and nonnatives, mesohabitat type, Froude number, 

etc.), only local velocity was a significant factor in determining which habitats were 

occupied by which life stages (Yarnell 2005, 2008). 

Overwintering is the least understood aspect of foothill yellow-legged frog 

habitat use. Van Wagner (1996) observed postmetamorphic frogs overwintering in 

velocity-protected areas of the channel (e.g., on the lee side of sedge [Carex spp.] 

tussocks). He found that adult frogs typically used root wads, woody debris, undercut banks, and large boulders adjacent to pools, whereas juvenile frogs were usually 

found in hollows at the stream edge created by sedges partially springing back from 

being pushed over during high flows. Van Wagner’s (1996) observations occurred 

in a relatively small stream, where enough protection from scour or bedload movement may exist in selected in-channel locations during high discharge. Recent 

metamorphs have been caught in pitfall traps moving upland away from mainstem 

channels (Twitty et al. 1967); observed in wet ditches along dirt roads (Kupferberg, 

2012), and in caves and tunnels (Devine Tarbell & Associates, Inc. and Stillwater 

Sciences 2005). In larger streams, frogs may use protected terrestrial sites that 

avoid the scour risk entirely. For example, in the South Santiam River in Oregon 

(a 6th-order channel), juveniles occupy seeps above the typical winter high-flow 

waterline (Rombough 2006b); whether adults overwinter terrestrially at this site is 

unknown. Adult frogs observed moving upland along the Trinity River during fall 

rains may be movement into terrestrial sites (M. Hayes, personal observation, 1994; 

Jennings 1990), or to lateral tributaries for overwintering, where scour risk may 
12 

GENERAL TECHNICAL REPORT PSW-GTR-248

Figure 7—Variation in density of young-of-the-year (YOY) foothill yellow-legged 

frogs during fall 1998 with hydraulic geometry (adapted from Yarnell 2000). For each 

panel, the vertical axis indicates YOY density (individuals/m2

) as a function of each of 

hydraulic variable under two contrasting bed conditions: a coarser, more stable bed (low 

q*) versus a less stable, less coarse bed (high q*). Hydraulic variable exponents depicted 

are channel width (b), depth (f), and flow velocity (m). 
13 

Foothill Yellow-Legged Frog Conservation Assessment

be considerably lower (Kupferberg 1996a). Frogs have been observed in terrestrial 

habitats far from streams in the South Fork Eel and Mattole watersheds of the Coast 

Ranges in late fall.1 

Life History 

Foothill yellow-legged frogs initiate breeding in spring when air and water temperatures increase and streamflow declines (Gonsolin 2010; Kupferberg 1996a, 

1996b; Wheeler 2007; Wheeler and Welsh 2008; Wheeler et al. 2013; Zweifel 1955); 

approximately 10 °C may be the minimum temperature required for oviposition 

(table 1). Wheeler et al. (2014) found that the average water temperature at breeding 

sites along the mainstem and six tributaries of the Trinity River (Trinity County) 

was correlated with the start of breeding activity. Breeding takes place during the 

transition between wet and dry seasons when unpredictable discharge presents 

a physical threat of scour to egg masses and hatchlings. This risky timing may 

represent a tradeoff; oviposition must occur early enough for tadpoles to metamorphose and juveniles to gain mass prior to overwintering (Cooper et al. 1992). 

When conditions are appropriate, frogs congregate at breeding sites where adult 

males call for mates, primarily underwater (Davidson 1995, MacTague and Northen 

1993). Above-water calling also occurs, but is less frequent and faint (Davidson 

1995). In a coastal population, males vocally and physically defended specific sites 

that included above-water calling substrates within a breeding area (Wheeler 2007, 

Wheeler and Welsh 2008). 

Oviposition occurs between late March and June, depending on location and 

seasonal conditions. Most observations in the Sierra Nevada occurred in May and 

early June (fig. 8). Duration of breeding activity varies by population, with some 

breeding intervals as short as 2 weeks (Storer 1925, Zweifel 1955), and others 

lasting up to 31 days (Van Wagner 1996). Weather patterns may determine breeding 

chronology; breeding is more protracted during cold, rainy springs than warm, 

dry ones (Kupferberg 1996a, Wheeler and Welsh 2008). Breeding on the Stanislaus 

River below New Melones Reservoir can occur as late as July, likely owing to the 

relatively low temperature of water released, which comes from the bottom of the 

reservoir. In a study of the mainstem and six tributaries of the Trinity River (Trinity 

County), Wheeler et al. (2014) found that oviposition occurred later at breeding sites 

with colder average water temperatures. GANDA (2008) provided detailed 

1

 Welsh, H. 1985. Unpublished data. Research wildlife biologist, U.S. Department of 

Agriculture, Forest Service, Pacific Southwest Research Station. On file with: Pacific 

Southwest Research Station, 1700 Bayview Dr., Arcata, CA 95521. 
14 

GENERAL TECHNICAL REPORT PSW-GTR-248

Figure 8—Variation in dates at which Rana boylii oviposition was observed in Sierran 

streams at different elevations. 

observations regarding the timing of breeding for a population on the North Fork 

Feather River. In late April/early May of 2004 and 2005, when mean daily tributary 

temperatures were ≥10 °C, females left home ranges on tributaries to breed on the 

mainstem river. Most of the frogs laid eggs when mean mainstem temperatures 

were between 10 and 16 °C, and discharge was between baseflow and less than 

55 percent above baseflow. Length of stay by females at river breeding sites was 

extended by high flows; females may be waiting for suitable flows prior to oviposition. On one reach of the North Fork Feather River, where relatively few males were 

present, females also remained at breeding sites longer, indicating that sex ratio may 

influence breeding site tenure. Overall population size may influence the length 

of the breeding season, as larger populations (>100 breeding adults) in Oregon 

appeared to consistently have a longer breeding interval than smaller populations.2 

Typically, larger females breed earlier, and the number of eggs per clutch decreases 

as the breeding season progresses (Gonsolin 2010, Kupferberg et al. 2009b). 

Rates of embryonic development are highly temperature-dependent. Thermal 

tolerance experiments on foothill yellow-legged frog embryos (Gosner [1960] stages 

4 to 12) revealed a critical minimum at ~6 °C, and a critical maximum at 26 °C 

(Zweifel 1955). Zweifel (1955) found significant acceleration in embryonic development with relatively small increases in temperature; he reported a large range of 

2

 Hayes, M. 1994–1996. Unpublished data. On file with: Washington Department of Fish 

and Wildlife, 600 Capitol Way North, Olympia, WA 98501. 
15 

Foothill Yellow-Legged Frog Conservation Assessment

variation in the length of embryonic development across the species’ range (5 to 30+ 

days), which he presumed was a reflection of temperature variation during embryonic development. At water temperatures of 16 to 20 °C in the South Fork Eel River, 

hatching occurred over a 1- to more than 3-week period, with colder water temperatures resulting in longer times to hatching (Kupferberg et al. 2011a). In the Trinity 

River mainstem, eggs hatch in 27 to 36 days (A. Lind, personal observation, 1991). 

Length of the tadpole period is 3 to 4 months (Zweifel 1955) and varies in 

relation to both temperature and the quantity and quality of algal food (Catenazzi 

and Kupferberg 2013, Kupferberg et al. 2011a). Kupferberg et al. (2011a) found that a 

diet rich in diatoms from the genus Epithemia, which host cyanobacterial nitrogenfixing endosymbionts, ameliorated the effects of cold temperature on the length of 

the larval period. Tadpoles reared in a cool, shady stream (maximum 30-day average [M30DAT] = 16 °C) were able to reach metamorphosis only with supplemented 

algae harvested from a warm, sunny site after 122.2 ± 0.6 days. At M30DAT = 

21.6 °C, tadpoles metamorphosed 79.3 ± 1.7 days after oviposition (Kupferberg et 

al. 2011a). These results are consistent with many anurans, for which temperature 

and diet strongly influence larval growth and development, with cooler water 

temperatures lengthening the time to metamorphosis (e.g., Álvarez and Nicieza 

2002, Licht 1974). Foothill yellow-legged frogs from some Sierra Nevada rivers 

that receive hypolimnetic water from upstream reservoirs appear to have extended 

tadpole periods, and recently metamorphosed frogs have been observed into late 

October (Seltenrich 2002). However, in laboratory experiments, tadpoles reared 

from eggs collected at Sierran sites exhibited a capacity for higher growth and 

faster development than those from coastal populations (Kupferberg et al. 2011a). 

Growth is most rapid during the year after metamorphosis (see table 2 and 

fig. 9). Growth rates may vary by location; Gonsolin (2010) found that frogs on 

Coyote Creek (Santa Clara County) had higher growth rates than Sierra Nevada 

and Coast Range populations and suggested that warm water temperature and 

higher food availability may explain these differences. Frogs from a Sierran population grew faster than those from a coastal population, and females grew faster 

than males (GANDA 2015). Reproductive organs mature in the first summer after 

metamorphosis, but first breeding activity usually occurs in the second year following metamorphosis (Zweifel 1955). However, Jennings (1988) observed males 

reproducing as early as 6 months after metamorphosis, and Van Wagner (1996) 

found that juveniles that attained 35 mm in snout/urostyle length (SUL) by late 

fall were at spawning locations the following spring. Reports of size at maturity 
16 

GENERAL TECHNICAL REPORT PSW-GTR-248

Table 2—Mean growth rates of foothill yellow-legged frogs from 

Clear Creek, Nevada County, California 

Age class 

Gender Juvenile 1-year old ≥ 2 years old 

Millimeters SUL/day (standard error) 

Male 0.041± 0.034 (59) 0.019 ± 0.016 (26) 0.007 ± 0.016 (11) 

Female 0.090 ± 0.031 (?) 0.026 ± 020 (21) 0.013 ± 0.008 (9) 

SUL = snout/urostyle length. 

Data are pooled across years for age and sex classes. Sample sizes (n) are in 

parentheses. The range of number of days for which growth rates were calculated is 

30 to 363 (adapted from Van Wagner 1996). 

Figure 9—Composite growth curves for foothill yellow-legged frogs from Clear Creek, Nevada 

County, California. Points are values calculated from mean growth rates of each age class multiplied 

by 365 days. Adapted from Van Wagner (1996). 

for foothill yellow-legged frogs vary by study, specifically for females; minimum 

size at maturity can vary with sex, environmental conditions, and the degree to 

which a population may be stressed. Because studies reported size at maturity at 

various locations throughout the species’ range, discrepancies in size at maturity 

may also be due to geographic influences (e.g., elevation and or latitude/longitude). 

In general, males mature at a body size of about 40 mm SUL, and females mature 

between 40 to 50 mm SUL (Van Wagner 1996, Wheeler 2007, Wheeler and Welsh 

2008, Zweifel 1955). Foothill yellow-legged frog longevity estimates are based on 
17 

Foothill Yellow-Legged Frog Conservation Assessment

 

a few individuals recaptured during long-term studies. In the Sierra Nevada, Van 

Wagner (1996) reported a recaptured female to be at least 3 years old, and GANDA 

(2015) estimated a maximum age of 13 years for males and females in a Sierran 

population, and maximum ages of 12 years for males and 11 years for females in 

a coastal population. In a northwestern California coastal population, Wheeler 

determined the longevity for males to be at least 6 years, and for females to be at 

least 7 years, based on recaptures.3 

The least understood aspect of foothill yellow-legged frog life history is the 

annual disappearance of frogs preceding overwintering. The cues for this disappearance are unclear, but movements observed during fall rains and periods of declining 

temperatures suggested that relative humidity and precipitation are possible triggers 

for movement (Bourque 2008; see also “Habitat Requirements” section). 

Population Dynamics 

Frog density or density index information, and egg mass counts are two types of 

data that provide some insight into population changes. However, no historical data 

exist to compare with current population levels of foothill yellow-legged frogs and 

no data pre-date the interval when foothill yellow-legged frog populations began to 

decline in California. Some data exist on differences in population densities relative 

to the season and degree of disturbance, human-induced and otherwise. 

In a 3-year mark-recapture study on Clear Creek (Nevada County), Van Wagner 

(1996) observed postmetamorphic “densities” (expressed as the number of frogs 

per meters of stream length) that ranged from 0.19 frogs/m of stream in early summer to 0.61 frogs/m in fall; densities were highest in the fall as a result of recent 

3

 Wheeler, C. 2008. Unpublished data. On file with: U.S. Department of Agriculture, Forest 

Service, Pacific Southwest Research Station, 1700 Bayview Dr., Arcata, CA 95521. 

Table 3—Postmetamorphic Rana boylii population density above and 

below barriers to native and nonnative fish movement in three northern 

California drainages 

Fish absent Fish present 

(n = 30) (n = 18) 

R. boylii mean density (frogs/m of stream) 0.72 0.22
 

Range in frog density 0.47–0.97 0.07–0.37
 

Differences in frog density were significant (two-tailed Mann-Whitney U-test; P < 0.001) (adapted 

from Hayes and Jennings 1986). 
18 

GENERAL TECHNICAL REPORT PSW-GTR-248

recruitment of the new annual cohort, and spring/summer densities were lowest 

owing to the presumed attrition of juveniles during overwintering. Van Wagner’s 

(1996) density estimates were similar to less labor-intensive counts obtained from 

similarly sized streams in three inner Coast Range drainages of the Sacramento 

Valley (table 3). 

Egg mass counts, recorded as the number of egg masses laid per length of 

stream (table 4), provide estimates that may better reflect effective population sizes 

(N ), the number of individuals actually contributing to reproduction over time. 

e

Individually marked gravid females have been recaptured over several consecutive 

years, suggesting that females reproduce every year (C. Wheeler, personal observation, 2003–2008). Each female is assumed to lay one mass of eggs and a successful 

male may mate with more than one female during the breeding season (Wheeler 

2007, Wheeler and Welsh 2008), so the egg mass counts best reflect the number of 

Table 4—Egg mass densities (number of egg masses per linear kilometer of streambank) of foothill yellowlegged frogs in California 

Watershed (upstream No./ Standard Years 

dam or reach name) km error Length sampled Data source 

Kilometers 

Regulated coastal: 

Trinity (Lewiston Dam) 

Eel (Scott Dam) 

0.45 

2.9 

0.17 

— 

22.5, 

33.3 

12.8 

1991–1994, 

2004–2006 

2010 

Lind 2005; Ashton, 

Bettaso, and Welsha 

Catenazzib 

Alameda (Calaveras Dam) 3.7 1.6 1.9 2003–2010 Bobzien and 

DiDonato 2007 

Regulated Sierran: 

North Fork of North Fork American 

(Lake Valley Canal Diversion Dam) 

0.5 — 4 2008 Nevada Irrigation District and 

PG&E 2010 

Middle Fork American (French 

Meadows Dam) 

0.65 — 3.1 2007 Placer County Water Agency 

2008 

McCloud (McCloud Dam) 1.23 — 9.73 2008 PG&E and Stillwater 

Sciences 2009 

South Fork Yuba (Spaulding Dam) 1.9 — 10 2008 Nevada Irrigation District 

and PG&E 2010 

North Fork Feather (Cresta Dam) 2.1 0.4 7.6 2002–2010 PG&E 2010 

Butte Creek (Forks of Butte 

Diversion) 

4.1 — 1.9 2006 PG&E 2007 

Middle Fork Stanislaus (Sand Bar 

Dam) 

6.2 3.6 1.0 2001–2003 PG&E 2004a 

Pit (Pit 4 Dam) 8 2.7 7 2002–2005 PG&E 2004b; 

M. Ellisc 
19 

Foothill Yellow-Legged Frog Conservation Assessment

Table 4—Egg mass densities (number of egg masses per linear kilometer of streambank) of foothill yellowlegged frogs in California (continued) 

Watershed (upstream No./ Standard Years 

dam or reach name) km error Length sampled Data source 

Kilometers 

Butte Creek (Centerville Dam) 9.1 — 5.9 2006 PG&E 2007 

Rubicon (Hell Hole Dam) 9.2 — 7.9 2007 Placer County Water Agency 

2008 

North Fork Feather (Poe Dam) 10.5 1.7 8.3 2001–2010 PG&E 2010 

Middle Fork Yuba (Milton Diversion 13 — 4 2008 Nevada Irrigation District and 

Dam) PG&E 2010 

W Br. Feather (Hendricks Head 15.1 — 3.4 2006 PG&E 2007 

Dam) 

Unregulated coastal: 

Coyote (U.S. Coyote Lake) 11.2 — 7.8 2004–2005 Gonsolin 2010 

Eel (Ten Mile Creek) 12.3 2.6 4 1993–2003, 

2008–2010 

Kupferberg 1996a; unpublished 

datad 

Alameda (Camp Ohlone) 21.9 4.3 1.6 1997–2010 Bobzien and DiDonato 2007 

Smith (Hurdygurdy Creek) 34.6 4.5 4.8, 1.7 1991–1992, Lind 2005; Wheeler and Welsh 

1998-2000; 2008 

2002–2007 

Trinity (South Fork Trinity) 69.9 22.5 15.6, 

5.9 

1992–1994, 

2004–2006 

Lind 2005; Ashton, Bettaso, 

and Welsha 

Eel (SF Eel) 105.7 6.5 5.2 1992–2010 Kupferberg 1996a 

Unregulated Sierran: 

San Joaquin (Jose Creek) 4.6 — 1.2 1995, 2002 Lind et al. 2003b 

Tuolumne (North Fork Tuolumne) 9 — 0.3 2001 Lind et al. 2003b 

Yuba (Shady Creek) 14.4 — 3.2 2003 Yarnell 2005 

Stanislaus (Rose Creek) 29 — 0.65 2001 Lind et al. 2003b 

Yuba (Clear Creek) 29 9.5 0.82 1992–1994 Van Wagner 1996 

— = No standard error for sites with fewer than 3 years of data.
 

Table adapted from Kupferberg et al. (2012).
 

a Ashton, D.; Bettaso, J.; Welsh, H. [N.d.]. Unpublished data. On file with: USDA, Forest Service, Pacific Southwest Research Station, 1700 

Bayview Dr., Arcata, CA 95521. 

b Catenazzi, A. [N.d.]. Unpublished data. On file with: Department of Zoology, Southern Illinois University, Carbondale, IL 62901.
 

c Ellis, M. [N.d.]. Personal communication. Ecologist, Spring Rivers Ecological Sciences, P.O. Box 153, Cassel, CA 96016.
 

d Kupferberg, S. [N.d.]. Unpublished data. On file with: Questa Engineering, 1220 Brickyard Cove Road, Suite 206, 

Pt. Richmond, CA 94807. 
20 

GENERAL TECHNICAL REPORT PSW-GTR-248

reproductive females. Further, comparison of these data with census counts reveals 

a disparity between census counts and estimates of breeding female population 

size using egg mass data; studies have typically detected more egg masses than the 

number of female frogs observed. Populations appear to have higher densities in 

coastal rivers and streams compared to those in the Sierra, and egg mass densities 

are five to six times higher in unregulated rivers compared to systems with dams 

and diversions (table 4). 

Annual fluctuations in a population based on egg mass counts on the unregulated South Fork Eel River appeared to be unlinked to the magnitude of winter peak 

discharge, but rather were most tightly correlated with the negative effects of high 

spring flow events 3 years prior (Kupferberg et al. 2008). The 3-year time lag may 

reflect the time most females need to recruit into the breeding population at northern latitudes. 

The extent to which groups of frogs at breeding sites scatter within a stream 

system function as metapopulations is unknown, and population dynamics may 

be site -specific. On larger, high-gradient Sierran rivers, breeding sites are highly 

discontinuous, separated by hundreds to thousands of meters (GANDA 2008). 

However, frogs have been reported traveling such distances (see “Movement” 

section). Genetic (mtDNA, RAPD) evidence has demonstrated significant isolation by distance between individuals greater than 10 km apart in a coastal river 

(Dever 2007). In Sierran rivers with hydroelectric projects and reservoirs spaced 

between study reaches, foothill yellow-legged frog populations had lower genetic 

diversity and greater genetic drift that was not associated with isolation by distance 

in comparison to free-flowing rivers within the same watersheds (Peek 2010). This 

lack of gene flow suggests that if isolated populations are extirpated, the likelihood 

of recolonization of unoccupied sites is quite low. Moreover, these results imply that 

the likelihood that foothill yellow-legged frogs are capable of negotiating potential 

barriers such as reservoirs and dams is small. If recolonization typically results 

from rare long-distance movements, then reservoirs with introduced predators may 

be barriers. A generic matrix population model for foothill yellow-legged frogs 

has been developed as a tool for assessing foothill yellow-legged frog population 

dynamics in streams subjected to different types and severities of hydrologic alteration. However, complete demographic data for a particular stream are still needed to 

effectively test the general predictions of this model (Kupferberg et al. 2009b). 
21 

Foothill Yellow-Legged Frog Conservation Assessment

Movement 

Unless disturbed, hatchling tadpoles remain with the egg mass remnants for several 

days, and then disperse into the interstices of the local gravel bed, often moving 

downstream in areas of moderate flow (Ashton 1995–1996). Following metamorphosis, Twitty et al. (1967) observed an upstream bias in movement; >90 percent of 

recently metamorphosed frogs moved upstream. 

Data on postmetamorphic foothill yellow-legged frog movements come primarily from mark-recapture and radiotelemetry investigations in the Coast Range and 

Sierra Nevada. In general, adult frogs moved greatest distances in the spring when 

moving to and away from breeding sites (Van Wagner 1996, Wheeler et al. 2006). 

Several studies found that females moved greater distances than males; females 

have been reported to move thousands of meters (Bourque 2008, GANDA 2008, 

Gonsolin 2010, Wheeler et al. 2006), with a maximum observed distance of 7 km 

(Bourque 2008). Movement was more restricted during the nonbreeding season 

(Van Wagner 1996), and males may remain near the breeding area for months 

after breeding activity ends (Wheeler et al. 2006). Frogs typically remained near 

the stream channel (<12 m), using watercourses as movement corridors (Bourque 

2008). Movements in the spring were not associated with weather variables; however, fall/winter movements were associated with increasing rain and humidity 

(Bourque 2008). 

Juveniles and adults have been observed moving into upland habitats, offchannel pools, or smaller tributary streams during the nonbreeding season 

(GANDA 2008). Young-of-the-year metamorphs have been recaptured in upland 

traps during the fall (Twitty et al. 1967) and adults have also been observed moving 

upslope during fall rains (M. Hayes, personal observation, 1994) (Jennings 1990). 

Frog movement away from the river channel may be a behavioral response to avoid 

high discharge events, may represent movements into overwintering sites, or some 

combination of both. 

Feeding 

Food habit studies indicate that postmetamorphic foothill yellow-legged frogs are 

generalist predators primarily of insects; they eat mostly terrestrial but also aquatic 

invertebrates. Stomach contents have included grasshoppers, beetles, mosquitoes, 

hornets, bees, wasps, termites, ants, water striders, other flies, moths, aquatic 

snails, true bugs, and spiders (Fitch 1936, Haggarty 2006, Storer 1925, Van Wagner 

1996). Haggarty (2006) found no differences in the selection of prey by age class. 

Foothill yellow-legged frog tadpoles feed on periphyton scraped from rocks 

or plants (Nussbaum et al. 1983). Tadpoles grow faster and larger when they eat a 
22 

GENERAL TECHNICAL REPORT PSW-GTR-248

diet rich in diatoms (which have high protein and lipid contents), and are known 

to prefer this food type to lower quality algae (Kupferberg 1997b, Kupferberg et 

al. 1996b). When availability of high-quality algae is reduced, as occurs in the 

presence of bullfrog (Lithobates [Rana] catesbeianus) tadpole grazing, foothill 

yellow-legged frog mass at metamorphosis has been observed to decline by about 

one quarter (Kupferberg 1997a). Regulated stream environments with altered 

hydrologic and thermal regimes may be dominated by low-quality periphyton, and 

tadpoles may not grow or may even lose weight by feeding on mucilaginous stalked 

diatoms (Furey et al. 2014). Large metamorphic size may increase survival probability, decrease the time to maturity, and increase male mating success and female 

fecundity (Berven 1981, 1982, 1990; Berven and Gill 1983; Howard 1978; Pough 

and Kamel 1984; Semlitsch et al. 1988; Smith 1987). Foothill yellow-legged frog 

tadpoles have also been observed actively congregating on dead tadpoles of their 

own species, and dead, open bivalve mollusks (A. Lind, personal observation, N.d.). 

They appeared to be feeding either on diatoms or algae attached to the carcasses or 

directly on the necrotic tissue. Besides a rich nutrient and protein source, another 

possible advantage of consuming dead tadpoles is to consume tissue rich in thyroid 

hormone, which enhances development (Crump 1990). 

Mortality 

Floods or dam releases have been documented as the primary cause of egg mortality in several studies (Kupferberg 1996a, Kupferberg et al. 2012, Lind et al. 1996). 

Extreme floods in southern California in 1969 may have been responsible for the 

regional extirpation of this species (Sweet 1983). In one study, large-magnitude 

flows reduced egg survival, but smaller-magnitude flows later in the season 

appeared to cause higher mortality (Kupferberg et al. 2008). Kupferberg et al. 

(2012) found that variability in spring and summer flows was correlated with high 

egg mass and tadpole mortality. Furthermore, population size on the unregulated 

South Eel River was correlated with spring freshets 3 years prior, suggesting that 

spring flows directly influence egg and tadpole survival (Kupferberg et al. 2008); 

this population has likely remained stable despite occasional low-recruitment 

years because of the lengthy recurrence interval between large, late-spring storms 

(Kupferberg 1996a, 1996b). Decreasing river levels can desiccate eggs through 

stranding (Kupferberg 1996a, 1996b, Wheeler et al. 2013). In regulated systems 

such as the mainstem Trinity River, Poe and Cresta reaches of the North Fork 

Feather River, Pit River, and South Fork American River, stranding likely occurred 

as a result of the timing of flow releases and cessation of spill, in which relatively 

high water stage prior to oviposition was followed by a drop in stage immediately 
23 

Foothill Yellow-Legged Frog Conservation Assessment

after oviposition (Wheeler et al. 2013) (table 2.6 in Kupferberg et al. 2009b). When 

the mean and maximum scouring and stranding survival rates compiled from these 

regulated rivers were used in a population projection model instead of scouring and 

stranding rates observed in unregulated rivers, probability of extinction over 30 

years increased from 2.2 to 4.6 times. Scouring and stranding events occur more 

frequently early in the breeding season when large females breed, so the lower 

fecundity of late-breeding females compounds the effect of the losses to scouring 

and stranding. The 30-year extinction rates increased 17-fold when the diminished 

contribution to future generations from the most fecund females was accounted for 

(Kupferberg et al. 2009b). Flow regimes on many regulated rivers appear to exceed 

the capacity of foothill yellow-legged frog populations to rebound from embryonic 

mortality caused by extreme discharge fluctuation. 

Hydrologic factors also influence mortality posthatching. Summer pulsed 

flows may scour and strand tadpoles, as tadpoles have limited abilities for sustained 

swimming at flow velocities typical near shore during a pulsed flow (Kupferberg 

et al. 2011b). Depending on the frequency and duration of summer pulsed flows, a 

range of tadpole mortality estimates (best-case to worst-case scenarios, one lowmortality to four high-mortality pulses) caused risk of extinction to increase 3.2- to 

20-fold beyond background rates in a population viability analysis (PVA) 

(Kupferberg et al. 2009b). When the negative effects of cold water temperatures on 

larval survival were incorporated in the PVA, the 30-year extinction rate increased 

2.4 times. In a series of field experiments, thermal regime influenced the recruitment success of foothill yellow-legged frog populations; in colder tributaries, 

tadpoles did not attain metamorphosis (Catenazzi and Kupferberg 2013) and tadpole 

mortality increased when water temperatures deviated from temperatures preferred 

by tadpoles (16.5 to 22.2 °C). In three Sierran watersheds (Tuolumne, American, 

and Feather), where R. boylii populations occur in both regulated and free-flowing 

river reaches, Kupferberg et al. (2011a) found that maximum average temperature 

during the warmest 30-day period (M30DAT) was a useful metric to characterize 

the period critical for recruitment. Based on thermal monitoring of sites used for 

breeding and cooler sites farther upstream where frogs were sparse and tadpoles 

absent, the realized thermal niche for successful reproduction was 17.6 to 24.2 °C 

(average of 2009 and 2010, 1 dry and 1 wet year). The densest Sierran populations 

were in reaches where M30DAT ≥20 °C. In field tadpole-rearing experiments, 

peak production of metamorphs (combined highest survival and largest size) was at 

M30DAT = 20 to 22 °C. 

Among the documented predators of foothill yellow-legged frogs at various life 

stages are aquatic insects including caddisfly larvae (Limnephilidae), waterstriders 
24 

GENERAL TECHNICAL REPORT PSW-GTR-248

(Gerridae), and veliid bugs (Veliidae) (Kupferberg 1996a, Rombough and Hayes 

2005c); signal crayfish (Pacifastacus leniusculus) (Rombough and Hayes 2005c, 

Wiseman et al. 2005); introduced bullfrogs (Crayon 1998); California tiger salamander (Ambystoma californiense) larva (Fidenci 2006); garter snakes, predominantly 

the aquatic garter snake (Thamnophis atratus) and the Sierran garter snake (T. 

couchii) (Fitch 1936, 1940, 1941; Jennings and Hayes 1994; Lind and Welsh 1994; 

Nussbaum et al. 1983; Stebbins 1951; Zweifel 1955); North American river otters 

(Lutra canadensis) (Rose 2015); mallard ducks (Anas platyrhynchos) (Rombough 

et al. 2005b); Sacramento pikeminnow (Ptychocheilus grandis) (Ashton and 

Nakamoto 2007, Brown and Moyle 1997, Corum 2005); and other fish species are 

suspected to be predators (Hayes and Jennings 1988, Rombough and Hayes 2005c). 

Numerous parasites have been documented for foothill yellow-legged frogs, but 

the extent of their effects on survival is unknown. Foothill yellow-legged frogs are 

apparently susceptible to a variety of helminths (Bursey et al. 2010, Walker 1965) as 

well as other parasites (Walton 1964). The copepod Lernaea cyprinacea, a known 

parasite of Rana chalconota (a Javanese ranid frog), has been shown to cause limb 

deformities (Leong 2001). A widespread introduced parasite of fish (Piasecki et 

al. 2004), L. cyprinacea has been recorded along the South Fork of the Eel River 

from foothill yellow-legged frogs as well as co-occurring California roach (Lavinia 

symmetricus) and American bullfrogs (Kupferberg et al. 2009a). Kupferberg et al. 

(2009a) observed this copepod in approximately 10 percent of metamorphs sampled 

on the South Fork of the Eel River; affected individuals had morphological deformities, most frequently on the hind limbs. Because this parasite has the potential to 

cause significant tadpole mortality, its prevalence and effects on survival warrant 

further study. Occurrence of L. cyprinacea among Sierran foothill yellow-legged 

frog populations has been reported in the Clavey and Rubicon Rivers (Kupferberg 

et al. 2009a, Peek 2014). 

Summary of the Ecology 

Several features of foothill yellow-legged frog ecology are pertinent to the development of a conservation strategy. Foothill yellow-legged frogs occupy low-gradient 

streams and adjacent terrestrial stream-margin habitats across the foothills of 

the Sierra Nevada, and interior and west-side Coast Ranges of California. Considerable genetic differentiation exists between coastal and Sierra Nevada populations 

as well as between northern and southern populations within the Sierra Nevada. 

Stream hydrology, especially the predictable seasonal variation in flow and complex interactions among seasonal flows, stream substrates, and riparian habitat 

strongly structure the spatial distribution and population dynamics of this species. 
25 

Foothill Yellow-Legged Frog Conservation Assessment

Reproduction and early rearing depend on low flows that occur during the descending limb of the seasonal hydrograph and on structurally sheltered portions of stream 

channels such as gravel and cobble bars. The spatial and temporal distribution of 

frogs varies seasonally; adult frogs congregate at common breeding sites during 

the reproductive season and then disperse following reproductive activity. Seasonal 

movements occur among breeding, postbreeding summer, and overwintering 

habitats. In larger streams, tributary streams may be important seasonal refuges for 

postmetamorphic life stages. Foothill yellow-legged frogs are vulnerable to various 

predators, which include several introduced species. High egg mass and tadpole 

mortality caused by scouring and stranding following high waterflow events or 

unseasonal (nonnatural) dam releases have the capacity to cause profound changes 

in long-term population viability. 

Status 

The following sections provide comparisons between more recent (1980 to 2001) 

and historical (prior to 1980) distributions and abundances. Limited additional 

locality data for the period after 2001 are also presented. 

The following information was compiled from national forest biologists, 

National Park Service biologists, and other academic and independent biologists 

working in the Sierra Nevada, and from literature and museum sources. Documentation from museum collections is listed according to the standard symbolic codes 

for each institution (app. 2) and the pertinent specimen number(s). More detailed 

documentation by administrative unit (including national forests outside the Sierra 

Nevada region) is provided in appendix 3. 

Rangewide Overview 

Sweet (1983), the first to provide substantive comment on declines in the foothill 

yellow-legged frog, documented its complete disappearance from southern coastal 

California. From data collected through the early 1990s, Jennings and Hayes (1994) 

estimated that foothill yellow-legged frogs had been extirpated over roughly half of 

their California range and extirpated across about two-thirds of their Sierra Nevada 

historical range (Jennings 1996). Examining historically occupied sites in the 

late 1990s, Borisenko and Hayes (1999) and Borisenko (2000) obtained a similar 

estimate for contraction in its Oregon range. 

The fairly recent work of Lind (2005) is the only assessment undertaken for 

foothill yellow-legged frogs across their entire geographic range, excluding a lone 

locality record for northwestern Mexico (Loomis 1965). That assessment revealed 
26 

GENERAL TECHNICAL REPORT PSW-GTR-248

that foothill yellow-legged frogs had disappeared from 51 percent of their historical localities in the Sierra Nevada. However, the degree of disappearance across 

the geographic range may be underestimated. Ongoing surveys suggest that local 

extirpation of foothill yellow-legged frogs is continuing, and the species appears to 

be moving slowly, but inexorably toward extirpation across its range in a northerly 

direction (Jennings 2006). 

California 

Pre-1980— 

Historical data indicate that foothill yellow-legged frogs were widespread throughout Pacific drainages in California (Stebbins 1951, 2003) with some topographic 

relief southward to the San Gabriel River system (Jennings and Hayes 1994; Storer 

1923, 1925; Zweifel 1955 (fig. 10). Historical data provide anecdotal information on 

abundance. Cope (1879) stated that, “During my expedition to Oregon in 1879, I... 

found [foothill yellow-legged frog] rather abundant in the mountainous regions of 

northern California...,” a comment he later repeated (Cope 1883). 

Pre-1980 collections also reinforce the notion that this species was historically 

abundant. On 17 October 1893, Henry Henshaw collected 19 foothill yellow-legged 

frogs during a short visit to Orrs Creek, a tributary of the Russian River (USNM 

20885–20903); from 11–23 June 1911, Walter Taylor and Norman Stern “casually” 

collected 35 foothill yellow-legged frogs on the Kern River near Bodfish (MVZ 

2965–2999); Joseph R. Slevin collected 112 foothill yellow-legged frogs at Skaggs 

Spring (Sonoma County) over 3 days (17, 19, and 20 April 1911) (CAS 28165­

28276); on 4 May 1911, Slevin also collected 40 foothill yellow-legged frogs from 

near Willits in Mendocino County (CAS 28718–28757); and on 11 September 1922, 

John Van Denburgh and Slevin collected 17 foothill yellow-legged frogs along 

Whiskey Creek, 4.8 km east of Raymond in Madera County (CAS 55746–55762). 

Large pre-1980 collections were not restricted to the interval around 100 years ago. 

On 28 April 1928, Charles Hibbard collected 57 foothill yellow-legged frogs from 

Lagunitas Creek in Marin County (CAS 63665–63721); on 8 June 1950, Richard 

Zweifel collected 30 foothill yellow-legged frogs from the North Fork of the San 

Gabriel River (MVZ 51314–51343); on 31 May 1952, Zweifel also collected 27 

foothill yellow-legged frogs from Last Chance Creek in Plumas County (MVZ 

58058–58084); and on 9 October 1955, Thomas Rodgers collected 50 foothill 

yellow-legged frogs at a location 1.6 km south of Denny in Trinity County (CSUC 

1264–1313). 

Over 4,000 specimens representing about 500 localities across the geographic 

range in California were obtained starting with the earliest collection in 1850 
27 

Foothill Yellow-Legged Frog Conservation Assessment

Figure 10—Status of the foothill yellow-legged frog (Rana boylii) in California based on an update of Lind (2005). Lind (2005) assessed 

status prior to year 2000. This map overlays new sightings from post-2000 localities on that previous analysis. 
28 

GENERAL TECHNICAL REPORT PSW-GTR-248

(USNM 3350); relatively large numbers were still being collected in the 1970s. 

The first indications of declines came as a result of the work of Sweet (1983), who 

initiated his studies on foothill yellow-legged frog distribution in southern coastal 

California during the late 1970s, when declines of this species across that region 

were already widespread. An initial disbelief at not finding frogs led Sweet to 

do extensive resurveys, especially in Santa Barbara County (Sweet 1985); these 

surveys did not detect the presence of foothill yellow-legged frogs. The last known 

southern California sighting deemed reliable, though not verifiable by a photograph or specimen, was made on 6 July 1977 along Piru Creek, 1 to 2 km south of 

Frenchman’s Flat (Los Angeles County) (Jennings and Hayes 1994). Areas outside 

of southern coastal California were not systematically surveyed to determine the 

status of foothill yellow-legged frogs until after 1980.
 

1980 to present— 

The surveys begun by Sweet (1983) during the late 1970s that indicated the disappearance of the foothill yellow-legged frog in southern California extended into the 

1980s: these surveys were also unsuccessful in detecting frogs.
 

In an assessment addressing the entire California range through the early 

1990s, Jennings and Hayes (1994) added that foothill yellow-legged frogs also 

seemed to have disappeared from much of the central Coast Ranges and most of 

the southern Sierra Nevada (see also Jennings 1995, 1996; and fig. 10). Overall, this 

assessment implied that the species had disappeared from about half its geographic 

range (based on tallying individual localities) in California (Jennings 1995). The 

foothill yellow-legged frog is now a California Species of Special Concern, though 

Jennings and Hayes (1994) recommended endangered status for this species in 

southern and central California south of the Salinas River in Monterey County, and 

threatened status in the west-slope drainages of the Sierra Nevada and southern 

Cascade Range east of the Sacramento-San Joaquin River axis. 

In a statewide evaluation, Fellers (2005) noted that, since 1993, his field crews 

had conducted extensive surveys for foothill yellow-legged frogs in California, 

visiting 804 sites in 40 counties (California has 57 counties overall, and several 

desert and east-side counties lack historical records or habitat for foothill yellowlegged frogs). At least one foothill yellow-legged frog was found at 26.5 percent of 

sites (n = 213) and 70 percent (n = 28) of the counties visited. A distribution of sites 

and counties visited was not provided, but Fellers (2005) stated that foothill yellowlegged frog sites are unevenly distributed across California. He added that extant 

sites were most numerous in northwest California, about 40 percent of surveyed 

sites, whereas the Cascade Range and south Coast Range (south of San Francisco 

Bay) each had about 30 percent occupancy and the Sierra Nevada had about 
29 

Foothill Yellow-Legged Frog Conservation Assessment

12 percent occupancy. Comparison to the Jennings (1995) assessment may be inappropriate because limitations of the historical record prevent knowing whether all 

the sites that Fellers’ crews surveyed were occupied in the recent past. Lack of data 

on detectability as a function of effort or other covariates for both surveys further 

confounds comparison. Nevertheless, the patterns of occupancy he reports are 

cause for concern because even in the region with the least-altered habitat (i.e., the 

northwest coast), occupancy was still less than half of surveyed sites. 

Fellers (2005) also provided insight into abundance at surveyed sites. Of the 

213 sites at which he found at least one frog, he observed 20 or more adults at only 

14 percent (n = 30) of sites. As expected, the largest numbers were observed in 

the northwest coast region, where six sites had adult frog numbers over 100 and 

an additional nine sites had more than 50 frogs. Fellers’ assessment is in general 

agreement with casual and systematic observations of other investigators. Kupferberg et al. (2012) compiled egg mass surveys for 27 northern California populations 

(coastal and Sierran) and found that the foothill yellow-legged frog still occurs 

in significant numbers in some coastal drainages in the Coast Range north of the 

Salinas River, but the species was on average five to six times less abundant where 

anthropogenic threats, i.e., flow regulation, were present, similar to those described 

in the “Risk Factors” section. 

Sierra Nevada 

Pre-1980— 

Historical data show that foothill yellow-legged frogs occurred in west-side 

streams at low to moderate elevations all along the west slope of the Sierra Nevada 

(Jennings and Hayes 1994; Stebbins 1951, 2003; Storer 1925; Zweifel 1955) (fig. 10). 

In the Sacramento Valley hydrographic basin, low-elevation areas make up a large 

portion of the valley floor, where presumably suitable foothill yellow-legged frog 

breeding habitat once existed. The scarcity of records undoubtedly underestimates 

the historical distribution of the species in this region, as all records are pre-1930, 

prior to the major hydrological changes and expansion of exotic aquatic predators 

that changed much of the lowland Central Valley in California to its present condition (Moyle 2002). However, no quantitative abundance data exist for the Sierran 

slope prior to the introduction of exotic fishes and major hydrological changes. 

Storer (1925) suggested that the species was widespread on the Sierran slope, and 

Zweifel (1955) stated that the species was at least moderately abundant at scattered locations over that region. Moyle (1973), whose data were collected after 

significant incursion by introduced fish fauna, demonstrated that the species was 

still moderately abundant in foothill streams in the 1970s. However, Moyle’s data 
30 

GENERAL TECHNICAL REPORT PSW-GTR-248

were obtained at the time when the range had been reduced because the historical record shows that the species extended to the valley floor margin at least in the 

1920s, 1930s, and 1940s (Storer 1925, Wright and Wright 1949). Whether the species occasionally turning up on the Central Valley floor during the latter part of the 

historical era were waif dispersal events, as Livezey (1962) suggests, or part of the 

historical pattern that helped maintain populations in areas of suitable habitat on the 

Central Valley floor (see Grinnell et al. 1930), as noted previously, is unclear. 

1980 to present— 

Surveys extending back to the 1990s suggest that foothill yellow-legged frogs have 

disappeared from most of the southern half of the Sierran slope, from approximately Madera County southward (Jennings 1995, 1996; Jennings and Hayes 1994). 

These data generally agree with the more recent survey efforts of Lind (2005) 

(fig. 10), demonstrating that foothill yellow-legged frog populations have become 

even more sparse over this portion of the Sierran slope. Further, evidence exists of 

considerable local extirpation from different drainage systems in the northern half 

of the Sierra Nevada, a pattern that becomes less widespread as one moves north 

(Lind 2005) (fig. 10). In Fellers’ (2005) assessment (which included data collected 

since 1993), occupancy of foothill yellow-legged frog sites in the Sierra Nevada was 

about 12 percent, but historical occupany of these sites is unknown. Lind (2005) 

used a randomized selection of 47 historically occupied sites from across the Sierra 

Nevada and found that 51 percent (n = 24) of the sites were currently unoccupied. 

Summary of Status 

Foothill yellow-legged frogs, once common across stream ecosystems of the lower 

west-slope Sierra Nevada, have become increasingly rare. The most recent analyses 

reveal that foothill yellow-legged frogs have disappeared from 51 percent of their 

historical localities in the Sierra Nevada. Disappearance is more pronounced with 

decreasing latitude and the species is near extirpation over roughly the southern 

half of its Sierran range. The low number of frogs at occupied sites over the Sierran range and documented patterns of population declines in Sierra Nevada merit 

focused conservation efforts. 

Risk Factors Affecting the Status of the Species 

Many factors, individually and probably in combination, have contributed to the 

species’ decline. However, frog populations are more often absent from historically 

occupied locations when close to a large dam (Kupferberg et al. 2012, Lind 2005). 

Water development and diversion, introduction of predators, drought and climate 
31 

Foothill Yellow-Legged Frog Conservation Assessment

change, livestock grazing, pesticides, ultraviolet radiation, pathogens, acidification 

from atmospheric deposition, nitrate deposition, and recreational activities have all 

been identified as potential factors affecting this species and its habitat (Borisenko 

2000, Borisenko and Hayes 1999, Jennings 1996, Jennings and Hayes 1994, Lind 

2005, Olson and Davis 2009, Sweet 1983). 

Risk factors include environmental conditions and human activities that may 

adversely affect individuals or populations of foothill yellow-legged frogs, or their 

habitat. The following are the 17 risk factors identified and evaluated in this foothill 

yellow-legged frog conservation assessment: 

• Acid deposition 

• Airborne contaminants (including pesticides) 

• Climate change 

• Disease 

• Fire management 

• Habitat loss, urbanization, and fragmentation 

• Introduced species 

• Locally applied pesticides 

• Livestock grazing 

• Mining 

• Recreational activities (including packstock) 

• Research activities 

• Restoration 

• Roads 

• UV-B radiation 

• Vegetation and fuels management 

• Water development and diversion 

Weighing the importance of each risk factor provides the rationale for the 

conservation actions to be developed in the conservation strategy. The following 

evaluation criteria were used to assess the importance of each risk factor relative to 

other risk factors (table 5): 

• Spatial extent of the risk 

• Duration and persistence of the risk 

• Intensity of the risk 

• Ecological permanence of the risk 

• Was risk management addressed or is it addressable? 

• Agency jurisdiction 

• Is risk quantifiable? What is the weight of evidence? 
32 

GENERAL TECHNICAL REPORT PSW-GTR-248

Table 5—Evaluation criteria for assessing relative importance of risk factors 

Criteria Definition 

Spatial extent of risk factor 

Duration/persistence of 

risk factor 

Intensity of risk factor 

Ecological permanence of 

risk factor 

Potential for management to 

reverse or reduce risk factor 

and degree of management 

effectiveness 

Jurisdiction of participating 

agencies 

Quantifiable/weight of 

evidence 

Geographic area affected by the risk factor. The larger 

the affected area, the greater the importance of the risk 

factor. 

The time period and periodicity over which the species is 

affected by the risk factor. The longer the time period and 

the shorter the periodicity between impacts, the greater 

the importance of the risk factor. 

The impact severity. The likelihood that the risk factor will 

result in a rapid decline in the species or its habitat. The 

higher the intensity, the greater the importance. 

The degree to which a system can recover ecologically and 

the length of time it would require. The more permanent 

the impact, the greater the importance. 

The degree to which management is needed or can be 

applied to reduce or reverse the effects of the risk factor. 

For example, management can alter fish stocking levels, 

but may have limited capability to address disease 

epidemics. The more management is needed and can be 

effective, the greater the importance. 

Political complexities and feasibility of applying or 

influencing management. The greater the ability to apply 

or influence management, the greater the importance. 

Certainty and reliability of information linking the risk 

factor with the declines in the species. The greater the 

certainty, the greater the importance. 

Five risk factors were regarded to be of current or future concern for species persistence, as supported by research and expert knowledge. These primary 

risk factors are described in the following section. The other 12 risk factors are 

described in appendix 4 and a summary of all risk factors can be found in table 6. 

The five major risk factors, in order of greatest concern, include: 

• Water development and diversion 

• Climate change 

• Habitat loss, urbanization, and fragmentation 

• Introduced species 

• Mining 
33 

Foothill Yellow-Legged Frog Conservation Assessment

Table 6—Evaluation summary of risk factors for the foothill yellow-legged frog (Rana boylii, RABO) (continued) 

Potential for management to reverse or reduce impacts/degree 

Spatial extent Duration and Intensity of Ecological of management effectiveness and Quantifiable/weight

Risk factor of the risk persistence the threat permanence jurisdiction of evidence 

Water develop- Rangewide but effects Long-term and High, but variable Permanent Yes, where projects are removed or Effects on RABO 

ment and linked to specific persistent based on scale if project is flow regimes and impoundment well-documented; also diversion local projects. except for small and dam opera- permanent. management can be significantly excellent documentation 

fish-related tions; larger improved; effectiveness of of habitat changes likely projects. projects gener- improved dam operations is to directly influence

ally present probably high if populations RABO habitat. greater threats. are extant and low if population 

reestablishment/recolonizationis needed. Participating agencies have opportunities to revise flow regimes through FERC relicensing of hydropower projects. 

Climate change Global, regional Long-term and Probably high, Permanent within No, and beyond jurisdictional scope Climate change is welleffects documented. persistent; extent of human time of agencies, but agency-influenced documented; effects on 

changes effect poorly scale, i.e., on management of flow regime RABO are not; science regional understood. time scales that could ameliorate effects on water needs to inform; interachydrology. management temperature; public awareness tions with other factors 

addresses. may bring about change. potentially numerous.

Mining Widespread but local- Long-term and Variable, poten- Likely somewhat Yes, potentially effective through Few data relative to 

ized to individual persistent tially high reversible. regulation of mining activities. RABO, negative acid 

mining opera- if operation with acid mine mine drainage effects 

tions; most at low remains active drainage. documented for other elevations. or mine is not amphibian species. 

decommissioned, though sometimes long after operation ceases. 
34 

GENERAL TECHNICAL REPORT PSW-GTR-248 Table 6—Evaluation summary of risk factors for the foothill yellow-legged frog (Rana boylii, RABO) (continued) Potential for management to reverse or reduce impacts/degree Spatial extent Duration and Intensity of Ecological of management effectiveness and Quantifiable/weight Risk factor of the risk persistence the threat permanence jurisdiction of evidence Introduced Regionally wide- Long-term and Variable, poten- Potentially, but Yes, effectiveness untested, but may Bullfrog and crayfish fish and other spread in RABO persistent in tially high constant exotic be difficult owing to recoloniza- effects have been docu­ predators habitat; generally RABO habitat. with direct and recolonization tion through stream network. mented. Fish-RABO worse in lowlands. indirect effects. through stream interactions just begin- network likely ning to be studied; mag- an issue. nitude of effect probably species-specific. Habitat loss, Urbanization now Typically High where Reversibility Yes, effectiveness depends on basis No data exist for habitat 

urbaniza- limited, but likely to long-term and habitat is lost. depends on of losses. loss to RABO from 

tion, and be important in the persistent. basis of habitat urbanization or land use 

fragmentation next few decades; loss; not well conversion; or evidence 

most loss and frag- understood. of fragmentation effects mentation a function on RABO from land use of other risk factors, conversion; basic data especially water needed to inform issue. development. 

Airborne Regional, minor Long-term Unknown, Unknown; may No, and beyond jurisdictional scope Strong evidence of 

contaminants extra-regional with seasonal interactive accumulate or of agencies, but agency-influenced airborne transport and including contribution; vari- flows linked or immuno- flush; effect public awareness may bring about deposition in Sierra pesticides able due to composi- to annual suppressive chemical- change. Nevada, indirect evition and regional snow-melt and effects likely, dependent. dence from correlative 

loading. precipitation but unstudied. data with RABO less 

events. Persis- frequent in areas upwind tence depends from agriculture. on chemical use and type. 

Acid deposition Probably limited, but Unknown, if Low for direct Little basis for Little basis for evaluation. Direct evidence for risk 

condition is vulner- conditions effects, but evaluation. factor limited; threshold able because of low change cumula- unidentified tolerance levels to pH acid neutralizing tive effects may interactions with for RABO unknown; capacity. be persistent other factors limited experimental 

and long-term. may exist. data from other species implies interactive 

effects likely. 
35 

Foothill Yellow-Legged Frog Conservation Assessment

Table 6—Evaluation summary of risk factors for the foothill yellow-legged frog (Rana boylii, RABO) (continued) 

Potential for management to reverse or reduce impacts/degree 

Spatial extent Duration and Intensity of Ecological of management effectiveness and Quantifiable/weight

Risk factor of the risk persistence the threat permanence jurisdiction of evidence 

Disease Globally widespread, Unknown. Seems low, but Unlikely, but Unclear and unknown; depends on Limited evidence of 

but poor under- incompletely incompletely transmission and other factors not chytrid and that it standing of distribu- understood. understood. currently understood. does not seem to be a tion in RABO. problem; interaction 

with other factors poorly understood. 

Fire Rangewide, but Long-term, Likely variable, Reversible, but Yes, effectiveness likely depends on Unstudied relative to 

management depends on local seasonal and but not well recovery likely implementation approach; not well RABO; studies on fire 

fire events. sporadic, understood. to vary with understood. management and its 

depends on local condi- effects on riparian and 

climate. tions; not well aquatic habitat provide 

understood. insight. Interaction 

with other factors needs study. 

Livestock Widespread region- Seasonally and Likely low Likely reversible, Yes, effectiveness depends on Grazing effects on RABO 

grazing ally and over range long-term. but depends but different management implementation, largely unstudied; only 

of RABO. on grazing grazing levels poorly studied. negative correlation to 

level; poorly result in dif- livestock grazing exists. understood. ferent recovery Basic data needs to 

rates. inform. 

Locally applied Local and variable Short-term for Probably low, Probably revers- Yes, potentially effective through No field data. Toxicity 

pesticides in composition most in current but largely ible, but poorly regulation of application (amount, data on other species 

and loading levels, use; persistence unstudied. known and timing, and constituent). indicates surfactants documentation lim- depends on effect chemical- used with pesticides ited to use patterns. chemical use dependent. more toxic than 

and type. pesticides, chemicaldependent toxicity.

Recreational Widespread region- May be persis- May be locally May be revers- Yes, potentially effective but Anecdotal documentaactivities ally though local- tent and long high; depends ible, likely untested for RABO. tion; effects inferred 

(including ized to use sites. term; depends on use levels. depends on primarily from impacts packstock) on use. length of time on habitat. Basic data 

impacted. needs to inform. 
36 

GENERAL TECHNICAL REPORT PSW-GTR-248 Table 6—Evaluation summary of risk factors for the foothill yellow-legged frog (Rana boylii, RABO) (continued) Potential for management to reverse or reduce impacts/degree Spatial extent Duration and Intensity of Ecological of management effectiveness and Quantifiable/weight Risk factor of the risk persistence the threat permanence jurisdiction of evidence Research Localized at research Typically sea- Likely low, but Likely reversible; Yes, probably effective, but Issues hypothetical and activity sites, sometimes sonal, potential unstudied; dis- recovery likely unstudied. unstudied. Needs basic representing wide- for long-term; ease transmis- issue-dependent. data to inform. spread arrays. depends on sion a possible objectives. threat. Restoration Localized at restora- Seasonal, Likely low, but Likely reversible; Yes, through the regional planning One study suggested that tion sites, extent whether long- almost entirely unstudied. process and permitting. caution is needed in project-dependent. term or persis- unstudied. planning where restora­ tent depends on tion target is not RABO; 

type. otherwise unstudied.

Roads Widespread but Persistent and Likely variable Reversible Yes, through various planning Roads unstudied for their 

localized to the road long term depend on road where roads processes. effects on RABO, but matrix. except where type and use are decommis- effects demonstrated 

roads are level. sioned. and broadly studied for decommis- other species. sioned. 

UV-B radiation Global, but locally Persistent and Low for direct Permanent in the No, and beyond jurisdictional scope Evidence of direct effect 

and regionally miti- long-term; effects, but short term; long of agencies, but agency-influenced controversial; indirect gated by elevation, persistence in unidentified term depends on public awareness may bring about effects or interactions dissolved organic future depends synergisms with human actions. change. with other factors 

carbon. on continued other factors unstudied for RABO. 

influence on possible. Effects for other species atmosphere. demonstrated. 

