\ =-‘!% OLYMPIC SALAMANDE \ n ----____ 

Olympic 

k +, 

North j 

-_----.__ 

Dunn’s salamander often occurs along creeks and streams. 

In seeps and headwater habitats, the species may be found 

in the same microhabitat with the Olympic salamander 

(Nussbaum and others 1983). Dunn’s salamander does not 

occur in the Cascade Range of Washington (fig. 3). This 

species lacks larvae; individuals develop directly from egg 

to adult. 

Material and Methods 

We sampled 59 streams (see frontispiece) in three physiographic provinces: the Southern Washington Cascade Range, 

the Oregon Cascade Range, and the Oregon Coast Range 

(Franklin and Dymess 1973). A similar study was conducted 

in northwestern California and southwestern Oregon (Welsh 

and Lind, this volume). We sampled six streams in each 

forest age-class (young, mature, old growth) in the Oregon 

and Washington Cascades. In the Oregon Coast Range, we 

sampled streams in 3 young, 10 mature, and 10 old-growth 

stands. We sampled an additional 20 streams flowing 

through managed second-growth forests to study the 

long-term effects of logging (Corn and Bury 1989). 

Proximity of streams to established terresbial study-areas 

varied. In the Oregon Cascades, all of the streams flowed 

through stands used in the terrestrial community studies (see 

Gilbert and Allwine, this volume c). Few of the streams 

selected in the Oregon Coast Range or Washington Cascades 

were in the terrestrial study areas. Ages of these stands were 

based on visual inspection of dominant trees and available 

timber maps (USDA Forest Service and U.S. Department of 

the Interior, Bureau of Land Management). We selected 

permanent, l- to 2-m wide, first- or second-order streams. 

We adapted the habitat variables sampled from standard 

stream-survey techniques of Platts and others (1983). Bury 

and Corn (in press) and Corn and Bury (1989) describe these 

techniques in detail. Briefly, sampling consisted of an intensive search of 10 m of water and bank along a representative 

stretch of each stream. We used standarized techniques for 

measuring water depth, stream width, percentage gradient, 

pool-to-riffle ratio (100 percent pool = 1.0; 100 percent riffle 

= 0). percentage slope of the channel on each side of the 

stream, and water temperature. 

355 
ITAILED FROG DUNN’S SALAMANDER 

We estimated by eye the particle size of the subsaatum that 

was most abundant across the stream at ten l-m intervals. 

We categorized substrata as silt or sand (~2 mm diameter), 

gravel (2-32 mm), pebble (32-64 mm), cobble (64-256 mm), 

and boulder (>256 mm). When possible, we recorded where 

each animal was fast seen (pool, riffle or bank-seep) and 

measured the depth of water and size of the cover object 

over individual animals. All animals were collected by hand. 

Representative vouchers of each species were retained from 

many sites and deposited at the National Museum of Natural 

History in Washington, DC, the Burke Museum at the University of Washington, or the Conner Museum at Washington 

State University. 

We identified significant differences in stream characteristics 

among forest age-classes and among provinces with a oneway analysis of variance, which we also used to test for differences in amphibian densities among age-classes. Densities 

were transformed as the natural log of (density + 1). and 

percentage variables (stream gradient, pool-to-riffle ratio) 

were arcsine-transformed. 

Results and Discussion 

Scope of Comparisons 

Considerable variation was found in the biotic communities 

both within and among streams in each province we studied, 

yet we sampled a relatively small number of streams (minimum N = 18 in each province). Thus, our results should be 

viewed as a first attempt to compare aquatic amphibian 

communities in the Pacific Northwest. 

Naturally Regenerated Stands 

Stream characteristics-The streams we sampled in young, 

mature, and old-growth forests had similar gradients, widths, 

depths, side-slope gradients, and water temperatures (table 1). 