Vegetation Rangewide, but Sporadic, but Unknown, likely Likely revers- Yes, effectiveness likely depends on Unstudied relative 

and fuels project-specific in potentially long variable but ible, recovery implementation approach. to RABO; fire and 

management effects. term. unstudied. likely to vary vegetation studies imply 

by project, but possible effects. Basic unstudied. data needed to inform.

FERC = Federal Energy Regulatory Commission. 
37 

Foothill Yellow-Legged Frog Conservation Assessment

Water Development and Diversion 

Water developments on natural waterways have greater potential to alter habitat for 

the foothill yellow-legged frog than any other risk factor. In California, the Mediterranean climate produces a very distinct hydrologic signature with high and variable 

waterflows in the fall, winter, and spring; and low, receding, stable flows in the 

summer. Native biotas, including foothill yellow-legged frogs, are adapted to this 

“natural flow regime,” especially spring (rain or snowmelt) recession flows (Yarnell 

et al. 2010). Modifications to that hydrologic regime can disrupt species responses 

to environmental cues and have direct effects on survival of aquatic life stages. 

Water developments exist as two major types: impoundments and diversions. 

Impoundments block streams with a structure such that natural flows are impeded 

and water is pooled upstream. Impoundment size varies throughout the foothill 

yellow-legged frog range, ranging from smaller dams created for water gaging 

stations and improved fisheries to larger dams created for hydroelectric generation 

or flood control. Diversions are created for the purpose of removing and delivering water to offsite locations. Some diversions are associated with impoundments, 

whereas others involve pumping water directly from the waterway or indirectly 

through groundwater pumping. The California Water Plan Update (CDWR 1998) 

reports that dams and diversions are found on most Sierra Nevada streams (Moyle 

and Randall 1998), and a majority of these alterations exist within the elevational 

range of the foothill yellow-legged frog. 

Impoundments— 

In a recent study, regulation of flows downstream of dams was associated with 

lower abundances, where breeding populations were on average five times smaller 

in regulated rivers than in unregulated rivers (Kupferberg et al. 2012). Lind (2005) 

(also summarized in Kupferberg et al. 2012) previously found an impoundment 

effect on foothill yellow-legged frogs; the species was associated with streams lacking dams or with streams with small dams located far upstream of sites occupied by 

foothill yellow-legged frogs. Large regulated streams typically have substantially 

lower numbers of foothill yellow-legged frogs than unregulated streams (table 4). 

At least one large reservoir (≥ 0.12 km3

 [100,000 ac-ft]) exists in the foothill region 

of every major Sierran stream below 600 m (1,968 ft). Several major streams (e.g., 

Pit River, Feather River, American River, Mokelumne River, Tuolumne River, San 

Joaquin River) have two or more reservoirs (of varying size) in linear sequence, and 

a few large reservoirs also occur at higher elevations on major stream tributaries 
38 

GENERAL TECHNICAL REPORT PSW-GTR-248

(table 7). Additionally, several hundred medium-sized (< 0.12 km3 [100,000 ac-ft] 

and ≥ 0.03 km3 [25,000 ac-ft]) and small reservoirs (< 0.03 km3 [25,000 ac-ft]) are 

broadly distributed at elevations below 1828 m (6,000 ft) over the Sierra Nevada 

(Mount 1995). In Oregon, proximities to hydropower and dams with reservoirs 

larger than 50 ha were negatively associated with frog occurrence (Olson and 

Davis 2009). 

Reservoir placement on Sierran streams has converted many lotic aquatic 

habitats to lentic conditions, resulting in habitat with reduced flows, increased 

depths, and altered temperature and dissolved oxygen regimes (Mount 1995; Petts 

1980, 1984). These changes result in direct loss of required habitat for streamdwelling foothill yellow-legged frogs, which have evolved to inhabit free-flowing, 

well-oxygenated water with coarse substrates (see “Habitat Requirements” section). 

In an evaluation of the distribution of reservoirs in the Sierra Nevada, Kondolf et 

al. (1996) found that reservoirs had eliminated an estimated 9,972 km (6,209 mi) 

of aquatic habitat. Given the distribution of reservoirs, foothill yellow-legged frogs 

could have been historically present in much of this lost habitat. Sierran reservoirs 

currently inundate at least eight sites once occupied by foothill yellow-legged frogs 

(table 8). 

Regulation of flows downstream of impoundments may result in altered timing, 

duration, and magnitude of stream discharge, creating conditions in which runoff 

is not synchronous with the species’ life-history requirements (Kupferberg et al. 

2008, Yarnell et al. 2010). Greater short-term (diel, weekly, or monthly) variation 

in flows affects foothill yellow-legged frog egg mass and tadpole survival. Lind et 

al. (1996) observed high losses of foothill yellow-legged frog egg masses following 

relatively high, periodic releases of water from Lewiston Dam on the Trinity River 

that deviated in timing from pre-dam flow patterns. Egg mass mortality related 

to aseasonal releases has been documented on other regulated California streams 

(table 2.6 in Kupferberg et al. 2008; Kupferberg et al. 2012; Mount 1995; Spring 

Rivers Ecological Sciences 2003) as well as for freshets occurring during seasonal 

intervals on hydrologically unaltered streams (Kupferberg et al. 2008 and studies 

cited therein). Kupferberg et al. 2012 found that variability in timing and magnitude 

of flows was associated with mortality of early life stages; egg mass survival was 

negatively correlated with the ratio of maximum:minimum discharge after the 

initiation of oviposition. In an examination of the effect of flow augmentation for 

whitewater rafting, foothill yellow-legged frog egg mass density decreased along 

a regulated river reach, whereas density increased on a reach with stable flows, 

typical of summer flows in an unregulated river (Kupferberg et al. 2012). Shortterm flow variation may also affect tadpole or metamorphosing stages by stranding 
39 

Foothill Yellow-Legged Frog Conservation Assessment

Table 7—Large reservoirs (≥ 0.12 km3 [100,000 ac-ft]) on major streams within the Sierra 

Nevada Planning Area 

Year completed 

Stream Reservoir (year filled) Elevation Volume 

Cubic kilometers 

Meters (feet) (acre-feet) 

Sacramento River Shasta 1945 (1954) 325 (1,067) 5.61 (4,552,000) 

Feather River Oroville 1968 (1969) 274 (900) 4.36 (3,537,580) 

North Fork Almanor 1927 (1964) 1,366 (4,482) 1.61 (1,308,000) 

Bucks Creek Bucks 1928 (1951) 1,581 (5,168) 0.13 (105,600) 

Yuba (North Fork) Bullards Bar 1970 (1971) 581 (1,907) 1.20 (969,900) 

Yuba (South Fork) Spaulding 1946 (1946) 1,643 (5,390) 0.18 (144,591) 

Bear River Camp Far West 1963 (1964) 79 (260) 0.13 (104,000) 

American River Folsom 1956 (1956) 142 (466) 1.21 (977,000) 

Middle Fork French Meadows 1966 (1966) 1,604 (5,263) 0.17 (136,400) 

South Fork Union Valley 1963 (1963) 1,484 (4,870) 0.34 (277,300) 

Rubicon River Hell Hole 1966 (1967) 1,411 (4,630) 0.26 (207,600) 

Mokelumne River Camache 1963 (1966) 72 (236) 0.51 (417,120) 

Mokelumne River Pardee 1929 (1951) 173 (568) 0.24 (197,950) 

North Fork Salt Springs 1931 (1951) 1,204 (3,949) 0.17 (141,857) 

Calaveras River New Hogan 1963 (1965) 169 (554) 0.39 (317,100) 

Stanislaus River New Melones 1963 (1965) 346 (1,135) 2.99 (2,420,000) 

North Fork New Spicer Meadows 1990 (1990) 1,986 (6,516) 0.23 (190,000) 

Tuolumne River New Don Pedro 1970 (1974) 253 (830) 2.50 (2,030,000) 

Tuolumne River Hetch-Hetchy 1923 (1952) 1,180 (3,870) 0.44 (360,400) 

Tuolumne River Cherry 1957 (1957) 1,437 (4,715) 0.33 (268,000) 

Merced River Lake McClure 1926 (1926) 264 (867) 1.26 (1,024,600) 

Chowchilla River Eastman 1975 (1978) 137 (450) 0.19 (150,000) 

San Joaquin River Millerton 1942 (1946) 177 (581) 0.64 (520,000) 

San Joaquin River Mammoth Pool 1960 (1960) 1,015 (3,330) 0.15 (122,700) 

San Joaquin River Shaver 1927 (1951) 1,637 (5,370) 0.17 (135,400) 

South Fork Thomas A. Edison 1954 (1956) 2,329 (7,642) 0.15 (125,000) 

Kings River Pine Flat 1954 (1956) 296 (970) 1.23 (1,000,000) 

Helms Creek Courtright 1958 (1962) 2,497 (8,192) 0.15 (123,200) 

North Fork Wishon 1958 (1959) 1,999 (6,560) 0.16 (128,300) 

Kaweah River Kaweah 1962 (1964) 229 (752) 0.23 (185,600) 

Kern River Isabella 1953 (1953) 803 (2,635) 0.70 (568,000) 

Note: Streams are ordered north to south. Reservoir elevation and volume are at full pool based on data from original 

construction. Streams indented on the list are tributaries of the non-indented stream above them. 
40 

GENERAL TECHNICAL REPORT PSW-GTR-248

Table 8—Reservoirs on major streams within the Sierra Nevada Planning 

Area for which foothill yellow-legged frog (Rana boylii) records exist where 

the historically occupied site is now inundated by the reservoir 

Rana boylii record 

Years prior to 

Stream Reservoir Year Collection reservoir filling 

Sacramento Shasta 1884 USNM 13795, 13929 70 

Pit Pit 7 1953 FMNH 71474 12 

Feather Oroville 1941 MVZ 34837–34839 28 

1946 MVZ 51662 23 

1961 CSUC 1197 8 

Butte De Sabla 1945 MVZ 42726, 42739 0 

Little Butte Paradise 1960 CSUC 1563–1564 4 

Yuba New Bullards Bar 1899 USNM 38817–38819 73 

Tuolumne Don Pedro 1932 USNM 88468–88473 42 

Merced Lake McClure 1915 MVZ 5779–5780 11 

Kings Pine Flat 1910 CAS 17952 46 

Kern Isabella 1891 USNM 18951–18952 63 

Note: Streams are ordered north to south. 

(Kupferberg et al. 2008 and studies cited therein) or sweeping individuals into less 

suitable (e.g., predator-rich) habitats. Experiments simulating high pulse flows 

suggested that foothill yellow-legged frog tadpoles seek refuge from higher velocities in the substrate, but many were swept downstream (Kupferberg et al. 2008, 

2011b). Furthermore, large spring flow pulses have been documented to decrease 

survival of embryonic stages, but smaller pulses later in spring appeared to cause 

even higher mortality, presumably because surviving tadpoles are directly affected 

by flows (Kupferberg et al. 2008). 

Population viability analyses suggested that small population sizes combined 

with the mortality effects on early life stages associated with pulse flows can 

have negative consequences on cumulative risk of extinction (Kupferberg et al. 

2009b). When evaluated using the mean number of breeding females observed per 

kilometer, the 30‐year probability of extinction increased substantially (fourfold) 

in regulated rivers, and 13-fold with a starting population size equal to that in a 

Sierran river (Cresta reach of North Fork Feather), where frogs have been declining 

over the past decade. Modeled populations were unable to persist when hydrologic 

stressors were combined because the effects on population dynamics were multiplicative. For example, egg mass scouring, which occurs most frequently early in the 

breeding season, eliminates the reproductive effort of highly fecund large females. 

When these two effects were considered together, a disproportionate increase in 
41 

Foothill Yellow-Legged Frog Conservation Assessment

the 30‐year risk of extinction became manifest, five times greater than the sum 

of the first-order effects. When tadpole mortality from a single annual summer 

pulsed flow was combined with high rates of egg mass stranding and scouring, the 

multiplicative increase in extinction risk was twice as high as the additive effects. 

The results of the population modeling effort illustrates that any one anthropogenic 

hydrologic impact (e.g., cold water temperature effects on development, abrupt cessation of spring spills causing mass mortality through stranding, reduced availability of suitable breeding habitat) cannot be assessed in isolation. Each impact may 

result in population‐level consequences that would underestimated if not considered 

in concert. 

Loss of variation in flows may have long-term impacts on riparian vegetation, 

sediment transport, and stream channel morphology. Lind et al. (1996) found significant changes in riparian habitat along the Trinity River downstream of Lewiston 

Dam that resulted from reduced and more stable year-round flows. Reduced flows 

may be insufficient to effectively scour banks and set-back succeeding vegetation, 

leading to substantial encroachment by riparian vegetation (Mount 1995) and less 

available habitat for foothill yellow-legged frogs. In a stream restoration project 

on the Trinity River mainstem, 10 of 24 foothill yellow-legged frog egg masses 

were found at bank feathering (vegetation removal treatment) sites within a year of 

implementation; encroaching bank vegetation at untreated sites may have limited 

foothill yellow-legged frog reproduction (Lind et al. 1996). Reservoirs trap large 

amounts of sediment, which may affect the distribution of substrate particle sizes 

downstream of dams (Ligon et al. 1995). In general, smaller particles (finer than 

gravels) are reduced downstream from dams because most available flows can only 

entrain those substrate sizes and these same smaller substrates settle out rapidly 

in the inflow to the impoundment upstream (Mount 1995). The availability and 

distribution of diverse stream substrates is important to foothill yellow-legged 

frogs because the life stages have different substrate requirements; e.g., cobble 

and boulder substrates are used for oviposition sites and provide refuge habitat for 

tadpoles (see “Ecology” section). Sufficient sediment is also needed for bedform 

development within the channel, such as riffles, and for cross-sectional channel 

shapes favorable to oviposition and tadpole rearing (see “Ecology” section). Streams 

below dams that are typically perennial may be converted to spatially intermittent 

or ephemeral (seasonally intermittent), or naturally ephemeral streams may dry up 

faster than they did historically (Mount 1995); channel drying may increase the risk 

of egg mass and tadpole desiccation and predation (see Kupferberg 1996a, 1996b). 

Impoundments can alter downstream water temperatures for many kilometers. 

These effects largely depend on the volume of water released and the elevation in 
42 

GENERAL TECHNICAL REPORT PSW-GTR-248

the reservoir’s water column from which flows are released. For example, dams that 

release water from a location deep in the reservoir (hypolimnetic) promote cooling 

downstream, whereas dams that release water from surface spillways may have a 

warming effect (Petts 1984). Many combinations are possible if dams have more 

than one release point. Likewise, varying effects on both foothill yellow-legged 

frogs and associated instream biota are possible depending on whether the water is 

warmed or cooled, and the downstream extent of the thermal alteration. Wheeler 

et al. (2014) found that oviposition and metamorphosis were delayed for foothill 

yellow-legged frog populations on cold tributaries and the regulated mainstem 

Trinity, where summer water temperatures are unseasonably low owing to hypolimnetic releases. At cooler temperatures, foothill yellow-legged frog growth and 

development rates may be inhibited, both directly as a function of temperature, and 

indirectly as a function of food resources. The composition of the periphyton flora 

is sensitive to flow regulation. For example, spread of the invasive benthic diatom, 

Didymosphenia geminata, which has been found in several Sierran regulated rivers, 

is associated with cool summer water temperatures and artificially stable base 

flows (Kirkwood et al. 2009, Kumar et al. 2009). Didymosphenia, which produces 

copious amounts of inedible mucilaginous stalk material, can displace more nutritious algal taxa and does not provide adequate nutrition for growth of foothill 

yellow-legged frog tadpoles (Furey et al. 2014, Kupferberg et al. 2011a). Water 

temperatures that remain colder than natural conditions may delay metamorphosis 

of tadpoles, increasing risk of predation (Lind et al. 1996), especially because of 

small tadpole size (Kupferberg et al. 2011a). Metamorphs on the mainstem Trinity, 

which is cooled by water released from the Trinity Dam, were generally smaller 

compared to metamorphs from tributaries (Wheeler et al., 2014); however, the 

potential mechanisms for these differences (e.g., food quality and quantity, feeding 

rate) remain unexamined. Catenazzi and Kupferberg (2013) found that, in a thermal 

gradient, foothill yellow-legged tadpoles selected temperatures between 16.5 and 

22.2 °C and mortality was higher when temperatures deviated from preferred 

temperatures. Supplementing tadpole diet lessened the negative effects of cold 

temperatures on tadpole survival to metamorphosis, but tadpoles were smaller at 

colder sites compared to those at warmer sites (Catenazzi and Kupferberg 2013). 

Dam and reservoir-induced changes in habitat can influence native species 

composition and affect food resources for postmetamorphic stages, competitive 

relationships, and predator assemblages. For example, regulated flows may modify 

macroinvertebrate species composition and density (e.g., Hax and Golladay 1998), 

resulting in changes in food availability. Such effects have not been studied for foothill yellow-legged frogs. Reservoir construction also creates habitat for introduced 
43 

Foothill Yellow-Legged Frog Conservation Assessment

species (Fuller et al. 2011, Moyle 2002) (see “Introduced Fish and Other Predators” 

section). These may include a diverse assemblage of warmwater fishes (e.g., bass 

[Micropterus], sunfish [Lepomis], crappies [Pomoxis], catfish/bullheads [Ictaluridae], carp [Cyprinus carpio]), coldwater fishes (e.g., rainbow trout and brown 

trout [Oncorhynchus mykiss, Salmo trutta]), bullfrogs (Lithobates catesbeianus), 

and several species of crayfish. If impoundments are sufficiently large and deep 

to allow stratification, both warm- and coldwater fisheries may occur, resulting in 

a potential barrier to both the presence and the up- and downstream movement of 

foothill yellow-legged frogs. Nonnative, coldwater fisheries are often established 

downstream of impoundments as a result of hypolimnetic releases of water. Populations of coldwater species that occurred only seasonally in some streams may 

become permanently established with year-round coldwater flows below dams 

(Moyle 2002). 

Impoundments fragment riverine habitat and disrupt dispersal routes for juvenile and adult frogs. These effects are significant in the Sierra Nevada because large 

reservoirs are located in the lower foothill region of almost every major stream 

draining the western slopes of this mountain range (tables 7 and 8). Kondolf et al. 

(1996) evaluated the distribution of reservoirs in the Sierra Nevada and found that 

they had created more than 150 spatial gaps in riparian areas greater than 0.5 km 

(0.3 mi) long. This is greater than the maximum movement range of foothill yellowlegged frogs in several studies (see “Movement in Ecology” section). Peek (2010) 

analyzed foothill yellow-legged frog populations relative to stream habitat connectivity and gene flow in three regulated and three unregulated rivers in the northern 

Sierra Nevada. In this study, more foothill yellow-legged frogs were found in river 

reaches closer to tributary streams in regulated versus unregulated rivers, suggesting that populations in regulated rivers may be more concentrated and spatially 

fragmented than populations in unregulated rivers. Gene flow and genetic drift 

were generally lower in regulated versus unregulated rivers (Peek 2010). Reservoirs 

are inhospitable to foothill yellow-legged frogs yet favorable to exotic aquatic 

predators, and generally fragment Sierran streams into headwater and downstream 

regions. These artificially disjunct regions possess habitat that may be suitable to 

one particular foothill yellow-legged frog life stage but perhaps not another. For 

example, very small headwater subbasins may offer overwintering habitat for adults 

but be too cool and shaded to create the habitats with high algal productivity needed 

by grazing tadpoles. In general, the areas upstream of reservoirs provide more suitable habitat than the areas downstream because of the establishment of nonnative 

species in downstream reaches (Moyle 2002). Lind (2005) stated that the likelihood 
44 

GENERAL TECHNICAL REPORT PSW-GTR-248

of foothill yellow-legged frog extirpation was higher when the area of the stream 

network above reservoirs was small. The current distribution of foothill yellowlegged frogs in the Sierra Nevada is largely upstream of reservoirs in systems that 

have a substantial length of stream network that still lies within their elevational 

range. Downstream of reservoirs with hypolimnetic releases, it may take 10 to 20 

km for water to warm to the lower limit of the thermal niche for reproduction of 

foothill yellow-legged frogs (PCWA 2011, PG&E and Stillwater Sciences 2009b). 

In regulated river reaches, intact tributary streams may provide key refugia when 

mainstem habitat quality has been compromised (Peek 2010). 

Diversions— 

Water diversions may cause streams to dry up more rapidly than they did when undiverted. For example, removal of water from diversions currently causes sections 

of the San Joaquin River to seasonally dry across the Central Valley floor (Moyle 

2002). Diversion of water may also result in modifications to stream habitat (e.g., 

local reaches may become less lotic in nature). Even small operations, such as those 

used to divert water for growing marijuana (Cannabis sativa), may have significant 

impacts on foothill streams with limited summer flows (E. Gonsolin, pers. comm., 

2006). Suspected direct effects of water diversions that may occur include the 

removal of foothill yellow-legged frogs, tadpoles, or egg masses by water pumps, 

or impingement and mutilation of animals on pump screens. Diversions used for 

interbasin movement of water may introduce fish and other predators, or transfer 

disease-bearing vectors and disease-contaminated water. Open-channel canals that 

are used to move water from one location to another (e.g., from an upstream to a 

downstream impoundment) may impede movements and survival. 

Extent of risks related to water development and diversions— 

The risk to foothill yellow-legged frogs from flow alteration resulting from water 

impoundments and diversions is high. Negative effects have been well studied and 

water projects are widespread across this species’ range in the Sierra Nevada and 

elsewhere. 

Conservation options related to water development and diversions— 

Addressing management of water development and diversions for the foothill 

yellow-legged frog is within the jurisdiction of agencies involved in this assessment through regional planning, permitting, and the Federal Energy Regulatory 

Commission (FERC) hydropower project relicensing process. Coordination among 

resource agencies and research will more effectively address knowledge gaps and 

facilitate the feedback of information to refine management approaches. Owing to 
45 

Foothill Yellow-Legged Frog Conservation Assessment

the recent focus on foothill yellow-legged frogs during FERC hydropower project 

relicensing, several new tools for evaluating effects of new flow regimes on habitat and strand/scour risk of aquatic life stages have been developed (Bondi et al. 

2013; Yarnell et al. 2011, 2012). These tools may help water managers develop flow 

regimes (timing and patterns) that may reduce impacts on foothill yellow-legged 

frogs. A summary of conservation options for foothill yellow-legged populations in 

regulated rivers was presented by Kupferberg et al. (2009a) (see table 9). 

Climate Change 

Temperatures in California are estimated to increase from 1.5 to 4.5 °C by the end 

of the 21st century (Cayan et al. 2008). Climate models predict more variable annual 

precipitation and decreased spring and summer runoff as a result of lower annual 

snowpack (Johnson et al. 1999, Smith and Tirpak 1989, USEPA 1997). Moreover, 

more precipitation in early spring has been predicted to come in the form of rain 

rather than snow. Consequently, the hydrograph will shift to earlier snowmelt, lower 

snowpack, more winter rain, and higher winter storm runoff events (Maurer et al. 

2007, Stewart 2009, Young et al. 2009). The low-flow season will likely be longer, 

so water temperatures may be higher, which may result in stress for species adapted 

to more moderate temperature regimes. Whether hydroelectric power project 

operations will exacerbate or ameliorate the effects of climate change is not known. 

Given that many miles of Sierran rivers downstream of dams are now too cold for 

foothill yellow-legged frogs, a possibility that requires investigation is that warming 

water temperatures may create suitable habitat in some managed systems. 

Changes in frequency, duration, and magnitude of droughts or severe winters 

resulting from climate variability may have considerable negative impacts on foothill yellow-legged frog populations. Population declines of foothill yellow-legged 

frogs have been attributed in part to extended drought (Jennings and Hayes 1994). 

Decreases in summer runoff may result in the loss of foraging and refuge habitat 

for adults and juveniles. Changes in temperature may affect parasite prevalence 

(Kupferberg et al. 2009a) and pathogen virulence (Carey et al. 1999), making foothill yellow-legged frogs more susceptible to disease. Further, experimental increase 

in stream water temperature has been shown to decrease invertebrate density and 

biomass in invertebrates (Hogg and Williams 1996) and may have a negative impact 

on the foothill yellow-legged frog prey base. 

Changes in climatic patterns, particularly those linked to precipitation, may 

have substantial impacts on foothill yellow-legged frogs. Low precipitation and 

increased variability in precipitation were both negatively related to frog presence 

(Lind 2005). Evidence also suggests that low precipitation may exacerbate dam 
46 

GENERAL TECHNICAL REPORT PSW-GTR-248 Table 9—A summary of potential mitigation and restoration options for Rana boylii in regulated rivers Project operations Short-term impacts Long-term impacts Mitigation/restoration Intentional aseasonal flows (power generation, recreation, outmigration of salmonid smolts); unintentional spill of water over dam Intentional dewatering of stream channels for rescue operations Unintentional powerhouse outages

resulting in rapid increase in flows in bypass reaches, followed by rapid decrease in flows 

Reduced winter/spring flows Altered summer baseflows Movement of water among river basins 

• Scouring or desiccation of egg 

masses

a b /tadpolesc

• Export spring and summer algal 

productivity,d e reduced resources for

tadpoles, reduced insect abundance,e 

food web repercussions 

• Desiccation of egg masses/tadpoles • Changes in margin water temperature, 

depth, and velocity,

• Scouring/desiccation of eggs/tadpoles, 

depending on ramping rate, magnitude of change, channel shape 

• Absence of scouring/depositional flows 

that prevent riparian encroachment

• Reduced breeding habitat, greater 

distances between breeding sitesc 

• Lower water temperatures• Change in available habitat (channel 

shape) 

• Potential for increased disease and parasite transmission 

• Discharge decoupled from 

environmental cues (e.g., rainfall, air temperature) triggering inappropriate behavioral responses by adults, juveniles, delayed onset of breedinga f

• Smaller population sizesa b Unknown Unknown • Vegetation encroachment, altered 

channel morphology, reduced breeding habitat

• Population loss/fragmentation,c 

reduced gene flow, altered metapopulation dynamics 

• Promotes habitats that support 

non-native predatory fish,amphibians, and invertebrates, increased predation on eggs, tadpoles 

Unknown 

• Mimic natural hydrograph to degree 

possible

• Flow regimes and ramping rates to 

minimize impacts during breeding and rearing periods

• Change management of water elevation in 

upstream reservoir

• Observe minimum instream flow 

requirements

• Post-event ramping rates that minimize 

disturbance 

• Change timing of planned outages (for 

repairs, etc.) to outside of breeding and rearing season 

• Mimic natural hydrograph to degree 

possible

• Restore some components of spring 

snow-melt hydrographg

• Adjust water release temperatures (mix of 

depths)

• Develop basin-scale plans for fish stocking relative to frog needs • Reassess water redistribution to eliminate, or shift timing to decrease disease 

(fall, winter)

a GANDA 2008.b Kupferberg et al. 2008. c Lind et al. 1996.d Spring Rivers Ecological Sciences 2003.e GANDA 2006.f Bourque 2008.g McBain and Trush, Inc. 2009. Source: reproduced from Kupferberg et al. 2008.
47 

Foothill Yellow-Legged Frog Conservation Assessment

effects (Lind 2005). Climate change is predicted to reduce the habitat suitability 

for foothill yellow-legged frogs at lower latitudes and elevations. Current foothill 

yellow-legged frog distribution (fig. 10) may be a sign that climate change has 

already influenced the species (Lind et al. 2005). Although other factors may 

confound the influence of climate change on distribution patterns, short-term oscillations and drought severity have been greater at lower latitudes in California (Cook 

et al. 2004), where foothill yellow-legged frogs appear to be in dramatic decline 

(see “Status” section). Davidson et al. (2002) found no relationship between foothill 

yellow-legged frog-occupied sites and elevation. Severe drought may also lead to 

water-management decisions that may affect frog populations. For example, water 

held in reservoirs may be diverted to ameliorate the impact of dry conditions on 

agricultural and municipal water supplies; this can exacerbate the already low water 

levels and promote even warmer summer water temperatures. 

Extent of risks related to climate change— 

Climate change may be a factor in the decline of foothill yellow-legged frogs, and 

the higher frequency of weather extremes expected under future climate change 

(e.g., extended droughts and large-magnitude, shorter duration flows), may contribute to future population declines. This risk is greatest in the southern portions of 

the Sierra Nevada and California, where populations are rare and small, other risks 

are present, and climate change will have the greatest impact on habitat. 

Conservation options related to climate change— 

Agencies may implement management practices at the local scale to ameliorate the 

predicted effects of climate change on foothill yellow-legged frogs and their habitat. 

For example, by carefully setting minimum streamflow requirements during relicensing of FERC-licensed hydropower projects, agencies can balance water temperature needs of native warm and cold-water associated aquatic species in regulated rivers. A more complete understanding of how habitat modifications linked 

to climate change may affect foothill yellow-legged frog population dynamics, and 

how climate change may interact with other risk factors, will be needed to focus 

conservation efforts. 

Habitat Loss, Urbanization, and Fragmentation 

Direct habitat loss is one of the most visible causes of amphibian population 

declines (Cushman 2006, Lehtinen et al. 1999, Stuart et al. 2004). Habitat loss for 

many amphibians can be attributed to the conversion of wetlands to urban or agricultural use (Corn 1994); foothill yellow-legged frogs are no exception. Habitat loss 

is frequently a consequence of other risk factors and is discussed in corresponding 
48 

GENERAL TECHNICAL REPORT PSW-GTR-248

sections (see “Water Development and Diversion” and “Livestock Grazing” sections). However, the elevational range of foohill yellow-legged frogs, in the Sierra 

Nevada and elsewhere, overlaps with large areas of private land and urban/suburban 

development in foothill communites. Conversion of land for agricultural and urban 

use has been implicated as a factor in the decline of foothill yellow-legged frogs 

(Lind 2005). In Oregon, Olson and Davis (2009) found that proximity to cities and 

agricultural lands was negatively associated with frog occurrence. Habitat loss 

will continue in the future as a result of increasing urbanization and the associated 

spread of invasive plants. 

Urbanization in the west-slope Sierra Nevada foothills exists in the form of 

a series of more than 40 small towns with populations over 1000, many of them 

located in the old gold mining districts. Of the nearly 1 million inhabitants of the 

Sierra Nevada west slope, about half live in these small towns (CDFI 2013). Significant growth, largely around these small urban centers, is projected for the west 

slope, and by 2050, the human population is anticipated to reach 2 million (CDFI 

2013). This growth pattern is expected to result in habitat changes near these urban 

areas that may influence local foothill yellow-legged frog populations. Urbanization along Sierran foothill streams increasingly isolates foothill yellow-legged 

frog populations, which appear smaller today than historically, making populations 

more vulnerable to extirpation from random events (Noss and Cooperrider 1994, 

Pimm 1991). 

Habitat loss or alteration can also be facilitated by invasive plant species 

(Bossard et al. 2000). Invasive plants replacing native vegetation can transform vast 

areas in a few decades (Lovich and DeGouvenain 1998) and may have contributed 

to the decline of northern leopard frogs in Nevada (Hitchcock 2001). Invasive plants 

can degrade habitat quality by limiting the quantity or quality of food resources for 

larval or postmetamorphic frogs (Brown et al. 2006; Maerz et al. 2005a, 2005b). 

The effects of invasive plants on foothill yellow-legged frogs are unstudied, 

but observation of aggressive colonization of river bar habitat by butterfly bush 

(Buddleja davidi) (M. Hayes, personal observation, 1999), a landscape species only 

recently recognized for its invasive potential (King County 2012), suggests that 

invasive plant impacts may need attention. Invasive exotic plants may fragment 

habitat by converting patches of riparian areas to unsuitable habitat for foothill 

yellow-legged frogs. 

Extent of risks related to habitat loss, urbanization, and fragmentation— 

The greatest risk to populations and habitats of foothill yellow-legged frogs from 

urbanization relates to water issues and is described in the “Water Development and 
49 

Foothill Yellow-Legged Frog Conservation Assessment

Diversions” section. The effects of habitat loss resulting from human population 

growth, land development, and non-native plant invasion are currently unknown. 

Conservation options related to habitat loss, urbanization, and 

fragmentation— 

On Forest Service and National Park Service lands, restrictions on land development and control of invasive plants are within agency purview and can be addressed 

in the regional planning process. However, most urbanization and development lies 

in municipal jurisdictions, so coordination among city, county, state, and federal 

agencies will be necessary to effectively limit habitat loss and fragmentation. 

Introduced Species 

Introduced species have long been recognized as a major risk factor to native 

populations (Soulé 1990). Amphibians have been widely cited as being vulnerable 

to exotic predators such as fish, crayfish, and bullfrogs (e.g., Adams 1999; Drost 

and Fellers 1996; Fisher and Shaffer 1996; Jennings and Hayes 1994; Kiesecker 

and Blaustein 1997b). Several introduced species such as crayfish, bullfrogs, and 

introduced fish, which occur within the range of the foothill yellow-legged frog, 

may be particularly problematic. 

Crayfish did not historically occur with the foothill yellow-legged frog across 

much of the frog’s California range and may pose the greatest introduced species 

threat. Several introduced crayfish, including two subspecies of the signal crayfish 

(Pacifastacus. l. trowbridgii and P. l. leniusculus), the red or Louisiana swamp 

crayfish (Procambarus clarkii), and the northern or virile crayfish (Orconectes 

virilis), collectively now co-occur with the frog in California (see McGriff 1982). 

Crayfish are primarily scavengers but will graze on algae and other vegetation, 

and will prey upon invertebrates, fish, reptiles, and amphibians (Gamradt and Kats 

1996, McGriff 1982). With video cameras mounted near foothill yellow-legged frog 

egg masses, Wiseman et al. (2005) documented crayfish predation on embryos in 

the North Fork Feather River. In southern California, red swamp crayfish locally 

reduced California newt (Taricha torosa) recruitment to zero (Gamradt and Kats 

1996). Guan and Wiles (1997) found that introduced P. leniusculus outcompeted 

two native benthic fish species for shelter, and that fish mortality was significantly 

higher with crayfish present. Effects of predation and competition may be magnified when other non-native predators are present (Gamradt and Kats 1996). Also, 

crayfish expansion and abundance in Sierran streams is linked to altered flow 

regimes (Light 2003), so water management could exacerbate these patterns. 

Expansion by the American bullfrog (Lithobates catesbeianus [formerly Rana 

catesbeiana]) into riverine environments may have negatively affected the foothill 
50 

GENERAL TECHNICAL REPORT PSW-GTR-248

yellow-legged frog. It now occurs nearly throughout the foothill yellow-legged 

frog’s geographic and elevation range (Hayes and Jennings 1988, Kupferberg 

1996b). The successful expansion of the bullfrog’s range is due to several influences, including climate-related factors. Kupferberg (1996a, 1996b) showed 

that drought-year freshets allowed bullfrogs to exploit habitat farther upstream, 

whereas more substantial freshets in non-drought years appeared to keep bullfrogs 

in check. Foothill yellow-legged frogs colonized portions of Butte Creek (Butte 

County) where bullfrogs were removed by high flows during floods in 1987 (Hill 

2002). With climate warming trends, within-year attainment of metamorphosis 

in bullfrogs appears to be expanding north geographically and upward in elevation (M. Hayes, unpublished data, 1994–19994

; M.R. Jennings, unpublished data, 

2004–20135), which may increase the success of bullfrogs in river environments. 

It is difficult to disentangle impacts attributable to bullfrogs because habitat 

alteration and fish introductions are almost invariably confounded with bullfrog 

presence or abundance (Hayes and Jennings 1986, 1988). Bullfrogs may have 

contributed to the decline of foothill yellow-legged frogs via predation (Moyle 

1973; but see Hayes and Jennings 1986 for caveats on this interpretation). Bullfrog 

tadpoles, the largest among North American anurans, are known to prey upon other 

amphibian larvae (Corse and Metter 1980, Kiesecker and Blaustein 1997b, Stebbins 2003), and an anecdotal observation documents adult bullfrog predation on 

postmetamorphic foothill yellow-legged frogs (Crayon 1998). In field manipulations 

and enclosure experiments in northwestern California, Kupferberg (1997a) showed 

decreased survivorship and mass at metamorphosis in foothill yellow-legged frog 

tadpoles where bullfrog tadpoles were present, reflecting a competitive disadvantage in resource utilization. An observation of reproductive interference involving 

male foothill yellow-legged frogs in amplexus with subadult bullfrogs suggests 

another mechanism that may result in wasted reproductive effort (Lind et al. 2003a); 

however, the extent of such interactions beyond these observations is unknown 

(see Pearl et al. 2005). Assuming that scale effects are insignificant, reaches on 

the mainstem South Eel River, which have a complement of exotic species that 

include bullfrogs and introduced pike minnows, have substantially lower foothill 

yellow-legged frog production than upstream reaches of the mainstem lacking these 

exotics. Reaches with bullfrogs had an average of 12.3 egg masses per kilometer, 

4

 Hayes, M. 1994–1999. Unpublished data. On file with: Washington Department of Fish 

and Wildlife, 600 Capitol Way North, Olympia, WA 98501. 

5

 Jennings, M. 2004–2013. Unpublished data. On file with: Rana Resources, Davis, CA. 
51 

Foothill Yellow-Legged Frog Conservation Assessment

whereas those without exotics had an average of 106.3 egg masses per kilometer 

(Catenazzi and Kupferberg 2013; S. Kupferberg, unpublished data, 1992–20146). 

Several species of fishes were introduced into California beginning in the 

1800s to promote game fishing, provide forage for game fishes, or serve as biological control agents (Dill and Cordone 1997). Foothill yellow-legged frog abundance 

was negatively correlated to abundance of 9 out of 11 fish species in the Sierran 

foothills (table 10). Smallmouth bass, green sunfish, mosquitofish, and trout feed 

on aquatic insects or insect larvae (Moyle 2002) and may compete with foothill 

yellow-legged frogs for food resources. These species may also exploit stream 

habitats used by foothill yellow-legged frogs. Adult smallmouth bass have been 

documented eating amphibian larvae (Kiesecker and Blaustein 1998) and preying 

on foothill yellow-legged frogs (Rombough 2006a). Foothill yellow-legged frog 

tadpoles do not respond to chemical or visual cues from smallmouth bass (Paoletti 

et al. 2011). These findings suggest that smallmouth bass may be a significant threat 

to foothill yellow-legged frogs in Oregon, where smallmouth bass have dramatically 

expanded (Simon and Markle 1999). Synergistic negative effects may occur when 

bullfrogs and smallmouth bass are both present (see Hayes and Jennings 1986 and 

Kiesecker and Blaustein 1998 for a discussion). The Sacramento pikeminnow coexists with foothill yellow-legged frogs in portions of its range, but this species has 

been introduced into several coastal California streams, where it has been observed 

eating tadpoles and frogs (Corum 2005). Green sunfish are suspected predators of 

frog eggs, and trout likely prey on all life stages. Fish may act as vectors of disease; 

two studies have demonstrated that pathogens can be transferred between amphibians and fish (Kiesecker et al. 2001, Mao et al. 1999), but transfer of disease from 

fish has not been studied specifically for foothill yellow-legged frogs. 

Extent of risks related to nonnative species— 

The presence of nonnative species within the foothill yellow-legged frog’s range 

likely presents a significant risk to existing populations. Some evidence exists 

suggesting that bullfrogs, crayfish, and smallmouth bass in particular may have 

negative effects on foothill yellow-legged frog populations; however, the particular 

degree of risk to the species is not known. The impact of nonnative species, particularly introduced fishes, on amphibians has been studied extensively in lentic but not 

stream systems. Many of these studies have demonstrated a negative effect on presence and densities of frog populations. 

6

 Kupferberg, S. 1992–2014. Unpublished data. On file with: Questa Engineering, 1220 

Brickyard Cove Road, Suite 206, Pt. Richmond, CA 94807. 
52 

GENERAL TECHNICAL REPORT PSW-GTR-248

 

Table 10—Spearman rank correlation between the numerical abundance of the vertebrate 

macrofauna and the abundance (coded) of the foothill yellow-legged frog as recorded by Moyle 

(1973) from the foothills of the Sierra 

Sample Correlation
 

Species Common name size (n) coefficient (ρ) Probability (P)
 

Catostomus occidentalis Sacramento sucker 71 -0.404** <0.001 

Gambusia affinis* Mosquito fish 62 -0.835** <0.001 

Ictalurus catus* White catfish 41 -0.798** <0.001 

Lavinia exilicauda Hitch 40 -0.760** <0.001 

Lavinia symmetricus California roach 55 -0.316 0.020 

Lepomis cyanellus* Green sunfish 88 -0.742** <0.001 

Lepomis macrochirus* Bluegill 59 -0.827** <0.001 

Micropterus dolomieu* Smallmouth bass 35 -0.538** 0.001 

Mylopharadon conocephalus Hardhead 38 -0.607** <0.001 

Oncorhynchus mykiss Rainbow trout 44 -0.425 0.005 

Ptychocheilus grandis Sacramento pikeminnow 66 -0.541** <0.001 

Lithobates [Rana] catesbeianus* American bullfrog 90 -0.800** <0.001 

Note: Sample size is based on the total number of sites where either the foothill yellow-legged frog or the species being compared 

was present. A single asterisk (*) indicates introduced species. A double asterisk (**) identifies significant correlations in a twotailed test adjusted for 24 comparisons (α = 0.002; 11 below and 13 comparisons of physical habitat variables not presented here). 

Probability (P) is the probability of obtaining the calculated Spearman correlation coefficient (ρ). Adapted from Hayes and Jennings 

(1988). 

Conservation options related to introduced species— 

Direct eradication of introduced species populations may not be within the practical 

scope of management of the agencies contributing to this document. However, these 

agencies may have opportunities to reduce the effects of introduced species through 

restoration actions. Examples include managing flow regimes in regulated rivers to 

benefit multiple native species, modifying fish-stocking programs, regulating the 

use of live bait, and minimizing human-induced dispersal of existing introduced 

species. Consideration of the risks associated with introduced species is important 

in the development of a conservation strategy for the foothill yellow-legged frog. 

Mining 

Mining may have contributed to habitat loss and fragmentation for foothill yellowlegged frogs. Several types of mining have occurred in the Sierra Nevada and 

elsewhere; aggregate, hardrock, hydraulic, and suction-dredge mining are discussed 

as potential contributors to the declines of foothill yellow-legged frogs and current 

or future threats of various mining practices to populations are reviewed. 
53 

Foothill Yellow-Legged Frog Conservation Assessment

Aggregate mining is mechanical extraction of materials from unconsolidated 

matrices from streams or stream terraces for use in construction of various infrastructures, including roads. Industries that conduct aggregate mining often prefer 

instream to terrace mining because the extracted aggregate requires minimal sorting and washing (CSLC 1993). Instream mining affects stream geomorphology by 

changing sediment transport regimes, eroding beds and banks, and incising channels (CSLC 1993). Terrace mining, which occurs outside of the wetted perimeter 

of the river but within the flood plain or adjacent terrace features, may create large 

ponds filled by groundwater; in flood events, these ponds may become connected 

to the river (CSLC 1993). Instream and terrace mining may increase sedimentation 

downstream of mining activities (Mount 1995), alter or eliminate refuge habitat (see 

“Ecology” section), and increase exposure to bullfrogs and nonnative warmwater 

fishes that may enter or exit created ponds during freshets (Fuller et al. 2011, Moyle 

2002). Aggregate operations are typically associated with large riverine channels in 

the lower elevational range of foothill yellow-legged frogs, although some aggregate 

operations also exist in selected portions of larger streams at middle and higher 

elevations, e.g., the upper Feather River system. Over the range of the foothill 

yellow-legged frog in the Sierra Nevada, major sand and gravel aggregate operations exist in every river system in which foothill yellow-legged frogs were historically recorded (Mount 1995). 

Hardrock mining involves digging by various means (e.g., picks and shovels, 

rock drills, dynamite) into solid rock to find minerals (CSLC 1993). This form of 

mining often involves digging shafts that go either straight down to follow ore bodies and veins, or at least somewhat horizontally into rock faces. Shafts and tunnels, 

typically supported with large timbers to prevent cave-ins, would eventually flood 

as they hit the water table, which can be a source of pollution; even slightly acidic 

water can solubilize potentially toxic metals such as copper (Deanovic et al. 1999). 

Many shaft or tunnel hardrock mines exist in Sierra Nevada national forests, but 

the extent of overlap within the Sierran range of foothill yellow-legged frogs is 

unclear. Most of these mines are at low- to mid-elevations within the species’ range; 

however, the hardrock operations with the highest potential of affecting foothill 

yellow-legged frogs occur in the northern Sierra Nevada. 

Hydraulic mining consists of methods that use water, typically under pressure, 

to erode hillsides of placer (gravel, sand, or silt) and other unconsolidated deposits 

(CSLC 1993). This extreme approach drastically alters water quality and stream 

geomorphology (CSLC 1993, Larson 1996). This method exposes rock to immediate weathering and erosion, increasing pollutants such as acid, cadmium, mercury, 

and asbestos in waterways (CSLC 1993). The practice was outlawed in 1884, but its 
54 

GENERAL TECHNICAL REPORT PSW-GTR-248

effects on water pollution may still be apparent in northern Sierra streams such as 

portions of the mid-elevation Feather River (Larson 1996) and in parts of the Trinity and Sacramento River drainages of northern California. Water developments 

in some streams (e.g., Englebright Reservoir on the Yuba River) were constructed 

largely for the purpose of trapping potentially polluting sediments mobilized during 

high-water events that date from the hydraulic mining era (Childs et al. 2003). 

Further, the extensive use of mercury in the mining and recovery of gold during the 

late 19th and early 20th centuries has led to widespread mercury contamination of 

water, sediment, and biota in the Sierra Nevada foothills. Study of the watersheds 

of the Bear and Yuba Rivers revealed significant mercury levels in aquatic food 

chains; analysis of Pacific chorus frogs, foothill yellow-legged frogs, and American 

bullfrogs detected mercury contamination (Alpers et al. 2001). The results suggest 

that historical use of mercury still affects the Bear and Yuba Rivers and their 

associated aquatic communities. A recent study in the Cache Creek watershed 

of northern Sacramento Valley of California demonstrated that three species of 

frogs (bullfrogs, foothill yellow-legged frogs, and Pacific chorus frogs) were 

bioaccumulating mercury at levels above those typically resulting in Environmental 

Protection Agency health advisories for fish. The primary source of mercury in 

this watershed is also believed to be hydraulic mining, though geothermal springs 

and agricultural runoff may also contribute (Hothem et al. 2010). Much of the historical hydraulically mined region of California is within the elevation range where 

foothill yellow-legged frogs are (or were) present, so effects of this practice on the 

species, albeit unstudied, were likely significant. 

Suction-dredge mining is a method in which water, sediment, and rocks are 

vacuumed from portions of streams and rivers, sorted to obtain gold, and the spoils 

redeposited in the stream (CSLC 1993, Harvey and Lisle 1998). A moratorium 

in California currently prohibits CDFW from issuing suction-dredge permits 

(California Fish & Game Code §5653.1, subdivision a), and use of related equipment in any river, stream, or lake through 30 June 2016 (California Fish & Game 

Code §5653.1, subdivision b). However, suction-dredge mining may be permitted 

in the future. Suction dredging may increase suspended sediment, modify stream 

geomorphology, directly remove aquatic organisms, and rearrange the substrate of 

streams (CDFG 1994, 2012). This form of mining may have effects on reproduction by disturbing adults during courtship and breeding activities, or disrupting 

habitat during the reproductive season. Dredging up stream substrates can result in 

displacement, burial, or suffocation of eggs or tadpoles (CDFG 1994, Harvey and 

Lisle 1998). Depending on the size and stage of foothill yellow-legged frog tadpoles, 

they would not be able to swim away from the strong current created by suction 
55 

Foothill Yellow-Legged Frog Conservation Assessment

dredging, as they can be entrained into flows as slow as 0.33 ft per sec (Kupferberg 

et al. 2011b). In response to elevated currents, these tadpoles seek shelter in interstitial spaces in the substrate. Because of this behavior, this species is particularly 

vulnerable to suction of sediments. Sweet (1992) observed mortality of eggs and 

larvae of the stream-breeding arroyo toad (Anaxyrus californicus); mortality was a 

direct effect of increased sedimentation that resulted from suction dredge mining. 

Suction dredging may cause movement of instream habitat features such as rock 

substrates and woody debris, which may be used by foothill yellow-legged frogs 

for overwintering (see “Ecology” section). Dredging may also affect the foothill 

yellow-legged frog prey base. The composition of the invertebrate fauna changes in 

dredge-disturbed areas; however, the recovery to a predredging community appears 

to be rapid (Harvey 1986, Somer and Hassler 1992). 

Extent of risks related to mining— 

Considerable overlap exists between mining activities and foothill yellow-legged 

frog habitat, so mining may pose a potentially significant risk. Historical (and a few 

current) aggregate and hardrock mining and historical hydraulic mining practices 

have altered physical habitat structure and water quality in streams occupied by 

foothill yellow-legged frogs. Bioaccumulation of heavy metals has been demonstrated, but the overall contribution of mining activities to foothill yellow-legged 

frog habitat degradation and declines is unknown. Instream aggregate and suctiondredge mining, in particular, pose the greatest threat to foothill yellow-legged frogs, 

given the potential effects of these practices on populations. The risk of suctiondredge mining is low under the current moratorium, but may increase substantially 

should the moratorium be lifted. One of the most significant problems should the 

moratorium be lifted is the inherent difficulty of enforcing proposed environmental 

regulations. By its nature, the activity is widely dispersed in remote areas where the 

lack of visibility to law enforcement is a prime concern. 

Conservation options related to mining— 

Mining activities are directly within the jurisdiction of the agencies participating 

in this assessment. An assessment of the overlap of mining activities with foothill 

yellow-legged frog localities and habitats, and research examining the potential effects of mining on foothill yellow-legged frogs is needed. 

Summary of Risk Factors 

This conservation assessment reviewed the ecology of the foothill yellow-legged 

frog and evaluated 17 risk factors that resulted in conservation options for consideration in the development of a conservation strategy. Of risk factors examined, water 
56 

GENERAL TECHNICAL REPORT PSW-GTR-248

development (impoundment and diversion) was identified as the primary risk factor 

and is, at least in part, responsible for species’ decline in the Sierra Nevada and 

elsewhere. Extensive research has demonstrated that this risk factor can have severe 

impacts on frog populations and that proper management is critical for persistence 

of the species. Studies have shown that frogs more often occur and have higher 

abundances along streams lacking large dams. Ill-timed waterflows can result in 

scouring or stranding of egg masses, and high-water events and dam releases are 

a primary cause of egg mass mortality. Cold-water releases from upstream reservoirs impair growth, development, and survival of tadpoles. Water development, 

management of flow regimes, and dams that block sediment flow collectively alter 

downstream channel morphology; these changes may result in the modification or 

fragmentation of critical habitats used by frogs. Management of regulated streams 

to mimic the natural flow regime is ideal, but frequently impractical or infeasible 

implement. Instead, by focusing on reducing impacts during critical times (e.g., 

refraining from high pulse flows during the brief spring reproductive season and 

avoiding cold-water releases during tadpole development) and by using tools that 

evaluate effects of present flow regimes on habitat and strand/scour risk, water 

managers may develop flow regimes that minimize effects on foothill yellowlegged frogs. 

Climate change, mining, introduced species, and habitat loss were identified as 

high risk factors. Modification of precipitation patterns, and therefore water availability, is a potential outcome of climate change. Impacts of climate variability on 

foothill yellow-legged frogs may include alteration of the frequency, duration, and 

magnitude of droughts, severe winters, and late-spring freshets. Ensuing variability 

in the timing and magnitude of streamflows may result in mortality to vulnerable 

life stages of foothill yellow-legged frogs analogous to the effects of hydrological 

management. Variable water temperature as a result of climate change may also 

affect rate of and size at metamorphosis. Drought conditions may increase the susceptibility of frogs to disease or contaminants, and reduce their prey base. Climate 

change is a global problem and the impacts of this risk factor are unknown and 

cannot easily be assessed. Management options relative to this factor are beyond 

the scope of agency jurisdiction; however, agencies can ameliorate impacts of 

climate change by reducing the impacts of other risk factors such as water development. Mining activities, especially suction-dredge mining, frequently overlap with 

foothill yellow-legged frog habitat. Various mining methods may cause direct frog 

mortality, and studies have demonstrated bioaccumulation of mine-related contaminants in foothill yellow-legged frogs. Research has shown that mining activities 
57 

Foothill Yellow-Legged Frog Conservation Assessment

do alter the stream environment by modifying stream morphology, increasing 

sediment loads, and introducing contaminants, but the contribution to declines 

and extent of the impacts on foothill yellow-legged frogs remains unstudied. A 

current moratorium restricting suction dredging in California reduces the threat of 

this factor, but if that moratorium is lifted, the risk is potentially high. Introduced 

crayfish, bullfrogs, and fish are identified as a major risk factor, and studies support 

the impacts of these nonnative species on the foothill yellow-legged frog. Introduced species may prey on frogs, compete for resources, and act as disease vectors. 

Eradication or management efforts to control the distribution of introduced species 

may reduce the impact of this risk factor. Habitat loss, alteration, and fragmentation 

occur in various forms that encompass many, if not most, of the other risk factors 

examined in this assessment. Also, development of land commonly occurs in the 

Sierran foothills, and therefore overlaps with foothill yellow-legged frog habitat. 

Agency regulation of urbanization and land development may minimize the threat 

of human encroachment upon frogs and their critical habitats. 

Other risk factors may alter and degrade stream habitat, but data are lacking to 

establish the extent of risk to foothill yellow-legged frogs. These factors include fire 

management; livestock grazing; recreational, research, and restoration activities; 

roads; and vegetation and fuels management (see app. 4). Activities related to these 

risk factors may modify stream hydrology and geomorphology and may increase 

sediment loads. Airborne contaminants, locally applied pesticides, contaminants 

introduced by fire suppression, vegetation and fuels management, livestock use, 

recreational activities, and roads may reduce water quality; however, data are 

lacking to ascertain the extent of risk to foothill yellow-legged frogs. Based on 

studies of the impact of disease (particularly chytridiomycosis) on other amphibian 

species, this factor may pose some risk but also lacks species-specific information. 

Although many of these factors have extensive overlap with foothill yellow-legged 

frogs and have the potential for impact, they were ultimately considered lower risk 

because current management practices protect stream habitat and adjacent riparian 

zones; this safeguards or reduces impacts on frogs as long as they are implemented 

by agencies. Re-evaluation of changes in current practices may be required as 

new information becomes available. Several risk factors fall largely outside the 

purview of participating agencies (acid deposition, airborne contaminants including pesticides, climate change, and increased UV-B exposure). However, agencies 

participating in this assessment could, in partnerships, contribute to and guide the 

development of extraregional management strategies to address these risk factors. 
58 

GENERAL TECHNICAL REPORT PSW-GTR-248

Future Conservation and Management 

The review of the species ecology, current status of the species, and evaluation of 

the risk factors identified in this assessment suggest that waterflow management, 

followed by stream habitat management and watershed management, would have 

the most significant effect on conservation of foothill yellow-legged frogs. The following options are intended to facilitate the development of a conservation strategy. 

Waterflow Management 

•	 Maintain or restore hydrological functions of streams to mimic natural flow 

and temperature regimes to the degree practicable, with the specific objectives of: 

•	 Minimizing flow-related impacts (e.g., pulse flows and overly fast 

changes in waterflows and depths) during the spring reproductive season. 

•	 Minimizing thermal-related impacts (e.g., unseasonably cold water 

temperature resulting from hypolimnetic release) during the tadpole 

growth and development period. 

•	 Allowing for seasonally appropriate high flows to maintain natural 

channel geomorphology.
 

Stream Habitat and Nonnative Species Management 

•	 Maintain or restore riparian vegetation that is characteristic of channels with dynamic flow regimes (e.g., reduce vegetation encroachment to 

enhance breeding habitat). 

•	 Carefully evaluate the potential impacts of any new mining permits 

requested in key streams and watersheds. 

•	 Evaluate the distribution and abundance of introduced species (e.g., bullfrogs, crayfish, and smallmouth bass) and consider mitigation actions to the 

degree practicable in key streams and watersheds. 

Watershed-Scale Management 

•	 Identify key watersheds that are likely to have the greatest contribution to 

sustaining the species throughout its range, with selections considering current population status, habitat conditions, geographic location, and current 

and projected future risks. 

•	 Develop target watershed conditions (e.g., vegetation conditions) that are 

conducive to supporting sustainable populations in key watersheds. 
59 

Foothill Yellow-Legged Frog Conservation Assessment

•	 Watershed management approaches will be most robust if they reflect consideration of (1) habitat quality, quantity, and diversity within individual 

streams; and (2) connectivity among populations within and among watersheds to enhance gene flow and recolonization potential. 

Population and Habitat Monitoring 

•	 Consider developing a multiscale monitoring approach that integrates 

habitat and population measures to track status and trends and to mitigate 

uncertainty in our understanding of risk factors and the fate of existing 

populations. 

Future Research Priorities 

Although much still exists to learn about the ecology and life history of the foothill 

yellow-legged frog, selected key information gaps have the greatest bearing 

on helping management determine how best to meet population and habitat conservation objectives. 

•	 Additional study on the mechanism(s) underlying the effects of flow and 

thermal regimes on size at metamorphosis, a trait related to adult fitness (i.e., effect of water temperature on development, growth, or feeding 

rate; effect of flow and water temperature on quality and quantity of food 

resources). 

•	 Influence of climate change on hydrology and resulting changes in dam 

operations. 

•	 Impacts of recreational activities (including suction-dredge mining); use, 

construction, or maintenance of roads or trails near frog habitat; and movement of pathogens or diseases related to human activity. 

•	 Effects of predation by fish, crayfish, and American bullfrogs on foothill yellow-legged frog survival in regulated and unregulated streams and 

potential mitigation. 

•	 Effects of pesticides (local and airborne), fire management, and livestock 

grazing to gain a better understanding of the relative level of risk of these 

factors. 

•	 Identification of cumulative effect thresholds for population persistence at 

watershed and basin scales. 
60 

GENERAL TECHNICAL REPORT PSW-GTR-248

Acknowledgments 

Our sincere thanks go to all members of the Foothill Yellow-Legged Frog Working Group (app. 5), all of whom contributed to this assessment. It has been very 

much a team effort and members at all stages of the process contributed ideas, 

information, writing, and reviews. We give a special acknowledgment to Catherine 

Brown for her early guidance and significant contributions to all aspects of this 

document. Because this document was written in conjunction with assessments for 

four other frog species, members of other conservation teams also contributed to 

this document. Robert Bingham, Nichole Patrick, and Matt Wacker wrote several of 

the risk factor sections. David Bakke commented on the section on locally applied 

pesticides. Kevin Thomas, George Garcia, Michael Kellett, Barry Hill, and Bret 

Harvey provided comments of earlier drafts. Chris Pearl, Jim Rorabaugh, and 

Sarah Kupferberg provided peer reviews and comments. Becky Howard assisted 

in retrieving survey data, and Diane Montoya provided GIS help. The following 

individuals provided data on specimen records from their respective institutions: 

Darrel Frost (American Museum of National History, New York), Roy McDiarmid 

and Steve Gotte (United States National Museum, Washington, D.C.), and Greg 

Schneider (University of Michigan Museum of Zoology, Ann Arbor, Michigan). 

English Equivalents 

When you know: Multiply by: To get: 

Millimeters (mm) 0.00394 Inches 

Centimeters (cm) .394 Inches 

Kilometers (km) .621 Miles 

Degrees Celsius: (°C) 1.8 °C + 32 Degrees Fahrenheit 

Literature Cited 

Adams, M.J. 1999. Correlated factors in amphibian decline: exotic species and 

habitat change in western Washington. Journal of Wildlife Management. 63: 

1162–1171. 

Adams, M.J.; Pearl, C.A.; McCreary, B.; Galvan, S.K.; Wessell, S.J.; Wente, 

W.H.; Anderson, C.W.; Kuehl, A.B. 2009. Short-term effect of cattle exclosures 

on Columbia spotted frog (Rana luteiventris) populations and habitat in 

northeastern Oregon. Journal of Herpetology. 43: 132–138. 

Adams, M.J.; Schindler, D.E.; Bury R.B. 2001. Association of amphibians with 

attenuation of ultraviolet-b radiation in montane ponds. Oecologia. 128: 519–525. 
61 

Foothill Yellow-Legged Frog Conservation Assessment

Adkins Giese, C.L.; Greenwald, D.N.; Curry, T. 2012. A petition to list 53 

amphibians and reptiles in the United States as threatened or endangered 

under the Endangered Species Act. Portland, OR: Center for Biological 

Diversity. 454 p. 

Alpers, C.N.; Hunerlach, M.P.; Hothem, R.L.; May, J.T.; Taylor, H.E.; De 

Wild, J.F.; Olson, M.L.; Krabbenhoft, D.P.; Marvin-DiPasquale, M. 2001. 

Mercury contamination and bioaccumulation associated with historical gold 

mining in the Bear and Yuba River watersheds, Sierra Nevada, California. 

EOS, Transactions of the American Geophysical Union. 82 (47), Fall meeting 

supplement: Abstract at: http://abstractsearchagu.org/meetings/2001/FM/ 

H521I-06.html. 

Álvarez, D.; Nicieza, G. 2002. Effects of temperature and food quality on anuran 

larval growth and metamorphosis. Functional Ecology. 16: 640–648. 

Anzalone, C.R.; Kats, L.B.; Gordon, M.S. 1998. Effects of solar UV-B radiation 

on embryonic development in Hyla cadaverina, Hyla regilla, and Taricha torosa. 

Conservation Biology. 12: 646–653. 

Ashton, D.T. 1995–1996. Personal observation. U.S. Department of the Interior, 

Geological Survey, Forest and Rangeland Ecosystems Science Center, 3200 

Jefferson Way, Corvallis, OR 97331. 

Ashton, D.T.; Marks, S.B.; Welsh, H.H., Jr. 2006. Evidence of continued effects 

from timber harvesting on lotic amphibians in redwood forests of northwestern 

California. Forest Ecology and Management. 221: 183–193. 

Ashton, D.T.; Nakamoto, R.J. 2007. Rana boylii (foothill yellow-legged frog): 

predation. Herpetological Review. 38(4): 442. 

Aston, L.S.; Sieber, J.N. 1997. Fate of summertime airborne organophosphate 

pesticide residues in the Sierra Nevada mountains. Journal of Environmental 

Quality. 26: 1483–1492. 

Bartelt, P.E. 1998. Bufo boreas (western toad) mortality. Herpetological Review. 

29: 96. 

Belden, L.K.; Blaustein, A.R. 2002. Exposure of red-legged frog embryos to 

ambient UV-B radiation in the field negatively affects tadpole growth and 

development. Oecologia. 130: 551–554. 

Belden, L.K.; Wildy, E.L.; Blaustein, A.R. 2000. Growth, survival, and 

behaviour of larval long-toed salamander (Ambystoma macrodactylum) 

exposed to ambient levels of UV-B radiation. Journal of Zoology. 251: 473–479. 
62 

GENERAL TECHNICAL REPORT PSW-GTR-248

Belsky, A.J.; Matzke, A.; Uselman, S. 1999. Survey of livestock influences on 

stream and riparian ecosystems in the western United States. Journal of Soil and 

Water Conservation. 54: 419–431. 

Berrill, M.; Bertram, S.; McGillivray, L.; Kolohon, M.; Pauli, B. 1994. Effects 

of low concentrations of forest-use pesticides on frog embryos and tadpoles. 

Environmental Toxicology and Chemistry. 13: 657–664. 

Berven, K.A. 1981. Mate choice in the wood frog, Rana sylvatica. Evolution. 

35: 707–722. 

Berven, K.A. 1982. The genetic basis of altitudinal variation in the wood frog, 

Rana sylvatica. I. An experimental analysis of life-history traits. Evolution. 

36: 962–983. 

Berven, K.A. 1990. Factors affecting population fluctuations in tadpole and adult 

stages of the wood frog (Rana sylvatica). Ecology. 71: 1599–1608. 

Berven, K.A.; Gill, D.E. 1983. Interpreting geographic variation in life-history 

traits. American Zoologist. 23: 85–97. 

Bidwell, J.R.; Gorrie, J.R. 1995. Acute toxicity of a herbicide to selected frog 

species. Technical Series 79. Perth, Australia: Department of Environmental 

Protection. 9 p. 

Blankenship, A.; Burns, K.; Hayward, G.D.; Kratz, A.; Sidle, J.G.; SwiftMiller, S.M.; Warder, J. 2001. Protocol defining process and procedure to 

develop species assessments for the Region 2 Species Conservation Project. 

Golden, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain 

Region. http://www.fs.fed.us/r2/projects/scp/contractingopps/protocol.shtml. 

(11 April 2014). 

Blaustein, A.R.; Belden, L.K. 2003. Amphibian defenses against ultraviolet-B 

radiation. Evolution and Development. 5: 89–97. 

Blaustein, A.R.; Hoffman, P.D.; Hokit, D.G.; Kiesecker, J.M.; Walls, S.C.; 

Hays, J.B. 1994a. UV repair and resistance to solar UV-B in amphibian eggs: 

A link to population declines? Proceedings of the National Academy of Sciences. 

91: 791–1795. 

Blaustein, A.R.; Hoffman, P.D.; Kiesecker, J.M.; Hays, J.B. 1996. DNA repair 

activity and resistance to solar UV-B radiation in eggs of the red-legged frog. 

Conservation Biology. 10: 1398–1402. 
63 

Foothill Yellow-Legged Frog Conservation Assessment

Blaustein, A.R.; Hokit, D.G.; O’Hara, R.K.; Holt, R.A. 1994b. Pathogenic 

fungus contributes to amphibian losses in the Pacific Northwest. Biological 

Conservation. 67: 251–254. 

Blaustein, A.R.; Kiesecker, J.M.; Chivers, D.P.; Hokit, D.G.; Marco, A.; 

Belden, L.K.; Hatch, A. 1998. Effects of ultraviolet radiation on amphibians: 

field experiments. American Zoologist. 38: 799–812. 

Blaustein, A.R.; Wake, D.B. 1990. Declining amphibian populations: A global 

phenomenon? Trends in Ecology and Evolution. 5: 203–204. 

Bobzien, S.; DiDonato, J.E. 2007. The status of the California tiger salamander 

(Ambystoma californiense), California red-legged frog (Rana aurora draytonii), 

foothill yellow-legged frog (Rana boylii) and other aquatic herpetofauna in the 

East Bay Regional Park District, California. Oakland, CA: East Bay Regional 

Park District. 67 p. 

Bondi, C.A.; Yarnell, S.M.; Lind, A.J. 2013. Transferability of habitat suitability 

criteria for a stream breeding frog (Rana boylii) in the Sierra Nevada, California. 

Herpetological Conservation and Biology. 8(1): 88–103. 

Borisenko, A.N. 2000. The status of Rana boylii in Oregon: analysis of selected 

biotic and abiotic variables at historical Rana boylii locations. Portland, OR: 

Portland State University. 72 p. M.S. thesis. 

Borisenko, A.N.; Hayes, M.P. 1999. Status of the foothill yellow-legged frog 

(Rana boylii) in Oregon. Final report. Contracts ORFO080197-1 and 1448­

13420-7-M262. Portland, OR: U.S. Department of the Interior, Fish and Wildlife 

Service.39 p. 

Bosch, J.; Martinez-Solano, I.; Garcia-Paris, M. 2001. Evidence of a chytrid 

fungus infection involved in the decline of the common midwife toad (Alytes 

obstetricans) in protected areas of central Spain. Biological Conservation. 97: 

331–337. 

Bossard, C.C.; Randall, J.M.; Hoshovsky, M.C. 2000. Invasive plants of 

California’s wildlands. Berkeley, CA: University of California Press. 360 p. 

Boubée, J.; Jowett, I.; Nichols, S.; Williams, E. 1999. Fish passage at culverts: a 

review with possible solutions for New Zealand indigenous species. Wellington, 

New Zealand: Department of Conservation. 111 p. 
64 

GENERAL TECHNICAL REPORT PSW-GTR-248

Bourque, R. 2008. Spatial ecology of an inland population of the foothill yellowlegged frog (Rana boylii) in Tehama County, California. Arcata, CA: Humboldt 

State University. 93 p. M.S. thesis. 

Boyle, S.A.; Samson, F.B. 1985. Effects of non-consumptive recreation on 

wildlife: a review. Wildlife Society Bulletin. 13: 110–116. 

Bradford, D.F. 1991. Mass mortality and extinction in a high elevation population 

of Rana muscosa. Journal of Herpetology. 25: 174–177. 

Bradford, D.F.; Gordon, M.S. 1992. Aquatic amphibians in the Sierra Nevada: 

current status and potential effects of acidic deposition on populations. Contract 

A932-139. Sacramento, CA: California Air Resources Board. 85 p. 

Bradford, D.F.; Gordon, M.S.; Johnson, D.F.; Andrews, R.D.; Jennings, W.B. 

1994. Acidic deposition as an unlikely cause for amphibian decline in the Sierra 

Nevada, California. Biological Conservation. 69: 155–161. 

Briggs, C.J.; Knapp, R.A.; Vredenburg, V.T. 2010. Enzootic and epizootic 

dynamics of the chytrid fungal pathogen of amphibians. Proceedings of the 

National Academy of Sciences. 107: 9695–9700. 

Brown, C.J.; Blossey, B.; Maerz, J.C.; Joule, S.J. 2006. Invasive plant and 

experimental venue affect tadpole performance. Biological Invasions. 8: 327–338. 

Brown, L.R.; Moyle, P.B. 1997. Invading species in the Eel River, California: 

successes, failures, and relationships with resident species. Environmental 

Biology of Fishes. 49: 271–291. 

Bryer, P.J.; Elliott, J.N.; Willingham, E.J. 2006. The effects of coal tar based 

pavement sealer on amphibian development and metamorphosis. Ecotoxicology. 

15: 241–247. 

Buhl, K.J.; Hamilton, S.J. 2000. Acute toxicity of fire-control chemicals, 

nitrogenous chemicals, and surfactants to rainbow trout. Transactions of the 

American Fisheries Society. 129: 408–418. 

Bull, E.L.; Hayes, M.P. 2000. Effects of livestock on reproduction of the Columbia 

spotted frog. Journal of Range Management. 53: 291–294. 

Bursey, C.; Goldberg, S.; Bettaso, J. 2010. Persistence and stability of the 

component Helminth community of the foothill yellow-legged frog, Rana boylii 

(Ranidae), from Humboldt County, California, 1964–1965, versus 2004–2007. 

American Midland Naturalist. 163(2): 476–482. 
65 

Foothill Yellow-Legged Frog Conservation Assessment

Burton, E.C.; Gray, M.J.; Schmutzer, A.C.; Miller, D.L. 2009. Differential 

responses of postmetamorphic amphibians to cattle grazing in wetlands. The 

Journal of Wildlife Management. 73: 269–277. 

Byron, E.; Axler, R.; Goldman, C. 1991. Increased precipitation acidity in the 

Central Sierra Nevada. Atmospheric Environment. 25A: 271–275. 

Cahill, T.A.; Carroll, J.J.; Campbell, D.; Gill, T.E. 1996. Air quality. In: SNEP 

Science Team, eds. Sierra Nevada ecosystem project: final report to Congress. 

Vol. II: Assessments and scientific basis for management options. Report No. 37. 

Davis, CA: Centers for Water and Wildland Resources, University of California– 

Davis: 1227–1262. Chapter 48. 

California Department of Finance [CDFI]. 2013. Historical census populations of 

counties and incorporated cities in California, 1850–2010. http://www.dof.ca.gov/ 

research/demographic/state_census_data_center/historical_census_1850-2010/ 

view.php. (5 February 2015). 

California Department of Fish and Game [CDFG]. 1994. Adoption of 

regulations for suction dredge mining: amended draft environmental impact 

report. Rancho Cordova, CA. 182 p. 

California Department of Fish and Game [CDFG]. 2012. Findings of fact of the 

California Department of Fish and Game as a lead agency under the California 

Environmental Quality Act (Pub. Resources Code §21000 et seq.) for the Suction 

Dredge Permitting Program (Fish and Game Code, §5653 et seq.) as analyzed in 

the Suction Dredge Permitting Program subsequent environmental impact report 

(SCH No. 2009112005). Sacramento, CA. 82 p. 

California Department of Pesticide Regulation [CDPR]. 1989–2012. Pesticide 

use statistics. http://www.cdpr.ca.gov/docs/pur/purmain.htm. (5 February 2015). 

California Department of Water Resources [CDWR]. 1998. California Water 

Plan Update. Bulletin 160-98. Sacramento, CA. 63 p. 

California State Lands Commission [CSLC]. 1993. California’s rivers: a public 

trust report. Sacramento, CA. 334 p. 

Carey, C.; Cohen, N.; Rollins-Smith, L. 1999. Amphibian declines: an 

immunological perspective. Developmental and Comparative Immunology. 

23: 459–472. 

Carr, L.W.; Fahrig, L. 2001. Effect of road traffic on two amphibian species of 

differing vagility. Conservation Biology. 15: 1071–1078. 
66 

GENERAL TECHNICAL REPORT PSW-GTR-248

Catenazzi, A.; Kupferberg, S.J. 2013. The importance of thermal conditions to 

recruitment success in stream-breeding frog populations distributed across a 

productivity gradient. Biological Conservation. 168: 40–48. 

Cayan, D.R.; Maurer, E.P.; Dettinger, M.D.; Tyree, M.; Hayhoe, K. 2008. 

Climate change scenarios for the California region. Climatic Change. 87 

(Suppl. 1): S21–S42. 

Chen, C.Y.; Hathaway, K.M.; Folt, C.L. 2004. Multiple stress effects of Vision® 

herbicide, pH, and food on zooplankton and tadpole amphibian species from 

forest wetlands. Environmental Toxicology and Chemistry. 23: 823–831. 

Childs, J.R.; Snyder, N.P.; Hampton, M.A. 2003. Bathymetric and geophysical 

studies of Englebright Lake, Yuba-Nevada Counties, California. Open File 

Report 03-383. Reston, VA: U.S. Department of the Interior, Geological 

Survey. 20 p. 

Cole, D.N.; Fichtler, R.K. 1983. Campsite impact on three western wilderness 

areas. Environmental Management. 7: 275–288. 

Cole, D.N.; Marion, J.L. 1988. Recreation impacts in some riparian forests of the 

Eastern United States. Environmental Management. 12: 99–107. 

Cook, E.R.; Woodhouse, C.A.; Eakin, C.M.; Meko, D.M.; Stahle, D.W. 2004. 

Long-term aridity changes in the western United States. Science. 306: 1015–1018. 

Cooper, E.L.; Wright, R.K.; Klempau, A.E.; Smith, C.T. 1992. Hibernation 

alters the frog’s immune system. Cryobiology. 29: 616–631. 

Cope, E.D. 1879. A contribution to the zoology of Montana. American Naturalist. 

13: 432–441. 

Cope, E.D. 1883. Notes on the geographical distribution of Batrachia and Reptilia 

in western North America. Proceedings of the Academy of Natural Sciences of 

Philadelphia. 35: 10–35. 

Cope, E.D. 1889. The Batrachia of North America. Bulletin of the United States 

National Museum. 34: 1–525. 

Corn, P.S. 1994. What we know and don’t know about amphibian declines in the 

West. In: Covington, W.W.; DeBano, F.L., tech. coords. Sustainable ecology 

systems: implementing an ecological approach to land management. Gen. Tech. 

Rep. RM-GTR-247. Fort Collins, CO: U.S. Department of Agriculture, Forest 

Service, Rocky Mountain Forest Range and Experiment Station: 59–67. 
67 

Foothill Yellow-Legged Frog Conservation Assessment

Corn, P.S. 1998. Effects of ultraviolet radiation on boreal toads in Colorado. 

Ecological Applications. 8: 18–26. 

Corse, W.A.; Metter, D.A. 1980. Economics, adult feeding and tadpole growth of 

Rana catesbeiana on a fish hatchery. Journal of Herpetology. 14: 231–238. 

Corum, S.D. 2005. Effects of Sacramento pikeminnow on foothill yellow-legged 

frogs in coastal streams. Arcata, CA: Humboldt State University. 39 p. M.S. 

thesis 

Cory, L.; Fjeld, P.; Serat, W. 1970. Distributional patterns of DDT residues in the 

Sierra Nevada Mountains. Pesticides Monitoring Journal. 3: 204–211. 

Crayon, J.J. 1998. Rana catesbeiana (Bullfrog). Diet. Herpetological Review. 

29: 232. 

Crother, B.; Boundy, J.; Burbrink, F.T.; Campbell, J.A.; de Queiroz, K.; Frost, 

D.R.; Highton, R.; Iverson, J.B.; Kraus, F.; McDiarmid, R.W.; Mendelson, 

J.R., III; Meylan, P.A.; Reeder, T.W.; Seidel, M.E., Jr.; Tilley, S.G.; Wake, 

D.B. 2008. Scientific and standard English names of amphibians and reptiles of 

North America north of Mexico, with comments regarding confidence in our 

understanding. Herpetological Circular 37. Society for the Study of Amphibians 

and Reptiles. 84 p. 

Crump, M.L. 1990. Possible enhancement of growth in tadpoles through 

cannibalism. Copeia. 1990: 560–564. 

Cunningham, A.A.; Langton, T.E.S.; Bennett, P.M.; Lewin, J.F.; Drury, S.E.; 

Gough, R.E.; MacGregor, S.K. 1996. Pathological and microbiological findings 

from incidents of unusual mortality of the common frog (Rana temporaria). 

Philosophical Transactions of the Royal Society of London B. 351: 1529–1557. 

Cushman, S.A. 2006. Effects of habitat loss and fragmentation on amphibians: a 

review and prospectus. Biological Conservation. 128: 231–240. 

Dale, D.; Weaver, T. 1974. Trampling effects on vegetation of the trail corridors of 

North Rocky Mountain forests. Journal of Applied Ecology. 11: 767–772. 

Datta, S.; Hansen, L.; McConnell, L.; Baker, J.; Lenoir, J.; Seiber, J.N. 1998. 

Pesticides and PCB contaminants in fish and tadpoles from the Kaweah River 

basin, California. Bulletin of Environmental Contamination and Toxicology. 

60: 829–836. 

Davidson, C. 1995. Frog and toad calls of the Pacific Coast. [CD-Audio]. Ithaca, 

NY: Cornell Laboratory of Ornithology. 
68 

GENERAL TECHNICAL REPORT PSW-GTR-248

Davidson, C. 2004. Declining downwind: amphibian population declines in 

California and historical pesticide use. Ecological Applications. 14: 1892–1902. 

Davidson, C.; Benard, M.F.; Shaffer, H.B.; Parker, J.M.; O’Leary, C.; Conlon, 

J.M.; Rollins-Smith, L.A. 2007. Effects of chytrid and carbaryl exposure 

on survival, growth and skin peptide defenses in foothill yellow-legged frogs. 

Environmental Science and Technology. 41: 1771–1776. 

Davidson, C.; Shaffer, H.B.; Jennings, M.R. 2002. Spatial tests of the pesticide 

drift, habitat destruction, UV-B and climate-change hypotheses for California 

amphibian declines. Conservation Biology. 16: 1588–1601. 

Deanovic, L.; Connor, V.M.; Knight, A.W.; Maier, K.J. 1999. The use of 

bioassays and toxicity identification evaluation (TIE) procedures to assess 

recovery and effectiveness of remedial activities in a mine drainage-impacted 

stream system. Archives of Environmental Contamination and Toxicology. 

36: 21–27. 

DeMaynadier, P.G.; Hunter, M.L. 2000. Road effects on amphibian movements 

in a forested landscape. Natural Areas Journal. 20: 56–65. 

Dever, J.A. 2007. Fine-scale genetic structure in the threatened foothill yellowlegged frog. Journal of Herpetology. 41: 168–173. 

Devine Tarbell & Associates, Inc.; Stillwater Sciences. 2005. Amphibians 

and aquatic reptiles. Technical Report. Upper American River Project (FERC 

Project No. 2101) and Chili Bar Project (FERC Project No. 2155). Sacramento, 

CA: Sacramento Municipal Utility District; San Francisco, CA: Pacific Gas and 

Electric Company. 115 p. http://hydrorelicensing.smud.org/docs/reports/amphib_ 

aqu_reptiles/Amphibians_Reptiles.pdf. (14 August 2014). 

Dill, W.A.; Cordone, A.J. 1997. History and status of introduced fishes in 

California, 1871–1996. Fish Bulletin. 178: 1–414. 

Drost, C.A.; Fellers, G.M. 1994. Decline of frog species in the Yosemite section 

of the Sierra Nevada. Tech. Rep. NPS/WRUC/NRTR 94-02 [UC CPSU TR #56]. 

Davis, CA: University of California–Davis, Cooperative National Park Studies 

Unit. 56 p. 

Drost, C.A.; Fellers, G.M. 1996. Collapse of a regional frog fauna in the Yosemite 

area of the California Sierra Nevada, USA. Conservation Biology. 10: 414–425. 
69 

Foothill Yellow-Legged Frog Conservation Assessment

Edginton, A.N.; Sheridan, P.M.; Stephenson, G.R.; Thompson, D.G.; 

Boermans, H.J. 2004. Comparative effects of pH and Vision® herbicide on two 

life stages of four anuran amphibian species. Environmental Toxicology and 

Chemistry. 23: 815–822. 

Fahrig, L.; Pedlar, J.H.; Pope, S.E.; Taylor, P.D.; Wenger, J.F. 1995. Effect of 

road traffic on amphibian density. Biological Conservation. 73: 177–182. 

Fellers, G.M. 2005. Rana boylii Baird, 1854: foothill yellow-legged frog. In: 

Lannoo, M., ed. Amphibian declines: the conservation status of United States 

species. Berkeley, CA: University of California Press: 534–536. 

Fellers, G.M.; Drost, C.A. 1993. Disappearance of the Cascades frog Rana 

cascadae at the southern end of its range, California, USA. Biological 

Conservation. 65: 177–181. 

Fellers, G.M.; McConnell, L.L.; Pratt, D.; Datta, S. 2004. Pesticides in mountain 

yellow-legged frogs (Rana muscosa) from the Sierra Nevada Mountains of 

California, USA. Environmental Toxicology and Chemistry. 23(9): 2170–2177. 

Fidenci, P. 2006. Rana boylii (foothill yellow-legged frog). Predation. 

Herpetological Review. 37: 208. 

Fijan, N.; Matasin, Z.; Petrinec, Z.; Valpotic, I.; Zwillenberg, L.O. 1991. 

Isolation of an iridovirus-like agent from the green frog (Rana esculenta L).
 

Veterinare Arhiv [Zagreb]. 61: 151–158.
 

Fisher, R.N.; Shaffer, H.B. 1996. The decline of amphibians in California’s Great 

Central Valley. Conservation Biology. 10: 1387–1397. 

Fitch, H.S. 1936. Amphibians and reptiles of the Rogue River basin, Oregon. 

American Midland Naturalist. 17: 634–652. 

Fitch, H.S. 1938. Rana boylii in Oregon. Copeia. 1938: 148. 

Fitch, H.S. 1940. A biogeographical study of the ordinoides Artenkreis of garter 

snakes (genus Thamnophis). University of California Publications in Zoology. 

44: 1–150. 

Fitch, H.S. 1941. The feeding habits of California garter snakes. California Fish 

and Game. 27: 1–32. 

Fite, K.V.; Blaustein, A.R.; Bengston, L.; Hewitt, H.E. 1998. Incidence of retinal 

light damage in Rana cascadae: a declining amphibian species. Copeia. 1998: 

906–914. 
70 

GENERAL TECHNICAL REPORT PSW-GTR-248

Folmar, L.C.; Sanders, H.O.; Julin, A.M. 1979. Toxicity of the herbicide 

glyphosate and several of its formulations to fish and aquatic invertebrates. 

Archives of Environmental Contamination and Toxicology. 8: 269–278. 

Forman, R.T.T.; Alexander, L.E. 1998. Roads and their major ecological effects. 

Annual Review of Ecology and Systematics. 29: 207–231. 

Freda, J. 1990. Effects of acidification on amphibians. In: Baker, J.P.; Bernard, 

D.P.; Christensen, S.W.; Sale, M.J.; Freda, J.; Heltcher, K.J.; Markmorek, D.R.; 

Rowe, L; Scanlan, P.F.; Suter, G.W. II; Watten-Hicks, W.J.; Welbourne, P.M. 

eds. Biological effects of changes in surface water acid-base chemistry. State of 

Science/Technology Report 13. Washington, DC: National Acid Precipitation 

Assessment Program: 114–129. 

Freda, J. 1991. The effects of aluminum and other metals on amphibians. 

Environmental Pollution. 71: 305–328. 

Fuller, D.D.; Lind, A.J. 1992. Implications of fish habitat improvement structures 

for other stream vertebrates. In: Harris, R.R.; Erman, D.C., tech. coords.; 

Kerner, H.M., ed. Proceedings of the symposium on biodiversity of northwestern 

California. Berkeley, CA: University of California, Wildland Resources Center, 

Division of Agriculture and Natural Resources: 96–104. 

Fuller, T.E.; Pope, K.L.; Ashton, D.T.; Welsh, H.H., Jr. 2011. Linking the 

distribution of an invasive amphibian (Rana catesbeiana) to habitat conditions in a 

managed river system in northern California. Restoration Ecology. 19: 204–213. 

Furey, P.C.; Kupferberg, S.J.; Lind, A.J. 2014. The perils of unpalatable 

periphyton: Didymosphenia and other mucilaginous stalked diatoms as 

food for tadpoles. Diatom Research. 29: 267–280. 

Gaikowski, M.P.; Hamilton, S.J.; Buhl, K.J.; McDonald, S.F.; Summers, 

C.H. 1996. Acute toxicity of three fire-retardant and two fire-suppressant 

foam formulations to the early stages of rainbow trout (Oncorhynchus mykiss). 

Environmental Toxicology and Chemistry. 15: 1365–1374. 

Gamradt, S.C.; Kats, L.B. 1996. Effect of introduced crayfish and mosquitofish 

on California newts. Conservation Biology. 10: 1387–1397. 

Garcia and Associates. [GANDA] 2005. Results of 2004 surveys and monitoring 

for foothill yellow-legged frogs (Rana boylii) within the Rock Creek-Cresta 

project area, North Fork Feather River and 2002-2004 recreation and pulse 

flow biological evaluation summary. San Ramon, CA: Pacific Gas and Electric 

Company; Job 332/80. 89 p. 
71 

Foothill Yellow-Legged Frog Conservation Assessment

Garcia and Associates [GANDA]. 2006. Evaluating the impacts of manufactured 

recreation streamflows on the macroinvertebrate community of a regulated river. 

CEC‐500‐2006‐078. Sacramento, CA: California Energy Commission, Public 

Interest Energy Research Program. 55 p. 

Garcia and Associates (GANDA). 2008, 2015 . Personal communication. 

1 Saunders Ave., San Anselmo, CA 94960. 

Garcia and Associates [GANDA]. 2008. Identifying microclimatic and water 

flow triggers associated with breeding activities of a foothill yellow‐legged 

frog (Rana boylii) population on the North Fork Feather River, California. 

CEC‐500‐2007‐041. Sacramento, CA: California Energy Commission, Public 

Interest Energy Research Program. 59 p. 

Garton, E.O.; Foin, T.C.; Bowen, C.W.; Everingham, J.M.; Schultz, R.O.; 

Holton, B., Jr. 1977. Quantitative studies of visitor impacts on environments 

of Yosemite National Park, California, USA and their implications for park 

management policy. Journal of Environmental Management. 5: 1–22. 

Giesy, J.P.; Dobson, S.; Solomon, K.R. 2000. Ecotoxicological risk assessment of 

Roundup® herbicide. Reviews of Environmental Contamination and Toxicology. 

167: 35–120. 

Gonsolin, E. 2006. Personal communication. Senior staff biologist, Cardno 

ENTRIX, 5415 SW Westgate Drive, Suite 100, Portland, OR 97221. 

Gonsolin, T.E. 2010. Ecology of foothill yellow-legged frogs in upper Coyote 

Creek, Santa Clara County, CA. San Jose, CA: State University of California. 

119 p. M.S. thesis. 

Gosner, K.L. 1960. A simplified table for staging anuran embryos and larvae with 

notes on identification. Herpetologica. 16: 183–190. 

Green, D.E.; Converse, K.A.; Schrader, A.K. 2002. Epi-zootiology of sixty-four 

amphibian morbidity and mortality events in the USA, 1996-2001. Annals of the 

New York Academy Sciences. 969: 323–329. 

Green, D.M.; Kauffman, J.B. 1995. Succession and livestock grazing in 

a northeast Oregon riparian ecosystem. Journal of Range Management. 

48: 307–313. 
72 

GENERAL TECHNICAL REPORT PSW-GTR-248

Grinnell, J.J.; Dixon, J.; Linsdale, J.M. 1930. Vertebrate natural history of a 

section of northern California through the Lassen Peak region. Berkeley, CA: 

University of California Press. 594 p. 

Grinnell, J.J.; Storer, T.I.; 1924. Animal life in the Yosemite. Berkeley, CA: 

University of California Press. 669 p. 

Guan, R.-Z.; Wiles, P.R. 1997. Ecological impact of crayfish on benthic fishes in a 

British lowland river. Conservation Biology. 11: 641–647. 

Haggarty, M. 2006. Habitat differentiation and resource use among different age 

classes of post-metamorphic Rana boylii on Red Bank Creek, Tehama County, 

California. Arcata, CA: Humboldt State University. 56 p. M.S. thesis 

Hall, R.J.; Langtimm, C.A. 2001. The US National Amphibian Research and 

Monitoring Initiative and the role of protected areas. George Wright Forum. 

18(2): 14–25. 

Hansen, B.; Nieber, J.; Johnson, S.; Marr, J. 2011. Performance assessment 

of oversized culverts to accommodate fish passage. St. Paul, MN: Minnesota 

Department of Transportation; final report. 39 p. 

Harvey, B.C. 1986. Effects of suction gold dredging on fish and invertebrates 

in two California streams. North American Journal of Fisheries Management. 

6: 401–409. 

Harvey, B.C.; Lisle, T.E. 1998. Effects of suction dredging on streams: a review 

and an evaluation strategy. Fisheries. 23: 8–17. 

Hatch, A.C.; Blaustein, A.R. 2000. Combined effects of UV-B, nitrate, and 

low pH reduce the survival and activity level of tadpole Cascades frogs (Rana 

cascadae). Archives Environmental Contamination and Toxicology. 39: 494–499. 

Hax, C.L.; Golladay, S.W. 1998. Flow disturbance of macroinvertebrates 

inhabiting sediments and woody debris in a prairie stream. American Midland 

Naturalist. 139: 210–233. 

Hayes, M.P.; Jennings, M.R. 1986. Decline of ranid frog species in western North 

America: Are bullfrogs (Rana catesbeiana) responsible? Journal of Herpetology. 

20: 490–509. 
73 

Foothill Yellow-Legged Frog Conservation Assessment

Hayes, M.P.; Jennings, M.R. 1988. Habitat correlates of the distribution of 

California red-legged frog (Rana aurora draytonii) and foothill yellow-legged 

frog (Rana boylii): implications for management. In: Szaro, R.C.; Severson, K.E.; 

Patton, D.R., tech. coords. Proceedings of a symposium on the management of 

amphibians, reptiles, and small mammals in North America, Gen. Tech. Rep. 

RM-GTR-166. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, 

Rocky Mountain Forest and Range Experiment Station: 144–158. 

Hayes, T.B.; Case, P.; Chui, S.; Chung, D.; Haeffele, C.; Haston, K.; Lee, 

M.; Mai, V.P.; Marjuoa, Y.; Parker, J.; Tsui, M. 2006. Pesticide mixtures, 

endocrine disruption, and amphibian declines: Are we underestimating the 

impact? Environmental Health Perspectives. 114 (Suppl. 1): 40–50. 

Hildebrand, L.D.; Sullivan, D.S.; Sullivan, T.P. 1982. Experimental studies of 

rainbow trout populations exposed to field applications of Roundup herbicide. 

Archives of Environmental Contamination and Toxicology. 11: 93–98. 

Hill, K. 2002. Personal communication. Environmental program manager, 

California Department of Fish and Wildlife, 1701 Nimbus Road, Suite A, 

Rancho Cordova, CA 95670. 

Hine, R.L.; Les, B.L.; Hellmich, B.F. 1981. Leopard frog populations and 

mortality in Wisconsin, 1974-76. Technical Bulletin 122. Madison, WI: 

Department of Natural Resources. 39 p. 

Hitchcock, C.J. 2001. The status and distribution of the northern leopard frog 

(Rana pipiens) in Nevada. Reno, NV: University of Nevada. 114 p. M.S. thesis. 

Hogg, I.D.; Williams, D.D. 1996. Response of stream invertebrates to a 

global-warming thermal regime: an ecosystem level manipulation. Ecology. 

77: 395–408. 

Hothem, R.L.; Jennings, M.R.; Crayon, J.J. 2010. Mercury contamination in 

three species of anuran amphibians from the Cache Creek watershed, California, 

USA. Environmental Monitoring and Assessment. 163: 433–448. 

Howard, R.D. 1978. The evolution of mating strategies in bullfrogs, Rana 

catesbeiana. Evolution. 32: 850–871. 

Howe, C.M.; Berrill, M.; Pauli, B.D.; Helbring, C.C.; Werry, K.; Veldhoen, 

N. 2004. Toxicity of glyphosate-cased pesticides to four North American frog 

species. Environmental Toxicology and Chemistry. 23: 1928–1938. 

Hynes, H.N.B. 1970. The ecology of running waters. Toronto, ON: University of 

Toronto Press. 510 p. 
74

GENERAL TECHNICAL REPORT PSW-GTR-248

Ingles, L.G.; Langston, C.I. 1933. A new species of bladder fluke from California 

frogs. Transactions of the American Microscopical Society. 52: 243–246. 

Jansen, A.; Healey, M. 2003. Frog communities and wetland condition: 

relationships with grazing by domestic livestock along an Australian floodplain 

river. Biological Conservation. 109: 207–219. 

Jennings, M.R. 1982. Geographic distribution: Rana boylii [sic] (foothill yellowlegged frog). Herpetological Review. 13: 51. 

Jennings, M.R. 1987. A biography of Dr. Charles Elisha Boyle, with notes on his 

19th century natural history collection from California. Wasmann Journal of 

Biology. 45(1–2): 59–68. 

Jennings, M.R. 1988. Natural history and decline of native ranids in California. 

In: DeLisle, H.P.; Brown, P.R.; Kaufman, B.; McGurty, B.M., eds. Proceedings 

of the conference on California herpetology. Van Nuys, CA: Southwestern 

Herpetologists Society: 61–72. 

Jennings, M.R. 1990. Personal observation. Senior associate ecologist and 

herpetologist, Live Oak Associates, Inc., 6840 Via Del Oro, Suite 220, San Jose, 

CA 95119. 

Jennings, M.R. 1995. Native ranids in California. In: LaRoe, E.T.; Farris, G.S.; 

Puckett, C.E.; Doran, P.D.; Mac, M.J., eds. Our living resources: report to 

the nation on the distribution, abundance, and health of U.S. plants, animals 

and ecosystems. Washington, DC: U.S. Department of the Interior, National 

Biological Service: 131–134. 

Jennings, M.R. 1996. Status of amphibians. In: SNEP Science Team, eds. Sierra 

Nevada ecosystem project: final report to Congress. Vol. II: Assessments and 

scientific basis for management options. Report No. 37. Davis, CA: Centers 

for Water and Wildland Resources, University of California–Davis: 921–944. 

Chapter 31. 

Jennings, M.R. 2003. Annotated check list of the amphibians and reptiles of 

California, third revised edition. California Fish and Game. (3): 1–48. 

Jennings, M.R. 2006. Personal communication. Senior associate ecologist and 

herpetologist Live Oak Associates, Inc., 6840 Via Del Oro, Suite 220, San Jose, 

CA 95119. 

Jennings, M.R.; Hayes, M.P. 1994. Amphibian and reptile species of special 

concern in California. Rancho Cordova, CA: California Department of Fish 

and Game. 255 p. 
75 

Foothill Yellow-Legged Frog Conservation Assessment

Johnson, P.T.; Lunde, K.B.; Ritchie, E.G.; Launer, A.E. 1999. The effect of 

trematode infection on amphibian limb development and survivorship. Science. 

284: 802–804. 

Johnson, T.; Dozier, J.; Michaelsen, J. 1999. Climate change and Sierra Nevada 

snowpack. IAHS Publication. 256: 63–70. 

Jones, J.A.; Swanson, F.A.; Wemple, B.C.; Snyder, K.U. 2000. Effects of roads 

on hydrology, geomorphology, and disturbance patches in stream networks. 

Conservation Biology. 14: 1523–1739. 

Jones, L.L.C.; Olson, D.H.; Leonard, W.P., eds. 2005. Amphibians of the Pacific 

Northwest. Seattle, WA: Seattle Audubon Society. 168 p. 

Kagarise-Sherman, C.; Morton, M.L. 1993. Population declines of Yosemite 

toads in the eastern Sierra Nevada of California. Journal of Herpetology. 

27: 186–198. 

Kattelmann, R. 1996. Hydrology and water resources. In: SNEP Science 

Team, eds. Sierra Nevada ecosystem project: final report to Congress. Vol. II: 

Assessments and scientific basis for management options. Report No. 37. Davis, 

CA: Centers for Water and Wildland Resources, University of California–Davis: 

855–820. Chapter 30. 

Kauffman, J.B.; Krueger, W.C. 1984. Livestock impacts on riparian ecosystems 

and streambank management implications: a review. Journal of Range 

Management. 37: 430–437. 

Kauffman, J.B.; Krueger, W.C.; Vavra, M. 1983a. Effects of late season 

cattle grazing on riparian plant communities. Journal of Range Management. 

36: 685–691. 

Kauffman, J.B.; Krueger, W.C.; Vavra, M. 1983b. Impacts of cattle on 

streambanks in northeastern Oregon. Journal of Range Management. 

36: 683–685. 

Kiesecker, J.M.; Blaustein, A.R. 1995. Synergism between UV-B radiation and 

a pathogen magnifies embryo mortality in nature. Proceedings of the National 

Academy of Science. 92: 11049–11052. 

Kiesecker, J.M.; Blaustein, A.R. 1997a. Influences of egg laying behavior on 

pathogenic infection of amphibian eggs. Conservation Biology. 11: 214–220. 

Kiesecker, J.M.; Blaustein, A.R. 1997b. Population differences in responses of 

red-legged frogs (Rana aurora) to introduced bullfrogs. Ecology. 78: 1752–1760. 
76 

GENERAL TECHNICAL REPORT PSW-GTR-248

 

 

Kiesecker, J.M.; Blaustein, A.R. 1998. Effects of introduced bullfrogs and 

smallmouth bass on microhabitat use, growth, and survival of native red-legged 

frogs (Rana aurora). Conservation Biology. 12: 776–787. 

Kiesecker, J.M.; Blaustein, A.R.; Miller, C.L. 2001. Transfer of a pathogen from 

fish to amphibians. Conservation Biology. 15: 1064–1070. 

King County. 2012. Noxious weeds. King County, Washington. http://www. 

kingcounty.gov/environment/animalsAndPlants/noxious-weeds/weedidentification/butterfly-bush.aspx. [17 April 2014]. 

Kirkwood, A.E.; Jackson, L.J.; McCauley, E. 2009. Are dams hotspots for 

Didymosphenia geminata blooms? Freshwater Biology. 54(9): 1856–1863. 

Knight, R.L.; Cole, D.N. 1991. Effects of recreational activity on wildlife in 

wildlands. Transactions of the 56th North American Wildlife and Natural 

Resources Conference. 56: 238–247. 

Knutson, M.G.; Richardson, W.B.; Reineke, D.M.; Gray, B.R.; Parmelee, 

J.R.; Weick, S.E. 2004. Agricultural ponds support amphibian populations. 

Ecological Applications. 14: 669–684. 

Koo, M.S.; Vindum, J.V. 1999. Amphibians and reptiles of the Plumas National 

Forest: historical collections and California Academy of Sciences 1998 and 1999 

surveys. San Francisco, CA: Department of Herpetology, California Academy of 

Sciences. 18 p. 

Kondolf, G.M.; Kattelman, R.; Embury, M.; Erman, D.C. 1996. Status 

of riparian habitat. In: SNEP Science Team, eds. Sierra Nevada ecosystem 

project: final report to Congress. Vol. II: Assessments and scientific basis for 

management options. Report No. 37. Davis, CA: Centers for Water and Wildland 

Resources, University of California–Davis: 1009–1030. 

Kreutzweiser, D.P.; Thompson, D.G.; Capell, S.S.; Thomas, D.R.; Staznik, 

B. 1995. Field evaluation of triclopyr ester toxicity to fish. Archives of 

Environmental Contamination and Toxicology. 28: 18–26. 

Kumar, S.; Spaulding, S.A.; Stohlgren, T.J.; Hermann, K.A.; Schmidt, T.S.; 

Bahls, L.L. 2009. Potential habitat distribution for the freshwater diatom 

Didymosphenia geminata in the continental US. Frontiers in Ecology and the 

Environment. 7(8): 415–420. 

Kupferberg, S.J. 1996a. Hydrologic and geomorphic factors affecting conservation 

of a river-breeding frog (Rana boylii). Ecological Applications. 6: 1332–1344. 
77 

Foothill Yellow-Legged Frog Conservation Assessment

Kupferberg, S.J. 1996b. The ecology of native tadpoles (Rana boylii and 

Hyla regilla) and the impacts of invading bullfrogs (Rana catesbeiana) in a 

northern California river. Berkeley, CA: University of California. 289 p. Ph.D. 

dissertation. 

Kupferberg, S.J. 1997a. Bullfrog (Rana catesbeiana) invasion of a California 

river: the role of tadpole competition. Ecology. 78: 1736–1751. 

Kupferberg, S.J. 1997b. The role of tadpole diet in anuran metamorphosis. 

American Zoologist. 37: 146–159. 

Kupferberg, S.J. 2012. Personal communication. Stream ecologist/amphibian 

biologist, Questa Engineering. 1220 Brickyard Cove Road, Suite 206, Pt. 

Richmond, CA 94807 

Kupferberg, S.J.; Catenazzi, A.; Lunde, K.; Lind, A.J.; Palen, W.J. 2009a. 

Parasitic copepod (Lernea cyprinacea) outbreaks in foothill yellow-legged frogs 

(Rana boylii) linked to unusually warm summers and amphibian malformations 

in northern California. Copeia. 2009: 529–537. 

Kupferberg, S.J.; Catenazzi, A.; Power, M.E. 2011a. The importance of water 

temperature and algal assemblage for frog conservation in northern california 

rivers with hydroelectric projects. CEC-500-2014-033. Sacramento, CA: 

California Energy Commission, Public Interest Energy Research Program. 96 p. 

Kupferberg, S.; Lind, A.; Yarnell, S.; Mount, J. 2008. Pulsed flow effects on the 

foothill yellow-legged frog (Rana boylii): integration of empirical, experimental 

and hydrodynamic modeling approaches. CEC-500-2009-002. Sacramento, CA: 

California Energy Commission, Public Interest Energy Research Program. 194 p. 

Kupferberg, S.; Lind, A.; Palen, W. 2009b. Pulsed flow effects on the foothill 

yellow-legged frog (Rana boylii): population modeling. Sacramento, CA: 

California Energy Commission. 80 p. 

Kupferberg, S.; Lind, A.J.; Thill, V.; Yarnell, S.M. 2011b. Water velocity 

tolerance in tadpoles of the foothill yellow-legged frog (Rana boylii): swimming 

performance, growth, and survival. Copeia. 2011(1): 141–152. 

Kupferberg, S.J.; Palen, W.J.; Lind, A.J.; Bobzien, S.; Catenazzi, A.; Drennan, 

J.; Power, M.E. 2012. Effects of flow regimes altered by dams on survival, 

population declines, and range-wide losses of California river-breeding frogs. 

Conservation Biology. 26: 513–524. 

Laird, L.B.; Taylor, H.E.; Kennedy, V.C. 1986. Snow chemistry of the CascadeSierra Nevada Mountains. Environmental Science and Technology. 20: 275–290. 
78 

GENERAL TECHNICAL REPORT PSW-GTR-248

Landers, D.H.; Eilers, J.M.; Brakke, D.F.; Overton, W.S.; Kellar, P.E.; 

Silverstein, M.E.; Schonbrod, R.D.; Crowe, R.E.; Lindhurst, R.A.; 

Omernik, J.M.; Teague, S.A.; Meier, E.P. 1987. Characteristics of lakes in 

the western United States. I: Population descriptions and physico-chemical 

relationships. EPA/600/3-86/054a. Washington, DC: U.S. Environmental 

Protection Agency. 176 p. 

Larson, D.J. 1996. Historical water-use priorities and public policies. In: SNEP 

Science Team, eds. Sierra Nevada ecosystem project: final report to Congress. 

Vol. II: Assessments and scientific basis for management options. Report No. 37. 

Davis, CA: Centers for Water and Wildland Resources, University of California– 

Davis: 163–185. Chapter 8. 

Lawrence, L. de K. 1973. The gray jays. Hinterland Bulletin. Ottawa, ON: 

Canadian Wildlife Service. [Pages unknown.] 

Lefcort, H.; Hancock, K.A.; Maur, K.M.; Rostal, D.C. 1997. The effects of used 

motor oil, silt and the water mold Saprolegnia parasitica on the growth and 

survival of mole salamanders (genus Ambystoma). Archives of Environmental 

Contamination and Toxicology. 32: 383–388. 

Lehtinen, R.M.; Galatowitsch, S.M.; Tester, J.R. 1999. Consequences of habitat 

loss and fragmentation for wetland amphibian assemblages. Wetlands. 19: 1–12. 

Leidy, R.A.; Gonsolin, E.; Leidy, G.A. 2009. Late-summer aggregation of the 

foothill yellow-legged frog (Rana boylii) in central California. The Southwestern 

Naturalist. 54(3): 367–368. 

Lenoir, J.S.; McConnell, L.L.; Fellers, G.M.; Cahill, T.M.; Seiber, J.N. 1999. 

Summertime transport of current-use pesticides from California’s Central Valley 

to the Sierra Nevada mountain range, USA. Environmental Toxicology and 

Chemistry. 18: 2715–2722. 

Leong, T.M. 2001. Parasitic copepods responsible for limb abnormalities. 

Froglog. 46: 3. 

Leviton, A.E.; Gibbs, R.H., Jr. 1988. Standards in herpetology and ichthyology. 

Standard symbolic codes for institutional resource collections in herpetology and 

ichthyology. Suppl. no. 1: additions and corrections. Copeia. 280−282. 

Leviton, A.E.; Gibbs, R.H., Jr.; Heal, E.; Dawson, C.E. 1985. Standards in 

herpetology and ichthyology: part I. Standard symbolic codes for institutional 

resource collections in herpetology and ichthyology. Copeia. 802–832. 
79 

Foothill Yellow-Legged Frog Conservation Assessment

Licht, L.E. 1974. Survival of embryos, tadpoles, and adults of the frogs Rana 

aurora aurora and Rana pretiosa pretiosa sympatric in southwestern British 

Columbia. Canadian Journal of Zoology. 52: 613–627. 

Licht, L.E. 1996. Amphibian decline still a puzzle. BioScience. 46: 172–173. 

Licht, L.E. 2003. Shedding light on ultraviolet radiation and amphibian embryos. 

BioScience. 53: 551–561. 

Licht, L.E.; Grant, K.P. 1997. The effects of ultraviolet radiation on the biology of 

amphibians. American Zoologist. 37: 137–145. 

Light, T. 2003. Success and failure in a lotic crayfish invasion: the roles of 

hydrologic variability and habitat alteration. Freshwater Biology. 48: 1886–1897. 

Ligon, F.R.; Dietrich, W.E.; Trush, W.J. 1995. Downstream ecological effects of 

dams: a geomorphic perspective. Bioscience. 45: 183–192. 

Lind, A.J. 2005. Reintroduction of a declining amphibian: determining an 

ecologically feasible approach for the foothill yellow-legged frog (Rana boylii) 

through analysis of decline factors, genetic structure, and habitat associations. 

Davis, CA: University of California. 169 p. Ph.D. dissertation. 

Lind, A.J.; Bettaso, J.B.; Yarnell, S.M. 2003a. Rana boylii (foothill yellow-legged 

frog). Reproductive behavior. Herpetological Review. 34: 234–235. 

Lind, A.J.; Conway, L.; Sanders, H.E.; Strand, P.; Tharalson, T. 2003b. 

Distribution, relative abundance, and habitat of foothill yellow-legged frogs 

(Rana boylii) on national forests in the Southern Sierra Nevada Mountains of 

California. Vallejo, CA: U.S. Department of Agriculture, Forest Service, Pacific 

Southwest Region. 30 p. 

Lind, A.J.; Spinks, P.Q.; Fellers, G.M.; Shaffer, H.B. 2011. Rangewide 

phylogeography and landscape genetics of the Western US endemic frog 

Rana boylii (Ranidae): implications for the conservation of frogs and rivers. 

Conservation Genetics. 12(1): 269–284. 

Lind, A.J.; Welsh, H.H., Jr. 1994. Ontogenetic changes in foraging behaviour and 

habitat use by the Oregon garter snake, Thamnophis atratus hydrophilus. Animal 

Behaviour. 48: 1261–1273. 

Lind, A.J.; Welsh, H.H., Jr.; Wilson, R.A. 1996. The effects of a dam on 

breeding habitat and egg survival of the foothill yellow-legged frog (Rana boylii) 

in northwestern California. Herpetological Review. 27: 62–67. 
80 

GENERAL TECHNICAL REPORT PSW-GTR-248

Lips, K.R.; Mendelson, J.R., III; Munoz-Alonso, A.; Canseco-Marquez, L.; 

Mulcahy, D.G. 2004. Amphibian population declines in montane southern 

Mexico: resurveys of historical localities. Biological Conservation. 119: 555–564. 

Livezey, R.L. 1962. Distribution of some California amphibians and reptiles. 

Herpetologica. 18: 279–281. 

Long, L.E.; Saylor, L.S.; Soulé, M.E. 1995. A pH/UV-B synergism in 

amphibians. Conservation Biology. 9: 1301–1303. 

Longcore, J.E.; Pessier, A.P.; Nichols, D.K. 1999. Batrachochytrium 

dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia. 

91: 219–227. 

Loomis, R.B. 1965. The yellow-legged frog, Rana boylii, from the Sierra San Pedro 

Martir, Baja California Norte, Mexico. Herpetologica. 21: 78–80. 

Lovich, J.E.; DeGouvenain, R.C. 1998. Saltcedar invasion in desert wetlands 

of the southwestern United States: ecological and political implications. In: 

Majumdar, S.K., ed. Ecology of wetlands and associated systems. Philadelphia, 

PA: Pennsylvania Academy of Science: 447–467. 