This finding was somewhat surprising considering the large 

geographic area and different mountain ranges where streams 

were examined (see frontispiece). We purposely selected 

headwaters and small streams that were about 1 to 2 m wide, 

however, and some variables (such as water depth) may 

simply reflect or be correlated to stream size (width). Sizes 

of substrata were evenly distributed (P = 0.27) in streams of 

young, mature, and old-growth forests (fig. 4). 
Table l-Mean values of physical characteristics of streams Table 2-Mean density (IndividualsIm~ of amphibians in 

sampled during stream surveys streams for different forest age-classes 

Variable Old growth Mature Young P Species Old-growth Mature Young P 

Number of Streams 22 22 15 

Gadicnt (9%) 11.4 14.4 8.3 0.23 

Width h) 1.23 1.16 1.17 0.85 

Depth &i) 4.8 4.6 4.5 0.81 

Pm1 ratio 0.38 0.40 0.40 0.83 

Side slope ($0) 43.4 44.1 46.9 0.82 

water temperature (‘C) to.9 10.9 11.4 0.73 

Siltkand Pebble Gravel Cobble Boulder 

Substrate 

Amphibian abundance and forest age-Abundance (individuals/m’) of each amphibian species was highly varied, but 

no significant differences in abundance were found among 

any of the forest types (table 2). 

Giant salamanders were the most common amphibians. Pacific giant salamanders were present in 50 of the 59 (85 percent) 

streams we sampled, and Cope’s giant salamander occurred 

in 11 of 24 (46 percent) streams within their limited geographic range. Together, these species were present in 53 of 

the 59 (90 percent) streams sampled. Tailed frogs were the 

next most frequent species, occurring in 45 of 59 (76 percent) 

streams. Olympic salamanders do not occur in the Mount 

Tailed frog 22 

0.86 

1.14 

22 

0.61 

1.09 

22 

1.21 

smams 8 

Mean 0.13 

SD 0.38 

streams 16 

Mea” 0.21 

0.26 

22 

2.89 

2.74 

22 

0.98 

1.71 

22 

0.37 

0.73 

22 

1.39 

1.70 

8 

0.50 

0.61 

16 

0.36 

0.60 

22 

3.19 

2.50 

15 

0.84 0.98 

1.03 

15 

0.15 0.23 

0.25 

15 

1.26 0.93 

1.48 

8 

0.37 0.28 

0.49 

9 

0.10 0.30 

0.27 

15 

2.50 0.62 

1.92 

0 1 2 3 4 

Number of species 

357 
Species - 

Rainier area, but we found this species in 31 of 55 (56 percent) streams within its geographic range. Dunn’s salamander occurred in 23 of 41 (56 percent) possible streams in the 

Oregon Cascades and Coast Range. Two streams lacked 

amphibians, but most (88 percent) had 2 to 4 spies present 

(fig. 5). Thus, almost all permanent streams flowing through 

the natural forests of the Pacific Northwest have multispecies 

communities of aquatic amphibians. 

Microhabitat association-We found no significant relations 

between the abundance of any amphibian species and the 

physical habitat variables we measured (stream gradient, pool 

ratio, mean depth or median subs&ate values). Significant 

differences (P < 0.05) were found among species in their use 

of microhabitats within streams we studied (fig. 6). however. 

Both tailed frogs and Olympic salamanders were found most 

often in riffles, and about 25 percent of the Olympic salamanders were taken on stream banks or in shallow seeps at 

stream margins. Cope’s giant salamander mostly frequented 

pools. but Pacific giant salamanders were taken about equally 

in riffles and pools. Dunn’s salamander is often semi-aquatic, 

and OUT captures of this species were almost entirely on 

stream-bank or seep habitats. 