Lowe, J. 2009. Amphibian chytrid (Batrachochytrium dendrobatidis) in postmetamorphic Rana boylii in the inner coast ranges of central California. 

Herpetological Review. 40: 180–182. 

Ludke, J.L.; Hill, E.F.; Dieter, M.P. 1975. Cholinesterase (ChE) response and 

related mortality among birds fed ChE inhibitors. Archives of Environmental 

Contamination and Toxicology. 3: 1–21. 

Macey, J.R.; Strasburg, J.; Brisson, J.; Vredenburg, V.; Jennings, M.; Larson, 

A. 2001. Molecular phylogenetics of western North American frogs of the Rana 

boylii species group. Molecular Phylogenetics in Evolution. 19: 131–143. 

MacTague, L.; Northen, P.T. 1993. Underwater vocalization by the foothill yellowlegged frog (Rana boylii). Transactions of the Western Section of the Wildlife 

Society. 29: 1–7. 

Maerz, J.C.; Blossey, B.; Nuzzo, V. 2005a. Green frogs show reduced 

foraging success in habitats invaded by Japanese knotweed. Biodiversity and 

Conservation. 14: 2901–2911. 

Maerz, J.C.; Brown, C.J.; Chapin, C.T.; Blossey, B. 2005b. Can secondary 

compounds of an invasive plant affect tadpole amphibians? Functional 

Ecology. 19: 970. 
81 

Foothill Yellow-Legged Frog Conservation Assessment

Mahaney, P.A. 1994. The effects of freshwater petroleum contamination on 

amphibian hatching and metamorphosis. Environmental Toxicology. 13: 

259–265. 

Mann, R.M.; Bidwell, J.R. 1999. The toxicity of glyphosate and several 

glyphosate formulations to four species of southwestern Australian frogs. 

Archives of Environmental Contamination and Toxicology. 26: 193–199. 

Mao, J.; Green, D.E.; Fellers, G.F.; Chinchar, V.G. 1999. Molecular 

characterization of iridoviruses isolated from sympatric amphibians and fish. 

Virus Research. 63: 45–52. 

Martin, D.L. 1992. Sierra Nevada anuran survey: an investigation of amphibian 

population abundance in the national forests of the Sierra Nevada of California. 

Vallejo, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest 

Region. 76 p. 

Maurer, E.P.; Stewart, I.T.; Bonfils, C.; Duffy, P.B.; Cayan, D. 2007. Detection, 

attribution, and sensitivity of trends toward earlier streamflow in the Sierra 

Nevada. Journal of Geophysical Research—Atmospheres. 112: 12. 

Maxell, B.A.; Hokit, D.G. 1999. Amphibians and reptiles. In: Joslin, J.; Youmans, 

H., committee chairs. Effects of recreation on Rocky Mountain wildlife: a 

compendium of the current state of understanding in Montana. Committee on 

Effects of Recreation on Wildlife, Montana Chapter of the Wildlife Society: 

2.1–2.30. 

McBain and Trush, Inc. 2009. Pulsed flow guidelines: managing the annual 

snowmelt hydrograph and winter floods in regulated boulder‐bedrock Sierra 

Nevada rivers. CEC‐500‐2008‐050. Sacramento, CA: California Energy Commission, Public Interest Energy Research Program. 162 p. http://www.energy. 

ca.gov/2008publications/CEC-500-2008-050/CEC-500-2008-050.pdf. 

(11 April 2014). 

McCarthy, M.A.; Parris, K.M. 2004. Clarifying the effects of toe clipping on 

frogs with Bayesian statistics. Journal of Applied Ecology. 41: 780–786. 

McConnell, L.L.; Lenoir, J.S.; Datta, S.; Seiber, J.N. 1998. Wet deposition of 

current-use pesticides in the Sierra Nevada mountain range, California, USA. 

Environmental Toxicology and Chemistry. 17: 1908–1916. 

McDonald, S.F.; Hamilton, S.J.; Buhl, K.J.; Heisinger, J.F. 1996. Acute 

toxicity of fire control chemicals to Daphnia magna (Straus) and Selenastrum 

capricornutum (Printz). Ecotoxicology and Environmental Safety. 33: 62–72. 
82 

GENERAL TECHNICAL REPORT PSW-GTR-248

McGriff, D. 1982. The crayfish of California. Inland fisheries informational leaflet 

No. 1. Sacramento, CA: California Department of Fish and Game. 12 p. 

Megahan, W.F.; King, J.G.; Seyedbagheri, K.A. 1995. Hydrologic and erosional 

responses of a granitic watershed to helicopter logging and broadcast burning. 

Forest Science. 41: 777–795. 

Melack, J.M.; Stoddard, J.L.; Ochs, C.A. 1985. Major ion chemistry and 

sensitivity to acid precipitation of Sierra Nevada lakes. Water Resources 

Research. 21: 27–32. 

Menke, J.W.; Davis, C.; Beesley, P. 1996. Rangeland Assessment. In: SNEP 

Science Team, eds. Sierra Nevada ecosystem project: final report to Congress. 

Vol. III: Assessments, commissioned reports, and background information. 

Report No. 38. Davis, CA: Centers for Water and Wildland Resources, University 

of California–Davis. 901–972. Chapter 22. 

Middleton, E.M.; Herman, J.R.; Celarier, E.A.; Wilkinson, J.W.; Carey, C.; 

Ruskin, R.J. 2001. Evaluating ultraviolet radiation exposure with satellite data 

at sites of amphibian declines in Central and South America. Conservation 

Biology. 15: 914–929. 

Minshall, G.W.; Brock, J.T. 1991. Observed and anticipated effects of forest fire 

on Yellowstone stream ecosystems. In: Keiter, R.B.; Boyce, M.S., eds. Greater 

Yellowstone ecosystem: redefining America’s wilderness heritage. New Haven, 

CT: Yale University Press: 123–135. 

Mitchell, D.; Chapman, P.; Long, T. 1987. Seawater challenge testing of Coho 

salmon smolts following exposure to Roundup herbicide. Environmental 

Toxicology and Chemistry. 6: 875–878. 

Morris, D.P.; Zagarese, H.; Williamson, C.E.; Balseiro, E.G.; Hargreaves, 

B.R.; Modenutti, B.; Moeller, R.; Queimalinos, C. 1995. The attenuation of 

solar UV radiation in lakes and the role of dissolved organic carbon. Limnology 

and Oceanography. 40: 1381–1391. 

Mount, J.F. 1995. California rivers and streams: the conflict between fluvial 

processes and land use. Berkeley, CA: University of California Press. 376 p. 

Moyle, P.B. 1973. Effects of introduced bullfrogs, Rana catesbeiana, on the native 

frogs of the San Joaquin Valley, California. Copeia. 1973: 18–22. 

Moyle, P.B. 2002. Inland fishes of California, revised and expanded. Berkeley, CA: 

University of California Press. 502 p. 
83 

Foothill Yellow-Legged Frog Conservation Assessment

Moyle, P.B.; Randall, P.J. 1998. Evaluating the biotic integrity of watersheds in 

the Sierra Nevada, California. Conservation Biology. 12: 1318–1326. 

Murray, D.L.; Fuller, M.R. 2000. A critical review of the effects of marking on 

the biology of vertebrates. In: Boitani, L.; Fuller, T.K., eds. Research techniques 

in animal ecology: controversies and consequences. New York: Columbia 

University Press: 15–64. Chapter 2. 

Muths, E.; Corn, P.S.; Pessier, A.P.; Green, D.E. 2003. Evidence for diseaserelated amphibian decline in Colorado. Biological Conservation. 110: 357–365. 

Myers, T.J.; Swanson, S. 1991. Aquatic habitat condition index, stream type, 

and livestock bank damage in northern Nevada. Water Research Bulletin. 27: 

667–677. 

Nagl, A.M.; Hofer, R. 1997. Effects of ultraviolet radiation on early tadpole stages 

of the alpine newt, Triturus alpestris, under natural and laboratory conditions. 

Oecologia. 110: 514–519. 

Nelson, S.K.; Hamer, T. 1995. Nest success and the effects of predation on 

marbled murrelets. In: Ralph, C.J.; Hunt, G.L., Jr.; Raphael, M.G.; Piatt, J.F., 

eds. The ecology and conservation of the marbled murrelet in North America: 

An interagency scientific evaluation. Gen. Tech. Rep. PSW-GTR-152. Arcata, 

CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research 

Station: 89–98. 

Neumann, J.R. 1997. Hatching success in relation to UV-B exposure in the eggs 

of the foothill yellow-legged frog. Arcata, CA: Humboldt State University. 14 p. 

B.S. thesis. 

Nevada Irrigation District; Pacific Gas and Electric Company [PG&E]. 

2010. Special-status amphibians, foothill yellow-legged frog surveys. YubaBear Hydroelectric Project (FERC No. 2266-096) and Drum-Spaulding 

Project (FERC No. 2310-173). http://www.eurekasw.com/NID/Technical%20 

Memoranda/2009,%202010%20and%202011%20Technical%20Memoranda/ 

Technical%20Memorandum%2003-06%20-%20Special-Status%20 

Amphibians%20-%20FYLF%20VES/Tech%20Memo%203-6%20-%20 

FYLF%20Surveys.pdf. [Date accessed unknown]. 

Newcombe, C.P.; Jensen, J.O.T. 1996. Channel suspended sediment and fisheries: 

a synthesis for quantitative assessment of risk and impact. North American 

Journal of Fisheries Management. 16: 693–727. 
84 

GENERAL TECHNICAL REPORT PSW-GTR-248

Newcombe, C.P.; MacDonald, D.D. 1991. Effects of suspended sediments on 

aquatic ecosystems. North American Journal of Fisheries Management. 11: 

72–84. 

Niehaus, A.C.; Ruthrauff, D.R.; McCaffery, B.J. 2004. Response of predators to 

western sandpiper nest exclosures. Waterbirds. 27: 79–82. 

Noss, R.F.; Cooperrider, A.Y. 1994. Saving nature’s legacy: protecting and 

restoring biodiversity. Washington, DC: Island Press. 443 p. 

Nussbaum, R.A.; Brodie, E.D., Jr.; Storm, R.M. 1983. Amphibians and reptiles 

of the Pacific Northwest. Moscow, ID: University of Idaho Press. 332 p. 

Obedzinski, R.A.; Shaw, C.G., III; Neary, D.G. 2001. Declining woody vegetation in riparian ecosystems of the western United States. Western Journal of 

Applied Forestry. 16: 169–180. 

Olson, D.H.; Davis, R.J. 2009. Conservation assessment for the foothill yellowlegged frog (Rana boylii) in Oregon. Version 2.0. Portland, OR: U.S. Department 

of Agriculture, Forest Service, Region 6; and U.S. Department of the Interior, 

Bureau of Land Management, Interagency Special Status Species Program. 

http://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-amphibians.shtml. 

(26 January 2015). 

Ovaska, K.; Davis, T.M.; Flamarique, I.N. 1997. Hatching success and 

tadpole survival of the frogs Hyla regilla and Rana aurora under ambient 

and artificially enhanced solar ultraviolet radiation. Canadian Journal of 

Zoology. 75: 1081–1088. 

Pacific Gas and Electric Company [PG&E]. 2004a. Foothill yellow-legged frog 

(Rana boylii) egg mass, tadpole, and habitat surveys in the Pit 4 in 2003, Pacific 

Gas and Electric Company Pit 3, 4, and 5 Hydroelectric Project (FERC No. 233). 

54 p. 

Pacific Gas and Electric Company [PG&E]. 2004b. Results of the 2003 foothill 

yellow-legged frog (Rana boylli) and mountain yellow-legged frog (Rana 

muscosa) studies at Spring Gap–Stanislaus Project. 

Pacific Gas and Electric Company [PG&E]. 2007. DeSabla-Centerville 

Hydroelectric Project (FERC No. 803-068). Supplemental initial study report, 

fifth quarterly progress report, volume II (section 6.3). Filed with the Federal 

Energy Regulatory Commission on 16 January 2007. 
85 

Foothill Yellow-Legged Frog Conservation Assessment

Pacific Gas and Electric Company [PG&E]. 2008. Updated study results 

and license application exhibit E, sections 6.0 and 7.0, De Sabla-Centerville 

Hydroelectric Project (FERC No. 803). http://www.eurekasw.com/DC/ 

relicensing/FERC%20Filing%20%20PGE/2008%20-%200321%202-D%20 

Amphibian%20Model/6.3.2.1%20Aquatics%20-%20Updated%20Mar08.pdf. 

[Date accessed unknown]. 

Pacific Gas and Electric Company [PG&E]; Stillwater Sciences. 2009a. Second 

year foothill yellow-legged frog visual encounter surveys and breeding habitat 

assessment in the lower McCloud River. Tech. memo. 29. San Francisco, CA: 

McCloud-Pit Project, FERC No. 2106. 

Pacific Gas and Electric Company [PGE]; Stillwater Sciences. 2009b. Specialstatus amphibians and aquatic reptiles. Surveys of special-status amphibians 

and aquatic reptiles near project reservoirs and project-affected stream reaches. 

Tech. memo. 09. McCloud-Pit Project, FERC No. 2106. http://www.eurekasw. 

com/MCP/Technical%20Memos/TM-09%20FAS2%20Amphibians%20and%20 

Reptiles%20Updated%20February%202009.pdf. [Date accessed unknown]. 

Pacific Gas and Electric Company [PG&E]. 2010. Results of 2009 surveys for 

foothill yellow-legged frogs on the Cresta and Poe reaches of the North Fork 

Feather River. Prepared by Garcia and Associates for Pacific Gas and Electric 

Company, Technical Project Services. San Ramon, CA. 

Padgett-Flohr, G.E.; Hopkins, R.L., II. 2009. Batrachochytrium dendrobatidis, 

a novel pathogen approaching endemism in central California. Diseases of 

Aquatic Organisms. 83: 1–9. 

Pahkala, M.; Räsänen, K.; Laurila, A.; Johanson, U.; Björn, L.O.; Merilä, 

J. 2002. Lethal and sublethal effects of UV-B/pH synergism on common frog 

embryos. Conservation Biology. 16: 1063–1073. 

Palen, W.J.; Schindler, D.E.; Adams, M.J.; Pearl, C.A.; Bury, R.B.; Diamond, 

S.A. 2002. Optical characteristics of natural waters protect amphibians from 

UV-B in the Pacific Northwest. Ecology. 83: 2951–2957. 

Palen, W.J.; Williamson, C.E.; Clauser, A.A.; Schindler, D.E. 2005. Impact 

of UV-B exposure on amphibian embryos: linking species physiology and 

oviposition behaviour. Proceedings of the Royal Society B: Biological Sciences. 

272: 1227–1234. 
86 

GENERAL TECHNICAL REPORT PSW-GTR-248

Paoletti, D.J.; Olson, D.H.; Blaustein, A.R. 2011. Responses of foothill yellowlegged frog (Rana boylii) larvae to an introduced predator. Copeia. 2011(1): 

161–168.
 

Pearl, C.A.; Hayes, M.P.; Haycock, R.; Engler, J.D.; Bowerman, J. 2005. 

Observation of interspecific amplexus between western North American 

ranid frogs and the introduced American bullfrog (Rana catesbeiana) and an 

hypothesis concerning breeding interference. American Midland Naturalist. 

154: 126–134. 

Peek, R. 2010. Landscape genetics of foothill yellow-legged frogs (Rana boylii) 

in regulated and unregulated rivers: assessing connectivity and genetic 

fragmentation. San Francisco, CA: University of San Francisco. 69 p. M.S. thesis. 

Peek, R. 2014. Personal communication. Aquatic ecologist, Center for Watershed 

Sciences, University of California–Davis, One Shields Ave., Davis, CA 95616. 

Perkins, P.J.; Boermans, H.J.; Stephenson, G.R. 2000. Toxicity of glyphosate 

and triclopyr using the frog embryo teratogenesis assay—Xenopus. 

Environmental Toxicology and Chemistry. 19: 940–945. 

Perret, N.; Joly, P. 2002. Impacts of tattooing and PIT-tagging on survival and 

fecundity in the alpine newt (Triturus alpestris). Herpetologica. 58: 131–138. 

Petts, G.E. 1980. Long-term consequences of upstream impoundment. 

Environmental Conservation. 7: 325–332. 

Petts, G.E. 1984. Impounded rivers: perspectives for ecological management. 

Chichester, United Kingdom: John-Wiley and Sons. 285 p. 

Piasecki, W.; Goodwin, A.E.; Eiras, J.C.; Nowak, B.F. 2004. Importance of 

Copepoda in freshwater aquaculture. Zoological Studies. 43: 193–205. 

Pilliod, D.S.; Bury, R.B.; Hyde, E.J.; Pearl, C.A.; Corn, P.S. 2003. Fire and 

amphibians in North America. Forest Ecology and Management. 178: 163–181. 

Pimm, S.L. 1991. The balance of nature. Chicago, IL: University of Chicago 

Press. 434 p. 

Placer County Water Agency [PCWA]. 2008. AQ 12—Special-status amphibian 

and aquatic reptile technical study report—2007. Middle Fork American River 

Project (FERC No. 2079). Auburn, CA: Placer County Water Agency. http:// 

relicensing.pcwa.net/html/science/padreportaquatic.php. (21 April 2014). 
87 

Foothill Yellow-Legged Frog Conservation Assessment

Placer County Water Agency [PCWA]. 2011. AQ 12—Special-status amphibian 

and aquatic reptile technical study report—2007. Application for new license. 

Middle Fork American River Project (FERC Project No. 2079). Vol. 3, Exhibit 

E, Book 5, Supporting document B. Auburn, CA: Placer County Water Agency. 

http://relicensing.pcwa.net/html/science/padreportaquatic.php. [Date accessed 

unknown]. 

Pough, F.H.; Kamel, S. 1984. Post-metamorphic change in activity metabolism of 

anurans in relation to life history. Oecologia. 65: 138–144. 

Power, M.E. 1990. The importance of sediment in the grazing ecology and size 

class interactions of an armored catfish, Aneistrus spinosus. Environmental 

Biology of Fish. 10: 173–181. 

Price, D.M.; Quinn, T.; Barnard, R.J. 2010. Fish passage effectiveness of 

recently constructed road crossing culverts in the Puget Sound region of 

Washington State. North American Journal of Fisheries Management. 30: 

1110–1125. 

Pringle, C.M.; Naiman, R.J.; Bretschko, G.; Karr, J.R.; Oswood, M.W.; 

Webster, J.R.; Welcomme, R.L.; Winterbourn, M.J. 1988. Patch dynamics 

in lotic systems: the stream as a mosaic. Journal of the North American 

Benthological Society. 7: 502–524. 

Rachowicz, L.J.; Knapp, R.A.; Morgan, J.A.T.; Stice, M.J.; Vredenburg, V.T.; 

Parker, J.M.; Briggs, C.J. 2006. Emerging infectious disease as a proximate 

cause of amphibian mass mortality. Ecology. 87: 1671–1683. 

Reid, L.M.; Dunne, T. 1984. Sediment production from forest road surfaces. Water 

Resources Research. 20(11): 1753–1761. 

Relyea, R.A. 2005a. Pesticides and amphibians: The importance of community 

context. Ecological Applications. 15: 1125–1134. 

Relyea, R.A. 2005b. The lethal impact of Roundup on aquatic and terrestrial 

amphibians. Ecological Applications. 15: 1118–1124. 

Richardson, E.V.; Simons, B.; Karaki, S.; Mahmood, M.; Stevens, M.A. 

1975. Highways in the river environment: hydraulic and environmental design 

considerations training and design manual. Washington, DC: U.S. Department 

of Transportation, Federal Highway Administration. 646 p. 

Roche, L.M.; Allen-Diaz, B.; Eastburn, D.J.; Tate, K.W. 2012. Cattle grazing 

and Yosemite toad (Bufo canorus Camp) breeding habitat in Sierra Nevada 

meadows. Rangeland Ecology and Management. 65: 56–65. 
88 

GENERAL TECHNICAL REPORT PSW-GTR-248

 

Rombough, C.J. 2006a. Distribution of foothill yellow-legged frogs (Rana boylii) 

in Cow Creek: evidence of smallmouth bass (Micropterus dolomieu) influence. 

Corvallis, OR: Oregon State University. 18 p. Honors senior thesis. 

Rombough, C.J. 2006b. Wintering habitat use by juvenile foothill yellow-legged 

frogs (Rana boylii): the importance of seeps [Abstract]. Northwestern Naturalist. 

87: 159. 

Rombough, C.J.; Chastain, J.; Schwab, A.M.; Hayes, M.P. 2005b. Rana boylii 

(foothill yellow-legged frog). Predation. Herpetological Review. 36: 438–439. 

Rombough, C.J.; Hayes, M.P. 2005a. Novel aspects of oviposition site preparation 

by female foothill yellow-legged frogs (Rana boylii). Northwestern Naturalist. 

87: 163–164. 

Rombough, C.J.; Hayes, M.P. 2005c. Rana boylii (foothill yellow-legged frog). 

Predation: eggs and hatchlings. Herpetological Review. 36: 163–164. 

Rose, T. 2015. Personal communication. Wildlife photographer, 83500 Hwy. 271, 

Piercy, CA 95587. 

Rouse, J.D.; Bishop, C.A.; Struger, J. 1999. Nitrogen pollution: an assessment 

of its threat to amphibian survival. Environmental Health Perspectives. 107: 

799–803. 

Sagar, J.P.; Olson, D.H.; Schmitz, R.A. 2007. Survival and growth of larval 

Coastal giant salamanders (Dicamptodon tenebrosus) in streams in the Oregon 

Coast Range. Copeia. 2007: 123–130. 

San Francisco Public Utilities Commission (SFPUC). 2014. O’Shaughnessy Dam 

Instream Flow Management Plan–Stakeholder Draft. Prepared as part of the 

Upper Tuolumne River Ecosystem Program by the SFPUC Natural Resources 

and Lands Management Division, with McBain & Trush, Inc., Jennifer Vick, 

Stillwater Sciences, Questa Engineering, Graham Matthews and Associates, 

Darnell Shaw Environmental, Watercourse Engineering, and Merritt Smith 

Consulting. 

Sawyer, J.O.; Keeler-Wolf, T. 1995. A manual of California vegetation. 

Sacramento, CA: California Native Plant Society. 412 p. 

Schulz, T.T.; Leininger, W.C. 1990. Differences in riparian vegetation 

structure between grazed areas and exclosures. Journal of Range Management. 43: 295–299. 
89 

Foothill Yellow-Legged Frog Conservation Assessment

Scully, N.M.; Lean, D.S. 1994. The attenuation of ultraviolet radiation in 

temperate lakes. Archives für Hydrobiologie. 43: 135–144. 

Seiber, J.N.; Woodrow, J.E.; David, M.D. 1998. Organophosphorus esters. 

In: Shibamoto, T., ed. Chromatographic analysis of environmental and food 

toxicants. New York: CRC Press: 229–257. 

Seltennich, C. 2002. Personal communication. Practice manager, DUDEK, 

605 Third St., Encinitas, CA 92024. 

Semlitsch, R.D.; Scott, D.E.; Pechmann, J.H.K. 1988. Time and size at 

metamorphosis related to adult fitness in Ambystoma talpoideum. Ecology. 

69: 184–192. 

Servizi, J.A.; Gordon, R.W.; Martens, D.W. 1987. Acute toxicity of Garlon 4 and 

Roundup herbicides to salmon, Daphnia, and trout. Bulletin of Environmental 

Contamination and Toxicology. 39: 15–22. 

Sessions, S.E.; Ruth, S.B. 1990. Explanation for naturally occurring 

supernumerary limbs in amphibians. Journal of Experimental Zoology. 

254: 38–47. 

Simon, D.C.; Markle, D.F. 1999. Evidence of a relationship between smallmouth 

bass (Micropterus dolomieu) and decline of Umpqua chub (Oregonichthys 

kalawatseti) in the Umpqua Basin, Oregon. Northwestern Naturalist. 80: 

110–113. 

Smith, D.C. 1987. Adult recruitment in chorus frogs: Effects of size and date at 

metamorphosis. Ecology. 68: 344–350. 

Smith, G.R. 2001. Effects of acute exposure to a commercial formulation of 

glyphosate on the tadpoles of two species of anurans. Bulletin of Environmental 

Contamination and Toxicology. 67: 483–488. 

Smith, J.; Tirpak, D., eds. 1989. Potential impacts of global climate change on 

the United States. Washington, DC: U.S. Environmental Protection Agency, 

Office of Policy, Planning and Evaluation (PM-221), Office of Research and 

Development. 689 p. 

Somer, W.L.; Hassler, T.J. 1992. Effects of suction-dredge gold mining on benthic 

invertebrates in a Northern California stream. North American Journal of 

Fisheries Management. 12: 244–252. 

Soulé, M.E. 1990. The onslaught of alien species, and other challenges in the 

coming decades. Conservation Biology. 4: 233–239. 
90 

GENERAL TECHNICAL REPORT PSW-GTR-248

Sparling, D.W.; Fellers, G.M. 2007. Comparative toxicity of chlorpyrifos, 

diazinon, malathion and their oxon derivatives to tadpole Rana boylii. 

Environmental Pollution. 147: 535–539. 

Sparling, D.W.; Fellers, G.M. 2009. Toxicity of two insecticides to California, 

U.S.A., anurans and its relevance to declining amphibian populations. 

Environmental Toxicology and Chemistry. 8 (8): 1696–1703. 

Sparling, D.W.; Fellers, G.M.; McConnell, L.L. 2001. Pesticides and amphibian 

population declines in California, U.S.A. Environmental Toxicology and 

Chemistry. 20: 1591–1595. 

Spellerberg, I.F. 1998. Ecological effects of roads and traffic: a literature review. 

Global Ecology and Biogeography Letters. 7: 317–333. 

Spring Rivers Ecological Sciences. 2003. Foothill yellow-legged frog 

(Rana boylii) studies in 2002 for Pacific Gas and Electric Company’s Pit 3, 4, 

and 5 Hydroelectric Project (FERC No. 233). San Ramon, CA: Pacific Gas and 

Electric Company, Technical and Ecological Services. 66 p. 

Spring River Ecological Sciences. 2004. Foothill yellow-legged frog (Rana boylii) 

egg mass, tadpole, and habitat surveys in the Pit 4 in 2003, Pacific Gas and 

Electric Company Pit 3, 4, and 5 Hydroelectric Project (FERC No. 233). San 

Ramon, CA: Pacific Gas and Electric Company. 54 p. 

Stebbins, R.C. 1951. Amphibians of western North America. Berkeley, CA: 

University of California Press. 539 p. 

Stebbins, R.C. 2003. A field guide to western reptiles and amphibians. 3rd ed. 

Boston, MA: Houghton Mifflin. 544 p. 

Stephenson, G.R.; Street, L.V. 1978. Bacterial variations in streams from a 

southwest Idaho rangeland watershed. Journal of Environmental Quality. 

7: 150–157. 

Stewart, I.T. 2009. Changes in snowpack and snowmelt runoff for key mountain 

regions. Hydrological Processes. 23: 78–94. 

Storer, T.I. 1923. Coastal range of yellow-legged frog in California. Copeia. 

(114): 8. 

Storer, T.I. 1925. A synopsis of the amphibia of California. University of 

California Publications in Zoology. 27: 1–343. 

Strahler, A.N. 1952. Dynamic basin of geomorphology. Geological Society of 

America Bulletin. 63: 923–938. 
91 

Foothill Yellow-Legged Frog Conservation Assessment

 

Stuart, S.N.; Chanson, J.S.; Cox, N.A.; Young, B.E.; Rodrigues, A.S.L.; 

Fischman, D.L.; Waller, R.W. 2004. Status and trends of amphibian declines 

and extinctions worldwide. Science. 306: 1783–1786. 

Sullivan, D.S.; Sullivan, T.P.; Bisalputra, T. 1981. Effects of Roundup® herbicide 

on diatom populations in the aquatic environment of a coastal forest. Bulletin of 

Environmental Contamination and Toxicology. 26: 91–96. 

Sweet, S.S. 1983. Mechanics of a natural extinction event: Rana boylii in southern 

California [Abstract]. In: Program of the 26th annual meeting of the Society 

for the Study of Amphibians and Reptiles and 31st annual meeting of the 

Herpetologists League. Salt Lake City, UT: University of Utah: 93. 

Sweet, S.S. 1985. Personal communication. Professor, Department of Ecology, 

Evolution, and Marine Biology, University of California–Santa Barbara, Santa 

Barbara, CA 93106. 

Sweet, S.S. 1992. Initial report on the ecology and status of the arroyo toad 

on the Los Padres National Forest of southern California, with management 

recommendations. Goleta, CA: U.S. Department of Agriculture, Forest Service, 

Los Padres National Forest. 198 p. 

Syracuse Environmental Research Associates, Inc. [SERA]. 2003a. 

Glyphosate—Human health and ecological risk assessments final report. 

Contract number SERA TR 02-43-09-04a. Washington, DC: U.S. Department 

of Agriculture, Forest Service, Forest Health Protection. 281 p. 

Syracuse Environmental Research Associates, Inc. [SERA]. 2003b. Triclopyr— 

Revised human health and ecological risk assessments final report. Contract 

number SERA TR 02-43-13-03b. Washington, DC: U.S. Department of 

Agriculture, Forest Service, Forest Health Protection. 264 p. 

Thompson, D.G.; Wojtaszek, B.F.; Staznik, B.; Chartrand, D.T.; Stephenson, 

G.R. 2004. Chemical and biomonitoring to assess potential acute effects of 

Vision® herbicide on native amphibian larvae in forest wetlands. Environmental 

Toxicology and Chemistry. 23: 843–849. 

Trombulak, S.C.; Frissell, C.A. 2000. Review of ecological effects of roads on 

terrestrial and aquatic communities. Conservation Biology. 14: 18–30. 

Twitty, V.C.; Grant, D.; Anderson, O. 1967. Amphibian orientation: An 

unexpected observation. Science. 155: 352–353. 
92 

GENERAL TECHNICAL REPORT PSW-GTR-248

U.S. Department of Agriculture, Forest Service [USDA FS]. 1998. Regional 

forester’s list of sensitive plant and animal species for Region 5. Vallejo, CA: 

Pacific Southwest Region. 

U.S. Department of Agriculture, Forest Service [USDA FS]. 2001. Sierra Nevada 

Forest Plan Amendment (SNFPA) Final Environmental Impact Statement (FEIS). 

Vallejo, CA: Pacific Southwest Region. 

U.S. Department of Agriculture, Forest Service [USDA FS]. 2004. Sierra 

Nevada Forest Plan Amendment (SNFPA) Final Supplemental Environmental 

Impact Statement and Record of Decision. R5-MB-046. Vallejo, CA: Pacific 

Southwest Region. http://www.fs.fed.us/r5/snfpa/final-seis/. [Date accessed 

unknown]. 

U.S. Department of the Interior, National Park Service [USDI NPS]. 1999. 

Natural and cultural resources management plan. Sequoia and Kings Canyon 

National Park. 

U.S. Department of the Interior, National Park Service [USDI NPS]. 2003. 

Resources management plan. Yosemite National Park. 

U.S. Department of the Interior, National Park Service [USDI NPS]. 2006. 

Management policies. Washington, DC: U.S. Government Printing Office. 

U.S. Environmental Protection Agency [USEPA]. 1997. National air pollutant 

emission trends, 1990–1996. EPA-454/R-97-011. Research Triangle Park, NC. 

Van Wagner, T.J. 1996. Selected life-history and ecological aspects of a population 

of foothill yellow-legged frogs (Rana boylii) from Clear Creek, Nevada County, 

California. Chico, CA: California State University. 143 p. M.S. thesis. 

Vinson, M. 1998. Effects of recreational activities on declining anuran species in 

the John Muir Wilderness, CA. Missoula, MT: University of Montana. 83 p. 

M.S. thesis. 

Vos, C.C.; Chardon, J.P. 1998. Effects of habitat fragmentation and road density 

on the distribution pattern of the moor frog Rana arvalis. Journal of Applied 

Ecology. 35: 44–56. 

Vredenburg, V.T.; Knapp, R.A.; Tunstall, T.S.; Briggs, C.J. 2010. Dynamics 

of an emerging disease drive large-scale amphibian population extinctions. 

Proceedings of the National Academy of Sciences. 107: 9689–9694. 
93 

Foothill Yellow-Legged Frog Conservation Assessment

Wake, D.B. 1991. Declining amphibian populations. Science. 253: 860. 

Walker, M.E. 1965. A survey of helminth parasites of Rana boylei from Humboldt 

County, California. Arcata, CA: Humboldt State University. 33 p. M.S. thesis. 

Walton, A.C. 1964. The parasites of amphibia. Wildlife Disease Association. 

40: 1–57. 

Wan, M.T.; Watts, R.G.; Moul, D.J. 1989. Effects of different dilution water 

types on the acute toxicity to juvenile Pacific salmonids and rainbow trout 

of glyphosate and its formulated products. Bulletin of Environmental 

Contamination and Toxicology. 43: 378–385. 

Waters, T.F. 1995. Sediment in streams: sources, biological effects and control. 

American Fisheries Society Monograph 7. Bethesda, MD: American Fisheries 

Society. 251 p. 

Weaver, T.; Dale, D. 1978. Trampling effects of hikers, motorcycles and horses in 

meadows and forests. Journal of Applied Ecology. 15: 451–457. 

Welsh, H.H., Jr.; Ollivier, L.M. 1998. Stream amphibians as indicators of 

ecosystem stress: a case study from California’s redwoods. Ecological 

Applications. 8: 1118–1132. 

Wheeler, C.A. 2007. Temporal breeding patterns and mating strategy of the 

foothill yellow-legged frog (Rana boylii). Arcata, CA: Humboldt State 

University. 42 p. M.S. thesis. 

Wheeler, C.A.; Bettaso, J.B.; Ashton, D.T.; Welsh, H.H., Jr. 2013. Effects of 

water temperature on breeding phenology, growth and timing of metamorphosis 

of foothill yellow-legged frogs (Rana boylii) on the mainstem and selected 

tributaries of California’s Trinity River—2004–2009. Report to the Trinity 

River Restoration Program. Arcata, CA: U.S. Department Agriculture, Pacific 

Southwest Research Station and U.S. Fish and Wildlife Service. 37 p. 

Wheeler, C.A.; Bettaso, J.B.; Ashton, D.T.; Welsh, H.H., Jr. 2014. Effects 

of water temperature on breeding phenology, growth, and metamorphosis of 

foothill yellow-legged frogs (Rana boylii): a case study of the regulated mainstem 

and unregulated tributaries of California’s Trinity River. River Research and 

Applications.doi:10.1002/rra.2820. 

Wheeler, C.A.; Welsh, H.H., Jr. 2008. Mating strategy and breeding patterns of 

the foothill yellow-legged frog (Rana boylii). Herpetological Conservation and 

Biology. 3: 128–142. 
94 

GENERAL TECHNICAL REPORT PSW-GTR-248

 

Wheeler, C.A.; Welsh, H.H., Jr.; Heise, L.L. 2003. Rana boylii (foothill yellowlegged frog). Oviposition behavior. Herpetological Review. 34: 234. 

Wheeler, C.A.; Welsh, H.H., Jr.; Roelofs, T. 2006. Oviposition site selection, 

movement, and spatial ecology of the foothill yellow-legged frog (Rana boylii). 

Final report. Sacramento, CA: California Department of Fish and Game. 20 p. 

Williams, M.R.; Melack, J.M. 1997. Atmospheric deposition, mass balances, 

and processes regulating streamwater solute concentrations in mixed-conifer 

catchments of the Sierra Nevada, California. Biogeochemistry. 37: 111–144. 

Wiseman, K.D.; Marlow, K.R.; Jackman, R.E.; Drennan, J.E. 2005. Rana boylii 

(foothill yellow-legged frog). Predation. Herpetological Review. 36: 162–163. 

Wojtaszek, B.F.; Staznik, B.; Chartrand, D.T.; Stephenson, G.R.; Thompson, 

D.G. 2004. Effects of Vision® herbicide on mortality, avoidance response, and 

growth of amphibian larvae in two forest wetlands. Environmental Toxicology 

and Chemistry. 23: 832–842. 

Wright, A.H.; Wright, A.A. 1949. Handbook of frogs and toads of the United 

States and Canada. 3rd ed. Ithaca, NY: Comstock Publishing Associates. 640 p. 

Yarnell, S.M. 2000. The influence of sediment supply and transport capacity on 

foothill yellow-legged frog habitat, South Yuba River, California. Davis, CA: 

University of California. 241 p. M.S. thesis. 

Yarnell, S.M. 2005. Spatial heterogeneity of Rana boylii habitat: physical 

processes, quantification, and ecological meaningfulness. Davis, CA: University 

of California. 238 p. Ph.D. dissertation. 

Yarnell, S.M. 2008. Quantifying physical habitat heterogeneity in an ecologically 

meaningful manner: a case study of the habitat preferences of the foothill yellowlegged frog (Rana boylii). In: Dupont, A.; Jacobs, H., eds. Landscape ecology 

research trends. New York: Nova Science Publishers: 89–112. Chapter 5. 

Yarnell, S.M. 2014. Personal communication. Associate project scientist, Center 

for Watershed Sciences, University of California–Davis, One Shields Ave., 

Davis, CA 95616. 

Yarnell, S.; Bondi, C.; Lind, A.; Peek, R. 2011. Habitat models for the foothill 

yellow-legged frog (Rana boylii) in the Sierra Nevada of California. Center for 

Watershed Sciences Technical Report. Davis, CA: University of California. 75 p. 
95 

Foothill Yellow-Legged Frog Conservation Assessment

Yarnell, S.M.; Lind, A.J.; Mount, J.F. 2012. Dynamic flow modeling of 

riverine amphibian habitat with application to regulated flow management. 

River Research and Applications. 28: 177–191. http://onlinelibrary.wiley.com/ 

doi/10.1002/rra.1447/pdf. (11 April 2014). 

Yarnell, S.M.; Viers, J.H.; Mount, J.F. 2010. Ecology and management of the 

spring snowmelt recession. BioScience. 60(2): 114–127. 

Young, C.A.; Escobar, M.; Fernandes, M.; Joyce, B.; Kiparsky, M.; Mount, 

J.F.; Mehta, V.; Viers, J.H.; Yates, D. 2009. Modeling the hydrology of 

California’s Sierra Nevada for sub-watershed scale adaptation to climate change. 

Journal of American Water Resources Association. 45: 1409–1423. 

Yuba County Water Agency [YCWA]. 2012. Special-status amphibians—foothill 

yellow-legged frog surveys. Tech. memo. 3-4. Yuba River Development Project 

(FERC No. 2246). http://www.ycwa-relicensing.com/Technical%20Memoranda/ 

TM%2003-04%20-%20Special-Status%20Amphibians%20-%20FYLF%20 

Surveys/TM%203-4,%20Part%201%20of%202%20.pdf. [Date accessed 

unknown]. 

Zabik, J.M.; Seiber, J.N. 1993. Atmospheric transport of organophosphate 

pesticides from California’s Central Valley to the Sierra Nevada Mountains. 

Journal of Environmental Quality. 22: 80–90. 

Zweifel, R.G. 1955. Ecology, distribution, and systematics of frogs of the Rana 

boylei group. University of California Publications in Zoology. 54: 207–292. 
96 

GENERAL TECHNICAL REPORT PSW-GTR-248

Appendix 1: Agency Direction 

USDA Forest Service 

The U.S. Department of Agriculture, Forest Service, Pacific Southwest Region 

(Region 5) listed the foothill yellow-legged frog (Rana boylii) on its Sensitive Species List in 1998 (USDA FS 1998). The Sensitive Species List is developed based 

on the Forest Service Manual (FSM 2670.5) for those plant and animal species 

identified by a regional forester for which population viability is a concern, as 

evidenced by: 

•	 Significant current or predicted downward trends in population numbers or 

density. 

•	 Significant current or predicted downward trends in habitat capability that 

would reduce a species’ existing distribution. 

Forest Service Manual 2672.1 states that sensitive species of native plants and 

animals must receive special management emphasis to ensure their viability and 

to preclude trends toward endangerment that would result in the need for federal 

listing. Sensitive species cannot be affected without an analysis of significance of 

adverse effects on the populations, their habitat, and on the viability of the species 

as a whole. The Forest Service Manual (FSM 2670.32) provides the following direction for sensitive species: 

•	 Assist states in achieving their goals for conservation of endemic species. 

•	 As part of the National Environmental Policy Act process, review programs 

and activities through a biological evaluation to determine their potential 

effect on sensitive species. 

•	 Avoid or minimize impacts to species whose viability has been identified as 

a concern. 

•	 If impacts are unavoidable, analyze the significance of potential adverse 

effects on the population or its habitat within the area of concern and on the 

species as a whole. 

•	 Establish management objectives in cooperation with the states when 

a project on National Forest System lands may have a significant effect 

on sensitive species population numbers or distribution. Establish objectives for Federal candidate species, in cooperation with the U.S. Fish and 

Wildlife Service and the states. 

For all Forest Service planned, funded, executed, or permitted programs and 

activities, a review for possible effects on endangered, threatened, proposed, or 
97 

Foothill Yellow-Legged Frog Conservation Assessment

sensitive species is conducted through a Biological Assessment (FSM 2670) and 

Evaluation (FSM 2672.4). Biological Assessment and Evaluation objectives (FSM 

2672.41) are to: 

1.	 Ensure that Forest Service actions do not contribute to loss of viability 

of any native or desired nonnative plant or animal species or contribute 

towards trends for federal listing of any species. 

2.	 Comply with the requirements of the Endangered Species Act (ESA) 

that actions of federal agencies not jeopardize federally listed species or 

adversely modify their critical habitat. 

3.	 Provide a process and standard by which threatened, endangered, proposed, 

and sensitive species receive full consideration in the decisionmaking 

process. 

Land and Resource Management Plans for forests in the Sierra Nevada were 

changed in January 2001 by the Sierra Nevada Forest Plan Amendment (SNFPA). 

This amendment is sometimes referred to as “The Framework” (USDA FS 2001). 

This 2001 Framework decision was subsequently adjusted 3 years later via a 

supplemental Environmental Impact Statement (EIS) and Record of Decision 

(ROD) (USDA FS 2004). The 2004 ROD is the only binding decision. Both Framework RODs establish an Aquatic Management Strategy. Pages 32–33 of the ROD 

(USDA FS 2004) state that the strategy for aquatic management includes broad 

goals (below) representing endpoints toward which management moves watershed 

processes and functions, habitats, attributes, and populations. These goals define 

a comprehensive framework for establishing desired conditions at larger scales, 

including river basin, watershed, and landscape scales. Moving ecosystem conditions toward these goals will restore and maintain the physical, chemical, and 

biological integrity of the region’s waters as mandated by the Clean Water Act, and 

will support the Forest Service mission to provide habitat for riparian- and aquaticdependent species under the National Forest Management Act, the Organic Act, the 

Safe Drinking Water Act, the ESA, and the Electric Consumers Protection Act. The 

following are Aquatic Management Strategy goals: 

1.	 Water quality—Maintain and restore water quality to meet the goals of the 

Clean Water Act, providing water that is fishable, swimmable, and suitable 

for drinking after normal treatment. 

2.	 Species viability—Maintain and restore habitat to support viable populations of native and desired nonnative plant, invertebrate, and vertebrate 

riparian-dependent species. Prevent new introductions of invasive species. 
98 

GENERAL TECHNICAL REPORT PSW-GTR-248

Where invasive species are adversely affecting the viability of native species, work cooperatively with appropriate state and federal wildlife agencies 

to reduce impacts to populations of native species. 

3.	 Plant and animal community diversity—Maintain and restore the species 

composition and structural diversity of plant and animal communities in 

riparian areas, wetlands, and meadows to provide desired habitats and ecological functions. 

4.	 Special habitats—Maintain and restore the distribution and health of biotic 

communities in special aquatic habitats (such as springs, seeps, vernal 

pools, fens, bogs, and marshes) to perpetuate their unique functions and 

biological diversity. 

5.	 Watershed connectivity—Maintain and restore spatial and temporal connectivity for aquatic and riparian species within and between watersheds to 

provide physically, chemically and biologically unobstructed movement for 

their survival, migration and reproduction. 

6.	 Floodplains and water tables—Maintain and restore the connections of 

floodplains, channels, and water tables to distribute flood flows and sustain 

diverse habitats. 

7.	 Watershed condition—Maintain and restore soils with favorable infiltration 

characteristics and diverse vegetation cover to absorb and filter precipitation and to sustain favorable conditions of streamflow. 

8.	 Streamflow patterns and sediment regimes—Maintain and restore instream 

flows sufficient to sustain desired conditions of riparian, aquatic, wetland, 

and meadow habitats and keep sediment regimes as close as possible to 

those with which aquatic and riparian biota evolved. 

9.	 Streambanks and shorelines—Maintain and restore the physical structure 

and condition of streambanks and shorelines to minimize erosion and sustain desired habitat diversity. 

In addition, the 2004 SNFPA ROD includes Riparian Conservation Objectives (RCO), and associated standards and guidelines (S&Gs) specific to aquaticdependent species, including foothill yellow-legged frogs. Management direction 

for carrying out this decision includes S&Gs for project design and implementation. 

The RCO S&Gs rely on minimizing the risk and impacts from project-related 

activities on aquatic- or riparian-dependent species without specifically identifying 

the species involved. 
99 

Foothill Yellow-Legged Frog Conservation Assessment

National Park Service (NPS) 

The guiding principles for managing biological resources on NPS lands include 

maintenance of animal populations native to park ecosystems, or more specifically: 

...preserving and restoring the natural abundances, diversities, dynamics, 

distributions, habitats, and behaviors of native plant and animal populations 

and the communities and ecosystems in which they occur; restoring native 

plant and animal populations in parks when they have been extirpated 

by past human-caused actions; and minimizing human impacts on native 

plants, animals, populations, communities, and ecosystems, and the processes that sustain them (USDI NPS 2006). 

These guiding principles also commit the NPS to “work with other land managers to encourage the conservation of the populations and habitats of these species 

outside parks whenever possible,” including a commitment to “participate in local 

and regional scientific and planning efforts, identify ranges of populations of native 

plants and animals, and develop cooperative strategies for maintaining or restoring 

these populations in the parks.” Subsequently, these principles direct the NPS to 

participate in the foothill yellow-legged frog conservation assessment process, and 

assist in conserving the species in the Sierra Nevada. 

The resource management plan for the Sequoia and Kings Canyon National 

Parks (USDI NPS 1999) discusses stressors contributing to the decline of foothill 

yellow-legged frogs, but it does not provide management language specific to this 

species. The plan provides resource goals for aquatic/water resources that have 

direct relevance to foothill yellow-legged frog conservation issues. The following 

resource goals have a direct bearing on foothill yellow-legged frog ecology and risk 

factor analysis: 

•	 Aquatic and water ecosystems are restored or maintained so that physical, 

chemical, and biotic processes function uninfluenced by human activities. 

•	 Aquatic environments are inventoried and classified by physical and 

chemical characteristics and biotic communities present. 

•	 A long-term monitoring program is developed to record ambient conditions 

and to document changes and trends in physical and chemical characteristics and biotic communities. 

•	 Impacts of acid deposition and contaminants from external influences are 

detected and evaluated. 

•	 Lakes with exotic trout are restored to natural conditions. 

•	 Extant native species or genetically unique groups are restored to their 

former range. 
100 

GENERAL TECHNICAL REPORT PSW-GTR-248

•	 Waters incapable of sustaining fish populations through natural reproduction will be allowed to become fishless. 

The resource management plan for Yosemite National Park (2003) notes 

under Aquatic Ecosystem/Fisheries Management that management must provide 

for “...self-perpetuating populations of (native) aquatic species” through restoration. 

Under “Disappearing Amphibians,” the plan puzzles over the worldwide decline of 

amphibians. It notes the decline and disappearance of several amphibian species in 

the park, including the foothill yellow-legged frog, and the urgent need for research 

to identify the cause(s). Yosemite National Park is collaborating with the City of 

San Francisco Public Utilities, U.S. Fish and Wildlife Service, and the Stanislaus 

National Forest on the Upper Tuolumne River Ecosystem Project. Through this 

multiagency project, studies are being conducted on the ecological effects of 

controlled riverflows from the Hetch Hetchy Reservoir. The goal of these studies 

is to make informed recommendations for water releases from the dam that would 

maximize ecological benefits. Restoration of the foothill yellow-legged frog is 

among the park’s top priorities for this project. Although the foothill yellow-legged 

frog was never very widespread in Yosemite, its loss from the fauna of the park is 

ecologically significant. 

Further, the three national parks that encompass a small portion of the historical range of the foothill yellow-legged frog (Yosemite, Kings Canyon, and Sequoia) 

play a pivotal role in implementation of the federal Amphibian Research and Monitoring Initiative (ARMI) developed in 2000 (Hall and Langtimm 2001). The goal of 

the initiative was to provide timely, reliable information on the status of amphibians 

in the United States so that causes of declines could be understood and appropriate 

management responses initiated. Prior to this initiative, broad-based replication of 

historical surveys that was initiated in the 1990s has provided invaluable insights 

into the status of the amphibian assemblages found in Yosemite National Park, 

which included the foothill yellow-legged frog (Drost and Fellers 1994, 1996; USDI 

NPS 1999; see also “Status” section for Yosemite National Park in app. 3). 

California Department of Fish and Wildlife 

The state of California considers the foothill yellow-legged frog to be a “Species 

of Special Concern” (SSC). This is an administrative designation and carries no 

formal legal status. The intent of designating SSCs is to: 

•	 Focus attention on animals at conservation risk by the department, other 

state, local and federal governmental entities, regulators, land managers, 

planners, consulting biologists, and others; 
101 

Foothill Yellow-Legged Frog Conservation Assessment

•	 Stimulate research on poorly known species; and 

•	 Achieve conservation and recovery of these animals before they meet 

California ESA criteria for listing as threatened or endangered. 

An SSC is a species, subspecies, or distinct population of an animal native to 

California that currently satisfies one or more of the following (not necessarily 

mutually exclusive) criteria: 

•	 Is extirpated from the state or, in the case of birds, in its primary seasonal 

or breeding role; 

•	 Is listed as federally, but not state-, threatened or endangered; 

•	 Meets the state definition of threatened or endangered but has not formally 

been listed; 

•	 Is experiencing, or formerly experienced, serious (noncyclical) population 

declines or range retractions (not reversed) that, if continued or resumed, 

could qualify it for state threatened or endangered status; and 

•	 Has naturally small populations exhibiting high susceptibility to risk from 

any factor(s), which if realized, could lead to declines that would qualify it 

for state threatened or endangered status. 

SSCs tend to have a number of factors in common, as follows: 

•	 Occur in small, isolated populations or in fragmented habitat, and are 

threatened by further isolation and population reduction; 

•	 Show marked population declines. Taxa that show a marked population 

decline, yet are still abundant, may not meet the SSC definition, whereas 

marked population decline in uncommon or rare species may meet the 

SSC definition. Note that population estimates are unavailable for the vast 

majority of California taxa; 

•	 Depend on a habitat that has shown substantial historical or recent declines 

in size and/or quality or integrity. This criterion infers the population 

viability of a species based on trends in the habitats in which it specializes. Coastal wetlands, particularly in the urbanized San Francisco Bay 

and south-coastal areas, alluvial fan sage scrub and coastal sage scrub in 

the southern coastal basins, vernal pools in the Central Valley, arid scrub 

in the San Joaquin Valley, and riparian habitat statewide, are examples 

of California habitats that have seen dramatic reductions in size in recent 

history; 
102 

GENERAL TECHNICAL REPORT PSW-GTR-248

•	 Occur only or primarily in or adjacent to an area where habitat is being 

converted to uses incompatible with the animal’s survival; 

•	 Have few California records, or which historically occurred in the state but 

for which there are no recent records; and 

•	 Occur largely in areas where current management practices are inconsistent 

with the animal’s persistence. 

More information about SSCs is available at https://www.dfg.ca.gov/wildlife/ 

nongame/ssc/. 

SSCs should be considered during the environmental review process. The 

California Environmental Quality Act (CEQA; California Public Resources Code 

§§ 21000–21177) requires state agencies, local governments, and special districts 

to evaluate and disclose impacts from “projects” in California. Section 15380 of 

the CEQA guidelines clearly indicates that SSCs should be included in an analysis 

of project impacts if they can be shown to meet the criteria of sensitivity outlined 

therein. 

Sections 15063 and 15065 of the CEQA guidelines, which address how an 

impact is identified as significant, are particularly relevant to SSCs. Project-level 

impacts on listed (rare, threatened, or endangered) species are generally considered significant, thus requiring lead agencies to prepare an environmental impact 

assessment to fully analyze and evaluate the impacts. In assigning “impact significance” to populations of nonlisted species, analysts usually consider factors such 

as population-level effects, proportion of the taxon’s range affected by a project, 

regional effects, and impacts to habitat features. 

More information about CEQA and CEQA guidelines is available at http:// 

resources.ca.gov/ceqa/. 

Sport take of foothill yellow-legged frogs with a fishing license is prohibited 

(Title 14, Section 5.05) and scientific take is regulated by permit (Title 14, Section 

650). 

U.S. Fish and Wildlife Service 

The overarching mission of the U.S. Fish and Wildlife Service (USFWS) is “working with others, to conserve, protect and enhance fish, wildlife, and plants and their 

habitats for the continuing benefit of the American people.” The long-term goals of 

the USFWS relevant to this assessment include: 

•	 Recovery of threatened and endangered species, 
103 

Foothill Yellow-Legged Frog Conservation Assessment

•	 Protection and conservation of trust species (i.e., threatened species, endangered species, and other species of concern), and 

•	 Habitat conservation. 

The recovery of threatened and endangered species, and the ecosystems 

on which they depend, fall under USFWS responsibilities under the ESA. The 

foothill yellow-legged frog has recently been petitioned for listing (Adkins Giese 

et al. 2012). 
104 

GENERAL TECHNICAL REPORT PSW-GTR-248

 

Appendix 2: Museum Standard Symbolic Codes 

Documentation of records from museum collections in the text are listed according 

to the standard symbolic code for each institution based on Leviton et al. (1985), 

and its update (Leviton et al. 1988). Institutions lacking a standard symbolic code 

for which one was added are indicated by an asterisk. 

Institution Symbolic code 

American Museum of Natural History (New York) AMNH 

California Academy of Sciences (San Francisco) CAS 

California Academy of Sciences–Stanford University 

Collection CAS-SU 

California State University–Chico* CSUC 

Field Museum of Natural History FMNH 

Los Angeles County Natural History Museum LACM 

Museum of Vertebrate Zoology (University of California 

at Berkeley) MVZ 

San Diego Natural History Museum SDNHM 

Sacramento State University SSU 

Texas Cooperative Wildlife Collection (Texas A&M University) TCWC 

University of Kansas Natural History Museum KU 

University of Michigan Museum of Zoology UMMZ 

University of Nevada at Reno UNR 

United States National Museum (Smithsonian Institution) USNM 

Literature Cited 

Leviton, A.E.; Gibbs, R.H., Jr. 1988. Standards in herpetology and ichthyology. 

Standard symbolic codes for institutional resource collections in herpetology and 

ichthyology. Suppl. no. 1: additions and corrections. Copeia. 1988: 280−282. 

Leviton, A.E.; Gibbs, R.H., Jr.; Heal, E.; Dawson, C.E. 1985. Standards in 

herpetology and ichthyology: part I. Standard symbolic codes for institutional 

resource collections in herpetology and ichthyology. Copeia. 1985: 802–832. 
105 

Foothill Yellow-Legged Frog Conservation Assessment

Appendix 3: Status—Federal Administrative Units 

This appendix provides information on status for individual national forest administrative units within the state of California and National Park Service administrative 

units within the Sierra Nevada Planning Area that encompass at least a portion of 

the recent historical range of the foothill yellow-legged frog (Rana boylii). Records 

were derived from museum and Forest Service databases and records. Results of 

more recent visual survey efforts were included if data were readily available; i.e., 

an exhaustive search was not made of unpublished reports. When available, we 

provided links to additional data sources. For regions outside of the Sierra Nevada 

Planning Area, we presented records within the boundaries of national forests. 

A significant proportion of the geographic range of foothill yellow-legged frogs 

occurs in the downstream portion of drainages whose headwaters occur in these 

administrative units. We address all historical foothill yellow-legged records for 

those drainages under each administrative unit, indicating which records occur 

within versus outside of the administrative unit discussed. The sequence of the 

presentation of administrative units is from north to south. 

Six Rivers National Forest 

Pre-1980— 

Three records exist from the Six Rivers National Forest for the 1940s. On 16 July 

1941, Ruth F. Myers and George S. Myers collected a foothill yellow-legged frog 

along a small stream along California highway SR-96, in Hoopa, 17.5 mi north of 

the town of Willow Creek (CAS 7400). On 23 March 1947, D.V. Brown collected 

one frog at an unknown location 3 mi south of Willow Creek (CAS 9529). On 

27 March 1947, Brown collected one frog along Tectah Creek, a tributary of the 

Klamath River (CAS 9527). 

Four records from Six Rivers National Forest were made during the 1950s. On 

23 June 1952, Lloyd Tevis collected two specimens at an unnamed site located 0.5 

mi northeast of the town of Willow Creek (CAS 218346, 218347). On 17 August 

1955, an unnamed individual collected one foothill yellow-legged frog along the 

Smith River (KU 50347). On 10 June 1956, A.C. Browne collected four frogs at an 

unknown site, 2 mi west of Gasquet School, and 12 mi northeast of Crescent City 

(CAS 188217–188220). On 7 August 1956, E.W. Jameson, Jr. collected one frog at 

Patrick Creek (CAS 218389). 

Two collections were recorded for the 1970s. On 16 August 1973, an unnamed 

individual collected one frog at a location 18 mi northeast of Gasquet along California highway SR-199 (TCWC 44325). On 19 March 1977, Thomas G. Balgooyen 
106 

GENERAL TECHNICAL REPORT PSW-GTR-248

collected one foothill yellow-legged frog near Boise Creek Campground on 

California highway SR-299 (CAS 195723). 

1980 to present— 

Two records based on foothill yellow-legged frog specimens at Six Rivers National 

Forest were made in the 1980s. In 1986, Gregory K. Pregill collected two frogs on 

26 August on Patrick Creek along highway SR-199 (SDNHM 65210 and 65211) and 

two frogs on 27 August at Hiouchi Campground along highway SR-199 (SDNHM 

65213 and 65214). 

One record of collection was made in the 1990s. On 24 April 1991, Marc R. 

Jennings and Marc P. Hayes collected one frog at an unnamed tributary of Hurdygurdy Creek in Del Norte County (CAS 178765). 

In 1986, Amy J. Lind and Hartwell H. Welsh, Jr., of the U.S. Department of 

Agriculture, Forest Service, Pacific Southwest Research Station (PSW), documented foothill yellow-legged frog breeding sites along Hurdygurdy Creek, a 

tributary of the South Fork Smith River. From 1987 to 2000, they recorded frog and 

egg mass locations along a 4.7 km (2.9 mi) study reach of Hurdygurdy Creek. Additional frog and egg mass surveys were conducted along Hurdygurdy Creek from 

2001 to 2008 by Clara A. Wheeler and Welsh of PSW. Data are available through 

PSW’s Redwood Sciences Laboratory. 

In 1994 and 1995, Lind and Welsh detected egg masses along Red Cap Creek. 

In 1995, herpetological surveys were conducted by the Six Rivers National Forest along the North Fork Eel River between 17 May and 31 October. A total of 

520 sightings were documented (USDA Forest Service NRIS database). Specific 

locations are available through the Six Rivers National Forest. On 23 July 1997, J. 

Donahue detected one foothill yellow-legged frog along Berry Creek, a tributary 

of the Mad River. On 23 April 1999, Sean Thobaben observed one frog at Boise 

Creek, a tributary of the Klamath River. 

On 30 March 2001, William C. Flaxington observed one foothill yellow-legged 

frog on the bank of the Smith River at the Jedediah Smith Campground in Jedediah 

Smith Redwoods State Park. On 17 January 2002, Flaxington also observed one 

frog beside Walker Road along a tributary of the Smith River in Jedediah Smith 

Redwoods State Park. On 18 February 2009, Flaxington observed another frog 

along Cedar Creek in Jedediah Smith Redwoods State Park. 

Thirty additional records of foothill yellow-legged frogs in Six Rivers National 

Forest during the 1990s and 2000s (USDA Forest Service NRIS database) indicate 

observations along Patrick Creek, Lower Middle Fork Smith River, Lost Creek (a 

tributary of Mad River), West Fork Van Duzen River, Shanty Creek (a tributary of 

Van Duzen River), Mill Creek (a tributary of Van Duzen River), Reynolds Creek (a 
107 

Foothill Yellow-Legged Frog Conservation Assessment

tributary of Klamath River), Slate Creek (a tributary of Klamath River), Horse Linto 

Creek, Mingo Creek (a tributary of South Fork Trinity River), Hardscrabble Creek 

(a tributary of Smith River), and Kettenpom Creek. 

Shasta-Trinity National Forest 

Pre-1980— 

Shasta Reservoir and Sacramento River tributaries—Likely the oldest data on 

foothill yellow-legged frogs from the area currently under Shasta-Trinity National 

Forest administration in this region date from observations made by Edward D. 

Cope, who stated that “the specimen [of foothill yellow-legged frog]...from El 

Dorado County, California [referring to one of the two type specimens collected by 

Charles E. Boyle; see Jennings 1987]...was for a long time the only one [i.e., record] 

in our collection [referring to the United States National Museum]. During my expedition to Oregon in 1879, I found it [the foothill yellow-legged frog] rather abundant in the mountainous regions of northern California” (Cope 1883, 1889). Cope 

did not provide precise locations, but he is known to have stopped at Baird (Cope 

1879), the historical salmon hatchery facility that is now inundated by the McCloud 

River arm of Shasta Lake. On 8 January 1884, Charles H. Townsend collected at 

least 11 foothill yellow-legged frogs at Baird (USNM 13795, 13929), collections that 

Cope discussed in 1889 (Cope 1889). This collection is the oldest for foothill yellowlegged frogs known from this region. 

One record from the 1890s exists for the Shasta area now under Shasta-Trinity 

National Forest administration. Cloudsley L. Rutter collected one foothill yellowlegged frog at Sims on the Sacramento River mainstem on 9 July 1898 (USNM 

38816). This location is above the inundation footprint of Shasta Lake. 

Two records from this region of the Shasta-Trinity National Forest were made 

in the 1900s, when Sterling A. Bunnell, Jr. collected three foothill yellow-legged 

frogs at a location 24.1 km (15 mi) east and 14.5 km (9 mi) north of the Baird hatchery facility on 1 June 1904 (MVZ 43327–43329). The precise location of this record 

is vague, but it is believed to be found along Potem Creek, a Pit River tributary. 

This location is probably above the inundation footprint of Shasta Lake. The second 

record involves two foothill yellow-legged frogs that Francis X. Williams collected 

at Sweetbriar Camp on the Sacramento River mainstem on 20 August 1907 (CAS 

13299–13300). This location is upstream of the inundation footprint of Shasta Lake. 

No foothill yellow-legged frog records from the 1910s exist for this region of 

the Shasta-Trinity National Forest, but one record was made from non-Forest Service lands during that decade. On 4 October 1911, J. Slevin collected three foothill 

yellow-legged frogs at Redding on the Sacramento River (CAS 30663–30665). 
108 

GENERAL TECHNICAL REPORT PSW-GTR-248

One record from the 1920s exists from the Shasta area of the Shasta-Trinity 

National Forest. On 21 August 1922, Raymond L. Dice collected one foothill yellow frog near Delta at the mouth of Dog Creek on the Sacramento River (UMMZ 

56966). 

No records of foothill yellow-legged frogs were made from this region of the 

Shasta-Trinity National Forest that date from the 1930s and 1940s. 

Seven records from the 1950s exist for the Shasta area now under ShastaTrinity National Forest administration. On 14 October 1950, Joseph B. Gorman, Jr., 

collected three foothill yellow-legged frogs from Low Pass Creek (MVZ 52327– 

52329), a tributary of Squaw Creek; and one foothill yellow-legged frog along 

Squaw Creek proper (MVZ 52330). The next day, Gorman collected one more foothill yellow-legged frog from Low Pass Creek (MVZ 52331), three foothill yellowlegged frogs from Bars Creek (MVZ 52332–52334), and one foothill yellow-legged 

frog from Dinner Gulch (MVZ 52335); the latter two drainages are also tributaries 

of Squaw Creek. On 27 March 1951, Gorman re-collected Squaw Creek, where he 

took one foothill yellow-legged frog (MVZ 84542). On 23 September 1951, Gorman 

also collected two more foothill yellow-legged frogs from Dinner Gulch at roughly 

the same locality (MVZ 55441–55442). On 24 March 1952, Gorman also collected 

two additional foothill yellow-legged frogs from Low Pass Creek (MVZ 55440, 

55555). On 20 June 1952, Robert C. Stebbins collected two foothill yellow-legged 

frogs along Salt Creek, 2.7 km (1.7 mi) by road east-northeast of Highway 99 (MVZ 

57039-57040). On 8 August 1952, one foothill yellow-legged frog was collected 

(collector unknown) along Salt Creek, 24.1 km (15 mi) east-southeast of Delta 

(USNM 543578). On 25 June 1953, Slevin also collected one foothill yellow-legged 

frog from Low Pass Creek (CAS 84959). On 24 October 1959, B. Lang collected 10 

foothill yellow-legged frogs along Brock Creek (CSUC 1150–1159). Because Brock 

Creek is a tributary of the Pit River that is now entirely isolated by Shasta Lake, 

the imprecision of this location makes it unclear whether some or all the foothill 

yellow-legged frogs collected were within the inundation footprint of Shasta Lake. 

Additionally, two records exist from the 1950s for non-Forest Service lands. On 5 

April 1953, Clifford H. Pope collected one foothill yellow-legged frog along the Pit 

River 12.8 km (8 mi) north-northwest of Round Mountain (FMNH 71474). On 31 

May 1953, Richard Russell collected 13 foothill yellow-legged frogs from private 

lands along Cold Creek, an upper Sacramento River tributary, 3.2 km (2 mi) south 

of the Mount Shasta Fish Hatchery (UMMZ 119016). 

Five records from the 1960s exist for the Shasta area now under Shasta-Trinity 

National Forest administration. On 25 June 1961, D. Collette collected two foothill 

yellow-legged frogs along Zinc Creek, 9.2 km (5.75 mi) north of Jones Valley 
109 

Foothill Yellow-Legged Frog Conservation Assessment

(CSUC 1624–1625). Because Zinc Creek is a tributary of Squaw Creek that is now 

entirely isolated by Shasta Lake, the imprecision of the Zinc Creek location makes 

it unclear whether the site of collection was located within the inundation footprint 

of Shasta Lake. On 11 August 1961, Stebbins re-collected Bars Creek, where he 

took two foothill yellow-legged frogs (MVZ 54343, 55392). On 3 August 1963, 

Charles S. Thaeler, Jr. collected one foothill yellow-legged frog along Squaw Creek 

0.5 km (0.3 mi) south and 0.5 km (0.3 mi) west of Madrone Guard Station (MVZ 

75818). On 2 September 1966, Raymond B. Huey re-collected the Dinner Gulch 

locality, from which he collected one foothill yellow-legged frog (MVZ 81261). 

On 18 May 1968, Alexander K. Johnson collected one foothill yellow-legged frog 

from an unspecified locality along Squaw Creek above Shasta Lake (MVZ 84452). 

Additionally, one record from the 1960s exists for non-Forest Service lands. On 

14 November 1969, James F. Lynch collected one foothill yellow legged frog from 

Soda Creek-Sacramento River confluence in Castle Crags State Park (MVZ 86997). 

Two records from the 1970s exist for the Shasta area now under Shasta-Trinity 

National Forest administration. On 14 September 1970, Ronald A. Nussbaum 

collected seven foothill yellow-legged frogs on Nosoni Creek at its crossing with 

Gilman Road (UMMZ 133393); Nosoni Creek is a tributary of the McCloud River. 

On 20 March 1977, Thomas G. Balgooyen collected one adult foothill yellow-legged 

frog on Salt Creek along Gilman Road near Shasta Reservoir (CAS 195725). Some 

additional data are available for the 1970s. During June–August 1974, M. Hayes 

conducted stream surveys on the upper McCloud River for about 8 river kilometers 

(5 river miles) below the confluence of Claiborne Creek and the McCloud River, a 

portion of which encompassed The Nature Conservancy McCloud River Preserve 

at that time; during these surveys, foothill yellow-legged frogs were found to be 

moderately common along this reach, with 3 to 22 postmetamorphs being observed 

per 100 m of stream. 

Trinity Reservoir and Trinity River tributaries—Only four records of foothill 

yellow-legged frog collections prior to 1980 exist for the Trinity River region of 

the Shasta-Trinity National Forest. On 16 October 1959, E. Harrington collected 

a specimen from Eagle Creek (CAS 188223). In October 1959, B. Kesse collected 

three frogs from Rush Creek (CAS 86108-86110). On 17–18 June 1967, an unnamed 

individual collected one frog from an unnamed creek near Salt Creek Camp, 4.5 

mi southeast of Peanut (LSU 16327), and another frog on an unnamed creek 9.5 mi 

west of Peanut (LSU 16328). 
110 

GENERAL TECHNICAL REPORT PSW-GTR-248

1980 to present— 

Shasta Reservoir and Sacramento River tributaries—Few records of foothill 

yellow-legged frogs from the 1980s exist for the Shasta area of the Shasta-Trinity 

National Forest. On 20 June 1981, M. Jennings collected one foothill yellow-legged 

frog on Deep Creek along Deep Creek Campground (MVZ 158969). This record, 

the upstream-most in the Pit River system, was one of two adult foothill yellowlegged frogs observed on that date (Jennings 1982). 

Several records of foothill yellow-legged frog observations were documented 

during the 1990s in the Shasta area of Shasta-Trinity National Forest. On 15 April 

1996, Jack Miller observed one adult frog at Ney Springs, one adult frog along 

Castle Creek, one adult frog along North Salt Creek, two adult frogs along Mears 

Creek, two adults along Mosquito Creek, 13 adult frogs on Slate Creek, two adult 

frogs on North Fork Slate Creek, three frogs on Little Slate Creek, three adults 

along Whitlow Creek, one adult frog on Campbell Creek, and five frogs on Boulder 

Creek. On 15 April 1996, C. Luke observed one frog at Sims Flat and two frogs at 

Conant River Access. On 16 April 1996, J. Miller observed one adult frog along 

Shotgun Creek, one adult frog on Little Castle Creek, and three frogs along Castle 

Creek, and C. Luke observed one frog along Castle Creek. 

In the 2000s, several observations of foothill yellow-legged frogs were documented in the Shasta region of Shasta-Trinity National Forest. On 16 March 2007, 

Michael Peters observed four foothill yellow-legged frogs along Cornish Creek 

between the Upper Sacramento Ditch Trail and the Sacramento River. On 21 June 

2009, Peters observed one foothill yellow-legged frog along Cornish Creek. On 9 

March 2010, Peters observed two frogs along Cornish Creek. On 16 January 2011, 

Peters observed one frog along Dry Creek, below the Dry Creek Trailhead in Lake 

Shasta National Recreation Area. On 30 April 2011, Peters observed two foothill 

yellow-legged frogs along Dry Creek upstream of Westside Road and one frog 

along a small tributary of Dry Creek. 

During the relicensing of the three dams along the Pit River encompassed 

in Pacific Gas and Electric Company’s Pit 3,4,5 hydroelectric project, foothill 

yellow-legged breeding sites have been located throughout the middle Pit 4 reach 

(Spring Rivers Ecological Sciences 2003, 2004). Some sightings of adult frogs have 

occurred in the Pit 5 reach and none have been found in the most-upstream Pit 3 

reach. Surveys for foothill yellow-legged frogs were also conducted for Pacific 

Gas and Electric Company’s McCloud/Pit Project. Foothill yellow-legged frog egg 

masses, tadpoles and young-of-year were observed along Lower McCloud River. In 

2007, one adult foothill yellow-legged frog was observed on 4 June. No life stages 
111 

Foothill Yellow-Legged Frog Conservation Assessment

of foothill yellow-legged frogs were detected at the Pit River (Pit 6, Pit 7 reaches), 

or Iron Canyon Creek sites (PG&E and Stillwater Sciences 2009b). 

Trinity Reservoir and Trinity River tributaries—In October 1990, M.R. Jennings 

collected four foothill yellow-legged frogs at a location along California highway 

SR-299, 22 to 23 mi west of Big Bar Ranger Station (CAS 178749, 178750, 180305, 

183178). On 11 March 1996, an unnamed individual observed two foothill yellowlegged frogs along Fawn Creek. 

From 1991 to 1994, A. Lind, H. Welsh, Jr., and Randolph Wilson (U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station, Redwood 

Sciences Laboratory) conducted surveys for foothill yellow-legged frogs along the 

mainstem Trinity between Lewiston and Helena (Lind et al. 1996). In 1994 and 

1995, Lind and Welsh surveyed breeding sites along the mainstem and South Fork 

of the Trinity River. In 1994, a total of two egg masses were observed at mainstem 

sites and 20 at South Fork sites. In 1995, no egg masses were detected at mainstem 

sites and a total of three egg masses were observed at South Fork sites. 

From 2004 to 2009, Jamie Bettaso, Don Ashton, and H. Welsh, Jr., conducted 

foothill yellow-legged frog egg mass surveys along sections of the mainstem, 

North Fork, and South Fork of the Trinity River. From 2006 to 2009, they also 

surveyed breeding sites along Canyon Creek and in 2008 and 2009 they added 

surveys at known breeding sites along the upper Trinity River, Stuart’s Fork, and 

Weaver Creek. Reproduction was detected at all sites, but egg mass counts varied 

by tributary. Egg masses were particularly sparse along the managed mainstem 

Trinity; they found fewer than two egg masses per river kilometer on the mainstem 

compared to 34 to 165 egg masses per kilometer on the South Fork and 39 to 83 egg 

masses per kilometer on the North Fork (Wheeler et al. 2013; additional data available from Bureau of Reclamation, Trinity River Restoration Program). 

On 23 June 2011, R.J. Adams observed several frogs along the South Fork Trinity River near Little Rock Picnic Area by the town of Hyampom. 

Fifteen additional records from surveys of the Shasta-Trinity National Forest 

during the 1990s and 2000s (USDA Forest Service NRIS database) document 

observations of foothill yellow-legged frogs at Sulphur Creek, South Fork Sacramento, Big Canyon Creek, and Charlie Creek within the Shasta region and at East 

Fork South Fork Trinity River, French Gulch (a tributary of Clear Creek), Lower 

Browns Creek, Lower North Fork Trinity River, East Fork Hayfork Creek, and 

Olson Creek (a tributary of Hayfork Creek, and Pelletreau Creek (a tributary of 

South Fork Trinity River) within the Trinity region. 
112 

GENERAL TECHNICAL REPORT PSW-GTR-248

Lassen National Forest 

Pre-1980— 

Only three pre-1980 records of foothill yellow-legged frogs exist for the Lassen 

National Forest. The oldest record for the Lassen National Forest appears to be 

from Rice Creek, a tributary of the North Fork of the Feather River, where Charles 

M. Miller collected one foothill yellow-legged frog on 21 July 1938 (MVZ 34703). 

On 20 March 1965, Kenneth Evans collected three foothill yellow-legged frogs on 

Little Butte Creek at its intersection with Hupp Coutolenc Road (CSUC 1568–1570). 

The latter site is located on an isolated patch of the Lassen National Forest that is 

administered by the Plumas National Forest. Over the interval 1973 to 1978, M. 

Hayes revisited the Coon Hollow localities and Hupp Coutolenc Road localities four 

times; one to four foothill yellow-legged frogs were recorded at each visit to the 

Coon Hollow locality, but no foothill yellow-legged frogs were found near the Hupp 

Coutolenc Road crossing despite searches that extended along Little Butte Creek 0.8 

km (0.5 mi) up and downstream from the collection record. Hence, by the end of the 

1970s, foothill yellow-legged frogs may have been extirpated from at least one site 

on the Lassen National Forest. 

Several additional pre-1980 records exist for drainages that extend onto Lassen National Forest lands, but these records are located downstream of the current 

national forest boundary; some records also exist for drainages that extend a shorter 

distance up the Sierran slope so that they do not extend onto national forest lands. 

Both types of records encompass eight drainage basins that are primary tributaries of the Sacramento River, including Battle, Big Chico, Butte, Cow, Dye, Mill, 

Paynes, Rock, and Stillwater Creeks; some records also exist for the mainstem 

Sacramento River. Discussion of these records is alphabetized by the drainage 

system in which they occur. 

Battle Creek—On 28 May 1926, Jean M. Linsdale collected one foothill yellowlegged frog at the mouth of Battle Creek near the Sacramento River (MVZ 10137). 

On 31 March 1932, Henry S. Fitch collected one foothill yellow-legged frog on the 

North Fork of Battle Creek (MVZ 14973). On 24 March 1964, E. Bryant collected 

one foothill yellow-legged frog near the Darrah Springs springhead close to the 

Darrah Springs Fish Hatchery (CSUC 1143); Darrah Springs flows into Baldwin 

Creek, a tributary of Battle Creek. 

Big Chico Creek—On 21 October 1945, Thomas L. Rodgers collected 12 foothill yellow-legged frogs from Big Chico Creek, 12.8 km (8 mi) northeast of Chico 

(MVZ 42727–42738). 
113 

Foothill Yellow-Legged Frog Conservation Assessment

Butte Creek—On 2 January 1946, B. Matthews collected one foothill yellowlegged frog near the Centerville Covered Bridge over Butte Creek (MVZ 51657). 

On 22 April 1952, P. Moretti collected one foothill yellow-legged frog 11.2 km 

(7 mi) east of Chico on the north side of Butte Creek (MVZ 56838). 

Cow Creek—On 13 November 1945, Robert C. Stebbins collected one foothill yellow-legged frog on Dry Creek 12.8 km (8 mi) northeast of the junction of Highways 

99 and 299 (MVZ 42167); Dry Creek is a tributary of Little Cow Creek, which 

flows into Cow Creek. On 3 May 1953, Richard Zweifel collected four foothill 

yellow-legged frogs 1.6 km (1 mi) northeast of Ingot along Little Cow Creek (MVZ 

59621–59624). On 27 March 1954, M. Hammon collected one foothill yellow-legged 

frog 8 km (5 mi) southwest of Whitmore along South Cow Creek (CSUC 1207). 

Dye Creek—On 1 April 1970, Reginald H. Barrett collected 14 foothill yellowlegged frogs on Dye Creek 9.6 km (6 mi) east and 5.6 km (3.5 mi) north of Gerber 

(MVZ 89694–89707). 

Mill Creek—Between 8 and 13 June 1912, Tracy I. Storer and Walter P. Taylor collected six foothill yellow-legged frogs 3.2 km (2 mi) northeast of Tehama (MVZ 

4063–4068). 

Paynes Creek—On 12 May 1924, Adrey E. Borell collected two foothill yellowlegged frogs at 105 m (400 ft) elevation along Paynes Creek (MVZ 9968–9969). 

On 14 May 1924, Borell collected another foothill yellow-legged frog at 92 m (350 

ft) elevation along Paynes Creek (MVZ 9970). On 18 May 1924, Joseph Grinnell 

collected one foothill yellow-legged frog at Dale’s Ranch on Paynes Creek (MVZ 

9974). Borell also collected one foothill yellow-legged frog at the same locality on 

each of two dates: 29 May and 1 June 1924 (MVZ 9975–9976). On 5 June 1924, 

Borell also collected four foothill yellow-legged frogs 8 km (5 mi) west of the 

Paynes Creek Post Office (MVZ 9977–9980). From 8 to 14 June 1924, Borell collected three foothill yellow-legged frogs from Lyman’s, a location on Paynes Creek, 

6.4 km (4 mi) northwest of Lyonsville (MVZ 10024–10026). On 19 July 1926, T. 

Storer collected one foothill yellow-legged frog at 305 m (1,000 ft) elevation along 

Paynes Creek (CAS 218321). On 15 February 1931, Lawrence V. Compton collected one foothill yellow-legged frog on an unnamed tributary of Paynes Creek at 

Meadow Ranch, 4.8 km (3 mi) west of the Paynes Creek Post Office (MVZ 12597). 

Rock Creek—On 2 April 1950, W. T. Byerly collected two foothill yellow-legged 

frogs from Cohasset Pioneer Springs on the Anderson Fork (MVZ 56831–56832), a 

tributary of Rock Creek. 
114 

GENERAL TECHNICAL REPORT PSW-GTR-248

Sacramento River proper—On 4 October 1911, J. Slevin collected three foothill 

yellow-legged frogs along the Sacramento River at Redding (CAS 30663–30665). 

On 14 May 1924, A. Borell collected three foothill yellow-legged frogs along the 

Sacramento River 8 km (5 mi) north of Tehama (MVZ 9971–9973). On 28 August 

1926, Carl L. Hubbs collected one foothill yellow-legged frog along the Sacramento 

River below Red Bluff (UMMZ 71494). On 5 April 1928, J. Linsdale collected four 

foothill yellow-legged frogs along the Sacramento River 12.8 km (8 mi) north of 

Red Bluff (MVZ 10902–10905). 

From 1973 to 1976, M. Hayes made 16 different visits to the Borell, Hubbs, 

Linsdale, and Slevin collection localities on the Sacramento River that comprised 

over 142 hours of effort, but no foothill yellow-legged frogs were found; American 

bullfrogs were the only ranid frog recorded during these sites visits. Extensive 

hydrological alteration and widespread warmwater fish and bullfrog introduction 

over the Sacramento Valley (Moyle 2002) since these mainstem records were made 

(all prior to 1930) make it possible that, by the mid-1970s, foothill yellow-legged 

frogs had been extirpated on the mainstem Sacramento River. 

Stillwater Creek—On 3 May 1953, R. Zweifel collected one foothill yellow-legged 

frog along Salmon Creek, 6.4 km (4 mi) west-southwest of Bella Vista (MVZ 

59625). Salmon Creek is a tributary of Stillwater Creek, which is a primary tributary of the Sacramento River. 

1980 to present— 

Scattered records for foothill yellow-legged frogs on the Lassen National Forest 

are a composite of few collections and a larger number of sightings based on various surveys and data compiled through the Federal Energy Regulatory Commission 

(FERC) relicensing process. Surveys on the Lassen National Forest that the 

California Academy of Sciences conducted over the period 2001 to 2003 document 

four localities based on specimens. On 16 August 2001, Guin Wogan collected one 

adult foothill yellow-legged frog on mossy rocks in falls near a large pool at 1,145 

m (4,360 ft) elevation in Mill Creek (CAS 221024). On 28–29 May 2003, Daniel G. 

Mulcahy collected foothill yellow-legged frogs from three localities in the Antelope 

Creek system: at 368 m (1,400 ft) elevation on Antelope Creek (CAS 226962), and 

375 m (1,430 ft) and 394 m (1,500 ft) elevation on Indian Creek (CAS 226983– 

226984). 

Several records documented since 1980 exist for drainages that extend onto 

Lassen National Forest, but these are from elevations below national forest lands. 

Dye Creek—During a site visit to the Dye Creek Ranch on 11 September 1996, 

M. Jennings collected one juvenile foothill yellow-legged frog on the North Fork 
115 

Foothill Yellow-Legged Frog Conservation Assessment

of Dye Creek on the Dye Creek Ranch (CAS 203175). Foothill yellow-legged 

frogs were only observed some distance up the foothill canyon of Dye Creek, but 

not on the portion of Dye Creek that emerges from the foothill canyon onto the 

Sacramento Valley floor (Jennings 2007). Foothill yellow-legged frogs became 

more abundant in tributaries of the Dye Creek mainstem where bullfrogs were 

sparse; there dozens of foothill yellow-legged frogs were observed over short 

reaches. This single-day survey covered more than 3.2 km (2 mi) of Dye Creek and 

its tributaries. 

Plumas National Forest 

Pre-1980— 

Many historical collections of foothill yellow-legged frogs are known from the 

Plumas National Forest and other lands either in inholdings or the west-slope Sierra 

below the Plumas National Forest boundary. The earliest record from the vicinity 

of what was to be the Plumas National Forest is a collection of nine foothill yellow-legged frogs made by C. Rutter on 2 September 1899 along Spanish Creek at 

Quincy (CAS-SU 1696–1704); this collection locality is on private land. On 26 May 

1912, Walter Penn Taylor collected two foothill yellow-legged frogs from Chambers 

Ravine, 6.4 km (4 mi) north of Oroville (MVZ 4057–4062). The earliest record 

from the Plumas National Forest proper consists of one foothill yellow-legged frog 

collected at Meadow Valley along Spanish Creek by Edwin C. Van Dyke in June 

1924 (CAS 63818). No additional foothill yellow-legged frog records exist for the 

Plumas National Forest from the 1920s. 

One record of foothill yellow-legged frogs exists for the Plumas National 

Forest from the 1930s. T. Storer collected three foothill yellow-legged frogs from 

Last Chance Creek at a point 9.6 km (6 mi) south of Milford on 18 July 1932 (CAS 

218328–218330). One additional record of foothill yellow-legged frogs was made 

on non-Forest Service land below the Plumas National Forest boundary during the 

1930s. On 9 April 1937, Victor C. Twitty collected 13 foothill yellow-legged frogs 

along Cherokee Creek in Sawmill Canyon (CAS-SU 2576–2588). By the end of the 

1930s, foothill yellow-legged frogs had been recorded from two localities on the 

Plumas National Forest, and three additional localities at elevations below Plumas 

National Forest lands. 

Two records of foothill yellow-legged frogs exist for the Plumas National Forest 

from the 1940s. Walter W. Dalquest collected six foothill yellow-legged frogs from 

Dooley Creek, a tributary of Last Chance Creek, at a point 2.4 km (1.5 mi) westsouthwest of McKesick Peak on 15 July 1941 (MVZ 35914–35919). In 1942 
116 

GENERAL TECHNICAL REPORT PSW-GTR-248

(no specific date), Robert R. Miller collected one foothill yellow-legged frog 14.4 

km (9 mi) north-northwest of Beckwourth (UMMZ 91679). Eight additional records 

of foothill yellow-legged frogs were made on non-Forest Service land below the 

Plumas National Forest boundary during the 1940s. On 9 March 1941, Harvey 

I. Fisher collected three foothill yellow-legged frogs at Bidwell Bar Park on the 

Feather River (MVZ 34837–34839); Lake Oroville now inundates this locality. On 

14 September 1945, T. Rodgers collected one foothill yellow-legged frog from Mud 

Creek at Richardson Springs (MVZ 42725). On 21 October 1945, Rodgers also 

collected two foothill yellow-legged frogs from Butte Creek at De Sabla, 12.8 km 

(8 mi) north of Paradise (MVZ 32726, 32739); De Sabla Reservoir inundates this 

locality today. On the same date, Rodgers collected 12 foothill yellow-legged frogs 

along Big Chico Creek, 12.8 km (8 mi) northeast of Chico (MVZ 42727–42738). 

On 2 January 1946, B. Matthews collected one foothill yellow-legged frog along 

Butte Creek at the Centerville Covered Bridge (MVZ 51657). On 20 March 1948, a 

collector by the name of Isaac collected one foothill yellow-legged frog 12 km (7.5 

mi) east of Chico (CSUC 1261). On 23 March 1946, P. Collett and B. Matthews each 

collected one foothill yellow-legged frog on Little Butte Creek below Magalia Dam 

(MVZ 51658–51659). On 18 May 1946, A. Santos collected one foothill yellowlegged frog at Cherokee along the North Fork of the Feather River, 32 km (20 mi) 

southeast of Chico. By the end of the 1940s, foothill yellow-legged frogs had been 

recorded from five localities on the Plumas National Forest, and 11 additional 

localities at elevations below Plumas National Forest lands. 

Four records of foothill yellow-legged frogs exist for the Plumas National 

Forest from the 1950s, three of which were new. On 19 June 1951, George B. Rabb 

re-collected the Meadow Valley locality, where he took one foothill yellow-legged 

frog (UMMZ 104997). On 7 July 1951, Rabb also collected one foothill yellowlegged frog along Rock Creek at a point 8 km (5 mi) southwest of Quincy (UMMZ 

104998). On 31 May 1952, R. Zweifel collected 28 foothill yellow-legged frogs at 

a different locality along Last Chance Creek: 8.8 km (5.5 mi) west of McKesick 

Peak (MVZ 58058–58172). On the same date, Frederick L. Turner collected one 

foothill yellow-legged frog 1.6 km (1 mi) east of Blairsden (LACM 8502). Nine 

additional records of foothill yellow-legged frogs were made on non-Forest Service 

land below the Plumas National Forest boundary during the 1950s. On 2 April 

1950, W. T. Byerly collected two foothill yellow-legged frogs along the Anderson 

Fork at Cohasset Pioneer Springs (MVZ 56831–56832). On 14 April 1950, G. Snow 

collected one foothill yellow-legged frog along Rich Gulch at Yankee Hill (MVZ 
117 

Foothill Yellow-Legged Frog Conservation Assessment

56836). On 15 April 1950, E. Schneegas collected one foothill yellow-legged frog at 

this same locality (MVZ 56833). On 20 April 1950, H. Meyer collected one foothill yellow-legged frog at Cole Canyon Falls, 4.8 km (3 mi) south of Pentz (MVZ 

56837). On 1 March 1952, R. Zweifel collected four foothill yellow-legged frogs 

along Butte Creek 2.6 km (1.6 mi) by road west of De Sabla (MVZ 58033–58036). 

On 1 April 1952, H. Wiedman collected one foothill yellow-legged frog along Rock 

Creek 0.8 km (0.5 mi) east of Richardson Springs (MVZ 56834). On 22 April 1952, 

P. Moretti collected two foothill yellow-legged frogs along Butte Creek, 11.7 km (7 

mi) east of Chico (MVZ 56838). On 28 March 1953, C. Dart collected one foothill 

yellow-legged frog at Forbestown on an unnamed tributary of the South Fork of 

the Feather River (CSUC 1425). On 2 May 1953, Zweifel also collected one foothill 

yellow-legged frog along Butte Creek at Magalia (CSUC 59657). On 6 May 1954, J. 

Campbell collected one foothill yellow-legged frog along Mud Creek above Richardson Springs (CSUC 1557). By the end of the 1950s, foothill yellow-legged frogs 

had been recorded from eight different localities on the Plumas National Forest, and 

20 additional localities at elevations below Plumas National Forest lands. 

Three records of foothill yellow-legged frogs exist for the Plumas National 

Forest from the 1960s; all were new. On 9 May 1961, Vicki Jones collected one 

foothill yellow-legged frog along the Middle Fork of the Feather River 1.6 km (1 mi) 

downstream of Feather Falls (CSUC 1197); Lake Oroville inundated this locality 

during its filling over the years 1967–1969. On 8 July 1961, D. Collett collected 

one foothill yellow-legged frog at a new locality along Spanish Creek: a location 

9.6 km (6 mi) above Quincy (CSUC 1179); some uncertainty exists regarding the 

language “above” used to record this locality; the most likely interpretation is one 

that refers to elevation on Spanish Creek above Quincy. On 9 July 1961, C. Williams collected two foothill yellow-legged frogs at McNair, a locality along Sulfur 

Creek, 11.2 km (7 mi) south of Blairsden (CSUC 1146–1147). Nineteen additional 

records of foothill yellow-legged frogs were made on non-Forest Service land below 

the Plumas National Forest boundary during the 1960s. On 22 February 1960, T. 

Rodgers collected one foothill yellow-legged frog on Little Butte Creek 183 m (200 

yd) below Magalia Reservoir (CSUC 1426). On 12 March 1960, R. Russel collected 

four foothill yellow-legged frogs on Big Chico Creek below 10-Mile House (CSUC 

1553–1556). On 24 March 1960, Rodgers collected two foothill yellow-legged frogs 

along Big Chico Creek at Salmon Hole (CSUC 1561–1562). On 1 April 1960, N. 

Jensen collected 27 foothill yellow-legged frogs along Mud Creek 0.8 km (0.5 mi) 

upstream from Richardson Springs (CSUC 1511–1537). On 30 April 1960, N. Jensen 

collected two foothill yellow-legged frogs where Little Butte Creek enters Paradise 

Reservoir (CSUC 1563–1564). On 26 May 1960, R. Parker collected one foothill 
118 

GENERAL TECHNICAL REPORT PSW-GTR-248

yellow-legged frog along the Anderson Fork, a tributary of Rock Creek, 12.8 km (8 

mi) northeast of the Chico Airport (CSUC 1199). On 2 May 1961, M. Attinger and 

N. Polston each collected one foothill yellow-legged frog along Mud Creek above 

Richardson Springs (CSUC 1558–1559). On 4 May 1961, D. Tener collected one 

foothill yellow-legged frog at this same locality (CSUC 1560). On 7 May 1961, G. 

Beem collected two foothill yellow-legged frogs on Butte Creek near Chico (CSUC 

1430–1431). On 8 May 1961, D. Winter collected three foothill yellow-legged frogs 

on Big Chico Creek, 1.6 km (1 mi) above its confluence with Mud Creek (CSUC 

1424, 1525–1526). On 9 May 1961, three foothill yellow-legged frogs were collected 

along Butte Creek 0.4 km (0.25 mi) above De Sabla (CSUC 1427–1429). On 3 July 

1961, D. Collett collected two foothill yellow-legged frogs along Butte Creek, 5.6 

km (3.5 mi) upstream of Centerville School (CSUC 1422–1423). On 26 July 1961, 

Darryl Torgerson collected two foothill yellow-legged frogs along the West Branch 

of the Feather River, 4.8 km southeast of Stirling City (CSUC 1144–1145). On 23 

March 1962, M. Frost collected one foothill yellow-legged frog along Rock Creek, 

9.6 km (6 mi) north of Chico (CSUC 1206). On 2 May 1963, G. Gaetsen collected 

one foothill yellow-legged frog at Bear Hole along Big Chico Creek (CSUC 746). On 

21 May 1963, R. Barden collected five foothill yellow-legged frogs along Big Chico 

Creek above Salmon Hole (CSUC 747–751). On 22 May 1963, P. Croner collected 

two foothill yellow-legged frogs along Big Chico Creek, 16 km (10 mi) upstream 

of the Bidwell Park golf course (CSUC 744–745). On 3 July 1963, D. Collette 

collected three foothill yellow-legged frogs in the upper Centerville Canal at De 

Sabla (CSUC 1171–1173). On 23 March 1964, an unnamed collector collected one 

foothill yellow-legged frog at the end of Helltown Road, 3.2 km (2 mi) northeast of 

Centerville (CSUC 1380). In spring (date not specified) of 1964, Christopher Dokos 

collected two frogs from Magalia Reservoir (CSUC 1382–1383). By the end of the 

1960s, foothill yellow-legged frogs had been recorded from 12 different localities on 

the Plumas National Forest, and 39 additional localities at elevations below Plumas 

National Forest lands. 

Three records of foothill yellow-legged frogs exist for the Plumas National 

Forest from the 1970s, but all represent sight records of previously collected sites. 

Over the interval 1973–1978, M. Hayes visited three of the historical localities on 

Plumas National Forest lands collected during the 1950s: the Meadow Valley and 

Rock Creek localities collected by Rabb, and the Last Chance Creek locality collected by Zweifel. A few (one to three) foothill yellow-legged frogs were recorded 

on each of four visits. Five records of foothill yellow-legged frogs were made on 
119 

Foothill Yellow-Legged Frog Conservation Assessment

 

non-Forest Service land below the Plumas National Forest boundary during the 

1970s; one represents a new record vouchered by a specimen, the remaining four 

are sight records from previously collected sites. On 29 November 1971, Theodore 

J. Papenfuss collected one foothill yellow-legged frog along the Little North Fork 

of the Feather River, 3.2 km (2 mi) upstream from the junction with the Middle 

Fork of the Feather River (MVZ 117615). Over the interval 1973–1978, M. Hayes 

visited four historical localities along Big Chico Creek at elevations below Plumas 

National Forest lands; these included Bear Hole, Salmon Hole, 1.6 km (1 mi) above 

its confluence with Mud Creek, and below 10-Mile House. All were visited at least 

eight times each. Foothill yellow-legged frogs were recorded at three of the four 

Big Chico Creek localities, all above where the stream enters its foothill canyon 

(i.e., in upstream progression, Salmon Hole, Bear Hole, and below 10-Mile House), 

but were absent from the valley floor location above the confluence of Big Chico 

Creek with Mud Creek, where only American bullfrogs were present. By the end of 

the 1970s, foothill yellow-legged frogs had been recorded from 12 different localities on the Plumas National Forest, and 40 additional localities at elevations below 

Plumas National Forest lands. Foothill yellow-legged frogs seem to have disappeared from at least one valley floor site at that time, but available data imply that 

the species was still present over its Sierra range in this region. 

1980 to present— 

Systematic surveys on the Plumas National Forest were not initiated until the 1990s. 

From 1998 to 1999, field crews from the California Academy of Sciences (CAS) 

spent significant time surveying for amphibians and reptiles on the Plumas National 

Forest (Koo and Vindum 1999). Crews consisted of two to four people. In 1998, 

crews spent 64 days conducting surveys between 27 April and 22 October; in 1999, 

46 days were spent conducting surveys between 5 June and 5 October. Surveys in 

1998 and 1999 covered about 35 and 30 sites, respectively, with potential habitat for 

foothill yellow-legged frogs; this included 24 sites (both years combined) where the 

species has been recorded historically. Foothill yellow-legged frogs were recorded 

at only 45 percent (n = 11) of the sites where they were historically found (voucher 

specimen numbers indicated in parentheses). Foothill yellow-legged frogs were 

recorded at all six historical sites in the Canyon Creek drainage (including Onion 

[CAS 206277, 206309] and Slate Creeks; [CAS 205984, 206276, 206297, 206308, 

209249]) and both historical sites in the South Fork Feather River drainage (including Oroleve Creek; CAS 206366); however, they were detected at two of four sites 

in the Middle Fork of the Feather River (i.e., two unnamed tributaries east of Milsap 
120 

GENERAL TECHNICAL REPORT PSW-GTR-248

Bar; CAS 205588, 205590), only one of seven sites in the East Branch of the North 

Fork Feather River (i.e., Spanish Creek; CAS 206271), and none were found in either of the two historical sites in Little Butte Creek or the one historical site in each 

of Dry Creek (3.2 km [2 mi] southwest of Forbestown), the North Fork Yuba River, 

and the West Branch Feather River. 

Since the CAS surveys, the Plumas National Forest has continued to conduct 

extensive amphibian surveys to detect additional foothill yellow-legged frog locations. Plumas National Forest surveys since the CAS surveys, found that all sites (or 

drainages) in which foothill yellow-legged frogs were detected during CAS surveys 

still appear to have foothill yellow-legged frogs present. Without a detailed study 

design and rigorous statistical analysis, population estimates cannot be made from 

the data collected on the forest. In the last 10 years, foothill yellow-legged frogs 

have been detected at several locations in addition to the 24 historical sites (contact 

K. Hopkins or G. Garcia, Plumas National Forest, for details on locations). 

Extensive surveys and monitoring of the frog populations in the Poe and Cresta 

reaches of the North Fork Feather River have been conducted by Garcia and Associates for Pacific Gas and Electric Company and the California Energy Commission 

since 2001 (GANDA 2005, 2006, 2008). The population on the Poe reach has been 

increasing over this period. In comparison, the Cresta population, which experienced 4 years of monthly spring and summer whitewater boating flows, declined 

significantly relative to Poe (PG&E data analyzed in Kupferberg et al. 2012). In 

2006, surveys conducted for Pacific Gas and Electric Company’s De Sabla-Centerville Project relicensing revealed the presence of all life stages of foothill yellowlegged frogs along both Butte Creek and West Branch Feather River, but in varying 

abundances (Pacific Gas and Electric Company 2008). These data along with other 

amphibian data collected during recent hydropower relicensing activities (FERC 

project nos. 2088, 2107, 1962) have not yet been incorporated into Plumas National 

Forest and other databases (GIS, NRIS). 

Mendocino National Forest 

Pre-1980— 

The first and only records of foothill yellow-legged frog specimens sampled on the 

Mendocino National Forest prior to the 1980s were three frogs collected by Edward 

L. Kessel on 19 November 1960; two were collected at an unnamed site located 1 

mi south of Red Bridge (CAS 88627 and 88628) and one frog was collected at a site 

1 mi north of Red Bridge (CAS 88629). 
121 

Foothill Yellow-Legged Frog Conservation Assessment

1980 to present— 

One record exists of specimens collected in Mendocino National Forest in the 

1980s. On 8 April 1989, M. Jennings collected four foothill yellow-legged frogs on 

an unnamed western tributary of the South Fork of Stony Creek at Davis Flat (CAS 

173738, 173739, 180303, 180304). 

Numerous specimens were collected from Mendocino National Forest during 

the 1990s. J.V. Vindum collected one frog on Beaver Creek (CAS 185330) on 4 

July 1992, and one frog on 29 August 1992 on Buck Rock Creek (CAS 186226). In 

1995, Jens V. Vindum collected one frog on Mendocino Pass Rd. (CAS 198828). 

In 1996, Vindum collected two frogs on 11 May; one was captured 2.6 mi west 

of Soda Creek (CAS 201244) and the other along Soda Creek (CAS 201248) and 

one frog on 18 August at Black Butte River (CAS 201571). On 24 February 1997, 

Vindum also collected one frog at North Fork Campground (CAS 202581) and one 

frog at Brittan Ranch (CAS 202583). On 29 March 1997, Vindum collected one 

frog at Brittan Ranch (CAS 202599). On 12 May 1997, John J. Crayon collected one 

frog along the north fork of Cache Creek at Spanish Creek (CAS 203612) and on 14 

May 1997, he collected one specimen along Wolf Creek at Salt Lick Canyon (CAS 

203682). On 25 April, 1997, M. Jennings collected one frog at Bear Creek, 0.4 mi 

upstream from Wilbur Springs Road Bridge (CAS 203203) and on 10 June 1997, 

he collected one frog along Bear Creek at Thompson Canyon (CAS 203204). On 

12 May 1997, Jennings also collected one frog along the north fork of Cache Creek 

at Spanish Creek (CAS 203613). Jennings and J. Crayon collected two frogs on the 

east fork of Middle Creek on 14 May 1997 (CAS 203652 and 203680). On 12 May 

1997, Norman J. Scott, Jr. collected one frog along Spanish Creek, 0.2 mi above the 

confluence, 10.7 mi north-northeast of Clearlake Oaks (CAS 203675). On 14 May 

1997, Scott, also collected three frogs from the west fork of Middle Creek at South 

Fork, 6.7 mi north-northeast of Upper Lake (CAS 203664, 203665, 203685). On 

24–26 May 1999, Michelle S. Koo and R.S. Lucas collected one frog along Wolf 

Creek (CAS 209138), one frog in Quartz Canyon, along a tributary of Wolf Creek 

(CAS 209147), and two frogs along East Fork Middle Creek (CAS 209152, 209167). 

On 14 June 1999, R.S. Lucas and Vindum collected one frog along Bar Creek (CAS 

208976). They collected one frog on 15 June 1999 along an unnamed creek (CAS 

208990), one frog on 16 June 1999 at Pothole Creek (CAS 209003), and one frog on 

18 June 1999 at South Fork Bear Creek (CAS 209038). Lucas and Vindum collected 

one frog on 19 June 1999 on Black Butte River, ca. 100 m upstream of Cold Creek 

confluence (CAS 209051) and one frog on 24 June 1999 on Black Butte River, 
122 

GENERAL TECHNICAL REPORT PSW-GTR-248

downstream of The Basin (CAS 209128). From 15–17 September 1999, Lucas and 

Vindum collected three frogs along South Fork Stony Creek (CAS 209515, 209520, 

209536) and one frog along Stony Creek (CAS 209542). 

Surveys by various individuals during the 1990s produced additional records of 

foothill yellow-legged frog detections in Mendocino National Forest (USDA Forest 

Service NRIS database). On 1 January 1994, Art Shapiro observed foothill yellowlegged frogs on Little Stony Creek between Ruby King Mine and the cattle guard. 

On 10 April 1995, George Elliot observed an unknown number of frogs at the north 

end of Davis Flat OHV area along an unnamed creek. Teresa Sue observed one frog 

at Alder Springs, near Camp Ellendale on 3 July 1996. On 16 October 1996, Lee 

Morgan observed numerous frogs (ca. 100) at Wolf Creek, upstream and adjacent 

to the Spring Valley subdivision. Linda Angerer observed one frog at Middle Creek 

on 1 January 1997 and one frog at Thomas Pocket, an undeveloped campground on 

24 July 1997. On 8 June 1997, Mike Ramsey observed two frogs (suspected to be 

foothill yellow-legged frogs) at Thomes Creek. 

Numerous collections occurred during the 2000s. On 31 July 2000, R. Lucas, 

R. Stoelting, Chris R. Feldman, and J. Vindum collected one frog along the North 

Fork Stony Creek (CAS 212559). On 1 August 2000, Stoelting and Vindum collected one frog along Mill Creek, upstream of Mill Creek Campground (CAS 

212578) and Lucas and Feldman collected one frog from an unnamed creek between 

Wolf Glade and Diversion Dam Campground (CAS 212585). On 3 August 2000, 

Lucas and Feldman collected one frog from Corbin Creek (CAS 212626). On 5 

August 2000, Feldman and Vindum collected one frog along Thomes Creek (CAS 

212653) and one frog along Willow Creek, upstream of Thomes Creek confluence 

(CAS 212659). On the same day, Stoelting and Lucas collected one frog along 

Thomes Creek (CAS 212672). On 7 August 2000, Stoelting and Feldman collected 

one frog along Sullivan Creek, upstream of Little Stony Creek confluence (CAS 

212693), and Lucas and Vindum collected one specimen from Little Stony Creek, 

between the Sullivan and Trout Creek confluences (CAS 212713). On 8 August 

2000, Feldman and Vindum collected one frog along Little Stony Creek, upstream 

of Trout Creek confluence (CAS 212727), and Lucas and Stoelting collected one 

frog along Little Stony Creek, downstream of Little Stony Creek Campground 

(CAS 212734). On 9 August 2000, Lucas and Feldman collected one frog along 

Little Sullivan Creek (CAS 212749). Between 6–7 June 2001, Lucas and Vindum 

collected five frogs along Rice Creek, a tributary of the Eel River (CAS 219461, 

219462, 219466, 219481, 291485). From 9–14 June 2001, Lucas and Vindum collected six frogs on the State Game Refuge; one frog was collected at each location 
123 

Foothill Yellow-Legged Frog Conservation Assessment

including Trout Creek (CAS 219509), Eel River (CAS 219528), Horse Creek (CAS 

219543), Corbin Creek (CAS 219556), Anderson Creek (CAS 219570), and Rattlesnake Creek (CAS 219585). On 15 June 2001, Lucas and Vindum collected one frog 

along Panther Creek (CAS 219590). On 21 August 2001, Wilkinson and Vindum 

collected one frog along an unnamed tributary to the Middle Fork Eel River in 

the Blands Cove area (CAS 220681). On 22 August 2001, Wilkinson and Vindum 

collected one frog along Rattlesnake Creek (CAS 220692). They collected one 

frog along Hammerhorn Creek (CAS 220714) on 23 August 2001, and two frogs 

on 24 August 2001, one along Maple Creek (CAS 220742) and one on Alder Creek 

(CAS 220749). Wilkinson and Vindum collected one frog on 25 August 2001 at 

Balm of Gilead Creek in the Yolla Bolly Wilderness (CAS 220765) and one frog 

on 26 August 2001 along the Middle Fork Eel River (CAS 220778). On 28 August 

2001, Wilkinson and Vindum collected two frogs, one along Skeleton Creek (CAS 

220801) and one along an unnamed tributary to Skeleton Creek (CAS 22803). On 29 

August, they collected one frog along Copper Butte Creek in the Snow Mountain 

Wilderness (CAS 220806), one frog along the Eel River between the Copper Butte 

and Berry Creek confluences (CAS 220812), and one frog along Berry Creek (CAS 

220814). On 30 August, Wilkinson and Vindum collected one frog along Thistle 

Glade Creek (CAS 220837) and one frog along Hummingbird Creek (CAS 220841) 

within the Snow Mountain Wilderness. On 31 August, they collected one specimen 

at Deer Creek (CAS 220844). On 7–8 August 2001, Wogan and Lucas collected one 

frog along Blue Slides Creek (CAS 220934) and one frog along Rice Fork of the 

Eel River (CAS 220946). On 11 August 2001, Wogan and Lucas collected one frog 

along an unnamed tributary of the Eel River (CAS 220989). Wogan and Lucas collected four frogs from 14 through 16 August 2001; one frog was collected from each 

location including a drainage adjacent to Forest Road 24N35 (CAS 221011), Murphy 

Canyon Creek (CAS 221015), Dark Canyon Creek (CAS 221023) and Mill Creek 

(CAS 221024). On 22 February 2002, Vindum collected one frog along Forest Road 

M4 (CAS 223704). On 2 May 2004, Vindum collected one frog along a tributary 

between Howard Lake and Howard Creek (CAS 238631). 

On 26 June 2011, R.J. Adams observed 12 foothill yellow-legged frogs at Sulfur 

Creek, Vichy Springs in Ukiah. 

Surveys during the 1990s and 2000s (USDA Forest Service NRIS database) 

document additional foothill yellow-legged frog localities in Mendocino National 

Forest. Frogs were detected at Auger Creek (a tributary of Thomes Creek), Trout 

Creek (a tributary of Eel River), and Lower Grindstone Creek. 
124 

GENERAL TECHNICAL REPORT PSW-GTR-248

Tahoe National Forest 

Pre-1980— 

Scattered pre-1980 records of foothill yellow legged frogs exist for the Tahoe 

National Forest. All records are for the tributary network of the Yuba River system; 

some records do exist for the northern portion of the American River system on 

Tahoe National Forest lands, but all these were recorded post-1980.
 

Yuba River—On 17 April 1960, B. Parker collected three foothill yellow-legged 

frogs along Willow Creek, 3.2 km (2 mi) north of Camptonville (CSUC 1176–1178). 

On the same date, R. Parker collected six foothill yellow-legged frogs on the 

Middle Fork Yuba River, 16 km (10 mi) south of Downieville (CSUC 1200–1205). 

On 1 July 1961, Harold Houser collected seven foothill yellow-legged frogs in 

Washington Creek, 1.6 km (1 mi) south of Washington (CSUC 1164–1170). On 2 

July 1961, Houser also collected four foothill yellow-legged frogs along the South 

Yuba River, 6.4 km (4 mi) east of Washington (CSUC 1139–1142). On 3 July 1961, 

Houser further collected three foothill yellow-legged frogs along the South Yuba 

River, 4.8 km (3 mi) above its confluence with Canyon Creek (CSUC 1136–1138). 