The majority of amphibians were found under rock or log 

cover (we were unable to determine the exact undisturbed 

position of all animals). Of those captures that provided data 

on the position of animals, 471 of 722 (65 percent) Pacific 

Table S-Depth of water and size of rocks used for cover for 

each specks of stream smphiblsn (adult includes all transformed 

juvenlks and sexually mature adults) 

Depth (4 cover size (Cm*) 

Sue&s A% N Mean SD N Mean SD 

Taikd frog Adult 93 4.1 2.9 60 1.011 3,579 

lava 491 4.9 4.1 302 415 668 

Olympic Adub 36 3.9 8.3 629 637 

salamander Larva 170 3.6 4.1 

z 

467 717 

Pkfi~ giant Adult 31 5.4 5.9 24 2.410 6,072 

rakmdcr Larva 728 6.8 6.2 347 712 2.032 

Cope’s giant Larva 76 8.0 7.5 37 807 699 

salamander 

lhnnk salamander Adult - - - 85 1.003 1,399 

giant salamanders, 418 of 564 (74 percent) tailed frogs, 184 

of 239 (77 percent) Olympic salamanders, 65 of 78 (83 percent) Cope’s giant salamanders, and 94 of 101 (93 percent) 

Dunn’s salamanders were collected from under a cover object. Larval giant salamanders were often found in open water 

in pools, and tailed frog tadpoles were observed attached to 

rocks in riffles by means of their suctorial mouth. 

Differences were found between amphibian age-classes (larvae versus all transformed individuals) and among species in 

the depth of water and the size of rock cover under which 

they were found (table 3). The larvae and neotenes of tbe 

Pacific giant salamander (P = 0.056) and tadpoles of the 

tailed frog (P = 0.015) were in deeper water than adults of 

each species. No difference was observed between the depth 

of occurrence for larval and adult Olympic salamanders (P = 

0.44). We found that the larvae of both the Pacific giant 

salamander (P < 0.001) and tailed frog (P = 0.001) were 

under smaller rocks than were adults, but no significant 

differences were found between the use of rocks by larval 

and adult Olympic salamanders (P = 0.11). 

Both adults (P = 0.035) and larvae (P = 0.001) of four speties (excluding Dunn’s salamander; table 3) were observed 

at different water depths. Differences in the size of rocks 

used for cover among five species (table 3) were also significant for both adults (P = 0.029) and larvae (P < 0.001). 

Many of these differences in the selection of cover objects 

likely reflect the marked variation in species size. Large 

adults of the Pacific giant salamander and adult tailed frogs 

were mostly found under larger rocks or boulders, whereas 

the smaller larvae of Olympic salamanders and tailed frogs 

often occurred under small rocks or in beds of gravel, 

pebble, and cobble. 

358 
Table 4-Physical characteristics ot streams in each province 

18 

19.1 

1.10 

4.2 

0.38 

48.5 

10.9 

IS 

8.8 

1.20 

4.6 

0.42 

38.8 

9.7 

o.oQ, 

0.45 

0.42 

0.63 

0.31 

0.002 

50 

Substrate 

Fire 7-Distribution of sizes of substrates in sueatns in the sotiem 

Washingtan Cascades (SW). the Oregon Cascades (Oc). and the Oregon 

Coast Range (CR). 

Regional Patterns 

Stream characteristics-Analysis of habitat variables suggested that tie s!xams we sampled in each province were 

similar. No significant differences were found in width, 

depth, or pool ratio among pmvinces (table 4). Streams 

sampled in the Oregon Cascades had steeper gradients than 

in the other regions (P < 0X01), mostly because of a few 

streams where very steep reaches (30-45 percent) were 

sampled. The mean water temperature in Coast Range 

streams was wanner, perhaps reflecting differences in 

regional climate. Sites in the interior parts of the Coast 

Range are in areas that are subject to higher summer 

temperatures than are streams at higher elevations in the 

Cascade Range. 

Table 5-Mean densities (inditiduals/m2) of stream amphibians 

in each province; subprovinces are listed from northern to southern (see frontispiece) 

ongon coast 

Range 03) 0.76 0.29 2.28 - 0.41 

Coast (4) 0.86 0.14 1.94 - 0.18 

Siuslaw (5) 0.76 0.16 2.41 - 0.24 

Umpqua (8) 0.81 0.22 2.28 - 0.57 

coquille (6) 0.65 0.58 2.40 - (1.49 

Qt&m Cascade%:; I 

m : 0.25 0.48 0.88 0.40 0.04 

: Mt.Hmd(@ i : 0.38, 1.40 1.75 0.40 0.07 

/_ Andrews (6) / 0.10 0.07 0.15 - 0.01 

$,,Roguem ‘_ 0.28 : : 0 0.15 - 0.02 

so. wasbiigum 

Cascades (18) 1.72 0.60 0.42 0.31 - 

ML Rainier (4) 0.35 - 0.10 0.22 - 

Cowlilz River (4) 1 .I 1 0.45 0.10 0.83 - 

Lewis River (5) 0.70 0.34 1.20 0 

Wind River (5) 4.32 0.97 0.16 0.29 - 

For OUT samples, statistically significant variation was found 

among provinces in substrate of streams. More boulders and 

fewer pebble or cobble-sized rocks were found in the streams 

we studied in the Oregon Cascades than in the other two 

regions (fig. 7). Some of the. Oregon Cascade streams may 

have been underlaid with bedrock, and the reduction in cover 

sites may partly explain the generally low abundance of amphibians in some of these streams. Streams we examined in 

the Washington Cascades had more gravel, pebble, and cobble than those in the Oregon Cascades. The Coast Range sites 

had more cobble and pebble substrate than either of the Cascade provinces, but the differences were minor. 

Amphibian abundance-Considerable variation was found 

in the abundance of each species among the streams we sampled in the three provinces (table 5). Pacific giant salamanders and Dunn’s salamanders were most abundant in the 

streams we studied in the Oregon Coast Range, and tailed 

frogs reached their highest densities in streams we sampled 

in the Washington Cascades. Olympic salamanders were 

more abundant in the streams we searched in the Washington 

Cascades than in those we sampled in the Oregon Cascades 

or Coast Range. 

Within each of the provinces, some clinal patterns were 

found. Abundance of amphibians in the Oregon Cascade sites 

varied fmm the southernmost streams that contained only 

three species in low numbers to streams in the northernmost 

area (Mount Hood) that had up to five species in moderate to 

359 
Table 6-Mean bfomass (g/m”) and dens&y (inditidualsh~ 

of stream amphibians and salmonid tlshes (from Platts and 

McHenry 1988) in the Pacillc Northwest 

high abundance. Except for Cope’s giant salamander, amphibians in Washington streams showed a reverse pattern with the 

most species and highest abundance in streams to the south. 

We found few differences from north to south among the 

streams in the Oregon Coast Range, except that Olympic 

salamanders were more abundant in the southernmost streams 

(Coquille River drainage). The four coastal streams in the 

Coast Range did not differ from inland streams. 

Some of these patterns may be due to regional variation in 

climate or stream productivity. Because of relatively small 

sample sizes, however, observed differences may also reflect 

variations in the collecting efficiency of field crews, or simply random variation among the streams sampled. Further 

work is needed to document possible clinal changes in the 

occurrence and abundance of species. 

Comparison to Salmonid Fishes 

Recently, Platts and McHemy (1988) summarized the known 

literature on density and biomass of salmonid fshes. For 

streams in the Pacific region, our data indicate that aquatic 

amphibians are 10 times more abundant with 4 times the 

biomass than what was reported for salmonids (table 6). We 

do not have comparable data for other fishes (for example, 

sculpins). Even if tailed frogs are excluded because their 

larvae are herbivorous and the adults forage above or out of 

the water, small streams still harbor populations of aquatic 

amphibians that exceed any known estimate for coldwater 

fishes. Several reamns may account for these differences. 

Amphibians may reach high densities and biomass because 

their adults can exploit both aquatic and terrestrial prey (Bury 

and Martin 1973, Nussbaum and others 1983). Salmonid 

fishes forage on invertebrates that land on or occur in water. 