On 9 July 1961, C. Williams collected 14 foothill yellow-legged frogs along the 

North Fork of the Yuba River at Ramshorn Creek (CSUC 1217–1230). On 1 June 

1966, Houser collected 12 foothill yellow-legged frogs on the Middle Yuba River 

below Graniteville (CSUC 1609–1620). On 17 July 1969, Houser also collected 

two foothill yellow-legged frogs 16 km (10 mi) north of Washington along South 

Poorman Creek (CSUC 1814–1815). 

Eleven historical records of foothill yellow-legged frogs also exist for portions 

of drainages below Tahoe National Forest lands. The oldest of these records is 

from 22 August 1899, when William F. Atkinson collected three foothill yellowlegged frogs from Bullards Bar (USNM 38817–38819); Bullards Bar Reservoir now 

inundates this locality. On 1 July 1903, J. G. Carlson collected one foothill yellowlegged frog along Deer Creek near Olympic Park, Nevada City, along the road 

to the Champion Mine (CAS 4753); this specimen was lost in the earthquake and 

fire of 1906 in San Francisco, but John Van Denburgh verified its identity against 

other foothill yellow-legged frog specimens currently in the CAS collection. On 22 

September 1938, Joel Hedgepeth collected two foothill yellow-legged frogs along 

the Yuba River at Moonshine Creek (USNM 312034–312035). On 11 September 

1943, Margaret Storey collected five foothill yellow-legged frogs along Dry Creek, 

4.8 km (3 mi) west of Challenge along the road between Brownsville and Challenge 

(CAS-SU 8605–8608, CAS 200842). On 15 April 1951, William Kamp collected 
125 

Foothill Yellow-Legged Frog Conservation Assessment

one foothill yellow-legged frog from a stream on Dean Ranch in the Sutter Buttes 

(CSUC 1106). On 2 March 1952, R. Zweifel collected nine foothill yellow-legged 

frogs along South Honcut Creek, a tributary of the lower mainstem Feather River, 

4.2 km (2.6 mi) east-northeast of Rackerby (MVZ 58049–58057). On the same date, 

Zweifel collected one foothill yellow-legged frog from Robinson Ravine, a tributary 

of South Honcut Creek, 5.0 km (3.1 mi) east of Bangor (MVZ 58037). On 12 April 

1953, Malcolm A. Miller collected one foothill yellow-legged frog along the North 

Fork American River, just above its confluence with the Middle Fork American 

River (CAS 218322). On 20 March 1960, B. Lang collected one foothill yellowlegged frog along New York Creek, a tributary of Dry Creek, 3.2 km (2 mi) southwest of Forbestown (CSUC 1160). On 23 September 1967, J. K. Barca collected two 

foothill yellow-legged frogs along Poorman Creek, 0.8 km (0.5 mi) west-northwest 

of Washington (CAS 181267–181268). On 15 July 1973, Susan M. Case collected 

13 foothill yellow-legged frogs near Washington along the South Yuba River and 

Washington Creek in the course of her studies on western North American ranid 

frogs (MVZ 136314–136326). 

1980 to present—
 

North Yuba River—Ten localities were recorded in the North Yuba River system. 

On 17 May 1997, Marilyn M. Tierney collected one foothill yellow-legged frog on 

an unnamed tributary of Woodruff Creek along Mountain House Road, 4.9 km 

(3.05 road mi) from Hwy 49 and 4.6 km (2.85 mi) south of Goodyears Bar (CAS 

202880). On the same date, Tierney also collected one foothill yellow-legged frog 

at the mouth of Humbug Creek along the North Yuba River (CAS 202875). On 20 

May 1997, Tierney collected one foothill yellow-legged frog along another unnamed 

tributary of Woodruff Creek 6.4 km (4 mi) from Hwy 49 (CAS 202918). On 16 June 

1997, Tierney collected one foothill yellow-legged frog along Kanaka Creek below 

the Silver Dollar Mine (CAS 203363). On 21 July 1997, Carol L. Spencer collected 

one foothill yellow-legged frog along Woodruff Creek, 0.96 km (0.6 mi) south of 

Goodyears Bar and 1.3 km (0.8 mi) south of Hwy 49 (CAS 203285). On the same 

date, Spencer also collected one foothill yellow-legged frog along Fiddle Creek at 

the Fiddle Creek trailhead (CAS 203284). On 21 August 1997, Spencer also collected one foothill yellow-legged frog from Youngs Ravine, ca. 100 m upstream 

from Forest Road 491-2 and Brandy City Road (= Forest Road 491-4) (CAS 203371). 

On 14 July 1998, Jeffrey A. Wilkinson collected a foothill yellow-legged frog at the 

mouth of Humbug Creek locality along the North Yuba River (CAS 205943). On 

the same date, Wilkinson also collected two foothill yellow-legged frogs along the 
126 

GENERAL TECHNICAL REPORT PSW-GTR-248

south bank of the mainstem North Yuba River at 630 m (2,400 ft) elevation (CAS 

205944, 205946); and another along St. Catherine Creek north of the north Yuba 

River trail (CAS 205945). On 15 July 1998, Wilkinson collected one foothill yellowlegged frog from the creek in Devil’s Canyon, a tributary of the North Yuba River 

(CAS 205953). 

Middle Yuba River—One locality was recorded on the Middle Yuba River system. 

On 20 May 1997, M. Tierney collected one foothill yellow-legged frog on Grizzly 

Creek at Pike City Road (CAS 202921). Between 2008 and 2010, the Nevada 

Irrigation District and Pacific Gas and Electric Company conducted surveys on the 

Middle Yuba and had a high number of detections in the Milton Diversion Dam 

Reach (Nevada Irrigation District and Pacific Gas and Electric Company 2010). 

South Yuba River—Two localities were recorded on the South Yuba River system. 

On 28 August 1997, Carol L. Spencer collected one foothill yellow-legged frog 

along the mainstem South Yuba River, ca. 200 m downstream of Keleher Picnic 

Area (CAS 203444). On the same date, Spencer collected another foothill yellowlegged frog on the east bank of the mainstem South Yuba River east of Golden 

Quartz Picnic Area (CAS 203450). 

North Fork American River—One locality was recorded on the North Fork 

American River system. On 2 July 1998, Michelle S. Koo collected one foothill 

yellow-legged frog along North Shirttail Creek upstream from Sugar Pine Reservoir 

(CAS 205873). 

Middle Fork American River—Two localities were recorded on the Middle Fork 

American River system. On 30 June 1998, M. Koo collected one foothill yellowlegged frog along Skunk Canyon Creek, ca. 16 km (10 mi) upstream from Mosquito 

Ridge Road (CAS 205859); Skunk Canyon Creek is a tributary of the North Fork 

of the Middle Fork of the American River. On 27 July 1998, Koo also collected one 

foothill yellow-legged frog along North Fork of the Middle Fork of the American 

River at the crossing of Mosquito Ridge Road (CAS 206178). 

Systematic surveys on the Tahoe National Forest were not initiated until the 

1990s. During 1998–1999, field crews from the California Academy of Sciences 

(CAS) spent significant time surveying for amphibians and reptiles on the Tahoe 

(Koo and Vindum 1999). Crews consisted of two to four people. During this interval, 

foothill yellow-legged frogs were recorded at a number of localities on the North, 

Middle, and South Yuba Rivers, and on the North and Middle Forks of the American 

River, including several localities for which historical records were lacking. 
127 

Foothill Yellow-Legged Frog Conservation Assessment

In the 2000s, numerous surveys were conducted on the Tahoe National Forest; many of these were associated with hydropower relicensing studies. In 2007, 

the Placer County Water Agency (PCWA) conducted surveys on the Rubicon and 

Middle Fork American Rivers; frogs were detected in varying abundances along 

the study reaches and breeding was observed primarily in the lower portions of the 

Rubicon and Middle Fork American River bypass reaches as well as along American Canyon Creek, Gas Canyon, Todd Creek, and Otter Creek (PCWA 2008). From 

2008 to 2010, the Nevada Irrigation District and Pacific Gas and Electric Company 

conducted surveys on the Middle Yuba and South Yuba; foothill yellow-legged 

frogs or evidence of reproduction (egg masses and tadpoles) were observed along 

various reaches of the two tributaries (Nevada Irrigation District and Pacific Gas 

and Electric Company 2010). In 2011, the Yuba County Water Agency (YCWA) 

performed foothill yellow-legged frog surveys on Oregon Creek, and, in 2012, 

YCWA surveyed sites along the Middle, North, and mainstem Yuba River. Most 

of the reaches surveyed were influenced by the Yuba River Development Project. 

One or more life stages were detected on some reaches influenced by the project as 

well as both reaches that were not influenced by the project (YCWA 2012). Results 

from additional surveys during hydropower relicensing studies in the South and 

Middle Forks of the Yuba River, the Bear River, the North Fork Middle Fork and 

the Middle Fork of the American River, and the Rubicon River (including tributary 

streams within these watersheds) (FERC Project Nos. 2310, 2266, 2079) are not 

included here but will be available upon completion of those relicensing studies and 

the filing of new license applications for these projects in 2011. 

Eldorado National Forest 

Pre-1980— 

Few historical records exist for the foothill yellow-legged frog on the Eldorado 

National Forest. The forest database lacks pre-1980 records for this species 

(Williams 2006), but two pre-1980 records exist for Eldorado National Forest lands. 

The oldest of these records dates from 31 July 1916, when Joseph S. Dixon collected 

two foothill yellow-legged frogs at Fyffe (current location of the 20-Mile Guard 

Station) along the South Fork of the American River (MVZ 6109–6110). The second 

record dates from 19 May 1935, when B.A. Wiley collected four foothill yellowlegged frogs at a location somewhat farther upstream, 4 km (2.5 mi) west of Kyburz 

along the South Fork of the American River (MVZ 19053–19056). 

Several additional pre-1980 records exist for drainages that extend onto Eldorado National Forest lands, but these records are located downstream of the current 

national forest boundary. Records exist for two major hydrographic basins: the 

American (including Middle and South Forks) and Cosumnes Rivers. Note that 
128 

GENERAL TECHNICAL REPORT PSW-GTR-248

because the Middle Fork American River is a tributary of the North Fork American River, the decision on where to place records from the North Fork American 

River downstream of its confluence with the Middle Fork American River, was 

arbitrary because North Fork American River records on a national forest upstream 

of the confluence are entirely on the Tahoe National Forest, whereas Middle Fork 

American River records on a national forest upstream of the confluence are entirely 

on the Eldorado National Forest. Placement here was based on latitude. Hence, all 

records from the North Fork American River below its confluence with the Middle 

Fork American River are discussed here, whereas all records from the North Fork 

American River above its confluence with the Middle Fork American River are 

discussed under the Tahoe National Forest account. Records are grouped by the 

major hydrographic basins noted above. 

American River—The oldest record from the American River is also the oldest 

record for the species, and consists of the type specimen that Charles E. Boyle collected in the spring of 1850 in the vicinity of Coloma (USNM 3370), presumably 

along the South Fork of the American River (Jennings 1987). Today, this locality 

is likely within the boundary of James W. Marshall State Historical Monument. 

All other records date from much later. On 14 November 1938, Thomas P. Maslin 

collected nine foothill yellow-legged frogs along Dry Creek, 11.2 km (7 mi) west 

and 1.6 km (1 mi) south of Placerville (MVZ 27306–27314). Dry Creek is a tributary to Weber Creek, which is a tributary of the South Fork of the American River. 

On 19 April 1946, Jerry B. Kimsey collected one foothill yellow-legged frog along 

the North Fork of the American River at Auburn (MVZ 51660). On 11 April 1952, 

J. Gorman, Jr. collected six foothill yellow-legged frogs 4.8 km northwest of Cool 

along the North Fork of the American River (MVZ 58290–58295). On 1 June 1952, 

R. Zweifel collected four foothill yellow-legged frogs along Weber Creek 3.5 km 

(2.2 mi) west-southwest of Placerville (MVZ 58038–58040, 58085). On 1 May 

1953, Zweifel also collected one foothill yellow-legged frog 6.4 km (4 mi) northwest 

of Coloma along the South Fork of the American River (MVZ 59654). On 31 March 

1961, E.K. Teberg collected one foothill yellow-legged frog along an unnamed creek 

3.2 km (2 mi) south of El Dorado (MVZ 187310). This unnamed creek is a tributary 

of Slate Creek, which is a tributary to Dry Creek. 

Cosumnes River—On 22 July 1942, Ralph G. Miller collected one foothill yellowlegged frog along Squaw Hollow Creek near Placerville (UMMZ 91972), a tributary 

of Martinez Creek, which is a tributary of the North Fork of the Cosumnes River. 

On 19 October 1942, Miller also collected one foothill yellow-legged frog along 

Martinez Creek proper, 6.4 km (4 mi) south of El Dorado (UMMZ 91971). 
129 

Foothill Yellow-Legged Frog Conservation Assessment

No foothill yellow frog records date from the 1970s from either the Eldorado 

National Forest or lands lower in elevation than Eldorado National Forest lands. 

Whether this means that foothill yellow-legged frogs had begun to decline in this 

region at that time is unclear, because systematic surveys in the region were not 

conducted until the 1990s. 

1980 to present— 

Martin (1992) and Canorus Limited made what are thought to be the first detections 

of foothill yellow-legged frogs on the Eldorado National Forest since 1980 on each 

of Bark Shanty, Camp, and Snow Creeks; the latter is a tributary to Camp Creek. 

Based on its elevation at 1911 m (6,270 ft), the Bark Shanty Creek record is thought 

to have represented Sierra Nevada mountain yellow-legged frogs (Rana sierrae), but 

this has never been confirmed, and native ranid frogs may no longer be extant at 

this location. 

In 1994, one adult foothill yellow-legged frog was sighted on Sopiago Creek 

(EA Consulting, Inc. 1994), a 3rd-order tributary of the Cosumnes River. No other 

sightings of foothill yellow-legged frogs have been made on Sopiago Creek despite 

significant survey efforts. 

Hydropower utilities involved in relicensing or in hydropower settlement 

conditions have been regularly collecting foothill yellow-legged frog occupancy and 

monitoring data in the following river systems: the Middle Fork of American River, 

the South Fork of the American River, and the North Fork of the Mokelumne River. 

Currently, four major hydrographic basins have foothill yellow-legged frog 

populations: 

•	 The Middle Fork of the American River and its tributaries, including the 

Rubicon River and Otter Creek. 

•	 South Fork American River and its tributaries, including Silver Creek and 

Soldier Creek. 

•	 The Cosumnes River system, especially Camp Creek and its tributaries. 

•	 North Fork Mokelumne and its tributaries, especially Camp, Green, and 

East Panther Creeks. 

Stanislaus National Forest 

Pre-1980— 

A number of historical foothill yellow-legged frog records exist for the Stanislaus 

National Forest; all are from the Middle or South Forks of the Tuolumne River or 

the North Fork of the Merced River.
 
130 

GENERAL TECHNICAL REPORT PSW-GTR-248

Tuolumne River—Four historical records for the Stanislaus National Forest exist from the Tuolumne River system. The earliest record from this system on the 

Stanislaus is that of William D. Clarke, who collected two foothill yellow-legged 

frogs along the South Fork Tuolumne River at Berkeley-Tuolumne Camp along 

Big Oak Flat Road on 12 June 1948 (MVZ 45819–45820). On 31 August 1962, 

Robert M. Winokur collected one foothill yellow-legged frog along the South Fork 

Tuolumne River, 6.4 km (4 mi) west of Harden Flat along Hwy 120 (MVZ 146338). 

On each of 8 July 1972 and 2 August 1974, Susan M. Case collected one foothill 

yellow-legged frog along the Middle Fork Tuolumne River, 457 m (500 yd) east of 

Middlefork Camp. Additionally, over the interval 8–15 July 1972, Case also collected nine foothill yellow-legged frogs at Middlefork Camp along the Middle Fork 

Tuolumne River (MVZ 136239, 136241–136248). 

North Fork Merced River—Two records exist for the Stanislaus National Forest 

on the North Fork Merced River. The earliest record from the North Fork Merced 

River as well as the earliest from the Stanislaus National Forest consists of six 

foothill yellow-legged frogs that T. Storer collected along Smith Creek, 9.6 km (6 

mi) northeast of Coulterville on 5 June 1915 (MVZ 5687–5692). Smith Creek is 

a tributary of the North Fork of the Merced River. On 7 August 1950, William E. 

Duellman collected one foothill yellow-legged frog at Bower Cave along the North 

Fork of the Merced River (UMMZ 102405). On 8 March 1953, an unspecified collector took another foothill yellow-legged frog from Bower Cave (MVZ 59599); 

and on 30 May 1959, Richard E. Graham collected two more foothill yellow-legged 

frogs from Bower Cave (MVZ 69454–69455). 

Several additional pre-1980 records exist for drainages that extend onto 

Stanislaus National Forest lands, but these records are located downstream of the 

current national forest boundary. Records exist for five major hydrographic basins; 

in north to south order, these are the Mokelumne, Calaveras, Stanislaus, Tuolumne, 

and Merced Rivers. Records for the Stanislaus National Forest for the Merced 

River are exclusively from the north bank or tributaries on the north side of the 

river; south bank or south side tributaries are discussed under the Sierra National 

Forest because the Merced River proper represents the boundary between these 

two national forests. The records for these hydrographic basins are discussed in 

alphabetical order. 

Calaveras River—On 10 and 23 March 1953, R. Zweifel collected two foothill 

yellow-legged frogs along Big Trees Creek along State Hwy 4 at the south boundary 

of Calaveras Big Trees State Park (MVZ 59572–59573). Big Trees Creek is a tributary of San Antonio Creek, which flows into the South Fork of the Calaveras River. 
131 

Foothill Yellow-Legged Frog Conservation Assessment

Merced River—On each of 17 and 24 May 1915, Charles L. Camp collected one 

foothill yellow-legged frog at Pleasant Valley (MVZ 5779–5780), a locality discussed in Grinnell and Storer (1924). Pleasant Valley is a historical gold mining 

camp located at roughly the intersection of Piney Creek and the Merced River, 

but which Lake McClure (Exchequer Reservoir) inundates today. On 3 June 1915, 

Camp also collected one foothill yellow-legged frog on an unnamed tributary of 

Cuneo Creek (MVZ 5686); Cuneo Creek is a tributary of Maxell Creek, which 

flows into the Merced River. On 11 May 1919, T. Storer collected one foothill 

yellow-legged frog on Blacks Creek, a tributary of Maxwell Creek, 1.6 km (1 mi) 

west of Coulterville (MVZ 7186). Grinnell and Storer (1924) discussed observing foothill yellow-legged frog tadpoles of considerable size at this same locality 

on the previous day. On 18 August 1940, Robert R. Miller collected one foothill 

yellow-legged frog tadpole from Maxell Creek at the bridge just below Coulterville 

(UMMZ 89806). 

Mokelumne River—The only historical record for the Mokelumne River system 

and the oldest record for this region is an old record from Licking Fork (Licking 

Creek). This record consists of three foothill yellow-legged frogs that W. Atkinson 

collected on 2 October 1899 (USNM 38822–38824). 

Stanislaus River—On 23 March 1953, R. Zweifel collected five foothill yellowlegged frogs from Angels Creek, 1.9 km (1.2 mi) west-southwest of Murphys 

(MVZ 59567–59571). Angels Creek is a primary tributary of the Stanislaus River. 

On 10 May 1953, Zweifel also collected two foothill yellow-legged frogs along 

Moran Creek, 2.4 km (1.5 mi) east and 4.8 km (3 mi) north of Avery (MVZ 59574– 

59575). Moran Creek is a tributary of Mill Creek, which flows into the North Fork 

Stanislaus River. 

Tuolumne River—On 16 August 1932, Charles H. Burt collected six foothill 

yellow-legged frogs along Woods Creek, 3.2 km northwest of Jacksonville (USNM 

88468–88473). On 18 August 1940, R. Miller collect one adult and 17 tadpole 

foothill yellow-legged frogs along Moccasin Creek, 14.4 km (9 mi) southeast of 

Jacksonville (UMMZ 89807). On each of 14 May 1949 and 23 April 1950, W. 

Clarke collected one foothill yellow-legged frog along Woods Creek near Sawmill 

Flat (MVZ 50250, 50963). On 15 April 1951, Clarke also collected one foothill 

yellow-legged frog along Turnback Creek, a tributary of the Tuolumne River 

(MVZ 53992). 

Historical records for foothill yellow frogs on the Stanislaus National Forest 

extend to the 1960s and early 1970s, whereas records below Stanislaus National 
132 

GENERAL TECHNICAL REPORT PSW-GTR-248

Forest lands extend only to the 1950s. Lack of systematic surveys and an incomplete historical record make it ambiguous as to whether foothill yellow-legged frogs 

had begun to decline regionally prior to 1980. 

1980 to present— 

Scattered sightings of foothill yellow-legged frogs exist for the Stanislaus National 

Forest and vicinity since 1980, but the earliest systematic surveys date from 1993 

(Lind et al. 2003b). Records exist for the Calaveras, Clavey, Merced, Stanislaus, and 

Tuolumne Rivers. Two of the historical (pre-1980) sites have foothill yellow-legged 

frog sightings since 1980, but surveys since 1993 have identified 19 previously 

known sites (Lind et al. 2003b). No post-1980 records exist for the Mokelumne 

River, but whether the Mokelumne River system was even surveyed or the 1899 

historical record for the Mokelumne was known to surveyors is unclear. Lind 

et al. (2003b) emphasized that summarized data are based on uneven survey efforts 

from composite sources. Post-1980 records from each of these systems are briefly 

discussed. 

Calaveras River—Lind et al. (2003b) reported the sighting of one foothill yellowlegged frog adult from San Antonio Creek, but the date, number of visits, and surveyor were not indicated. Moreover, the data provided in Lind et al. (2003b) do not 

specify whether the San Antonio Creek locality is the same as the historical locality 

of R. Zweifel. Marc Hayes visited the historical Zweifel San Antonio Creek locality 

on single visits in 2003, 2004, and 2005 totaling 14 hours of search time during the 

months of June or July, but only a few juvenile American bullfrogs were found during two of the site visits. Some possibility exists that foothill yellow-legged frogs 

have been extirpated from the Calaveras River. 

Clavey River—Lind et al. (2003b) reported foothill yellow-legged frogs records 

from three localities on the Clavey River system (Bull Meadow Creek, the Clavey 

River mainstem, and a Hull Creek tributary) from visits over the interval 1995– 

2001; notably, historical records of foothill yellow-legged frogs are lacking from 

the Clavey River system. Bull Meadow Creek was visited five times in 1997, three 

times in 1998, and twice in 2001. Nine foothill yellow-legged frog juveniles and 

142 tadpoles were observed over the composite of the five visits in 1997, five adults 

were observed over the three visits in 1998, and two adults and 84 tadpoles were 

observed over the two visits in 2001. One adult foothill yellow-legged frog, one juvenile, 180 tadpoles, and one egg mass were observed on three visits to the Clavey 

River in 2002. In 2009 and 2010, Kupferberg and Catenazzi found breeding sites 

with egg masses, tadpoles, and metamorphs on the Clavey at five separate elevations (385, 398, 432, 714, and 734 m). One adult foothill yellow-legged frog was 
133 

Foothill Yellow-Legged Frog Conservation Assessment

observed on one visit to the Hull Creek tributary in 1995. Overall, though reproduction seems to be occurring on at least the Clavey River mainstem and Bull Meadow 

Creek, low numbers of postmetamorphic foothill yellow-legged frogs were generally observed in the Clavey River system between 1995 and 2002. 

Merced River—One record exists from the 1980s, Robert L. Seib collected one 

foothill yellow-legged frog from Sherlock Creek, 4.8 km (3 mi) northeast of Bear 

Valley (MVZ 175103); Sherlock Creek is a primary tributary of the Merced River. 

Lind et al. (2003b) commented on foothill yellow-legged frog records from Bull 

Creek, a tributary of the North Fork of the Merced River from six visits over the interval 1995–2003. One or two adult foothill yellow-legged frog and one or no juveniles were observed at each visit, implying low numbers of postmetamorphic frogs; 

no evidence of reproduction (egg masses or tadpoles) was found at this location. 

Stanislaus River—Lind et al. (2003b) reported foothill yellow-legged frogs from 12 

localities on the Stanislaus River system between 1993 and 2002. Two sites, Rose 

Creek, a tributary of the mainstem Stanislaus River, and the Sand Bar Dam reach 

of the mainstem Middle Fork Stanislaus River, had evidence of reproduction; and 

a third site, Skull Creek, a tributary of the North Fork Stanislaus River, may have 

had foothill yellow-legged frog tadpoles present, but the species identity of the tadpoles observed was in question. The number of adults observed during individual 

surveys was always less than 10, and juveniles were likewise fewer than during 

individual surveys except for Rose Creek in 1999, and the mainstem Middle Fork 

Stanislaus River in 2001. Additionally, on 19 September 1993, B. Keimel collected 

one adult foothill yellow-legged frog on Coyote Creek in the reach between the 

Natural Bridge to 100 m downstream of Krappeau Gulch (CAS 201798). Overall, 

numbers of adults and juveniles at occupied sites on the Stanislaus River were low, 

and evidence of recruitment success was limited to 3 sites of the 12 occupied sites 

surveyed. 

Tuolumne River—Lind et al. (2003b) commented on foothill yellow-legged frogs 

from four localities in the Tuolumne River system between 1993 and 2002. Two 

sites, the North Fork Tuolumne River mainstem, and Hunter Creek, a tributary of 

the mainstem Tuolumne River, had evidence of reproduction. Numbers of adult 

and juvenile foothill yellow-legged frogs observed during individual surveys was 

always less than eight. A single juvenile foothill yellow-legged frog was found 

in the spring of 2008 upstream of Early Intake on the mainstem Tuolumne and a 

few tadpoles were found at nearby sites in 2010 by Kupferberg and 2012 by Mike 

Horvath of the San Francisco Public Utilities district. On 14 May 2010, D. Ashton 

observed tadpoles, one juvenile, and one adult along Drew Creek (a tributary of 
134 

GENERAL TECHNICAL REPORT PSW-GTR-248

Tuolumne River). Overall, numbers of adults and juveniles at occupied sites on the 

Tuolumne River were low, and indication of recruitment success was limited to one 

site. Survey data conducted from 2008 to 2010 are reported in San Francisco Public 

Utilities Commission (2014). 

Yosemite National Park 

Pre-1980— 

Few historical records exist for foothill yellow-legged frogs for Yosemite National 

Park; this partly reflects the limited habitat available for foothill yellow-legged 

frogs within this park. Foothill yellow-legged frog localities discussed by Grinnell 

and Storer (1924) for the east-west transect encompassing Yosemite National 

Park are all outside national park boundaries, and they did not document foothill 

yellow-legged frogs within Yosemite National Park; the Blacks and Smith Creeks 

and Pleasant Valley localities they addressed are discussed under the Stanislaus 

National Forest; the Felicana Mountain locality they discussed is addressed under 

the Sierra National Forest account. One historical record for foothill yellow-legged 

frogs from within Yosemite National Park is documented: on 31 July 1948, Carl L. 

Hubbs collected one foothill yellow-legged frog along the Merced River, 0.8 km 

(0.5 mi) below Cascade Creek at an elevation of 1042 m (3,420 ft) (UMMZ 99298). 

1980 to present— 

Systematic surveys of the amphibian fauna of Yosemite National Park were 

initiated in the early 1990s. Gary Fellers, his associate Charles Drost, and his field 

crews conducted surveys meant to replicate the west-to-east transect that Joseph 

Grinnell and his students sampled encompassing the region of the Sierra including Yosemite National Park (Drost and Fellers 1994, 1996). Drost and Fellers 

(1994, 1996) found no foothill yellow-legged frogs within Yosemite National Park 

boundaries. 

Subsequent surveys conducted by National Park Service personnel through 

2006 have also failed to reveal foothill yellow-legged frogs within the boundaries of 

Yosemite National Park. These surveys were largely focused on species other than 

foothill yellow-legged frogs; nevertheless, some survey effort was focused in areas 

that would have represented historical foothill yellow-legged frog habitat, i.e., along 

the lower portion of the Merced River within Yosemite National Park and its few 

larger tributaries in that area. Based on available data, foothill yellow-legged frogs 

are likely to be extirpated from Yosemite National Park. 
135 

Foothill Yellow-Legged Frog Conservation Assessment

 

Sierra National Forest 

Pre-1980— 

Few historical records for foothill yellow-legged frogs exist for the Sierra National 

Forest; all are in the Merced, San Joaquin, or Kings River systems. The oldest 

record from the Sierra National Forest is two foothill yellow-legged frogs that J. 

Gorman, Jr. collected 7.1 km (4.4 mi) northeast of Briceburg along the Merced 

River on 11 July 1952 (MVZ 59479–59480). On 19 April 1953, R. Zweifel collected 

foothill yellow-legged frogs at three additional localities in the Merced River system: two foothill yellow-legged frogs at Fish Camp along Big Creek (MVZ 59588– 

59589); six additional foothill yellow-legged frogs along the Merced River 3.1 km 

(1.9 mi) east of Indian Lodge (MVZ 59590–59595); and two foothill yellow-legged 

frogs along Feliciana Creek, 3.2 km (2 mi) east of Briceburg (MVZ 59596–59597). 

On 2 September 1953, John D. Cunningham collected three foothill yellow-legged 

frogs at an unspecified locality on the road to Huntington Lake (LACM 13578– 

13580). On 6 September 1953, Alan E. Leviton and H. Magarian collected four 

foothill yellow-legged frogs along the Middle Fork of the Kings River at Davis 

Creek (CAS-SU 13090–13093). 

However, the oldest records from streams below the Sierra National Forest 

boundary consists of 14 foothill yellow-legged frogs that Halstead G. White collected at Dunlap along Mill Creek, a tributary of the Kings River, on 27 and 30 

September and 1 October 1916 (MVZ 6230–6243). White also collected two foothill 

yellow-legged frogs at Minkler along Byrd Slough, also a tributary of the Kings 

River, on 11–12 October 1916 (MVZ 6244–6245). 

On 5 December 1970, Joseph W. Crim took one foothill yellow-legged frog 

4 km (2.5 mi) up the North Fork of the Kings River toward Balch Camp (MVZ 

94419). In 1970, Moyle (1973) sampled 49 stream crossings of either the mainstem 

or tributaries of the Merced, San Joaquin, or Kings Rivers for fishes and frogs, and 

recorded foothill yellow-legged frogs at 24 percent (n = 12) of the crossing points. 

All points at which Moyle sampled frogs during this study were downstream of 

Sierra National Forest lands. By the end of the 1970s, six foothill yellow-legged frog 

localities had been documented from the Sierra National Forest, and 14 additional 

foothill yellow-legged frog localities were documented from drainages downstream 

or outside of Sequoia National Forest lands. However, by the late 1970s, declines 

were evident, as foothill yellow-legged frogs had not been recorded in at least 10 

historical localities for several years (Hansen 2006, Holland 2006). 
136 

GENERAL TECHNICAL REPORT PSW-GTR-248

1980 to present— 

In the most recent analysis, Lind et al. (2003b) reported that none of the six historical localities on the Sierra National Forest have foothill yellow-legged frogs. They 

further reported that the only drainage confirmed to have foothill yellow-legged 

frogs on the Sierra National Forest is Jose Creek, a tributary of the San Joaquin 

River that is isolated by the presence of upper Redinger Lake at its mouth. Surveys 

of Jose Creek have been conducted with varying degrees of intensity since U.S. 

Geological Survey (USGS) personnel, under the direction of G. Fellers, confirmed 

a population there in 1994. Surveys have detected some adults, juveniles or tadpoles 

in every year between 1994 and 2003, but the maximum number of adults found 

was 19 in 1994, and numbers of adults in any post-1994 survey have never exceeded 

seven Surveys of historical sites downstream of Sierra Forest Service lands since 

1995 have failed to detect foothill yellow-legged frogs (Hansen 2006). Foothill 

yellow-legged frogs on the Sierra National Forest appear to be rare and limited in 

distribution, and may be near extirpation in the region. 

Sequoia and Kings Canyon National Parks 

Pre-1980— 

Three pre-1980 records of foothill yellow-legged frogs exist from Sequoia and 

Kings Canyon National Parks. All three records are for Sequoia National Park, and 

all three date from the 1930s; no historical records exist for Kings Canyon National 

Park. The oldest of these records dates from 1 July 1935, when Theodore H. Eaton, 

Jr. collected one foothill yellow-legged frog from the North Fork of the Kaweah 

River at 762 m (2,500 ft) elevation (MVZ 21820). On 5 August 1935, Eaton also collected one foothill yellow-legged frog from Alder Creek at 518 m (1,700 ft) elevation 

(MVZ 21817). On 7–8 August 1935, Eaton also collected five foothill yellow-legged 

frogs at 610 m (2,000 ft) elevation along the North Fork of the Kaweah River (MVZ 

21818–21819, 25167–25169). Historical records are lacking for Sequoia National 

Park for the 1940s, 1950s, 1960s, and 1970s.
 

1980 to present— 

No collections or sightings of foothill yellow-legged frogs exist from Sequoia 

National Park in the interval from 1980 to present.
 

Sequoia National Forest 

Pre-1980— 

Historical foothill yellow-legged frog records on Sequoia National Forest extend 

back 115 years, prior to the existence of either the Sequoia National Forest or the 

Forest Service (the latter was founded in 1905). Theodore S. Palmer, a member of 
137 

Foothill Yellow-Legged Frog Conservation Assessment

the Mount Whitney Expedition, made the earliest collections of this species on 23 

June 1891, when he collected two frogs along the Kern River at “Old Kernville” 

(USNM 18951–18952). The north arm of Isabella Lake (a reservoir), built in the 

interval 1948–1953, inundates this site today. On 4 July of the same year, Albert K. 

Fisher, another member of the Mount Whitney Expedition, collected one frog along 

the North Fork of the Kern River 40 km (25 mi) north of Old Kernville (USNM 

18953). However, the oldest foothill yellow-legged frog records from the region 

come from private lands along Tejon Creek, where Henry W. Henshaw collected 

eight frogs in 1875 (USNM 8683, 322025–322031). Through 1900, two foothill 

yellow-legged frog sites were documented that ultimately (post-1905) would represent localities on the Sequoia National Forest, and one foothill yellow-legged frog 

locality was documented on lands that would ultimately be outside the Sequoia 

National Forest. 

No additional collections were made on the Sequoia National Forest until 

nearly 20 years later, when Edwin C. Van Dyke collected one adult on 10 July 1910 

in the lower Kings River Canyon (CAS 17952) in an area now inundated by Pine 

Flat Reservoir, which was completed in 1954. Two additional sites on the Sequoia 

National Forest were collected in 1911. From 11 to 19 June 1911, Walter P. Taylor 

and N. Stern collected 30 foothill yellow-legged frogs at or near Bodfish in the 

Kern River Canyon (MVZ 2965–2994); Taylor and Stern collected five additional 

frogs at a location 19.3 km below Bodfish over the interval 21–23 June 1911 (MVZ 

2995–2999). Additionally, one locality was collected from private lands in the 

vicinity of the Sequoia National Forest in the 1910s; T. Storer collected one frog 

from Fay Creek, a tributary of the South Fork of the Kern River, on 13 July 1911 

(MVZ 3011). By the end of the 1910s, five foothill yellow-legged frog localities had 

been documented from the Sequoia National Forest, and two additional foothill 

yellow-legged frog localities were documented from drainages downstream or 

outside of Sequoia National Forest lands. 

No collections of foothill yellow-legged frogs were made on the Sequoia 

National Forest or adjacent private lands during the 1920s. Early on, Storer (1925) 

thought that a hiatus in the foothill yellow-legged frog range might exist at the 

southern end of the San Joaquin Valley, based on the failure to find the species in 

the vicinity of old Fort Tejon despite intensive collecting. As Storer was meticulous, 

it is difficult to believe that he was unaware of the 1875 Henshaw collections from 

Tejon Creek; however, if this was the case, foothill yellow-legged frogs may have 

been extirpated from this area at an early date. Regardless of precisely what the 

situation was, few historical data exist for foothill yellow-legged frog-occupied 

streams south of the Kern River. 
138 

GENERAL TECHNICAL REPORT PSW-GTR-248

Foothill yellow-legged frogs were recorded at one new locality on the Sequoia 

National Forest during the 1930s. On 25 November 1938, Alexander J. Calhoun collected two frogs along the Kern River, 28.9 km downstream of Hobo Hot Springs 

(CAS 159509, CAS-SU 6444). One new locality was also collected in the 1930s on 

private lands at elevations below Sequoia National Forest lands; on 9 June 1938, 

Joseph T. Marshall, Jr. collected one foothill yellow-legged frog along an unnamed 

tributary of Cottonwood Creek (MVZ 26205). Cottonwood Creek is a moderatesized stream that independently flows into the Tulare Lake Basin (sink) on the San 

Joaquin Valley floor. By the end of the 1930s, six foothill yellow-legged frog localities had been documented from the Sequoia National Forest, and three additional 

foothill yellow-legged frog localities were documented from drainages downstream 

or outside of Sequoia National Forest lands. 

Four localities on the Sequoia National Forest were collected during the 1940s, 

three of which were new. Robert R. Miller re-collected the Old Kernville locality on 

27 April 1940 (UMMZ 92311); on 10 August 1940, Miller also collected a foothill 

yellow-legged frog along the South Fork of the Kern River 8 km east of Onyx 

(UMMZ 89801) and on 20 August 1940, he collected another frog from Picacho 

Creek in the Kern River Canyon east of Bakersfield (UMMZ 89808). Additionally, 

F.E. Durham collected three foothill yellow-legged frogs along the North Fork of 

the Kern River, 0.8 km (0.5 mi) north of the Kern County line on 24 August 1946 

(LACM 1663–1665). Five additional collections were made from private lands in 

the 1940s. Miller also collected two frogs from Cedar Creek at a locality between 

6.4 and 8.0 km (4.0 and 5.0 mi) east of Glennville on 12 August 1940 (UMMZ 

89802, 139744); on the same date, he also collected two frogs from the White 

River, 32 km southeast of Porterville (UMMZ 89803, 139729) and two additional 

frogs from Deer Creek, 6.4 km below highway to Cal Hot Springs (UMMZ 89804, 

139745); H. Fitch collected two frogs from Tehachapi Creek on 16 May 1947 (MVZ 

44909–44910); and J. Gorman, Jr. collected two frogs from along the South Fork of 

the Kern River, 3.2 km east of Onyx on 4 August 1949 (MVZ 52197–52198). By the 

end of the 1940s, nine foothill yellow-legged frog localities had been documented 

from the Sequoia National Forest, and eight additional foothill yellow-legged frog 

localities were documented from drainages downstream or outside of Sequoia 

National Forest lands. 

Five new localities on the Sequoia National Forest were collected during the 

1950s. In the course of his work on yellow-legged frogs (Zweifel 1955), R. Zweifel 

collected seven foothill yellow-legged frogs on the North Fork of the Middle Fork 

of the Tule River, six frogs 14 km east-northeast of Springville on the road to Camp 

Wishon (MVZ 56596–56602) and one frog at Camp Wishon (MVZ 58171), all on 
139 

Foothill Yellow-Legged Frog Conservation Assessment

27 April 1952. On 29 April 1952, Zweifel also collected one frog on Clear Creek 

at Hobo Hot Springs (MVZ 56611). On the same date, Zweifel and Keith Murray 

collected five foothill yellow-legged frogs from Cowflat Creek in the Kern River 

Canyon, 32 km east-northeast of Bakersfield (MVZ 56612–56615, 58170). Then, on 

26 April 1953, Zweifel collected six more frogs on Salmon Creek in the Kern River 

Canyon 4 km southeast of Fairview. Eleven additional records were made on private 

or non-Forest Service lands during the 1950s. In June 1950, Lawrence Herbst 

collected two foothill yellow-legged frogs at Glennville along Angel Creek (LACM 

13628, 74421); Angel Creek is a tributary of Poso Creek that flows into the Tulare 

Lake basin on the San Joaquin Valley floor. On 27 April 1952, Keith F. Murray collected one frog along the Middle Fork of the Tule River 6.1 km east of Springville 

(MVZ 56609); on the same date, Murray and Zweifel collected four foothill yellowlegged frogs 8 km east-northeast of Springville (MVZ 56605–56607, 56610); and 

Zweifel also collected two foothill yellow-legged frogs 13.7 km (8.5 mi) northwest 

of Woodlake along Cottonwood Creek (MVZ 56603-56604). On 1 May 1952, Zweifel collected two foothill yellow-legged frogs 9.6 km northwest of Tehachapi (MVZ 

56616–56617); on the same date, Zweifel collected seven additional foothill yellowlegged frogs 9.6 km east-southeast of Caliente; on 2 July 1952, K. Murray collected 

five foothill yellow-legged frogs 12.8 km east of Caliente (MVZ 59921–59925); on 

7 February 1954, Robert Glaser collected eight foothill yellow-legged frogs along 

Canebrake Creek, 14.5 km east-northeast of Onyx; and on 11 April 1959, four 

foothill yellow-legged frogs were collected 6.1 km northwest of Tehachapi (LACM 

16602–16605). By the end of the 1950s, 14 foothill yellow-legged frog localities 

had been documented from the Sequoia National Forest, and 19 additional foothill 

yellow-legged frog localities were documented from drainages downstream or 

outside of Sequoia National Forest lands. 

Foothill yellow-legged frogs were recorded from two new localities on the 

Sequoia National Forest during the 1960s. Two frogs were taken at Fairview Camp 

along the North Fork of the Kern River (LACM 91148–91149), and one frog was 

19.9 km east-northeast of Springville on Camp Wishon Road (LACM 91150). Two 

additional collections were made from private lands in the 1960s. R. Stebbins 

collected two localities along Caliente Creek: two frogs were collected 4.8 km west 

of Loraine (MVZ 81767–81768) and four more frogs were collected 7.2 km west of 

Loraine (MVZ 81769–81772). By the end of the 1960s, 16 foothill yellow-legged 

frog localities had been documented from the Sequoia National Forest, and 21 

additional foothill yellow-legged frog localities were documented from drainages 

downstream or outside of Sequoia National Forest lands. 
140 

GENERAL TECHNICAL REPORT PSW-GTR-248

Only one foothill yellow-legged frog locality was collected on the Sequoia 

National Forest during the 1970s. On 6 December 1970, David B. Wake collected 

one frog along the Middle Fork of the Tule River 9.3 km (5.8 mi) northeast of 

Springville (MVZ 94422), and Robert Hansen (2006) stated that foothill yellowlegged frogs were extant along the North Fork of the Middle Fork of the Tule River 

through the mid-1970s, but were apparently extirpated by the late 1970s. In 1970, 

Moyle (1973) sampled 21 stream crossings of either the mainstem or tributaries of 

the Kaweah, Tule, or Kern Rivers for fishes and frogs, and recorded foothill yellowlegged frogs at 19 percent (n = 4) of the crossing points, two of which represented 

previously documented localities. All points at which Moyle sampled frogs during 

this study are downstream of Sequoia National Forest lands. By the end of the 

1970s, 17 foothill yellow-legged frog localities had been documented from the 

Sequoia National Forest, and 23 additional foothill yellow-legged frog localities 

were documented from drainages downstream or outside of Sequoia National Forest 

lands. However, by the late 1970s, declines were evident, as foothill yellow-legged 

frogs had not been recorded in at least four historical localities for several years 

(Hansen 2006, Holland 2006). 

1980 to present— 

No collections and few sightings of foothill yellow-legged frogs exist for the 

Sequoia National Forest and vicinity from 1980 to the present.
 

In the most recent analysis, Lind et al. (2003b) stated that none of the historical localities on the Sequoia National Forest have foothill yellow-legged frogs, 

but only six historical localities were reported. Which of these 6 are represented 

among the 17 reported in the previous section or even if some do not overlap these 

17 is unclear. The two most recently occupied localities on the Sequoia National 

Forest consist of unnamed tributaries of the North Fork Kern River, which have 

been given the names Ash and Jywood Creeks (Lind et al. 2003b), have each been 

surveyed multiple times from 1998 to 2002. Based on Lind et al. (2003b), the last 

foothill yellow-legged frogs reported to be seen at Ash Creek were three adult 

foothill yellow-legged frogs that Patrick Kleeman of the USGS found on 12 September 1998. However, because Lind et al. (2003b) reported that not all data were 

available from USGS surveys conducted annually at Ash and Jywood Creeks since 

1997, it is unclear whether the 1998 Kleeman sightings are actually the last known. 

However, no frogs were observed at the Ash Creek locality during three different 

surveys of the site that either A. Lind and/or T. Tharalson conducted in 2002–2003, 

so some likelihood exists that foothill yellow-legged frogs have been extirpated 

from Ash Creek. In Jywood Creek, at least two adult foothill yellow-legged frogs 

were observed during every survey between 1998 and September 2002 (Lind et al. 
141 

Foothill Yellow-Legged Frog Conservation Assessment

2003b). In 2003, Tharalson observed two frogs in Jywood Creek for which a positive identification could not be obtained. Regardless of the precise situation, known 

foothill yellow-legged frogs on the Sequoia National Forest appear to be very few 

and limited in distribution, and may be near extirpation in the region. 

Los Padres National Forest 

Pre-1980— 

The earliest specimen of foothill yellow-legged frog on the Los Padres National 

Forest was collected by Barton W. Evermann on 2 September 1914 along Sespe 

Canyon (CAS 39253). No other frogs were collected from the forest until the 

1940s. Few records exist of foothill yellow-legged frogs collected from Los Padres 

National Forest during the 1940s. On 6 September 1948, Robert Sanders collected one frog within Sespe Gorge (CAS 10223). In 1949, Sanders collected four 

frogs along Piru Creek, 19.6 km (12.2 mi) north of Piru (CAS 10224–10227) on 7 

May. On 15 June 1949, he collected two frogs along Piru Creek, 16.3 km (10.1 mi) 

north of Piru (CAS 10228, 11550). On 22 June, Sanders collected four frogs at Lion 

Canyon just above Sespe Creek (CAS 10229, 11549). 

There is only one record of collection on the Los Padres National Forest during 

the 1960s. An unnamed individual collected one frog at Piru Creek near Frenchman 

Flats on 27 March 1960 (TCWC 20690). No frogs were collected during the 1970s. 

Surveys in the 1970s by Samuel Sweet documented foothill yellow-legged frog 

declines in southern California (Sweet 1983). The last documented sighting of a 

foothill yellow-legged frog in southern California occured on 6 July 1977 along 

Piru Creek (Jennings and Hayes 1994). 

1980 to present— 

No collections are documented for the Los Padres National Forest from 1980 

to the present.
 

Only two relatively recent records of foothill yellow-legged frog detections 

exist from Los Padres National Forest; in August 1999, tadpoles and individuals of 

undetermined life stage were detected along San Carpoforo Creek, a coastal tributary of Big Sur (USDA Forest Service NRIS database). 

Angeles National Forest 

Pre-1980— 

All records of foothill yellow-legged frogs collected in the Angeles National Forest 

date before 1980. On 11 August 1940, John C. Marr collected four frogs from the 

San Gabriel River in the San Gabriel Mountains (CAS 7225–7228). On 26 June 

1969, Michael C. Long collected three frogs from Bear Creek, 0.40 km (0.25 mi) 
142 

GENERAL TECHNICAL REPORT PSW-GTR-248

north of the west fork of the San Gabriel River (CAS 199437–199439). Foothill 

yellow-legged frogs were historically found in Elizabeth Lake Canyon and Camp 

Rincon in the San Gabriel Mountains (Sweet 1983).
 

1980 to present— 

No records of foothill yellow-legged frogs specimens collected from 1980 to the 

present exist. 

Literature Cited 

Cope, E.D. 1879. A contribution to the zoology of Montana. American Naturalist. 

13: 432–441. 

Cope, E.D. 1883. Notes on the geographical distribution of Batrachia and Reptilia 

in western North America. Proceedings of the Academy of Natural Sciences of 

Philadelphia. 35: 10–35. 

Cope, E.D. 1889. The Batrachia of North America. Bulletin of the United States 

National Museum. 34: 1–525. 

Drost, C.A.; Fellers, G.M. 1994. Decline of frog species in the Yosemite section 

of the Sierra Nevada. Tech. Rep. NPS/WRUC/NRTR 94-02 [UC CPSU TR #56]. 

Davis, CA: University of California; U.S. Department of the Interior, National 

Park Service, Cooperative National Park Studies Unit. 56 p. 

Drost, C.A.; Fellers, G.M. 1996. Collapse of a regional frog fauna in the Yosemite 

area of the California Sierra Nevada, USA. Conservation Biology. 10: 414–425. 

EA Consulting, Inc. 1994. Personal communication. 1024 Iron Point Rd., 

Folsom, CA 95630. 

Garcia and Associates [GANDA]. 2005. Results of 2004 surveys and monitoring 

for foothill yellow-legged frogs (Rana boylii) within the Rock Creek–Cresta 

project area, North Fork Feather River, and 2002–2004 recreation and pulse 

flow biological evaluation summary. San Ramon, CA: Pacific Gas and Electric 

Company; Job 332/80. 89 p. 

Garcia and Associates [GANDA]. 2006. Evaluating the impacts of manufactured 

recreation streamflows on the macroinvertebrate community of a regulated river. 

CED-500-2006-078. Sacramento, CA: California Energy Commission, Public 

Interest Energy Research Program. 55 p. 
143 

Foothill Yellow-Legged Frog Conservation Assessment

Garcia and Associates [GANDA]. 2008. Identifying microclimate and water flow 

triggers associated with breeding activities of a foothill yellow-legged frog (Rana 

boylii) population on the North Fork Feather River, California. CEC-500-2007­

041. Sacramento, CA: California Energy Commission, Public Interest Energy 

Research Program. 59 p. 

Grinnell, J.J.; Storer, T.I. 1924. Animal life in the Yosemite. Berkeley, CA: 

University of California Press. 669 p. 

Hansen, R. 2006. Personal communication. District director, Penn State 

University, College of Agricultural Sciences, 200 Main St., Suite 3, Towanda, PA 

18848–0069. 

Holland, D. 2006. Personal communication. Principal investigator, Camp 

Pendleton Amphibian and Reptile Survey, Fallbrook, CA 92028. 

Jennings, M.R. 2007. Personal communication. Senior associate ecologist 

and herpetologist, Live Oak Associates, Inc., 6840 Via Del Oro, Suite 220, 

San Jose, CA 95119. 

Jennings, M.R. 1982. Geographic distribution: Rana boylii [sic] (foothill yellowlegged frog). Herpetological Review. 13: 51. 

Jennings, M.R. 1987. A biography of Dr. Charles Elisha Boyle, with notes on his 

19th century natural history collection from California. Wasmann Journal of 

Biology. 45(1–2): 59–68. 

Jennings, M.R.; Hayes, M.P. 1994. Amphibians and reptile species of special 

concern in California. Rancho Cordera, CA: California Department of Fish 

and Game. 255 p. 

Koo, M.S.; Vindum, J.V. 1999. Amphibians and reptiles of the Plumas National 

Forest: historical collections and California Academy of Sciences 1998 and 1999 

surveys. San Francisco, CA: Department of Herpetology, California Academy of 

Sciences. 18 p. 

Kupferberg, S.J.; Palen, W.J.; Lind, A.J.; Bobzien, S.; Catenazzi, A.; Drennan, 

J.; Power, M.E. 2012. Effects of flow regimes altered by dams on survival, 

population declines, and range-wide losses of California river-breeding frogs. 

Conservation Biology. 26: 513–524. 

Lind, A.J.; Welsh, H.H., Jr.; Wilson, R.A. 1996. The effects of a dam on 

breeding habitat and egg survival of the foothill yellow-legged frog (Rana boylii) 

in northwestern California. Herpetological Review. 27: 62–67. 
144 

GENERAL TECHNICAL REPORT PSW-GTR-248

Lind, A.J.; Conway, L.; Sanders, H.E.; Strand, P.; Tharalson, T. 2003b. 

Distribution, relative abundance, and habitat of foothill yellow-legged frogs 

(Rana boylii) on national forests in the Southern Sierra Nevada Mountains of 

California. Washington, DC: U.S. Department of Agriculture, Forest Service, 

Region 5, Fish Habitat Relationships (FHR) Program. 30 p. 

Martin, D.L. 1992. Sierra Nevada anuran survey: an investigation of amphibian 

population abundance in the national forests of the Sierra Nevada of California. 

Vallejo, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest 

Region. 76 p. 

Moyle, P.B. 1973. Effects of introduced bullfrogs, Rana catesbeiana, on the native 

frogs of the San Joaquin Valley, California. Copeia. 1973: 18–22. 

Moyle, P.B. 2002. Inland fishes of California, revised and expanded. Berkeley, CA: 

University of California Press. 502 p. 

Nevada Irrigation District; Pacific Gas and Electric Company. 2010. Specialstatus amphibians, foothill yellow-legged frog surveys. Yuba-Bear Hydroelectric 

Project (FERC No. 2266-096) and Drum-Spaulding Project (FERC No. 2310­

173). http://www.eurekasw.com/NID/Technical%20Memoranda/2009,%20 

2010%20and%202011%20Technical%20Memoranda/Technical%20 

Memorandum%2003-06%20-%20Special-Status%20Amphibians%20-%20 

FYLF%20VES/Tech%20Memo%203-6%20-%20FYLF%20Surveys.pdf. 

[Date accessed unknown]. 

Pacific Gas and Electric Company [PG&E]. 2008. Updated study results 

and license application exhibit E, sections 6.0 and 7.0, De Sabla-Centerville 

Hydroelectric Project (FERC No. 803). http://www.eurekasw.com/DC/ 

relicensing/FERC%20Filing%20%20PGE/2008%20-%200321%202-D%20 

Amphibian%20Model/6.3.2.1%20Aquatics%20-%20Updated%20Mar08.pdf. 

[Date accessed unknown]. 

Pacific Gas and Electric [PG&E]; Company and Stillwater Sciences. 2009b. 

Special-status amphibians and aquatic reptiles. Surveys of special-status 

amphibians and aquatic reptiles near project reservoirs and project-affected 

stream reaches. Tech. memo. 09. McCloud-Pit Project, FERC No. 2106. http:// 

www.eurekasw.com/MCP/Technical%20Memos/TM-09%20FA-S2%20 

Amphibians%20and%20Reptiles%20Updated%20February%202009.pdf. 

(21 April 2014). 
145 

Foothill Yellow-Legged Frog Conservation Assessment

Placer County Water Agency [PCWA]. 2008. AQ 12—Special-status amphibian 

and aquatic reptile technical study report—2007. Middle Fork American River 

Project (FERC No. 2079). Auburn, CA: Placer County Water Agency. http:// 

relicensing.pcwa.net/html/science/padreportaquatic.php. (21 April 2014). 

San Francisco Public Utilities Commission (SFPUC). 2014. O’Shaughnessy Dam 

Instream Flow Management Plan–Stakeholder Draft. Prepared as part of the 

Upper Tuolumne River Ecosystem Program by the SFPUC Natural Resources 

and Lands Management Division, with McBain & Trush, Inc., Jennifer Vick, 

Stillwater Sciences, Questa Engineering, Graham Matthews and Associates, 

Darnell Shaw Environmental, Watercourse Engineering, and Merritt Smith 

Consulting. 

Spring River Ecological Sciences. 2003. Foothill yellow-legged frog (Rana 

boylii) studies in 2002 for Pacific Gas and Electric Company’s Pit 3, 4, and 5 

Hydroelectric Project (FERC No. 233). San Ramon, CA: Pacific Gas and Electric 

Company, Technical and Ecological Services. 66 p. 

Spring River Ecological Sciences. 2004. Foothill yellow-legged frog (Rana boylii) 

egg mass, tadpole, and habitat surveys in the Pit 4 in 2003, Pacific Gas and 

Electric Company Pit 3, 4, and 5 Hydroelectric Project (FERC No. 233). San 

Ramon, CA: Pacific Gas and Electric Company. 54 p. 

Storer, T.I. 1925. A synopsis of the amphibia of California. University of 

California Publications in Zoology. 27: 1–343. 

Sweet, S.S. 1983. Mechanics of a natural extinction event: Rana boylii in southern 

California [Abstract]. In: Program of the 26th annual meeting of the Society 

for the Study of Amphibians and Reptiles and 31st annual meeting of the 

Herpetologists League. Salt Lake City, UT: University of Utah: 93. 

Williams, J. 2006. Personal communication. Fish biologist, El Dorado National 

Forest, 100 Forni Rd., Placerville, CA 95667. 

Wheeler, C.A.; Bettaso, J.B.; Ashton, D.T.; Welsh, H.H.; Jr. 2013. Effects of 

water temperature on breeding phenology, growth, and timing of metamorphosis 

of foothill yellow-legged frogs (Rana boylii) on the mainstem and selected 

tributaries of California’s Trinity River—2004–2009. Report to the Trinity 

River Restoration Program. Arcata, CA: U.S. Department of Agriculture, Forest 

Service, Pacific Southwest Research Station, and U.S. Department of the Interior, 

Fish and Wildlife Service. 37 p. 
146 

GENERAL TECHNICAL REPORT PSW-GTR-248

Yuba County Water Agency [YCWA]. 2012. Special-status amphibians—foothill 

yellow-legged frog surveys. Tech. memo. 3–4. Yuba River Development Project 

(FERC No. 2246). http://www.ycwa-relicensing.com/Technical%20Memoranda/ 

TM%2003-04%20-%20Special-Status%20Amphibians%20-%20FYLF%20 

Surveys/TM%203-4,%20Part%201%20of%202%20.pdf. 

[Date accessed unknown]. 

Zweifel, R.G. 1955. Ecology, distribution, and systematics of frogs of the Rana 

boylei group. University of California Publications in Zoology. 54: 207–292. 
147 

Foothill Yellow-Legged Frog Conservation Assessment

Appendix 4: Other Risk Factors 

Airborne Contaminants Including Pesticides 

The transport and deposition of pesticides from the Great Central Valley to the 

Sierra Nevada is well documented (Aston and Sieber 1997, Datta et al. 1998, Lenoir 

et al. 1999, McConnell et al. 1998) and pesticide residues have been detected in the 

bodies of Sierran anurans (Cory et al. 1970, Fellers et al. 2004). Pesticides currently 

used in the Central Valley can drift from sources to the Sierra Nevada on wind currents or storm systems (Aston and Seiber 1997, Cahill et al. 1996, Seiber et al. 1998, 

Zabik and Seiber 1993). Between 48 and 69 million kg (107 and 152 million lb) of 

pesticide active ingredient were recorded as having been used annually from 1990 

to 2012 in the Central Valley; use fluctuated prior to peaking in 2005, declined 

through 2009, and increased once again through 2012 (CDPR 1989–2012). 

Data from the Sierra Nevada implicate pesticide drift as a factor for frog 

declines, in general (Sparling et al. 2001), and specifically for foothill yellow-legged 

frogs in the Sierran portion of the species’ range (Davidson et al. 2002). Sparling 

et al. (2001) found depressed cholinesterase activity in Pacific chorus frog tadpoles 

in the Sierra Nevada east of the Central Valley when compared with sites along 

the coast or east of the valley; cholinesterase activity is a good bioindicator of 

exposure to organophosphorus pesticides (Ludke et al. 1975). Davidson et al. (2002) 

and Davidson (2004) examined 70 historical locations for presence of foothill 

yellow-legged frogs and analyzed the spatial patterns of declines. Declines had a 

strong positive association with the amount of upwind agricultural land use; there 

was approximately four times as much agricultural land use upwind of sites where 

foothill yellow-legged frogs had disappeared compared to sites where the species 

was still present (Davidson et al. 2002). In Oregon, proximity to agricultural areas 

was negatively associated with frog presence; however, how this relates to chemical 

applications has not been determined (Olson and Davis 2009). 

Two studies on the effects of pesticides (endosulfan, chlorpyrifos, malathion, 

and diazinon and their oxons) on foothill yellow-legged frogs demonstrated negative 

effects on tadpole growth and development and depressed cholinesterase (ChE) 

levels in metamorphs that survived pesticide treatments (Sparling and Fellers 2007, 

2009). Delays in development can result in smaller size at metamorphosis (Hayes 

et al. 2006) and may increase the likelihood of tadpole mortality from predation 

or desiccation by drought. Pesticides in combination have been shown to induce 

damage to the frog thymus, which increases immunosuppression and susceptibility 

to disease (Hayes et al. 2006). In an experiment, newly metamorphosed foothill 

yellow-legged frogs exposed to the insecticide carbaryl did not increase mortality 

relative to controls but did reduce production of skin peptides shown to suppress 
148 

GENERAL TECHNICAL REPORT PSW-GTR-248

growth of the often-lethal chytrid fungus, Batrachochytrium dendrobatidis (Davidson et al. 2007). Furthermore, exposure to a cocktail of pesticides may have lethal 

effects that are not observed when single pesticide applications are examined (as 

in Davidson et al. 2007), which may lead to gross underestimations of the role of 

pesticides in amphibian declines (Hayes et al. 2006). 

Extent of risks related to airborne contaminants— 

Currently, insufficient evidence exists to suggest that airborne contaminants are 

a significant threat to foothill yellow-legged frogs. The correlation between areas 

exposed to contamination in Sierra Nevada and foothill yellow-legged frog declines 

is merely suggestive. 

Conservation options related to airborne contaminants— 

Research is needed to further determine the level of risk airborne contaminants 

pose to foothill yellow-legged frogs, and possible interactions with other risk factors. The species’ proximity to extensive sources of contamination merits further 

study to determine the risk. 

Acid Deposition 

Acidic deposition has affected amphibian populations in the Eastern United 

States and Europe (Freda 1990). Lakes and streams in the Sierra Nevada have low 

buffering capacity, potentially making them sensitive to increases in the acidity of 

precipitation (Landers et al. 1987, Melack et al. 1985). In the 1980s, Sierran lakes 

had limited acidity (summertime pHs of 6 to 8), but more recent precipitation 

samples document that acidity has increased at some sampling stations in the Sierra 

Nevada (e.g., at ca. 2100 m elevation near Lake Tahoe) (see Byron et al. 1991). Snow 

samples have also shown increased acidity (pH 5.1 to 5.9) (Laird et al. 1986). 

Acidification in streams may be less likely than in still-water habitats, because 

biological and physical processes rapidly change stream waters (Hynes 1970); 

however, acid pulses at snowmelt can occur. Factors that influence the buffering 

capacity of streams include streamflow and source (e.g., relative contribution of 

snowmelt and groundwater) (Williams and Melack 1997). Williams and Melack 

(1997) found an inverse relationship between buffering capacity and streamflow 

volume. Acidification may potentially affect foothill yellow-legged frogs that occur 

in streams with flows large enough to flush acidifying ions (like sulfate) that have 

insufficient buffering, but are too low-flow to adequately dilute acidifying effects. 

The degree to which foothill yellow-legged frogs and their habitats are influenced 

by acidification has not been examined. 
149 

Foothill Yellow-Legged Frog Conservation Assessment

Sublethal, interactive effects of acidification with other factors, such as nitrates 

and UV-B radiation (Hatch and Blaustein 2000, Long et al. 1995) and dissolved 

aluminum (Bradford and Gordon 1992, Bradford et al. 1994, Freda 1991) have been 

observed for other amphibians. In experiments using Cascades frog tadpoles, Hatch 

and Blaustein (2000) found reduced survivorship at pH 5 when nitrate was added; 

and in one of the 2 years of experiments they also found a significant effect on survivorship between the pH-nitrate interaction at elevated levels of UV-B. Bradford 

and Gordon (1992) and Bradford et al. (1994) examined the tolerance of mountain 

yellow-legged frog and Yosemite toad embryos and tadpoles to aluminum at different acidic pHs in the laboratory and found that there were sublethal effects; there 

was a reduction of body size of tadpoles and earlier hatching time for embryos. 

Such interactions remain unstudied for foothill yellow-legged frogs. 

Acid deposition does not currently seem to be a significant risk to foothill 

yellow-legged frogs in the Sierra Nevada, but potential impacts have not been 

examined. An increasing human population in California has the potential to 

amplify acid deposition. Furthermore, foothill yellow-legged frogs generally occur 

at lower elevations (see “Status” section), in areas closer to potential sources of 

airborne acidifying compounds. 

Conservation options related to acid deposition— 

At this time, acid deposition does not warrant consideration in this conservation assessment. Should the risk level for this factor increase, effective management would 

require coordination with agencies outside the jurisdiction of those involved in this 

assessment. It will be important for agencies responsible for foothill yellow-legged 

frog management to participate in guiding the development of management and 

science to inform this issue. 

Disease 

Since 1993, new aquatic pathogens have been observed killing amphibian species 

in the Sierra Nevada and worldwide (Carey et al. 1999). However, the amphibian 

chytrid fungus Batrachochytrium dendrobatidis (“chytrid”) is currently of greatest concern (Longcore et al. 1999) and has been implicated in declines of many 

amphibians globally (e.g., Bosch et al. 2001, Lips et al. 2004, Muths et al. 2003), 

and in the Sierra Nevada of California (Briggs et al. 2010, Rachowicz et al. 2006, 

Vredenburg et al. 2010). 

Chytridiomycosis has been suspected as one of the contributing factors 

responsible for the near extinction of foothill yellow-legged frog populations in 

the southern portion of their range in the Sierra Nevada, and current efforts are 
150 

GENERAL TECHNICAL REPORT PSW-GTR-248

underway to determine how widespread chytrid may be in California populations. 

In an examination of chytrid prevalence in museum specimens, Padgett-Flohr and 

Hopkins (2009) found chrytrid prevalence in two museum specimens collected 

in 1966 from Santa Cruz and Alameda Counties. Chytrid has been found in some 

coastal California populations of foothill yellow-legged frogs (South Fork Eel River: 

Kupferberg 2006; Lowe 2009, Diablo range: Saulino 2006). However, evidence of 

mortality in the species has been limited (Kupferberg 2006, Padgett-Flohr 2006), 

and experimental data show that newly metamorphosed foothill yellow-legged frogs 

exposed to chytrid zoospores showed no difference in mortality relative to unexposed controls (Davidson et al. 2007). Foothill yellow-legged frog skin peptides 

appear to defend frogs from chytrid fungus infection, but exposure to the pathogen 

may have nonlethal effects such as decreased growth rates in juvenile frogs (Davidson et al. 2007). However, in 2013, a die-off of juvenile foothill yellow-legged frogs 

was observed along Alameda Creek and was attributed to an outbreak of chytrid 

(Kupferberg 2015). This suggests that this species is susceptible to lethal infection, 

particularly if other stressors such as drought conditions and nonnative species 

occur. 

Several other pathogens including molds, bacteria, and viruses are suspected 

but not all confirmed to infect foothill yellow-legged frogs. Saprolegnia ferax, a 

species of water mold, has been documented to cause die-offs of eggs in Cascades 

frogs (Rana cascadae) and Western toads (Anaxyrus [Bufo] boreas) in Oregon 

(Blaustein et al. 1994b, Kiesecker and Blaustein 1997a); however, high prevalence 

of S. ferax and die-offs of eggs have not been documented for foothill yellow-legged 

frogs. Red-leg “disease” symptoms, caused by a freshwater bacterium, Aeromonas 

pseudomonas, were observed in a bullfrog population in Burney Creek (a tributary 

to Pit River) near foothill yellow-legged frog sites (Willis [N.d.]); symptoms of 

Aeromonas spp. have not been documented in foothill yellow-legged frogs. Iridoviruses caused 25 of 44 amphibian mortality events in the United States between 

1996 and 2001 (Green et al. 2002). Mortality events linked to iridoviral infections 

involved tadpole or metamorphosing amphibians (Green et al. 2002; Knapp, 2002), 

but mortality in adult frogs has been reported in European ranids (Cunningham et 

al. 1996; Fijan et al. 1991). Ongoing iridovirus (genus Ranavirus) outbreaks have 

been observed in Sierra Nevada yellow-legged frog populations (Knapp 2002) but 

have not yet been documented in foothill yellow-legged frogs. Iridoviruses may 

move between fish and amphibians under natural conditions (Mao et al. 1999), 

raising the possibility that stocked fish may act as vectors for iridoviruses (see 

“Introduced Fishes and Other Predators”). 
151 

Foothill Yellow-Legged Frog Conservation Assessment

Technically not pathogens, trematodes are common parasites of different life 

stages of many anuran species and some have the ability to induce deformities. 

Sessions and Ruth (1990) inferred a relationship between parasitic infection and 

amphibian limb deformities in Pacific chorus frog populations in California. 

Johnson et al. (1999) also found limb abnormality correlated with the presence of 

the trematode Ribeiroia ondatrae in several California species (Pacific chorus frog, 

American bullfrog, and western toad). However, the frequency of limb abnormality 

from the presence of the R. ondatrae in ranid frogs is low, and has only been examined in one foothill yellow-legged frog population (Kupferberg et al. 2009a) where 

deformed individuals lacked trematode infection. The trematode Gorgoderina 

multilobata is known to infect foothill yellow-legged frogs (Ingles and Langston 

1933), but deformities are unreported for this species. 

Extent of risks related to disease— 

Risk from disease, including chytridiomycosis, for foothill yellow-legged frog populations in California appears limited, but much remains unknown about the role 

of recently emerging diseases in foothill yellow-legged frog population declines. 

Lower growth rates of juveniles resulting from chytrid infection may potentially 

have indirect effects on their survival. The effects of interactions between pathogens and other factors (e.g., pesticide exposure) are not well understood but may 

have consequences such as increased susceptibility to disease.
 

Conservation options related to disease— 

Based on current knowledge, disease does not warrant management consideration at 

this time. Research is needed to determine prevalence, effects of various diseases, 

and interactions between disease and other risk factors, to assess the degree of this 

risk to foothill yellow-legged frog populations. Agencies should participate in guiding the development of the management and science to further inform this issue.
 

Fire Management and Suppression 

Fire-suppression activities that may occur in the Sierra Nevada and could affect 

foothill yellow-legged frogs include water drafting from streams (or sometimes 

ponds), water application, retardant application, construction of hand or mechanical 

lines, and increased human presence in fire camps within riparian zones. Fire crews 

and other fire personnel attempt to minimize impacts to aquatic and semiaquatic 

species and their habitats, but inadvertent direct impacts can occur. For example, in 

1994, water was drafted for fire suppression by helicopter from a pond containing 

aquatic amphibians and reptiles; animals were accidentally taken up in the water 
152 

GENERAL TECHNICAL REPORT PSW-GTR-248

bucket and subsequently rained onto the fire site when it was emptied (Holland 2005). 

Mechanical fuels treatments, direct burning and back burning in riparian areas, fire 

salvage activities, and prescribed fires in the uplands can lead to direct burning of 

frogs, and pile burning in riparian areas may directly trap and kill frogs. 

Application of retardant has become an important wildlife issue (Pilliod et al. 

2003) and some fire-suppressant cocktails have been found to be toxic or hazardous 

to aquatic organisms (Buhl and Hamilton 2000, Gaikowski et al. 1996, McDonald 

et al. 1996). In large wildfires, ammonia-based fire retardants and surfactant-based 

fire-suppressant foams may be dropped from air tankers or sprayed from fire 

engines to slow or stop the spread of fire. Fire personnel make efforts to avoid 

riparian areas, but accidental contamination of aquatic habitats has occurred, 

especially from aerial applications (Minshall and Brock 1991). Amphibians appear 

less sensitive to ammonia toxicity than fishes, and problems may be restricted to 

smaller lentic bodies of water (Pilliod et al. 2003), and may be less of a problem for 

foothill yellow-legged frogs. 

During fire suppression, the construction of fire lines or firebreaks may be 

extensive and result in habitat changes similar to those associated with roads and 

road construction (see “Roads” section). Fire line or firebreak restoration features, 

such as water bars and revegetation, may mitigate erosion rates and road-like effects 

(Pilliod et al. 2003), but such features are not consistently implemented. Sedimentation may be the primary road-like risk of fire lining to foothill yellow-legged frogs; 

fine sediment may reduce refuge habitat by filling interstitial spaces in the coarsesubstrate dominated streams characteristically used by foothill yellow-legged frogs 

(see “Ecology” section). 

Prescribed fire can dramatically alter vegetation and soils and disturb foothill 

yellow-legged frog habitat if implemented during the time when fires would not 

naturally occur or with high fuel loading, which can lead to high fire intensities. 

However, prescribed fire can also benefit foothill yellow-legged frogs by reducing 

the risk of future high-intensity wildfire and preventing vegetation encroachment 

on stream margin habitat. Wildfire suppression policies that began early in the 

last century have resulted in landscape-scale habitat changes; forests have become 

denser, with high fuel loads, making them susceptible to catastrophic wildfires 

that can produce some of the most intensive and extensive changes in watershed 

condition of any disturbance (Kattelmann 1996). Dense forest stands also result in 

reduced water yields, which consequently alter peak flows and increase sediment 

yields in streams. 
153 

Foothill Yellow-Legged Frog Conservation Assessment

Extent of risks related to fire management— 

Too few data exist on the impact of fire suppression activities on amphibians to 

effectively evaluate the risk to foothill yellow-legged frogs. Based on the known 

effects of fire suppression, the possibility exists that these activities could affect 

foothill yellow-legged frogs, and risk is potentially high as these frogs occur in fireprone lower elevations. 

Conservation options related to fire management— 

Research is needed to inform how fire suppression and presuppression techniques 

may influence foothill yellow-legged frogs. Minimum-impact fire suppression and 

presuppression techniques may represent the best alternative for protecting foothill 

yellow-legged frogs and their habitat. 

Livestock Grazing 

The Sierra Nevada Ecosystem Project’s Final Report to Congress (known as 

the SNEP Report) (Kattelmann 1996) states that livestock grazing has “affected 

more area in the Sierra Nevada than any other management practice.” Historically, unregulated, unsustainable grazing practices existed over much of the Sierra 

Nevada, resulting in widespread damage to rangelands and riparian systems. Livestock numbers on federal land have decreased owing to public land management 

decisions and economic shifts in rural communities. Seasonal restrictions, limits on 

maximum annual use, riparian and streambank cover standards, and fencing have 

reduced grazing impacts in riparian and meadow ecosystems (USDA FS 2001). 

Livestock tend to concentrate in riparian areas that contain the primary source 

of forage on most allotments in the Sierra Nevada (Belsky et al. 1999, Kauffman 

and Krueger 1984, Menke et al. 1996). The magnitude of impacts can depend on 

a variety of factors including riparian community type and stocking and utilization rates (Green and Kauffman 1995; Kauffman et al. 1983a, 1983b; Myers and 

Swanson 1991; Schulz and Leininger 1990). Both negative and positive associations 

between livestock grazing and amphibian populations and habitat have been found 

(Adams et al. 2009, Bull and Hayes 2000, Burton et al. 2009, Jansen and Healey 

2003, Knutson et al. 2004, Lind et al. 2011, Roche et al. 2012). For the foothill 

yellow-legged frog, a retrospective study in Oregon found a negative association 

between grazed lands and frog occupancy (Borisenko and Hayes 1999). 

All life stages of foothill yellow-legged frogs are vulnerable to trampling by 

livestock. Mortality risk from livestock trampling is expected to be greatest for less 

mobile life stages (i.e., egg masses and tadpoles), when densities are highest such 
154 

GENERAL TECHNICAL REPORT PSW-GTR-248

as during breeding congregations, and when juveniles are metamorphosing along 

aquatic margins (see “Ecology” section). Trampling risk may therefore depend on 

the timing and duration of cattle presence in a grazing allotment. 

Some concern exists regarding livestock transport of pathogens (e.g., fecal 

coliforms, other bacteria, Batrachochytrium dendrobatidis [Bd]) between streams, 

and nutrient inputs that may promote algal growth in heavily used streams and 

water sources (Kattelmann 1996, Stephenson and Street 1978). Potential risk of 

pathogen transmission exists from livestock fecal material or transport on hooves or 

other body parts (e.g., transport of Bd zoospores). No studies have investigated the 

link between livestock and the transmission of disease-causing pathogens. Bacteria 

and nutrients from feces can reach a water source by direct deposit or overland flow 

from upland runoff. Fecal material can accumulate in streambed sediments and be 

dislocated by flow changes or cattle trampling. Amount of manure and its dilution 

ratio may determine the degree of risk to foothill yellow-legged frogs. Streams in 

the foothill yellow-legged frog range may support few bacteria in their sediments 

in the absence of significant nutrient inputs. Increased nutrient loads from livestock 

excrement may cause excessive amounts of aquatic vegetation, which may overconsume oxygen. 

Livestock grazing may affect habitat by altering riparian vegetation. Grazing 

can modify vegetation successional pathways, changing plant communities toward 

early-seral or disturbance-adapted species (Kauffman and Krueger 1984). Grazing 

has also been found to reduce overhanging vegetation along streams, simplify vertical and horizontal vegetation structure, alter individual plant phenology, and reduce 

herbaceous vegetation and shrub diversity, productivity, and cover (Belsky et al. 

1999). Grazing and trampling of riparian vegetation can eliminate plant cover used 

for refuge, but could also limit woody plant establishment on river bars, which may 

enhance foothill yellow-legged frog breeding and rearing habitat. 

Livestock grazing affects riparian area soils and associated hydrologic processes by increasing overland flow, peak flows, and flood velocity; decreasing 

summer and late-season flows; increasing bare ground and erosion; increasing soil 

compaction; decreasing soil fertility and infiltration; and reducing litter layers and 

organic soil inputs (Belsky et al. 1999). Modification of the soil surface influences 

water and sediment yields and may consequently cause changes in stream channel 

morphology. If alteration of the hydrologic regimes results in higher peak flows 

or shifts in timing of seasonal flows, there could be negative effects on foothill 

yellow-legged frog egg masses and tadpoles. Livestock grazing can result in 

widening and shallowing of the streambed channel (Kauffman and Krueger 1984), 
155 

Foothill Yellow-Legged Frog Conservation Assessment

and may reduce the number of pools, forming channels with fewer meanders and 

unvegetated gravel bars (Belsky et al. 1999, Kauffman and Krueger 1984). Foothill 

yellow-legged frogs use shallow water areas along gravel/cobble bars as breeding 

habitat, so formation of these stream features may be a positive consequence of 

grazing, at least at certain grazing intensities, for this species. Stream widening 

may increase exposure to solar radiation and subsequently increase water temperatures. The effects of increasing water temperatures on foothill yellow-legged frog 

reproduction, tadpole development, and spatial distribution within river networks 

have recently been investigated (Catenazzi and Kupferberg 2013, Kupferberg et 

al. 2011a). In Sierran rivers, egg masses and tadpoles occur and can be abundant 

at sites where the average water temperature during the warmest 30-day period of 

summer reaches 24 °C (e.g., at North Fork Feather River at Poe Powerhouse, Clavey 

River near the confluence with Tuolumne, the most downstream breeding site of the 

Rubicon) (Kupferberg et al. 2011a); however, in the Eel River watershed, population 

densities were low along reaches that exceeded a July (2010) mean water temperature of 19 °C (Catenazzi and Kupferberg 2013). 

Vegetation removal and trampling disturbance resulting from livestock activity may cause soil erosion and increased sedimentation. High sediment loads can 

lead to higher levels of embeddedness of streambed substrates by filling interstitial 

spaces, which are used by larval foothill yellow-legged frog tadpoles for instream 

cover. Excess sediment may reduce interstitial flow and decrease dissolved oxygen in microhabitats used by larvae. Fish reared in low-oxygen spawning gravels 

showed reduced rates of food consumption, growth, and survival (Belsky et al. 

1999); low dissolved oxygen may have similar effects on larval foothill yellowlegged frogs. Sediment accumulation on substrates may also reduce algal growth, 

the primary food source of larval foothill yellow-legged frogs. 

Extent of risks related to grazing— 

Studies are lacking to specifically assess the risk of grazing effects on foothill 

yellow-legged frogs. Grazing is widespread throughout the historical range of 

the foothill yellow-legged frog, but its prevalence, and therefore its risk, varies. 

Potential risk is high because of the overlap in habitat use between livestock and 

foothill yellow-legged frogs; however, properly managed grazing may have neutral 

or even positive effects on frog habitat. 

Conservation options related to grazing— 

As grazing allotments are permit based, livestock grazing represents a fundamental 

management consideration over which national forests and national parks have jurisdiction. The type and extent of grazing allowed can directly influence the degree 
156 

GENERAL TECHNICAL REPORT PSW-GTR-248

to which foothill yellow-legged frogs and their habitat may be affected. To minimize trampling risk, livestock could be kept away from occupied habitat to mitigate 

impacts during critical foothill yellow-legged frog breeding, rearing, and metamorphic seasons. However, the actual degree of risk from grazing to foothill yellowlegged frogs under current policies is unknown. 

Locally Applied Pesticides 

National forests in the Sierra Nevada occasionally use pesticides to control rodents, 

insects, and fungi, and to eliminate noxious weeds and brush. Pesticides are used 

in conifer plantations and private timberlands for controlling brush (Bakke 2004), 

throughout the national forests for controlling noxious weeds, and near buildings 

and other facilities. Hydropower projects also include the use of pesticides at their 

facilities, such as along canals and at reservoirs. Currently, nearly all herbicide 

application on national forests is conducted via backpack sprayers, which allows for 

control of the spray direction and coverage. Buffers from streams and water bodies 

are designated during the National Environmental Protection Act (NEPA) process 

for each project to facilitate protection of aquatic species from adverse effects. Buffer distances are site-specific depending on potential toxic effects of each herbicide 

type, the potential for them to enter the groundwater or move offsite, and the known 

aquatic species that could be affected downstream. The Sierra Nevada Forest Plan 

Amendment (USDA FS 2004) requires 500-ft (152-m) buffers from known locations of foothill yellow-legged frogs on national forest lands. 

The most common pesticides used on national forests, in descending order of 

frequency, are glyphosate, triclopyr, clopyralid, hexazinone, aminopyralid, chlorsulfuron, imazapyr, and aluminum phosphide (for burrowing rodents). Common 

surfactants, which help herbicides adhere to plant surfaces, include R-11, methylated seed oil (Hasten), and methylated seed oil/silicone blend (Syl-tac). Dyes used 

to view recently sprayed areas include Highlight Blue, Bas-Oil Red, and Colorfast 

Purple. 

The active ingredient in Roundup® and Rodeo®, an isopropylamine salt, has 

been found to be practically nontoxic to frogs (Mann and Bidwell 1999). These 

commercial pesticides, however, may contain (e.g., Roundup) or be combined with 

(e.g., Rodeo) surfactants such as polyethoxylated tallowamine (POEA), which have 

been shown to be toxic to aquatic life, including several species of ranid frogs 

(Folmar et al. 1979, Howe et al. 2004, Mann and Bidwell 1999, Mitchell et al. 1987, 

Servizi et al. 1987, Smith 2001, Wan et al. 1989). Surfactants may damage gills 

(SERA 2003a), which may be why tadpoles were found to be the most sensitive life 
157 

Foothill Yellow-Legged Frog Conservation Assessment

stage to the Roundup formulation of glyphosate (Bidwell and Gorrie 1995, Mann 

and Bidwell 1999). High toxicity of Roundup to tadpole and postmetamorphic 

northern leopard frogs may be a function of POEA, but this study did not isolate 

the effects of glyphosate and surfactant (Relyea 2005b). Other studies (Giesy et al. 

2000, Hildebrand et al. 1982, Mitchell et al. 1987, Sullivan et al. 1981, Thompson 

et al. 2004, Wojtaszek et al. 2004) have concluded that glyphosate-based herbicides 

under normal usage do not pose a hazard to aquatic environments, where both the 

glyphosate and surfactant would be diluted by large or flowing bodies of water or 

protected by a terrestrial buffer. Water quality monitoring in the Pacific Southwest 

Region of the Forest Service has concluded that glyphosate and triclopyr are rarely 

detected in surface water when these herbicides are used with stream buffers 

(USDA FS 2001). 

Triclopyr (Garlon®) is used to control noxious weeds and approaches toxicity to 

African clawed frog (Xenopus laevis) embryos, especially in its formulation marketed 

as Garlon 4 (Perkins et al. 2000). Field evaluation of this herbicide suggested that it 

can depress growth rates in brook trout at typical application levels (Kreutzweiser 

et al. 1995). Garlon 3A, the amine formulation of triclopyr (triclopyr TEA), is water 

soluble, less volatile (Bakke 2004), and less toxic than Garlon 4 (Perkins et al. 2000) 

because it does not appear to penetrate tissues or bioaccumulate (SERA 2003b). 

Berrill et al. (1994) measured the toxicity of three chemicals, including triclopyr and 

hexazinone, to embryos and tadpoles of three frog species. Embryos were not affected 

by triclopyr, whereas tadpoles became unresponsive to prodding (reflecting avoidance 

response) at exposures of 1.2 ppm (or higher) and mortality occurred at higher doses 

(2.4 and 4.8 ppm). Tadpoles whose behavioral responses were affected recovered 

within 3 days. No effects on either embryos or tadpoles were observed from exposure 

to hexazinone. 

Additive, multiplicative, or synergistic effects of herbicides with other risk 

factors have only recently begun to be studied among amphibians and remain 

unstudied in foothill yellow-legged frogs. Both Chen et al. (2004) and Edginton 

et al. (2004) found the Vision® formulation of glyphosate increased in toxicity to 

embryonic and tadpole stages of green frogs (Lithobates [Rana] clamitans) and 

northern leopard frogs at higher pH treatments (≥ 7.5). Relyea (2005b) found that 

high mortality of tadpoles and postmetamorphic northern leopard frogs exposed 

to Roundup may have been a function of relatively high pH (8.0) tap water used in 

the experiments. Relyea (2005a) also examined herbicide effects in a community 

context using outdoor mesocosms; he manipulated combinations of predators and 

pesticides and found that Roundup (at a level of 1.3 mg of active ingredient/L) had 

direct negative effects on the tadpoles, reducing total tadpole survival and biomass 
158 

GENERAL TECHNICAL REPORT PSW-GTR-248

by 40 percent. Roundup did not have indirect effects on the amphibian community 

via predator survival or algal abundance. 

Extent of risks related to locally applied pesticides— 

Locally applied pesticides are not known to have affected foothill yellow-legged 

frogs, but the extent of this risk factor is likely to be limited. Data on other amphibians suggest some level of risk of various pesticides, but no data exist evaluating the 

threat to foothill yellow-legged frogs. 

Conservation options related to locally applied pesticides— 

Management should continue to regulate the application of locally applied pesticides to reduce its impact on this species. Research is needed to inform knowledge 

gaps regarding species-specific application-level toxicities of pesticides and how 

they interact with other risk factors. Agencies participating in this conservation assessment have direct jurisdiction over this activity. 

Recreational Activities 

Approximately 30 percent of foothill yellow-legged frog geographic range in California is on national forest lands; about 8 percent is on Bureau of Land Management, National Park Service, and other federal lands; and the remaining 60 percent 

lies on private lands (USDA Forest Service GIS data available 2001). The Sierra 

Nevada region is the backdrop for a broad range of outdoor recreation, most of 

which occurs on national forest and national park lands (USDA FS 2004). Recreational activities include camping, hiking, fishing, off-highway vehicle (OHV) use, 

packstock use, suction-dredge mining (see above in “Mining” section), mountain 

biking, and whitewater boating. High overlap exists between foothill yellow-legged 

frog habitats and areas commonly used for these activities. Foothill yellow-legged 

frogs inhabit streams and their near vicinities (see “Habitat Requirements” under 

“Ecology” section), areas that are attractive to humans and receive a disproportionate amount of recreational use through whitewater boating in streams, and trail networks and campsites in or near riparian areas (Vinson 1998). Recreational activities 

have the potential for significant impacts directly on foothill yellow-legged frogs 

and indirectly on their habitats. 

The impacts of most recreational activities (e.g., hiking, bicycling, fishing, 

and off-highway vehicles) on foothill yellow-legged frogs have not been examined, 

and studies of amphibians with similar life histories are lacking. One recreational 

activity that has been evaluated for the species is the effect of manufactured pulsed 

flows, created for whitewater boating, on foothill yellow-legged frogs (GANDA 

2005; Kupferberg et al. 2008, 2009b) (see “Water Development and Diversion” 
159 

Foothill Yellow-Legged Frog Conservation Assessment

section). Aseasonal pulse flows, managed to accommodate whitewater boating, can 

have negative consequences, such as scouring or stranding early life stages of the 

foothill yellow-legged frog (Kupferberg et al. 2008 and studies cited therein) that 

may result in significant impacts on population densities (Kupferberg et al. 2012) 

(see “Water Development and Diversion” section). 

Recreational activities may result in direct effects such as crushing, trampling, 

and improper handling (e.g., see Kagarise-Sherman and Morton 1993). Packstock, 

like livestock, have the potential to damage or destroy eggs, tadpoles, and juveniles 

(see Bartelt 1998). Packstock on federal lands appear to be primarily a higher elevation phenomenon; however, we currently have little information regarding their 

occurrence across the low-elevation range of the foothill yellow-legged frog. 

Vegetation may be reduced as a result of trampling (Dale and Weaver 1974) by 

hikers, bicyclists, packstock, and OHVs. Low vegetation (e.g., sedges) along stream 

margins may be used as refuge and concealment by foothill yellow-legged frogs 

(see “Ecology” section). Packstock in particular apply intense downward force that 

can damage vegetation, compact soils, and reduce organic litter material (Weaver 

and Dale 1978). Terrestrial cover used by foothill yellow-legged frogs may be more 

important during the warmest part of the nonbreeding season, and may increase in 

importance with decreasing latitude (Lind, pers. obs., 2006). Establishment of trails 

and camps also disturbs vegetation and soil structure, resulting in changes in habitat structure and microclimate (Boyle and Samson 1985, Garton et al. 1977, Knight 

and Cole 1991). Heavy recreational use can mimic damage to vegetation and soils 

that results from grazing (Obedzinski et al. 2001). Studies in wilderness areas have 

found that even light-use recreation can create considerable and rapid impact, and 

recovery may require lengthy periods of non-use (Cole and Marion 1988). Impacts 

of low-intensity use of campsites include loss of vegetation cover, soil compaction 

resulting in slowed infiltration rates, and pronounced increases in soil pH, organic 

matter content, and nutrient content (Cole and Fichtler 1983). 

Recreational activities may affect stream hydrology and water quality. Hydrologic effects include diversion of water, down-cutting, and lowering of water tables. 

Changes in hydrology that induce shallowing and warming or aseasonal drying 

of stream shoreline habitat may affect foothill yellow-legged frogs. Disruption of 

hydrology is more likely to occur in shallower systems such as those that are used 

for oviposition or rearing, or low-volume springs or seeps, which may be important 

nonbreeding season habitat for juveniles (Rombough 2006b). Localized water pollution from camp-related substances such as detergent, sunscreen and insect repellent 

may occur through swimming and washing, and nitrogen may be introduced into 

streamwater from human wastes (Rouse et al. 1999). Contact with these substances 
160 

GENERAL TECHNICAL REPORT PSW-GTR-248

may place foothill yellow-legged frogs at risk owing to their permeable skin. Water 

quality may also be reduced by trampling or disturbance of streambanks by recreationists (e.g., increased sediment and nutrients). 

The potential for human activity to attract certain predators is a concern that 

has often been considered in studies of birds (e.g., Nelson and Hamer 1995, Niehaus 

et al. 2004), but remains unexamined for amphibians, including foothill yellowlegged frogs. Some predators, particularly corvids, may be attracted to areas of high 

human use, resulting in concentrations of the predators at greater than background 

levels (Lawrence 1973). Whether such attraction poses a significant threat to local 

foothill yellow-legged frog populations is unstudied. 

Extent of risks related to recreational activities— 

The impacts of most recreational activities on foothill yellow-legged frogs remain 

unstudied. The exception is the effects of aseasonal pulsed flows for whitewater 

boating; risk is high for foothill yellow-legged populations located on streams that 

are regulated to accommodate recreational boating. In high-use areas, various recreational activities may add to cumulative impacts on already stressed small populations. Dispersed activities like hiking, fishing, camping, and mountain biking 

may pose a moderate localized risk to the species. 

Conservation options related to recreational activities— 

Research is needed to investigate the extent of impacts of recreational activities and 

how best to manage them. Meanwhile, management should address the potential 

for localized recreational impacts to foothill yellow-legged frog habitat, and should 

focus on mitigating probable effects. Recreational activities are within the purview 

of agencies participating in this assessment. 

Research Activities 

Researchers have the potential to negatively affect anuran populations by handling 

or marking animals, attracting predators, or spreading pathogens among water 

bodies via clothing and equipment. Researchers have studied foothill yellow-legged 

frogs intensively at several sites over several-year periods (Kupferberg 1996a, 

1996b; Kupferberg et al. 2008; Van Wagner 1996; Wheeler and Welsh 2008; Yarnell 

2000). Intensive study in these populations included marking individual animals 

using different methods, handling animals for measurement, and monitoring 

specific locations with high (daily or every few day) frequency. Incidentally, none 

of these studies found that research activities had any negative impact on frogs; 

however, they did not quantitatively assess effects. 
161 

Foothill Yellow-Legged Frog Conservation Assessment

Historically, handling and marking of animals has been viewed as innocuous, 

but a study addressing marking techniques (Murray and Fuller 2000) and pathogen 

epidemiology has forced reassessment of this view. Excluding the possibility of disease transfer, capture and noninvasive processing (e.g., measuring and weighing) of 

frogs is likely harmless. A review of studies involving toe-clipping to individually 

mark animals revealed an incremental decrease in survivorship with each additional 

toe clipped, where previous analyses of the same data had revealed no effect across 

low numbers of clips (McCarthy and Parris 2004). This analysis did not address the 

effects of single clips, often used to obtain samples for genetic or aging (skeletochronological) studies; the consequences of single clips, if any, remain unknown. 

No effects on survival or body condition have been found using passive integrative 

transponder (PIT) tags, but comparison to unmarked reference animals have been 

restricted to laboratory analyses (Perret and Joly 2002). Research activities that 

involve movement of researchers (e.g., wading gear, dry suits) or equipment (e.g., 

dip nets, gill nets) between water bodies have the potential to move pathogens. 

Current research protocols contain provisions (largely specific equipment cleaning procedures) to limit the spread of pathogens into and between the environments 

of amphibians (Padgett-Flohr et al. [N.p.] ). 

Research activities that involve manipulation of stream habitat may negatively 

affect foothill yellow-legged frogs if the habitat enhancement for the target species 

is unfavorable to them. For example, when the instream flow incremental methodology (IFIM) is used to conduct fish habitat studies in regulated rivers, dam operations are often manipulated to release specific discharge levels to allow for habitat 

mapping. When field efforts that are routine elements of hydropower relicensing 

studies are ill-timed, mortality to early life stages of foothill yellow-legged frogs 

can occur; egg masses on the Pit River were scoured from attachment substrates 

during a fish habitat study (Spring Rivers Ecological Sciences 2003). 

Extent of risks related to research activity— 

Researchers typically have their study species’ best interest in mind when designing 

their studies, so research activity is unlikely to be a significant factor in the decline 

of foothill yellow-legged frogs. 

Conservation options related to research activity— 

When research activities in regulated rivers involve flow manipulation, precautionary timing of the artificial fluctuations in discharge should be practiced to minimize potential effects. Agencies should promote thoughtfully designed research 

projects and identify measures to reduce potential disease transmission.
 
162 

GENERAL TECHNICAL REPORT PSW-GTR-248

Restoration Activities 

Restoration represents a very broad class of activities that can apply to many habitat 

types. For foothill yellow-legged frogs, restoration activities that may have effects 

(negative or positive), are those that are implemented in stream and riparian corridors where breeding, rearing, or overwintering occur. Methods that are most likely 

to affect foothill yellow-legged frogs include restoration of flow regime in regulated 

river systems, and restoration of fish habitat through the improvement of fish passage structures or the addition of large wood for fish refugia. 

Restoration of natural flow regimes in regulated rivers may be the single most 

important approach to achieve positive effects for foothill yellow-legged frog 

populations (see the “Water Development and Diversion” section). In regulated 

stream systems, managing water velocities to emulate naturally occurring flows 

may lower mortality of egg masses and tadpoles and increase the quality and 

quantity of breeding and rearing habitat. Based on the results of habitat associations 

studies by Yarnell (2005, 2008), restoration activities that increase the heterogeneity 

of aquatic and riparian habitats may benefit foothill yellow-legged frogs. Managed 

flow regimes in regulated rivers, however, are often reconciling multiple resource 

goals (e.g., channel morphology, water temperatures for cold water-associated 

fish species, recreation, and amphibian population and habitat), so it is difficult to 

sort out their effectiveness for particular species. New flow regimes are currently 

being implemented in regulated rivers under Federal Energy Regulatory Commission (FERC) relicensing of water projects throughout California. These changes 

will provide opportunities for study and assessment of the effectiveness of these 

regimes. 

During a fish habitat improvement project, Fuller and Lind (1992) found that 

this restoration effort may have negatively affected foothill yellow-legged frogs. 

Foothill yellow-legged frogs were observed breeding (based on eggs or tadpoles) 

for 3 consecutive years prior to placement of a flow-deflecting structure that was 

designed largely as a flow refuge for small salmonids. After the placement of the 

structure, they found no evidence of foothill yellow-legged breeding over the next 

3 years (Fuller and Lind 1992). Fuller and Lind (1992) recognized the limitations of 

their uncontrolled, unreplicated study but emphasized that their results highlight the 

fact that attention should be given to entire local faunal assemblages rather than to a 

single target species when implementing restorations. 

Extent of risks related to restoration activities— 

Effects of most restoration activities on foothill yellow-legged frogs are unstudied, but their effects are anticipated to be both spatially and temporally localized. 
163 

Foothill Yellow-Legged Frog Conservation Assessment

Moreover, the long-term benefits of most restoration projects are anticipated to outweigh any short-term negative effects associated with the restoration activity. 

Conservation options related to restoration activities— 

Restoration activities are within the jurisdiction of agencies participating in this assessment, largely through the planning process that individual projects must follow 

prior to implementation. However, systematic study of the effects of different types 

of restoration on foothill yellow-legged frogs is almost nonexistent and is needed 

to inform how to better design restoration activities. Efforts to manipulate thermal 

regime via flow releases from dams to decrease temperature to accommodate coldwater fish species may have unintended negative consequences for foothill yellowlegged frog recruitment. 

Roads 

Roads have been shown to have several negative ecological effects (Forman and 

Alexander 1998) on aquatic and riparian ecosystems (Trombulak and Frissell 2000) 

and forested landscapes (DeMaynadier and Hunter 2000). Olson and Davis (2009) 

found that increasing road density was negatively associated with foothill yellowlegged frog occurrence in Oregon. Every major river system draining the Pacific 

slope of the Sierra has either a major highway or road up the drainage. Foothill 

yellow-legged frogs occur primarily on national forests and private lands, which 

may include numerous roads. National forests generally contain many unpaved 

roads with lower levels of traffic than in or near urban areas, but the presence of 

even a few roads may affect frog habitat. Populations of foothill yellow-legged frogs 

occurring on private lands, which include 60 percent of the species historical range, 

may be most susceptible to impacts associated with roads. 

The extent of the impacts of roads (presence, construction, or use) on foothill 

yellow-legged frogs and their habitat has not been studied, but likely depends on 

factors such as road density, road type, and traffic intensity. Studies have shown 

inverse relationships between amphibian densities with road density and traffic 

intensity (see Fahrig et al. 1995 and Vos and Chardon 1998). Road-related activities 

may cause direct mortality; mass mortalities of frogs have been documented for 

other species during dispersal (Fahrig et al. 1995; Hine et al. 1981; see also Trombulak and Frissell 2000). Traffic mortality can decrease population size and reduce 

movement between resources and conspecific populations (Carr and Fahrig 2001). 

Sedimentation was identified as a factor that negatively affected foothill yellowlegged frog occupancy in Oregon (Borisenko 2000, Borisenko and Hayes 1999). 

Transfer of sediment (and other material) to streams is an inevitable consequence of 
164 

GENERAL TECHNICAL REPORT PSW-GTR-248

roads and their construction (Bryer et al. 2006, Richardson et al. 1975, Spellerberg 

1998). The surfaces of unpaved roads can route fine sediments to streams, increasing turbidity of the water (Reid and Dunne 1984). Road construction in Redwood 

National Park introduced large amounts of sediment into neighboring streams, and 

densities of amphibians appeared to be lower in these streams compared to nearby 

control streams (Welsh and Ollivier 1998). High concentrations of suspended sediment may directly kill aquatic organisms and impair aquatic productivity (Newcombe 

and Jensen 1996) and inhibit growth and survival of aquatic plants, macroinvertebrates, and fish (Newcombe and MacDonald 1991, Power 1990, Waters 1995). Frog 

egg masses may collect sediment which if excessive, may result in egg suffocation 

(Jennings and Hayes 1994); the effects may be intensified if the sediments contain 

toxic materials (Maxell and Hokit 1999). Increased sedimentation also may reduce 

availability of important food resources (algae) for tadpoles (Power 1990). 

Vehicular emissions and road runoff contain chemical pollutants (e.g., heavy 

metals, salt, organic molecules, ozone, and nutrients) (Trombulak and Frissell 2000) 

that can reduce survival, cause deformities, elevate levels of stress hormones, and 

inhibit growth and metamorphosis (Lefcort et al. 1997, Mahaney 1994, Welsh and 

Ollivier 1998). 

Roads can affect foothill yellow-legged frogs by altering stream hydrology 

and geomorphology. The presence of roads is highly correlated with changes in 

the hydrologic and geomorphic processes that shape aquatic and riparian systems 

(Trombulak and Frissell 2000). A study on road networks constructed for forestry 

land use in the Pacific Northwest showed that roads can influence peak flows 

(floods) and debris flows in stream channels; these processes have major influences on riparian vegetation (Jones et al. 2000) as well as aquatic and riparian patch 

dynamics critical to stream ecosystems (Pringle et al. 1988). The effects of flow 

fluctuations on foothill yellow-legged frogs have been previously discussed (see 

“Water Development and Diversions” section). Hydrologic effects are likely 

to persist as long as the road remains a physical feature altering flow routing, 

even long after abandonment and revegetation of the road surface (Trombulak 

and Frissell 2000). 

Roads may fragment habitat and restrict foothill yellow-legged frog movement and migration. A study on the moor frog (Rana arvalis) showed that roads 

in a moderately fragmented habitat increased isolation, and hence contributed to 

fragmentation (Vos and Chardon 1998). The study also concluded that even in a 

relatively large and stable habitat patch, the effects of habitat fragmentation on frog 

populations were strongly negative (Vos and Chardon 1998). Many populations of 
165 

Foothill Yellow-Legged Frog Conservation Assessment

foothill yellow-legged frogs are already small and fragmented (see “Status” section), so further effects that result from fragmented habitat may be critical. If the 

species operates as metapopulations (Bradford 1991), road barriers could prevent 

recolonization of locations where extirpations have occurred. Seasonal movements made by foothill yellow-legged frogs are associated with stream corridors 

(see “Ecology” section) and roads affect the physical connectivity of lotic habitats 

at road-stream crossings. Some of this issue is analogous to fish passage issues 

created by culverts, which have been structurally improved to allow fish passage 

(Boubée et al. 1999, Hansen et al. 2011, Price et al. 2010), but whether these efforts 

effectively translate to allow passage for foothill yellow-legged frogs is unknown. 

Culvert passage typically involves lower order streams (per Strahler 1952) and is 

not likely a significant issue for premetamorphic life stages because foothill yellowlegged frogs typically breed in higher order (larger) streams. Postmetamorphic life 

stages that use lower order streams as seasonal refuge habitat may be more likely to 

be affected (see “Ecology” section). Passage issues for stream-associated amphibians are rarely examined (e.g., Sagar et al. 2007) and for foothill yellow-legged 

frogs remain unstudied.
 

Extent of risks related to roads— 

The substantial road matrix within the Sierran range of foothill yellow-legged frogs 

and their proximity to stream habitats used by foothill yellow-legged frogs suggest 

that roads are a potentially significant risk. This is supported by the existing science 

on the direct and indirect negative effects of roads on other amphibian and aquatic 

species. Hence, some risks from roads are likely, but no data exist on the specific 

impacts of roads on foothill yellow-legged frogs. 

Conservation options related to roads— 

Through their jurisdiction over road development and maintenance, and patterns of 

road use, agencies participating in this conservation assessment can have a significant influence over how roads may affect foothill yellow-legged frogs. However, 

significant science is needed to inform precisely how road-related management can 

be best implemented to minimize negative effects to foothill yellow-legged frogs.
 

UV-B Radiation 

Increases in mid-range ultraviolet radiation (UV-B; 290 to 320 nanometers) resulting from depletion of atmospheric ozone are hypothesized to contribute to amphibian declines, a pattern consistent with their apparent global nature (Blaustein and 

Wake 1990, Wake 1991). Experimental and field studies addressing UV-B are 

controversial and have produced mixed results (Licht and Grant 1997); effects of 
166 

GENERAL TECHNICAL REPORT PSW-GTR-248

increased UV-B on amphibian growth and survivorship appear to vary across conditions (e.g., species, life stages, habitats, and conditions such as dissolved organic 

content of water), making it difficult to assess the role of this risk factor in declines 

(Licht 2003, Palen et al. 2005). Differences in responses among species have been 

attributed in part to differences in the behavioral, physiological, and molecular 

defenses these amphibians possess against UV-B (Blaustein and Belden 2003). 

Much of the research on UV-B effects on amphibians has involved experiments 

examining the vulnerability of the eggs and embryos of several western North 

America species. Exposure to elevated UV-B resulted in reduced hatching success, 

reduced tadpole growth rates, or sometimes increased physical abnormalities in 

Cascades frogs and western toads (Blaustein et al. 1994a), long-toed salamanders 

(Belden et al. 2000), and California newts (Taricha torosa) (Anzalone et al. 1998). 

No effects were observed on Pacific treefrogs (Anzalone et al. 1998, Blaustein et 

al. 1994a, Ovaska et al. 1997), Columbia spotted frogs or Oregon spotted frogs 

(Blaustein et al. 1998), northern red-legged frogs (Blaustein et al. 1996, Ovaska et 

al. 1997), or western toads (Corn 1998). Experiments revealed that foothill yellowlegged frog embryos also lacked sensitivity to UV-B (Neumann 1997). UV-B 

exposure may have sublethal effects; Belden and Blaustein (2002) found depressed 

growth rates in red-legged frog embryos and tadpoles, and Fite et al. (1998) 

observed retinal damage in Cascades frog adults. 

Several studies have demonstrated that UV-B effects are more likely in combination with another stressor. Long et al. (1995) found that embryos of northern 

leopard frogs exposed to levels of UV-B and low pH, that were nonlethal when each 

was individually applied, produced significant mortality when the two stressors 

were applied simultaneously. A similar synergism between UV-B and low pH 

was observed for common frog, Rana temporaria, embryos (Pahkala et al. 2002). 

Kiesecker and Blaustein (1995) found that boreal toad and Cascades frog embryos 

exposed to UV-B had higher mortality caused by the pathogenic water mold Saprolegnia ferax compared to embryos subjected to each treatment alone. 

Environmental information suggests that habitat conditions for large geographic 

areas in western North America limit UV-B exposure (Licht 1996, 2003). Dissolved 

organic material (DOM) or dissolved organic carbon (DOC) can absorb UV-B 

(Morris et al. 1995, Scully and Lean 1994) and reduce it to levels below those that 

Blaustein et al. (1994a) found to affect embryos (Palen et al. 2002). The distribution of amphibians may also be influenced by site-specific UV-B levels (Adams et 

al. 2001, Nagl and Hofer 1997). UV-B transmission in lotic habitats occupied by 

foothill yellow-legged frogs is likely to be lower than in lentic habitats owing to 
167 

Foothill Yellow-Legged Frog Conservation Assessment

a combination of turbulence and small suspended particulates that attach to egg 

masses (Kupferberg 2006). 

There has not been a severe increase in UV-B levels at high elevations in the 

Sierra Nevada (≤ 5 percent) over the past several decades (Jennings 1996), suggesting that UV-B has not contributed directly to the decline of foothill yellow-legged 

frogs, especially in lower elevation areas that are more insulated from UV-B. 

Davidson et al. (2002) examined the spatial pattern of declines in foothill yellowlegged frogs to determine if these patterns could be explained by a UV-B effect 

(e.g., an increase in declines at higher elevations and lower latitudes, coincident 

with altitudinal and latitudinal patterns of increased UV-B); they found no significant pattern of change in occupancy with elevation. However, UV-B levels may still 

be increasing (Middleton et al. 2001) so continued monitoring may be important. 

Extent of risks related to UV-B radiation— 

Increased UV-B radiation does not appear to be a primary factor in the rangewide 

decline of foothill yellow-legged frogs. However, the relationship between UV-B, 

other stressors, and foothill yellow-legged frog declines is unstudied, so UV-B has 

the potential to contribute to declines in ways that remain unidentified. As levels of 

ambient UV-B appear to be on the increase (Middleton et al. 2001), the effects of 

increased UV-B on foothill yellow-legged frogs may occur at some threshold level 

that becomes manifest in the future.
 

Conservation options related to UV-B radiation— 

At this time, UV-B radiation does not warrant management consideration. Should 

the risk level for this factor increase, effective management would require coordination of agencies outside the jurisdiction of those involved in this assessment. 

Agencies responsible for foothill yellow-legged frog management should participate 

in guiding the development of the management and science to inform this issue.
 

Vegetation and Fuels Management 

Vegetation and fuels management encompasses management activities that alter 

vegetation structure and composition, which includes timber harvest, thinning, 

fuels management, salvage logging, and prescribed fire. Changes in vegetation, 

shade, and woody debris can alter habitat quality. Modification of vegetation can 

also influence soil stability, erosion, and sediment loading to aquatic habitats. 

These activities can pose a risk to foothill yellow-legged frogs in areas of their 

range where such activities are permitted. 
168 

GENERAL TECHNICAL REPORT PSW-GTR-248

Prescribed fire is one method of fuel reduction in the United States, although 

the effects of such controlled burns on fauna, including foothill yellow-legged frogs, 

are poorly understood (Pilliod et al. 2003). Prescribed fire may benefit foothill 

yellow-legged frogs by reducing the risk of future high-intensity wildfire; however, 

these controlled fires could also damage foothill yellow-legged frog habitat if not 

properly implemented. Prescribed fire can greatly alter vegetation and soils and 

may disturb frogs if applied when fires would not naturally occur and at high fuel 

loads that lead to high fire intensities. A large part of the foothill yellow-legged frog 

range is on granitic soils where erosion rates on such soils have been shown to be 

66 times higher in burned areas than on undisturbed watersheds, and burning may 

elevate annual sediment yields for 10 years or more (Megahan et al. 1995). 

Historical timber harvesting lacked standards and guidelines to provide protection for riparian areas or stream-associated fauna. Present-day practices limit 

harvest from riparian management zones, but erosion and sedimentation resulting 

from timber harvest activities may affect foothill yellow-legged frogs. Ashton et al. 

(2006) suggest that sedimentation can be a significant problem for foothill yellowlegged frogs in some streams, and deserves management attention. Issues related to 

increased sedimentation were addressed in other risk factor sections (see “Livestock 

Grazing” and “Roads” sections). 