Fish are attack predators and highly active, but amphibians 

often hide under cover as sit-and-wait predators and thus 

convert more energy to biomass than do fishes. Amphibians 

appear to be the predominant vertebrate predator in many 

headwaters and small streams in the Pacific Northwest. 

Managed Stands 

Timber harvest increases insolation on waterways and raises 

stream temperatures (see Beschta and others 1987, Hartman 

and others 1987). Such effects usually last only until the canopy is reestablished. In the Oregon Coast Range, Antis and 

Froehlich (1988) reported that shading over streams may 

reach 50 percent in less than 5 years after clearcutting and 

may approach prelogging cover by age 10. Tailed fmgs and 

Olympic salamanders, however, have low and narrow temperature tolerances, and these species are likely to be negatively affected by the increased water temperature in smeams 

in clearcuts (Bury and Corn 1988b, de Vlaming and Bury 

1970). Conversely, Pacific giant salamanders may be more 

abundant in streams traversing clearcuts than in densely 

forested stands (Hawkins and others 1983, Mtuphy and 

Hall 1981, Murphy and others 1981). possibly because of 

enhanced populations of invertebrate prey for several years 

after timber harvest. Invertebrates, salmonids and salamander 

populations decline once shade is reestablished over streams 

in western Oregon (Hawkins and others 19X2,1983; Murphy 

and others 1981). 

Logging can cause sedimentation in streams, which eliminates 

crevices and cover habitat apparently needed by larval salamanders (Bury 1988b, Bury and Corn 1988b. Hall and others 

1978). This habitat feature is the most important determinant 

of the number of amphibians over the long term (Corn and 

Bury 1989). 

Coarse woody debris in and along streams reduces debris 

torrents and channelization, functions as a sediment nap, 

and provides sources of nutrients and cover for animals in 

streams (Franklin and others 1981, Harmon and others 1986, 

S&l1 and Swanson 1984). Timber harvest can also reduce 

the introduction of new pieces of down wood into the streambed (Bryant 1985, &dell and Swanson 1984, Swanson and 

Lienkaemper 1978), and such material helps maintain the 

ecological role of streams (Meehan and others 1977, 

Scrivener and Andersen 1984). The juxtaposition and pattern of stand types resulting from forest fragmentation 

because of logging, furthermore, may influence the occurrence and abundance of stream amphibians. Corn and Bury 

(1989). for example, suggest that the presence of uncut 

timber upstream influences the presence and persistence of 

aquatic amphibians in streams flowing through logged areas 

downstream. 

The response of aquatic amphibians to clearcutting or other 

disturbances may vary regionally. Hawkins and others (1988) 

found that tailed frogs were virtually extinct in drainage 

basins deforested by the eruption of Mount St. Helens, 

Washington, whereas frog densities were high in partially or 

completely forested basins. In the Oregon Coast Range, Corn 

and Buy (1989) reported that the densities and biomass of 
amphibian species in unlogged streams were 2 to 7 times

greater than in logged streams. They suggested that logging

severely reduces microhabitats for larval salamanders because

streams in logged stands had more fine sediments than control

streams. Tailed frogs and Olympic salamanders were especially sensitive to logging, and in some streams these species

may experience local extinction immediately after clearcutting (Corn and Bury 1989, Nussbaum and others 1983).

Tailed frogs and Olympic salamanders are closely tied to the

stream habitats they occupy. These species appear to have

limited dispersal abilities that may prevent them from recolonizing altered streams even after the forest canopy has been

reestablished. The likelihood of recolonization by tailed frogs

is very low in streams surrounded by hot, arid environments

(see Daugherty and Sheldon 1982, Hawkins and others 1988,

Metter 1967).

There are fewer data on the response of aquatic amphibians

to timber harvest in the Cascade Range, on the Olympic

Peninsula, or in British Columbia. Aquatic amphibians in

these regions may have a higher probability of surviving the

effects of clearcutting because northern and higher elevation

montane regions are generally cooler than those at lower

elevations or lower latitudes.

The response of Pacific giant salamander populations to logging is dependent on stream gradient (Corn and Bury 1989,

Hall and others 1978). For several decades after logging, their

population numbers remain small in low gradient streams,

whereas they appear to be little influenced in high-gradient

streams. Logging does not appear to cause local extinction of

this species, and timber harvest may even temporarily enhance some giant salamander populations where there are

increases in stream productivity related to greater insolation.

I Research Needs and Management

Recommendations

Additional research is needed on:

l The effects of timber harvest on the occurrence and

abundance of aquatic amphibians in the Pacific

Northwest;

l The habitat preferences and environmental tolerances of

aquatic amphibians, especially the Olympic salamander;

l The life histories, ecology (particularly dispersal abilities),

and viable population sizes of tailed frogs and Olympic

salamanders;

l The effectiveness of different types and sizes of buffer

strips along streams to protect amphibians; and

l The value of different-sized patches of forested habitat in

watersheds as reservoirs or source areas for aquatic

amphibians.

We recommend that intensive research and improved streammanagement practices be directed at the Olympic salamander

and the tailed frog, which we consider to be the species most

sensitive to the effects of timber harvest. The survival of

aquatic amphibian populations in most forested areas of the

Pacific Northwest ultimately will depend upon their abilities

to persist in streams flowing through managed forests. Comprehensive planning and the protection of small streams

during logging are essential components of management

strategies aimed at protecting aquatic amphibian populations.

Bury and Corn (1988b) suggested that headwaters should be

surveyed for Olympic salamanders and tailed frogs before

timber sales, and if these species are present, then protection

efforts should be made. Buffer strips have been shown to be

effective at protecting stream biota and habitat by maintaining shade and reducing sedimentation (Beschta and others

1987, Hartman and others 1987, Murphy and others 1981,

Newbold and others 1980, Raedeke 1988). Costs of buffer

strips are higher on smaller streams than on larger streams

(Andrus and Froehlich 1988), and it may be difficult to

convince land managers that the benefits of buffer strips,

and riparian zones outweigh the costs (Bury and Corn

1988b). We therefore need to investigate alternatives for

reducing the costs of buffer strips and yet ensure the

protection of amphibians, fishes, and other wildlife along

headwaters.

Retention of deciduous vegetation (bigleaf maple, alder) and

unmerchantable conifers (small or cull trees) may be one

inexpensive way to preserve shade. We strongly recommend

that natural woody debris (large pieces that are partially

buried or decayed) be retained in streams. If merchantable

timber is felled away from the stream, the deciduous trees

within riparian areas would be left mostly intact. Cull or

broken trees that fall across streams or along the streambank

during timber harvest provide needed sources of nutrients,

sediment traps, shade and cover for wildlife. Moderate

amounts of slash and coarse woody debris are best left where

they fall. Retention of streamside trees and woody debris

also reduces the cost of removing logging debris.

361
Aquatic amphibians have small home ranges, and the protection of relatively small patches of streamside habitat might

Acknowledgments

provide habitat for viable populations. In the Oregon Coast We thank Robert M. Storm, and two anonymous reviewers

Range, we found that some species can occur in disturbed for their comments on the paper. Andrew B. Carey assisted

reaches if protected waters are present upstream in the same with development of the sampling design, and participated

drainage (Corn and Bury 1989). The protection of only part with work in the Oregon Coast Range. We also thank the

of a drainage (for example, a forest patch containing head- many biologists who assisted with the field work and stream

water creeks) or a buffer zone (for example, a 50-m wide surveys.

strip) may ensure survival of aquatic amphibian populations. This paper is contribution 127 of the Wildlife Habitat

Headwaters and streams comprise less than 5 percent of the Relationships in Western Washington and Oregon Research

total surface area of northwestern forests (Bury 1988). Wise Project, Pacific Northwest Research Station, USDA Forest

management of this rare and ecologically important resource, Service. q

however, is essential for maintaining the health and stability

of wildlife and fisheries populations in the Pacific Northwest.

362