Extent of risks related to vegetation management— 

Based on the known effects of vegetation and fuel management activities in stream 

ecosystems, these activities could affect foothill yellow-legged frogs; however, there 

is currently no species-specific data to substantiate any effects. Current practices 

may limit effects, but this needs to be evaluated with studies on species-specific 

population and habitat changes and responses. 

Conservation options related to vegetation management— 

Vegetation and fuels management are major activities that are directly within the 

jurisdiction of agencies participating in this conservation assessment. Research is 

needed to inform how vegetation and fuels management may affect foothill yellowlegged frogs and their habitat, including where these activities may amplify or 

reduce the effects of other risk factors. 
169 

Foothill Yellow-Legged Frog Conservation Assessment

Literature Cited 

Adams, M.J.; Pearl, C.A.; McCreary, B.; Galvan, S.K.; Wessell, S.J.; Wente, 

W.H.; Anderson, C.W.; Kuehl, A.B. 2009. Short-term effect of cattle exclosures 

on Columbia spotted frog (Rana luteiventris) populations and habitat in 

northeastern Oregon. Journal of Herpetology. 43: 132–138. 

Adams, M.J.; Schindler, D.E.; Bury R.B. 2001. Association of amphibians with 

attenuation of ultraviolet-b radiation in montane ponds. Oecologia. 128: 519–525. 

Anzalone, C.R.; Kats, L.B.; Gordon, M.S. 1998. Effects of solar UV-B radiation 

on embryonic development in Hyla cadaverina, Hyla regilla, and Taricha torosa. 

Conservation Biology. 12: 646–653. 

Ashton, D.T.; Marks, S.B.; Welsh, H.H., Jr. 2006. Evidence of continued effects 

from timber harvesting on lotic amphibians in redwood forests of northwestern 

California. Forest Ecology and Management. 221: 183–193. 

Aston, L.S.; Sieber, J.N. 1997. Fate of summertime airborne organophosphate 

pesticide residues in the Sierra Nevada mountains. Journal of Environmental 

Quality. 26: 1483–1492. 

Bakke, D. 2004. Personal communication. Pesticide-use specialist/invasive plants 

program manager, U.S. Department of Agriculture, Forest Service, Pacific 

Southwest Region, 1323 Club Drive, Vallejo, CA 94592. 

Bartelt, P.E. 1998. Bufo boreas (Western Toad). Mortality. Herpetological Review. 

29: 96. 

Belden, L.K.; Blaustein, A.R. 2002. Exposure of red-legged frog embryos to 

ambient UV-B radiation in the field negatively affects tadpole growth and 

development. Oecologia. 130: 551–554. 

Belden, L.K.; Wildy, E.L.; Blaustein, A.R. 2000. Growth, survival, and 

behaviour of tadpole long-toed salamander (Ambystoma macrodactylum) 

exposed to ambient levels of UV-B radiation. Journal of Zoology. 251: 473–479. 

Belsky, A.J.; Matzke, A.; Uselman, S. 1999. Survey of livestock influences on 

stream and riparian ecosystems in the western United States. Journal of Soil and 

Water Conservation. 54: 419–431. 

Berrill, M.; Bertram, S.; McGillivray, L.; Kolohon, M.; Pauli, B. 1994. Effects 

of low concentrations of forest-use pesticides on frog embryos and tadpoles. 

Environmental Toxicology and Chemistry. 13: 657–664. 
170 

GENERAL TECHNICAL REPORT PSW-GTR-248

Bidwell, J.R.; Gorrie, J.R. 1995. Acute toxicity of a herbicide to selected frog 

species. Technical Series 79. Perth, Australia: Department of Environmental 

Protection. 9 p. 

Blaustein, A.R.; Belden, L.K. 2003. Amphibian defenses against ultraviolet-B 

radiation. Evolution and Development. 5: 89–97. 

Blaustein, A.R.; Hoffman, P.D.; Hokit, D.G.; Kiesecker, J.M.; Walls, S.C.; 

Hays, J.B. 1994a. UV repair and resistance to solar UV-B in amphibian eggs: 

A link to population declines? Proceedings of the National Academy of Sciences. 

91: 1791–1795. 

Blaustein, A.R.; Hoffman, P.D.; Kiesecker, J.M.; Hays, J.B. 1996. DNA repair 

activity and resistance to solar UV-B radiation in eggs of the red-legged frog. 

Conservation Biology. 10: 1398–1402. 

Blaustein, A.R.; Hokit, D.G.; O’Hara, R.K.; Holt, R.A. 1994b. Pathogenic 

fungus contributes to amphibian losses in the Pacific Northwest. Biological 

Conservation. 67: 251–254. 

Blaustein, A.R.; Kiesecker, J.M.; Chivers, D.P.; Hokit, D.G.; Marco, A.; 

Belden, L.K.; Hatch, A. 1998. Effects of ultraviolet radiation on amphibians: 

field experiments. American Zoologist. 38: 799–812. 

Blaustein, A.R.; Wake, D.B. 1990. Declining amphibian populations: A global 

phenomenon? Trends in Ecology and Evolution. 5: 203–204. 

Borisenko, A.N. 2000. The status of Rana boylii in Oregon: analysis of selected 

biotic and abiotic variables at historical Rana boylii locations. Portland, OR: 

Portland State University. 72 p. M.S. thesis. 

Borisenko, A.N.; Hayes, M.P. 1999. Status of the foothill yellow-legged frog 

(Rana boylii) in Oregon. Portland, OR: U.S. Department of the Interior, Fish and 

Wildlife Service; final report; contracts ORFO080197-1 and 1448-13420-7-M262. 

Bosch, J.; Martinez-Solano, I.; Garcia-Paris, M. 2001. Evidence of a chytrid 

fungus infection involved in the decline of the common midwife toad (Alytes 

obstetricans) in protected areas of central Spain. Biological Conservation. 97: 

331–337. 

Boubée, J.; Jowett, I.; Nichols, S.; Williams, E. 1999. Fish passage at culverts: a 

review with possible solutions for New Zealand indigenous species. Wellington, 

New Zealand: Department of Conservation. 111 p. 
171 

Foothill Yellow-Legged Frog Conservation Assessment

Boyle, S.A.; Samson, F.B. 1985. Effects of non-consumptive recreation on 

wildlife. A review. Wildlife Society Bulletin. 13: 110–116. 

Bradford, D.F. 1991. Mass mortality and extinction in a high elevation population 

of Rana muscosa. Journal of Herpetology. 25: 174–177. 

Bradford, D.F.; Gordon, M.S. 1992. Aquatic amphibians in the Sierra Nevada: 

current status and potential effects of acidic deposition on populations. Contract 

A932-139. Sacramento, CA: California Air Resources Board. 85 p. 

Bradford, D.F.; Gordon, M.S.; Johnson, D.F.; Andrews, R.D.; Jennings, W.B. 

1994. Acidic deposition as an unlikely cause for amphibian decline in the Sierra 

Nevada, California. Biological Conservation. 69: 155–161. 

Briggs, C.J.; Knapp, R.A.; Vredenburg, V.T. 2010. Enzootic and epizootic 

dynamics of the chytrid fungal pathogen of amphibians. Proceedings of the 

National Academy of Sciences. 107: 9695–9700. 

Bryer, P.J.; Elliott, J.N.; Willingham, E.J. 2006. The effects of coal tar based 

pavement sealer on amphibian development and metamorphosis. Ecotoxicology. 

15: 241–247. 

Buhl, K.J.; Hamilton, S.J. 2000. Acute toxicity of fire-control chemicals, 

nitrogenous chemicals, and surfactants to rainbow trout. Transactions of the 

American Fisheries Society. 129: 408–418. 

Bull, E.L.; Hayes, M.P. 2000. Effects of livestock on reproduction of the Columbia 

spotted frog. Journal of Range Management. 53: 291–294. 

Burton, E.C.; Gray, M.J.; Schmutzer, A.C.; Miller, D.L. 2009. Differential 

responses of postmetamorphic amphibians to cattle grazing in wetlands. The 

Journal of Wildlife Management. 73: 269–277. 

Byron, E.; Axler, R.; Goldman, C. 1991. Increased precipitation acidity in the 

Central Sierra Nevada. Atmospheric Environment. 25A: 271–275. 

Cahill, T.A.; Carroll, J.J.; Campbell, D.; Gill, T.E. 1996. Air quality. In: SNEP 

Science Team, eds. Sierra Nevada ecosystem project: final report to Congress. 

Vol. II: Assessments and scientific basis for management options. Report No. 37. 

Davis, CA: Centers for Water and Wildland Resources, University of California– 

Davis: 1227–1262. Chapter 48. 

California Department of Pesticide Regulation [CDPR]. 1989–2012. Pesticide 

use statistics. http://www.cdpr.ca.gov/docs/pur/purmain.htm. (5 February 2015). 
172 

GENERAL TECHNICAL REPORT PSW-GTR-248

Carey, C.; Cohen N.; Rollins-Smith, L. 1999. Amphibian declines: an 

immunological perspective. Developmental and Comparative Immunology. 

23: 459–472. 

Carr, L.W.; Fahrig, L. 2001. Effect of road traffic on two amphibian species of 

differing vagility. Conservation Biology. 15: 1071–1078. 

Catenazzi, A.; Kupferberg, S.J. 2013. The importance of thermal conditions to 

recruitment success in stream-breeding frog populations distributed across a 

productivity gradient. Biological Conservation. 168: 40–48. 

Chen, C.Y.; Hathaway, K.M.; Folt, C.L. 2004. Multiple stress effects of Vision® 

herbicide, pH, and food on zooplankton and tadpole amphibian species from 

forest wetlands. Environmental Toxicology and Chemistry. 23: 823–831. 

Cole, D.N.; Fichtler, R.K. 1983. Campsite impact on three western wilderness 

areas. Environmental Management. 7: 275–288. 

Cole, D.N.; Marion, J.L. 1988. Recreation impacts in some riparian forests of 

the Eastern United States. Environmental Management. 12: 99–107. 

Corn, P.S. 1998. Effects of ultraviolet radiation on boreal toads in Colorado. 

Ecological Applications. 8: 18–26. 

Cory, L.; Fjeld, P.; Serat, W. 1970. Distributional patterns of DDT residues in the 

Sierra Nevada Mountains. Pesticides Monitoring Journal. 3: 204–211. 

Cunningham, A.A.; Langton, T.E.S.; Bennett, P.M.; Lewin, J.F.; Drury, S.E.; 

Gough, R.E.; MacGregor, S.K. 1996. Pathological and microbiological findings 

from incidents of unusual mortality of the common frog (Rana temporaria). 

Philosophical Transactions of the Royal Society of London B. 351: 1529–1557. 

Dale, D.; Weaver, T. 1974. Trampling effects on vegetation of the trail corridors of 

north Rocky Mountain forests. Journal of Applied Ecology. 11: 767–772. 

Datta, S.; Hansen, L.; McConnell, L.; Baker, J.; Lenoir, J.; Seiber, J.N. 1998. 

Pesticides and PCB contaminants in fish and tadpoles from the Kaweah River 

Basin, California. Bulletin of Environmental Contamination and Toxicology. 

60: 829–836. 

Davidson, C. 2004. Declining downwind: amphibian population declines in 

California and historical pesticide use. Ecological Applications. 14: 1892–1902. 
173 

Foothill Yellow-Legged Frog Conservation Assessment

Davidson, C.; Benard, M.F.; Shaffer, H.B.; Parker, J.M.; O’Leary, C.; Conlon, 

J.M.; Rollins-Smith, L.A. 2007. Effects of chytrid and carbaryl exposure 

on survival, growth and skin peptide defenses in foothill yellow-legged frogs. 

Environmental Science and Technology. 41: 1771–1776. 

Davidson, C.; Shaffer, H.B.; Jennings, M.R. 2002. Spatial tests of the pesticide 

drift, habitat destruction, UV-B and climate-change hypotheses for California 

amphibian declines. Conservation Biology. 16: 1588–1601. 

DeMaynadier, P.G.; Hunter, M.L. 2000. Road effects on amphibian movements in 

a forested landscape. Natural Areas Journal. 20: 56–65. 

Edginton, A.N.; Sheridan, P.M.; Stephenson, G.R.; Thompson, D.G.; 

Boermans, H.J. 2004. Comparative effects of pH and Vision® herbicide on two 

life stages of four anuran amphibian species. Environmental Toxicology and 

Chemistry. 23: 815–822. 

Fahrig, L.; Pedlar, J.H.; Pope, S.E.; Taylor, P.D.; Wenger, J.F. 1995. Effect of 

road traffic on amphibian density. Biological Conservation. 73: 177–182. 

Fellers, G.M.; McConnell, L.L.; Pratt, D.; Datta, S. 2004. Pesticides in mountain 

yellow-legged frogs (Rana muscosa) from the Sierra Nevada Mountains of 

California, USA. Environmental Toxicology and Chemistry. 23(9): 2170–2177. 

Fijan, N.; Matasin, Z.; Petrinec, Z.; Valpotic, I.; Zwillenberg, L.O. 1991. 

Isolation of an iridovirus-like agent from the green frog (Rana esculenta L). 

Veterinare Arhiv [Zagreb]. 61: 151–158. 

Fite, K.V.; Blaustein, A.R.; Bengston, L.; Hewitt, H.E. 1998. Incidence of retinal 

light damage in Rana cascadae: a declining amphibian species. Copeia. 1998: 

906–914. 

Folmar, L.C.; Sanders, H.O.; Julin, A.M. 1979. Toxicity of the herbicide 

glyphosate and several of its formulations to fish and aquatic invertebrates. 

Archives of Environmental Contamination and Toxicology. 8: 269–278. 

Forman, R.T.T.; Alexander, L.E. 1998. Roads and their major ecological effects. 

Annual Review of Ecology and Systematics. 29: 207–231. 

Freda, J. 1990. Effects of acidification on amphibians. In: Baker, J.P.; Bernard, 

D.P.; Christensen, S.W.; Sale, M.J., eds. Biological effects of changes in surface 

water acid-base chemistry. State of Science/Technology Report 13. Washington, 

DC: National Acid Precipitation Assessment Program: 114–129. 
174 

GENERAL TECHNICAL REPORT PSW-GTR-248

Freda, J. 1991. The effects of aluminum and other metals on amphibians. 

Environmental Pollution. 71: 305–328. 

Fuller, D.D.; Lind, A.J. 1992. Implications of fish habitat improvement structures 

for other stream vertebrates. In: Harris, R.R.; Erman, D.C., tech. coords.; 

Kerner, H.M., ed. Proceedings of the symposium on biodiversity of northwestern 

California. Berkeley, CA: University of California, Wildland Resources Center, 

Division of Agriculture and Natural Resources: 96–104. 

Gaikowski, M.P.; Hamilton, S.J.; Buhl, K.J.; McDonald, S.F.; Summers, 

C.H. 1996. Acute toxicity of three fire-retardant and two fire-suppressant 

foam formulations to the early stages of rainbow trout (Oncorhynchus mykiss). 

Environmental Toxicology and Chemistry. 15: 1365–1374. 

Garcia and Associates. [GANDA] 2005. Results of 2004 surveys and monitoring 

for foothill yellow-legged frogs (Rana boylii) within the Rock Creek-Cresta 

project area, North Fork Feather River and 2002–2004 recreation and pulse 

flow biological evaluation summary. San Ramon, CA: Pacific Gas and Electric 

Company; Job 332/80. 89 p. 

Garton, E.O.; Foin, T.C.; Bowen, C.W.; Everingham, J.M.; Schultz, R.O.; 

Holton, B., Jr. 1977. Quantitative studies of visitor impacts on environments 

of Yosemite National Park, California, USA and their implications for park 

management policy. Journal of Environmental Management. 5: 1–22. 

Giesy, J.P.; Dobson, S.; Solomon, K.R. 2000. Ecotoxicological risk assessment of 

Roundup® herbicide. Reviews of Environmental Contamination and Toxicology. 

167: 35–120. 

Green, D.E.; Converse, K.A.; Schrader, A.K. 2002. Epi-zootiology of sixty-four 

amphibian morbidity and mortality events in the USA, 1996–2001. Annals of the 

New York Academy Sciences. 969: 323–329. 

Green, D.M.; Kauffman, J.B. 1995. Succession and livestock grazing in 

a northeast Oregon riparian ecosystem. Journal of Range Management. 

48: 307–313. 

Hansen, B.; Nieber, J.; Johnson, S.; Marr, J. 2011. Performance assessment 

of oversized culverts to accommodate fish passage. St. Paul, MN: Minnesota 

Department of Transportation; final report. 39 p. 
175 

Foothill Yellow-Legged Frog Conservation Assessment

Hatch, A.C.; Blaustein, A.R. 2000. Combined effects of UV-B, nitrate, and 

low pH reduce the survival and activity level of tadpole Cascades frogs (Rana 

cascadae). Archives Environmental Contamination and Toxicology. 39: 494–499. 

Hayes, T.B.; Case, P.; Chui, S.; Chung, D.; Haeffele, C.; Haston, K.; Lee, 

M.; Mai, V.P.; Marjuoa, Y.; Parker, J.; Tsui, M. 2006. Pesticide mixtures, 

endocrine disruption, and amphibian declines: Are we underestimating the 

impact? Environmental Health Perspectives. 114 (Suppl. 1): 40–50. 

Hildebrand, L.D.; Sullivan, D.S.; Sullivan, T.P. 1982. Experimental studies of 

rainbow trout populations exposed to field applications of Roundup herbicide. 

Archives of Environmental Contamination and Toxicology. 11: 93–98. 

Hine, R.L.; Les, B.L.; Hellmich, B.F. 1981. Leopard frog populations and 

mortality in Wisconsin, 1974–76. Tech. Bull. 122. Madison, WI: Wisconsin 

Department of Natural Resources. 39 p. 

Holland, D. 2005. Personal communication. Principal investigator, Camp 

Pendleton Amphibian and Reptile Survey, Fallbrook, CA 92028. 

Howe, C.M.; Berrill, M.; Pauli, B.D.; Helbring, C.C.; Werry, K.; Veldhoen, 

N. 2004. Toxicity of glyphosate-cased pesticides to four North American frog 

species. Environmental Toxicology and Chemistry. 23: 1928–1938. 

Hynes, H.N.B. 1970. The ecology of running waters. Toronto, ON, Canada: 

University of Toronto Press. 510 p. 

Ingles, L.G.; Langston, C.I. 1933. A new species of bladder fluke from California 

frogs. Transactions of the American Microscopical Society. 52: 243–246. 

Jansen, A.; Healey, M. 2003. Frog communities and wetland condition: 

relationships with grazing by domestic livestock along an Australian floodplain 

river. Biological Conservation. 109: 207–219. 

Jennings, M.R. 1996. Status of amphibians. In: SNEP Science Team, eds. Sierra 

Nevada ecosystem project: final report to Congress. Vol. II: Assessments and 

scientific basis for management options. Report No. 37. Davis, CA: Centers 

for Water and Wildland Resources, University of California–Davis: 921–944. 

Chapter 31. 

Jennings, M.R.; Hayes, M.P. 1994. Amphibian and reptile species of special 

concern in California. Rancho Cordova, CA: California Department of Fish 

and Game. 255 p. 
176 

GENERAL TECHNICAL REPORT PSW-GTR-248

Johnson, P.T.; Lunde, K.B.; Ritchie, E.G.; Launer, A.E. 1999. The effect of 

trematode infection on amphibian limb development and survivorship. Science. 

284: 802–804. 

Jones, J.A.; Swanson, F.A.; Wemple, B.C.; Snyder, K.U. 2000. Effects of roads 

on hydrology, geomorphology, and disturbance patches in stream networks. 

Conservation Biology. 14: 1523–1739. 

Kagarise-Sherman, C.; Morton, M.L. 1993. Population declines of Yosemite 

toads in the eastern Sierra Nevada of California. Journal of Herpetology. 27: 

186–198. 

Kattelmann, R. 1996. Hydrology and water resources. In: SNEP Science 

Team, eds. Sierra Nevada ecosystem project: final report to Congress. Vol. II: 

Assessments and scientific basis for management options. Report No. 37. Davis, 

CA: Centers for Water and Wildland Resources, University of California–Davis: 

855–820. Chapter 30. 

Kauffman, J.B.; Krueger, W.C. 1984. Livestock impacts on riparian ecosystems 

and streambank management implications: A review. Journal of Range 

Management. 37: 430–437. 

Kauffman, J.B.; Krueger, W.C.; Vavra, M. 1983a. Effects of late season cattle 

grazing on riparian plant communities. Journal of Range Management. 36: 

685–691. 

Kauffman, J.B.; Krueger, W.C.; Vavra, M. 1983b. Impacts of cattle on 

streambanks in northeastern Oregon. Journal of Range Management. 36: 

683–685. 

Kiesecker, J.M.; Blaustein, A.R. 1995. Synergism between UV-B radiation and 

a pathogen magnifies embryo mortality in nature. Proceedings of the National 

Academy of Science. 92: 11049–11052. 

Kiesecker, J.M.; Blaustein, A.R. 1997a. Influences of egg laying behavior on 

pathogenic infection of amphibian eggs. Conservation Biology. 11: 214–220. 

Knapp, R. 2002, 2004. Personal communication. Research biologist, Sierra Nevada 

Aquatic Research Laboratory, University of California–Santa Barbara, 1016 

Mount Morrison Road, Mammoth Lakes, CA 93546–9566. 

Knight, R.L.; Cole, D.N. 1991. Effects of recreational activity on wildlife in 

wildlands. Transactions of the 56th North American Wildlife and Natural 

Resources Conference. 56: 238–247. 
177 

Foothill Yellow-Legged Frog Conservation Assessment

 

 

Knutson, M.G.; Richardson, W.B.; Reineke, D.M.; Gray, B.R.; Parmelee, 

J.R.; Weick, S.E. 2004. Agricultural ponds support amphibian populations. 

Ecological Applications. 14: 669–684. 

Kreutzweiser, D.P.; Thompson, D.G.; Capell, S.S.; Thomas, D.R.; Staznik, 

B. 1995. Field evaluation of triclopyr ester toxicity to fish. Archives of 

Environmental Contamination and Toxicology. 28: 18–26. 

Kupferberg, S.J. 1996a. Hydrologic and geomorphic factors affecting conservation 

of a river-breeding frog (Rana boylii). Ecological Applications. 6: 1332–1344. 

Kupferberg, S.J. 1996b. The ecology of native tadpoles (Rana boylii and 

Hyla regilla) and the impacts of invading bullfrogs (Rana catesbeiana) in a 

northern California river. Berkeley, CA: University of California. 289 p. Ph.D. 

dissertation. 

Kupferberg, S.J. 2006, 2015. Stream ecologist and amphibian biologist. Questa 

Engineering, 1220 Brickyard Cove Rd., Suite 206, Pt. Richmond CA 94807. 

Kupferberg, S.J.; Catenazzi, A.; Lunde, K.; Lind, A.J.; Palen, W.J. 2009a. 

Parasitic copepod (Lernea cyprinacea) outbreaks in foothill yellow-legged frogs 

(Rana boylii) linked to unusually warm summers and amphibian malformations 

in northern California. Copeia. 2009: 529–537. 

Kupferberg, S.J.; Catenazzi, A.; Power, M.E. 2011a. The importance of water 

temperature and algal assemblage for frog conservation in northern California 

rivers with hydroelectric projects. CEC-500-2014-033. Sacramento, CA: 

California Energy Commission, Public Interest Energy Research Program. 96 p. 

Kupferberg, S.; Lind, A.; Yarnell, S.; Mount, J. 2008. Pulsed flow effects on the 

foothill yellow-legged frog (Rana boylii): integration of empirical, experimental 

and hydrodynamic modeling approaches. Final report. Sacramento, CA: 

California Energy Commission, Public Interest Energy Research Program. 194 p. 

Kupferberg, S.J.; Palen, W.J.; Lind, A.J.; Bobzien, S.; Catenazzi, A.; Drennan, 

J.; Power, M.E. 2012. Effects of flow regimes altered by dams on survival, 

population declines, and range-wide losses of California river-breeding frogs. 

Conservation Biology. 26: 513–524. 

Laird, L.B.; Taylor, H.E.; Kennedy, V.C. 1986. Snow chemistry of the CascadeSierra Nevada mountains. Environmental Science and Technology. 20: 275–290. 
178

GENERAL TECHNICAL REPORT PSW-GTR-248

Landers, D.H.; Eilers, J.M.; Brakke, D.F.; Overton, W.S.; Kellar, P.E.; 

Silverstein, M.E.; Schonbrod, R.D.; Crowe, R.E.; Lindhurst, R.A.; 

Omernik, J.M.; Teague, S.A.; Meier, E.P. 1987. Characteristics of lakes in 

the western United States. I: Population descriptions and physico-chemical 

relationships. EPA/600/3-86/054a. Washington, DC: U.S. Environmental 

Protection Agency. 176 p. 

Lawrence, L. de K. 1973. The gray jays. Hinterland Bulletin. Ottawa, ON: 

Canadian Wildlife Service. [Pages unknown.] 

Lefcort, H.; Hancock, K.A.; Maur, K.M.; Rostal, D.C. 1997. The effects of used 

motor oil, silt and the water mold Saprolegnia parasitica on the growth and 

survival of mole salamanders (genus Ambystoma). Archives of Environmental 

Contamination and Toxicology. 32: 383–388. 

Lenoir, J.S.; McConnell, L.L.; Fellers, G.M.; Cahill, T.M.; Seiber, J.N. 1999. 

Summertime transport of current-use pesticides from California’s Central Valley 

to the Sierra Nevada mountain range, USA. Environmental Toxicology and 

Chemistry. 18: 2715–2722. 

Licht, L.E. 1996. Amphibian decline still a puzzle. BioScience. 46: 172–173. 

Licht, L.E. 2003. Shedding light on ultraviolet radiation and amphibian embryos. 

BioScience. 53: 551–561. 

Licht, L.E.; Grant, K.P. 1997. The effects of ultraviolet radiation on the biology 

of amphibians. American Zoologist. 37: 137–145. 

Lind A.J.; Spinks, P.Q.; Fellers, G.M.; Shaffer, H.B. 2011. Rangewide 

phylogeography and landscape genetics of the Western US endemic frog 

Rana boylii (Ranidae): implications for the conservation of frogs and rivers. 

Conservation Genetics. 12(1): 269–284. 

Lips, K.R.; Mendelson, J.R., III; Munoz-Alonso, A.; Canseco-Marquez, L.; 

Mulcahy, D.G. 2004. Amphibian population declines in montane southern 

Mexico: resurveys of historical localities. Biological Conservation. 119: 555–564. 

Long, L.E.; Saylor, L.S.; Soule, M.E. 1995. A pH/UV-B synergism in 

amphibians. Conservation Biology. 9: 1301–1303. 

Longcore, J.E.; Pessier, A.P.; Nichols, D.K. 1999. Batrachochytrium 

dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia. 

91: 219–227. 
179

Foothill Yellow-Legged Frog Conservation Assessment

Lowe, J. 2009. Amphibian chytrid (Batrachochytrium dendrobatidis) in postmetamorphic Rana boylii in the inner coast ranges of central California. 

Herpetological Review. 40: 180–182. 

Ludke, J.L.; Hill, E.F.; Dieter, M.P. 1975. Cholinesterase (ChE) response and 

related mortality among birds fed ChE inhibitors. Archives of Environmental 

Contamination and Toxicology. 3: 1–21. 

Mahaney, P.A. 1994. The effects of freshwater petroleum contamination 

on amphibian hatching and metamorphosis. Environmental Toxicology. 

13: 259–265. 

Mann, R.M.; Bidwell, J.R. 1999. The toxicity of glyphosate and several 

glyphosate formulations to four species of southwestern Australian frogs. 

Archives of Environmental Contamination and Toxicology. 26: 193–199. 

Mao, J.; Green, D.E.; Fellers, G.F.; Chinchar, V.G. 1999. Molecular 

characterization of iridoviruses isolated from sympatric amphibians and fish. 

Virus Research. 63: 45–52. 

Maxell, B.A.; Hokit, D.G. 1999. Amphibians and reptiles. In: Joslin, J.; Youmans, 

H., committee chairs. Effects of recreation on Rocky Mountain wildlife: a 

compendium of the current state of understanding in Montana. Committee on 

Effects of Recreation on Wildlife, Montana Chapter of the Wildlife Society: 

2.1–2.30. 

McCarthy, M.A.; Parris, K.M. 2004. Clarifying the effects of toe clipping on 

frogs with Bayesian statistics. Journal of Applied Ecology. 41: 780–786. 

McConnell, L.L.; Lenoir, J.S.; Datta, S.; Seiber, J.N. 1998. Wet deposition of 

current-use pesticides in the Sierra Nevada mountain range, California, USA. 

Environmental Toxicology and Chemistry. 17: 1908–1916. 

McDonald, S.F.; Hamilton, S.J.; Buhl, K.J.; Heisinger, J.F. 1996. Acute 

toxicity of fire control chemicals to Daphnia magna (Straus) and Selenastrum 

capricornutum (Printz). Ecotoxicology and Environmental Safety. 33: 62–72. 

Megahan, W.F.; King, J.G.; Seyedbagheri, K.A. 1995. Hydrologic and erosional 

responses of a granitic watershed to helicopter logging and broadcast burning. 

Forest Science. 41: 777–795. 
180 

GENERAL TECHNICAL REPORT PSW-GTR-248

Melack, J.M.; Stoddard, J.L.; Ochs, C.A. 1985. Major ion chemistry and 

sensitivity to acid precipitation of Sierra Nevada lakes. Water Resources 

Research. 21: 27–32. 

Menke, J.W.; Davis, C.; Beesley, P. 1996. Rangeland Assessment. In: SNEP 

Science Team, eds. Sierra Nevada ecosystem project: final report to Congress. 

Vol. III: Assessments, commissioned reports, and background information. 

Report No. 38. Davis, CA: Centers for Water and Wildland Resources, University 

of California–Davis: 901–972. Chapter 22. 

Middleton, E.M.; Herman, J.R.; Celarier, E.A.; Wilkinson, J.W.; Carey, C.; 

Ruskin, R.J. 2001. Evaluating ultraviolet radiation exposure with satellite data 

at sites of amphibian declines in Central and South America. Conservation 

Biology. 15: 914–929. 

Minshall, G.W.; Brock, J.T. 1991. Observed and anticipated effects of forest fire 

on Yellowstone stream ecosystems. In: Keiter, R.B.; Boyce, M.S., eds. Greater 

Yellowstone Ecosystem: redefining America’s wilderness heritage. New Haven, 

CT: Yale University Press: 123–135. 

Mitchell, D.; Chapman, P.; Long, T. 1987. Seawater challenge testing of Coho 

salmon smolts following exposure to Roundup herbicide. Environmental 

Toxicology and Chemistry. 6: 875–878. 

Morris, D.P.; Zagarese, H.; Williamson, C.E.; Balseiro, E.G.; Hargreaves, 

B.R.; Modenutti, B.; Moeller, R.; Queimalinos, C. 1995. The attenuation of 

solar UV radiation in lakes and the role of dissolved organic carbon. Limnology 

and Oceanography. 40: 1381–1391. 

Murray, D.L.; Fuller, M.R. 2000. A critical review of the effects of marking on 

the biology of vertebrates. In: Boitani, L.; Fuller, T.K., eds. Research techniques 

in animal ecology: controversies and consequences. New York: Columbia 

University Press: 15–64. Chapter 2. 

Muths, E.; Corn, P.S.; Pessier, A.P.; Green, D.E. 2003. Evidence for diseaserelated amphibian decline in Colorado. Biological Conservation. 110: 357–365. 

Myers, T.J.; Swanson, S. 1991. Aquatic habitat condition index, stream type, 

and livestock bank damage in northern Nevada. Water Research Bulletin. 

27: 667–677. 
181 

Foothill Yellow-Legged Frog Conservation Assessment

Nagl, A.M.; Hofer, R. 1997. Effects of ultraviolet radiation on early tadpole stages 

of the alpine newt, Triturus alpestris, under natural and laboratory conditions. 

Oecologia. 110: 514–519. 

Nelson, S.K.; Hamer, T. 1995. Nest success and the effects of predation on 

marbled murrelets. In: Ralph, C.J.; Hunt, G.L., Jr.; Raphael, M.G.; Piatt, J.F., 

eds. The ecology and conservation of the marbled murrelet in North America: 

an interagency scientific evaluation. Gen. Tech. Rep. PSW-GTR-152. Arcata, 

CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research 

Station: 89–98. 

Neumann, J.R. 1997. Hatching success in relation to UV-B exposure in the eggs 

of the foothill yellow-legged frog. Arcata, CA: Humboldt State University. 14 p. 

B.S. thesis. 

Newcombe, C.P.; Jensen, J.O.T. 1996. Channel suspended sediment and fisheries: 

a synthesis for quantitative assessment of risk and impact. North American 

Journal of Fisheries Management. 16: 693–727. 

Newcombe, C.P.; MacDonald, D.D. 1991. Effects of suspended sediments on 

aquatic ecosystems. North American Journal of Fisheries Management. 11: 

72–84. 

Niehaus, A.C.; Ruthrauff, D.R.; McCaffery, B.J. 2004. Response of predators 

to western sandpiper nest exclosures. Waterbirds. 27: 79–82. 

Obedzinski, R.A.; Shaw, C.G., III; Neary, D.G. 2001. Declining woody 

vegetation in riparian ecosystems of the western United States. Western Journal 

of Applied Forestry. 16: 169–180. 

Olson, D.H.; Davis, R.J. 2009. Conservation assessment for the foothill yellowlegged frog (Rana boylii) in Oregon. Version 2.0. Portland, OR: U.S. Department 

of Agriculture, Forest Service, Region 6; and U.S. Department of the Interior, 

Bureau of Land Management, Interagency Special Status Species Program. 

http://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-amphibians.shtml. 

(26 January 2015). 

Ovaska, K.; Davis, T.M.; Flamarique, I.N. 1997. Hatching success and 

tadpole survival of the frogs Hyla regilla and Rana aurora under ambient 

and artificially enhanced solar ultraviolet radiation. Canadian Journal of 

Zoology. 75: 1081–1088. 
182 

GENERAL TECHNICAL REPORT PSW-GTR-248

Padgett-Flohr, G. 2006. Personal communication. President and senior wildlife biologist, California Environmental Services, 3170 Crow Canyon Place, 

Suite 250, San Ramon, CA 94583. 

Padgett-Flohr, G.E.; Hopkins, R.L., II. 2009. Batrachochytrium dendrobatidis, a 

novel pathogen approaching endemism in central California. Diseases of Aquatic 

Organisms. 83: 1–9. 

Padgett-Flohr, G.; Knapp, R.; Vredenburg, V. [N.d.]. Personal communications. 

Padgett-Flohr is president and senior wildlife biologist, California Environmental 

Services, 3170 Crow Canyon Place, Suite 250, San Ramon, CA 94583; Knapp 

is a research biologist, Sierra Nevada Aquatic Research Laboratory, University 

of California–Santa Barbara, 1016 Mount Morrison Road, Mammoth Lakes, 

CA 93546-9566; Vredenburg is an associate professor, San Francisco State 

University, 1600 Holloway Avenue, San Francisco, CA 94132. 

Pahkala, M.; Räsänen, K.; Laurila, A.; Johanson, U.; Björn, L.O.; Merilä, 

J. 2002. Lethal and sublethal effects of UV-B/pH synergism on common frog 

embryos. Conservation Biology. 16: 1063–1073. 

Palen, W.J.; Schindler, D.E.; Adams, M.J.; Pearl, C.A.; Bury, R.B.; Diamond, 

S.A. 2002. Optical characteristics of natural waters protect amphibians from 

UV-B in the Pacific Northwest. Ecology. 83: 2951–2957. 

Palen, W.J.; Williamson, C.E.; Clauser, A.A.; Schindler, D.E. 2005. Impact 

of UV-B exposure on amphibian embryos: linking species physiology and 

oviposition behaviour. Proceedings of the Royal Society B: Biological Sciences. 

272: 1227–1234. 

Perkins, P.J.; Boermans, H.J.; Stephenson, G.R. 2000. Toxicity of glyphosate 

and triclopyr using the frog embryo teratogenesis assay—Xenopus. 

Environmental Toxicology and Chemistry. 19: 940–945. 

Perret, N.; Joly, P. 2002. Impacts of tattooing and PIT-tagging on survival and 

fecundity in the alpine newt (Triturus alpestris). Herpetologica. 58: 131–138. 

Pilliod, D.S.; Bury, R.B.; Hyde, E.J.; Pearl, C.A.; Corn, P.S. 2003. Fire and 

amphibians in North America. Forest Ecology and Management. 178: 163–181. 

Power, M.E. 1990. The importance of sediment in the grazing ecology and size 

class interactions of an armored catfish, Aneistrus spinosus. Environmental 

Biology of Fish. 10: 173–181. 
183 

Foothill Yellow-Legged Frog Conservation Assessment

Price, D.M.; Quinn, T.; Barnard, R.J. 2010. Fish passage effectiveness of 

recently constructed road crossing culverts in the Puget Sound region of 

Washington State. North American Journal of Fisheries Management. 30: 

1110–1125. 

Pringle, C.M.; Naiman, R.J.; Bretschko, G.; Karr, J.R.; Oswood, M.W.; 

Webster, J.R.; Welcomme, R.L.; Winterbourn, M.J. 1988. Patch dynamics 

in lotic systems: the stream as a mosaic. Journal of the North American 

Benthological Society. 7: 502–524. 

Rachowicz, L.J.; Knapp, R.A.; Morgan, J.A.T.; Stice, M.J.; Vredenburg, V.T.; 

Parker, J.M.; Briggs, C.J. 2006. Emerging infectious disease as a proximate 

cause of amphibian mass mortality. Ecology. 87: 1671–1683. 

Reid, L.M.; Dunne, T. 1984. Sediment production from forest road surfaces. Water 

Resources Research. 20(11): 1753–1761. 

Relyea, R.A. 2005a. Pesticides and amphibians: the importance of community 

context. Ecological Applications. 15: 1125–1134. 

Relyea, R.A. 2005b. The lethal impact of Roundup on aquatic and terrestrial 

amphibians. Ecological Applications. 15: 1118–1124. 

Richardson, E.V.; Simons, B.; Karaki, S.; Mahmood, M.; Stevens, M.A. 

1975. Highways in the river environment: hydraulic and environmental design 

considerations training and design manual. Washington, DC: U.S. Department of 

Transportation, Federal Highway Administration. 646 p. 

Roche, L.M.; Allen-Diaz, B.; Eastburn, D.J.; Tate, K.W. 2012. Cattle grazing 

and Yosemite toad (Bufo canorus Camp) breeding habitat in Sierra Nevada 

meadows. Rangeland Ecology and Management. 65: 56–65. 

Rombough, C.J. 2006b. Wintering habitat use by juvenile foothill yellow-legged 

frogs (Rana boylii): the importance of seeps [Abstract]. Northwestern Naturalist. 

87: 159. 

Rouse, J.D.; Bishop, C.A.; Struger, J. 1999. Nitrogen pollution: An assessment 

of its threat to amphibian survival. Environmental Health Perspectives. 107: 

799–803. 

Sagar, J.P.; Olson, D.H.; Schmitz, R.A. 2007. Survival and growth of larval 

Coastal giant salamanders (Dicamptodon tenebrosus) in streams in the Oregon 

Coast Range. Copeia. 2007: 123–130. 
184 

GENERAL TECHNICAL REPORT PSW-GTR-248

Saulino, R. 2006. Personal communication. Biological science technician, 

National Park Service, Pinnacles National Monument, 5000 California 146, 

Paicines, CA 95043. 

Schulz, T.T.; Leininger, W.C. 1990. Differences in riparian vegetation structure 

between grazed areas and exclosures. Journal of Range Management. 43: 

295–299. 

Scully, N.M.; Lean, D.S. 1994. The attenuation of ultraviolet radiation in 

temperate lakes. Archives für Hydrobiologie. 43: 135–144. 

Seiber, J.N.; Woodrow, J.E.; David, M.D. 1998. Organophosphorus esters. 

In: Shibamoto, T., ed. Chromatographic analysis of environmental and food 

toxicants. New York: CRC Press: 229–257. 

Servizi, J.A.; Gordon, R.W.; Martens, D.W. 1987. Acute toxicity of Garlon 4 and 

Roundup herbicides to salmon, Daphnia, and trout. Bulletin of Environmental 

Contamination and Toxicology. 39: 15–22. 

Sessions, S.E.; Ruth, S.B. 1990. Explanation for naturally occurring 

supernumerary limbs in amphibians. Journal of Experimental Zoology. 

254: 38–47. 

Smith, G.R. 2001. Effects of acute exposure to a commercial formulation of 

glyphosate on the tadpoles of two species of anurans. Bulletin of Environmental 

Contamination and Toxicology. 67: 483–488. 

Sparling, D.W.; Fellers, G.M. 2007. Comparative toxicity of chlorpyrifos, 

diazinon, malathion and their oxon derivatives to tadpole Rana boylii. 

Environmental Pollution. 147: 535–539. 

Sparling, D.W.; Fellers, G.M. 2009. Toxicity of two insecticides to California, 

U.S.A., anurans and its relevance to declining amphibian populations. 

Environmental Toxicology and Chemistry. 8 (8): 1696–1703. 

Sparling, D.W.; Fellers, G.M.; McConnell, L.L. 2001. Pesticides and amphibian 

population declines in California, U.S.A. Environmental Toxicology and 

Chemistry. 20: 1591–1595. 

Spellerberg, I.F. 1998. Ecological effects of roads and traffic: a literature review. 

Global Ecology and Biogeography Letters. 7: 317–333. 
185 

Foothill Yellow-Legged Frog Conservation Assessment

Spring Rivers Ecological Sciences. 2003. Foothill yellow-legged frog (Rana 

boylii) studies in 2002 for Pacific Gas and Electric Company’s Pit 3, 4, and 5 

Hydroelectric Project (FERC No. 233). San Ramon, CA: Pacific Gas and Electric 

Company, Technical and Ecological Services. 66 p. 

Stephenson, G.R.; Street, L.V. 1978. Bacterial variations in streams from a 

southwest Idaho rangeland watershed. Journal of Environmental Quality. 

7: 150–157. 

Strahler, A.N. 1952. Dynamic basin of geomorphology. Geological Society of 

America Bulletin. 63: 923–938. 

Sullivan, D.S.; Sullivan, T.P.; Bisalputra, T. 1981. Effects of Roundup® herbicide 

on diatom populations in the aquatic environment of a coastal forest. Bulletin of 

Environmental Contamination and Toxicology. 26: 91–96. 

Syracuse Environmental Research Associates, Inc. [SERA]. 2003a. Glyphosate 

Human health and ecological risk assessments final report. Contract number 

SERA TR 02-43-09-04a. Washington, DC: U.S. Department of Agriculture, 

Forest Service, Forest Health Protection. 281 p. 

Syracuse Environmental Research Associates, Inc. [SERA]. 2003b. Triclopyr— 

Revised human health and ecological risk assessments final report. Contract 

number SERA TR 02-43-13-03b. Washington, DC: U.S. Department of 

Agriculture, Forest Service, Forest Health Protection. 264 p. 

Thompson, D.G.; Wojtaszek, B.F.; Staznik, B.; Chartrand, D.T.; Stephenson, 

G.R. 2004. Chemical and biomonitoring to assess potential acute effects of 

Vision® herbicide on native amphibian larvae in forest wetlands. Environmental 

Toxicology and Chemistry. 23: 843–849. 

Trombulak, S.C.; Frissell, C.A. 2000. Review of ecological effects of roads on 

terrestrial and aquatic communities. Conservation Biology. 14: 18–30. 

U.S. Department of Agriculture, Forest Service [USDA FS]. 2001. Sierra 

Nevada Forest plan amendment (SNFPA) final environmental impact statement 

(FEIS). Vallejo, CA: U.S. Department of Agriculture, Forest Service, Pacific 

Southwest Region. 

U.S. Department of Agriculture, Forest Service [USDA FS]. 2004. Sierra 

Nevada Forest plan amendment (SNFPA) final supplemental environmental 

impact statement and record of decision. R5-MB-046. Vallejo, CA: Pacific 

Southwest Region. http://www.fs.fed.us/r5/snfpa/final-seis/. [Date accessed 

unknown]. 
186 

GENERAL TECHNICAL REPORT PSW-GTR-248

Van Wagner, T.J. 1996. Selected life-history and ecological aspects of a population 

of foothill yellow-legged frogs (Rana boylii) from Clear Creek, Nevada County, 

California. Chico, CA: California State University. 143 p. M.S. thesis. 

Vinson, M. 1998. Effects of recreational activities on declining anuran species 

in the John Muir Wilderness, CA. Missoula, MT: University of Montana. 83 p. 

M.S. thesis. 

Vos, C.C.; Chardon, J.P. 1998. Effects of habitat fragmentation and road density 

on the distribution pattern of the moor frog Rana arvalis. Journal of Applied 

Ecology. 35: 44–56. 

Vredenburg, V.T.; Knapp, R.A.; Tunstall, T.S.; Briggs, C.J. 2010. Dynamics 

of an emerging disease drive large-scale amphibian population extinctions. 

Proceedings of the National Academy of Sciences. 107: 9689–9694. 

Wake, D.B. 1991. Declining amphibian populations. Science. 253: 860. 

Wan, M.T.; Watts, R.G.; Moul, D.J. 1989. Effects of different dilution 

water types on the acute toxicity to juvenile Pacific salmonids and rainbow 

trout of glyphosate and its formulated products. Bulletin of Environmental 

Contamination and Toxicology. 43: 378–385. 

Waters, T.F. 1995. Sediment in streams: sources, biological effects and control. 

American Fisheries Society Monograph 7. Bethesda, MD: American Fisheries 

Society. 251 p. 

Weaver, T.; Dale, D. 1978. Trampling effects of hikers, motorcycles and horses in 

meadows and forests. Journal of Applied Ecology. 15: 451–457. 

Welsh, H.H., Jr.; Ollivier, L.M. 1998. Stream amphibians as indicators of 

ecosystem stress: a case study from California’s redwoods. Ecological 

Applications. 8: 1118–1132. 

Wheeler, C.A.; Welsh, H.H., Jr. 2008. Mating strategy and breeding patterns of 

the foothill yellow-legged frog (Rana boylii). Herpetological Conservation and 

Biology. 3: 128–142. 

Willis, M. [N.d.] Personal communication. Fish pathologist, California Department 

of Fish and Wildlife, Region 1, 601 Locust Street, Redding, CA 96001. 

Williams, M.R.; Melack, J.M. 1997. Atmospheric deposition, mass balances, 

and processes regulating streamwater solute concentrations in mixed-conifer 

catchments of the Sierra Nevada, California. Biogeochemistry. 37: 111–144. 
187 

Foothill Yellow-Legged Frog Conservation Assessment

Wojtaszek, B.F.; Staznik, B.; Chartrand, D.T.; Stephenson, G.R.; Thompson, 

D.G. 2004. Effects of Vision® herbicide on mortality, avoidance response, and 

growth of amphibian larvae in two forest wetlands. Environmental Toxicology 

and Chemistry. 23: 832–842. 

Yarnell, S.M. 2000. The influence of sediment supply and transport capacity on 

foothill yellow-legged frog habitat, South Yuba River, California. Davis, CA: 

University of California. 241 p. M.S. thesis. 

Yarnell, S.M. 2005. Spatial heterogeneity of Rana boylii habitat: physical 

processes, quantification, and ecological meaningfulness. Davis, CA: University 

of California. 238 p. Ph.D. dissertation. 

Yarnell, S.M. 2008. Quantifying physical habitat heterogeneity in an ecologically 

meaningful manner: a case study of the habitat preferences of the foothill yellowlegged frog (Rana boylii). In: Dupont, A.; Jacobs, H., eds. Landscape ecology 

research trends. New York: Nova Science Publishers: 89–112. Chapter 5. 

Zabik, J.M.; Seiber, J.N. 1993. Atmospheric transport of organophosphate 

pesticides from California’s Central Valley to the Sierra Nevada Mountains. 

Journal of Environmental Quality. 22: 80–90. 
188 

GENERAL TECHNICAL REPORT PSW-GTR-248

Appendix 5—Foothill Yellow-Legged 

Frog Working Group 

Arnold, Jonathan 

Forester 

Lassen Volcanic National Park 

P.O. Box 100 

Mineral, CA 96063-0100 

(530) 595-4444 x5171 

(530) 595-3262 

jonathan_arnold@nps.gov 

Boiano, Daniel 

Aquatic Ecologist 

Sequoia/Kings Canyon National Parks 

47050 Generals Highway 

Three Rivers, CA 93271 

(559) 565-4273 

danny_boiano@nps.gov 

Bolster, Betsy 

Staff Environmental Scientist (retired) 

Amphibians and Reptile Species of Special Concern 

California Department of Fish and Wildlife 

Nongame Wildlife Program 

1812 9th St. 

Sacramento, CA 95811 

Brown, Catherine 

Monitoring Team Leader 

Sierra Nevada Monitoring Strategy 

Pacific Southwest Research Station 

USDA Forest Service 

800 Buchanan Street 

Albany, CA 94710 

(510) 559-6433— Albany 

(209) 532-3571 x241— Sonora 

cathybrown@fs.fed.us 

Carlson, Ann D. 

District Ranger 

Eagle Lake Ranger District 

Lassen National Forest 

477-050 Eagle Lake Road 

Susanville, CA 96130 

(530) 257-4188 

adcarlson@fs.fed.us 
189 

Foothill Yellow-Legged Frog Conservation Assessment

Davidson, Carlos 

Director, Associate Professor 

Environmental Studies Program 

College of Behavioral and Social Sciences 

San Francisco State University 

1600 Holloway Avenue 

San Francisco, CA 94132 

(415) 405-2127 

carlosd@sfsu.edu 

Eddinger, Holly (Sanders) 

USDA Forest Service 

Ecosystem Conservation Department 

Lake Tahoe Basin Management Unit 

35 College Drive 

South Lake Tahoe, CA 96150 

(530) 543-2633 

heddinger@fs.fed.us 

Elliott, George 

Wildlife Biologist (retired) 

Eldorado National Forest 

USDA Forest Service 

100 Forni Road 

Placerville, CA 95667 

Epanchin, Peter 

Museum of Vertebrate Zoology 

University of California, Berkeley 

Science Advisor (current) 

United States Agency for International Development 

Washington, D.C. 

Graber, David 

Chief Scientist (retired) 

Sequoia/Kings Canyon National Parks 

National Park Service 

47050 Generals Highway 

Three Rivers, CA 93271-9651 

Hill, Kathy 

Environmental Program Manager 

California Department of Fish and Wildlife 

1701 Nimbus Road, Suite A 

Rancho Cordova, CA 95670 

(916) 651-8193 

Kathy.Hill@wildlife.ca.gov 
190 

GENERAL TECHNICAL REPORT PSW-GTR-248

Hopkins, Kristina 

Forest Fisheries Biologist 

Plumas National Forest 

USDA Forest Service 

159 Lawrence Street 

Quincy, CA 95971 

Jennings, Mark R. 

Herpetologist/Fishery Biologist 

Rana Resources 

P.O. Box 2185 

Davis, CA 95617-2185 

(530) 753-2727 

ranaresources@aol.com 

Kleinfelter, John 

Fisheries Biologist 

California Department of Fish and Wildlife 

1234 East Shaw Ave. 

Fresno, CA 93710 

Kupferberg, Sarah 

Stream Ecologist/Amphibian Biologist 

Questa Engineering Corp. 

P.O. Box 70356 

1220 Brickyard Cove Rd., Suite 206 

Pt. Richmond, CA 94807 

(510) 367-4546 

skupferberg@gmail.com 

Lehr, Stafford 

Senior Environmental Scientist 

California Department of Fish and Wildlife 

1701 Nimbus Rd., Suite A 

Rancho Cordova, CA 95670 

(530) 626-3687 

Stafford_Lehr@wildlife.ca.gov 

Lind, Amy J. 

Wildlife Biologist 

Pacific Southwest Research Station 

USDA Forest Service 

Hydroelectric Coordinator (current) 

Tahoe and Plumas National Forests 

TNF Supervisor’s Office 

631 Coyote St. 

Nevada City, CA 95959 

(530) 478-6298 

alind@fs.fed.us 
191 

Foothill Yellow-Legged Frog Conservation Assessment

Macfarlane, Diane 

Wildlife Biologist 

Region 5 Regional Office 

USDA Forest Service 

1325 Club Drive 

Vallejo, CA 94592 

(707) 562-8931 

dmacfarlane@fs.fed.us 

McFarland, Melanie 

Forest Fisheries Biologist 

Ecosystems Staff 

Supervisor’s Office 

Lassen National Forest 

USDA Forest Service 

2550 Riverside Drive 

Susanville, CA 96130 

(530) 252-6663 

mmcfarland02@fs.fed.us 

Mitchell, Dale 

Environmental Services Supervisor 

California Department of Fish and Wildlife 

1234 East Shaw #155 

Fresno, CA 93710 

Dale_Mitchell@wildlife.ca.gov 

Perrot, Laurie 

Environmental Coordinator 

Tahoe National Forest 

USDA Forest Service 

631 Coyote Street 

P.O. Box 6003 

Nevada City, CA 95959 

(530) 478-6244 

lperrot@fs.fed.us 

Schlick, Kary 

Wildlife Biologist 

Six Rivers National Forest 

USDA Forest Service 

1330 Bayshore Way 

Eureka, CA 95501 

(707) 441-3625 

kschlick@fs.fed.us 
192 

GENERAL TECHNICAL REPORT PSW-GTR-248

Smith, Dennis E. 

Region 5, RHAT Fisheries Biologist 

USDA Forest Service 

(707) 562-9176 

dennissmith@fs.fed.us 

Strand, Philip 

Fisheries Program Manager (retired) 

Sierra National Forest 

USDA Forest Service 

1600 Tollhouse Road 

Clovis, CA 93611 

(559) 297-0706 x4883 

pstrand@fs.fed.us 

Tibstra, Robert 

Environmental Scientist 

California Department of Fish and Wildlife 

Robert.Tibstra@wildlife.ca.gov 

Van Wagner, Tom 

12655 Butterfly Dr.
 

Nevada City, CA 95959 

tvanwagner@spjusd.org (Downieville School) 

(530) 289-3473 x22 

Welsh, Hart H., Jr. 

Research Wildlife Biologist (retired) 

Pacific Southwest Research Station 

USDA Forest Service 

1700 Bayview Drive 

Arcata, CA 95221 

(707) 825-2956 

hwelsh@fs.fed.us 

Werner, Harold 

Wildlife Ecologist (retired) 

Sequoia/Kings Canyon National Parks 

47050 Generals Highway 

Three Rivers, CA 93271 

Wheeler, Clara A. 

Ecologist 

Pacific Southwest Research Station 

USDA Forest Service 

1700 Bayview Dr. 

Arcata, CA 95521 

(530) 739-9190 

cawheeler@fs.fed.us 
193 

Foothill Yellow-Legged Frog Conservation Assessment

Williams, Jann O. 

Aquatic Biologist 

Eldorado National Forest 

USDA Forest Service 

100 Forni Road 

Placerville, CA 95667 

(530) 621-5240 

jowilliams@fs.fed.us 

Yarnell, Sarah 

Associate Project Scientist 

Center for Watershed Sciences 

One Shields Ave. 

University of California, Davis 

Davis, CA 95616 

(530) 752-0350 

smyarnell@ucdavis.edu 
This publication is available online at www.fs.fed.us/psw/.

Pacific Southwest Research Station

800 Buchanan Street

Albany, CA 94710