[Federal Register Volume 62, Number 225 (Friday, November 21, 1997)]
[Proposed Rules]
[Pages 62276-62282]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-30553]



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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AE40


Endangered and Threatened Wildlife and Plants; Proposed 
Endangered Status for the Riparian Brush Rabbit and Riparian Woodrat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: The Fish and Wildlife Service (Service) proposes to list the 
riparian brush rabbit (Sylvilagus bachmani riparius) and the riparian 
(San Joaquin Valley) woodrat (Neotoma fuscipes riparia) as endangered 
species pursuant to the Endangered Species Act of 1973, as amended 
(Act). The brush rabbit and woodrat inhabit riparian communities along 
the lower portions of the San Joaquin and Stanislaus rivers in the 
northern San Joaquin Valley, California. Only a single remaining 
population of each species has been confirmed. Potential threats to 
these species include flooding, wildfire, predation, and other random 
factors. This proposal, if made final, would extend the Act's 
protective provisions to these animals.

DATES: Comments from all interested parties must be received by January 
20, 1998. Public hearing requests must be received by January 5, 1998.

ADDRESSES: Comments and materials concerning this proposal should be 
sent to the U.S. Fish and Wildlife Service, 3310 El Camino Ave., Suite 
130, Sacramento, California 95821. Comments and materials received will 
be available for public inspection, by appointment, during normal 
business hours at the above address.

FOR FURTHER INFORMATION CONTACT: Diane Windham at the above address 
(telephone 916/979-2725).

SUPPLEMENTARY INFORMATION:

Background

    The riparian brush rabbit (Sylvilagus bachmani riparius) was 
described as a distinct subspecies by Orr (1935) and is one of 13 
subspecies of S. bachmani (Hall 1981). Sylvilagus bachmani belongs to 
the order Lagomorpha and family Leporidae. The riparian brush rabbit is 
a medium to small cottontail with a total length of 300 to 375 
millimeters (mm) (11.8 to 14.8 inches (in)) and a mass of 500 to 800 
grams (g) (1.1 to 1.8 pounds). It is unique in that the sides of the 
rostrum (nasal/upper jaw region of the skull), when viewed from above, 
are noticeably convex instead of straight or concave as in other races 
of bachmani (Orr 1940). The color varies from dark brown to gray above 
to white underneath. The subspecies visually resembles the desert 
cottontail (Sylvilagus audubonii), a species that also occurs in 
riparian habitats within the historic range of the riparian brush 
rabbit. In-hand identification is required to definitively distinguish 
between young individuals of these species (Williams 1993).
    Brush rabbits in general breed between December and May or June 
(Mossman 1955). After a gestation period of 26 to 30 days, the young 
are born in nest cavities lined mainly with fur and covered with a 
grass plug (Davis 1936, Orr 1940, Orr 1942). The young are born naked, 
blind, and helpless and open their eyes in 10 days (Orr 1940, Orr 
1942). Young rabbits remain in the nest about 2 weeks before venturing 
out, and the female will continue to suckle her young for 2 to 3 weeks 
after their birth. Orr (1940) reported a mean litter size of between 
three and four with a range of two to five, while Mossman (1955) 
reported an average of four with a range of three to six. Riparian 
brush rabbits grow to adult size in 4 to 5 months, but do not reach 
sexual maturity until the winter following birth. Females give birth to 
about 5 litters per season with an estimated average of 9 to 16 young 
per breeding season (Basey 1990). The percentage of females active 
during the breeding season is unknown, but in 1 study, 9 of 25, or 36 
percent of, female adults examined showed no signs of reproductive 
activity (Basey 1990).
    The habitat of the riparian brush rabbit is riparian forests with a 
dense shrub layer. Common food plants in riparian brush rabbit habitat 
include Rosa californica (California wild rose), Rubus ursinus (Pacific 
blackberry), Vitis californica (wild grape), Sambucus mexicana 
(elderberry), and grasses (Williams 1988, Basey 1990). Brush rabbits 
have relatively small home ranges that usually conform to the size and 
shape of available brushy habitat (Basey 1990). In general, the home 
ranges of males are larger than those of females but male home ranges 
do not overlap the primary activity centers within female territories 
(Basey 1990).
    The riparian brush rabbit is currently restricted to a single 
population at Caswell Memorial State Park, San Joaquin County, along 
the Stanislaus River (Williams and Basey 1986). In surveys conducted in 
all potential habitat along the Merced, San Joaquin, Stanislaus, and 
Tuolumne rivers during 1985 and 1986, no additional populations of 
riparian brush rabbits were located (Williams 1988). A maximum of about 
81 hectares (ha) (198 acres (ac)) in Caswell Memorial State Park are 
suitable habitat for riparian brush rabbit (Williams 1993). During 
periods of heavy flooding, when virtually no suitable habitat remains 
exposed as a refugium, the population can drop dramatically. Williams 
(1988) estimated a population low of 10 or fewer individuals after 
severe winter flooding in 1985-86. Extended flooding occurred during 
the winter and spring of 1997, but no population estimate is yet 
available (see factor A in the ``Summary of Factors Affecting the 
Species'' section). Such low population levels may make this subspecies 
extremely vulnerable to detrimental genetic processes and random events 
(see factor E in the ``Summary of Factors Affecting the Species'' 
section). Maximum population estimates from surveys conducted in recent 
years at Caswell Memorial State Park are 88 to 452 individuals 
(Williams 1988), 320 to 540 individuals (Basey 1990), and 170 to 608 
individuals (Williams 1993).
    Because this subspecies was not described until after it is 
believed to have been extirpated from most of its historic range, 
definitive information on its former distribution is lacking. Even 
though riparian brush rabbit specimen records and sightings were known 
only from along the San Joaquin River near the boundary of San Joaquin 
and Stanislaus counties, Orr (1940) believed, based on the presence of 
suitable habitat, that its historic range extended along the San 
Joaquin river system, from Stanislaus County north to the Sacramento-
San Joaquin River Delta. It apparently has been extirpated from the 
Delta, as well as most of the lower San Joaquin River and its 
tributaries--the Stanislaus, Tuolumne, and Merced rivers (Williams 
1986). The range of the subspecies likely extended farther upstream 
south of the Merced River, assuming that suitable habitat occurred 
historically along the length of the San Joaquin River system (Williams 
and Basey 1986).
    The riparian (San Joaquin Valley) woodrat (Neotoma fuscipes 
riparia) was first described by Hooper (1938) and is 1 of 11 subspecies 
of N. fuscipes in the family Muridae (order Rodentia). The subspecies 
has been retained by Hall (1981) and Williams (1986 and 1993). The 
riparian woodrat is a medium-sized rodent, its total length averaging 
443 mm (17.4 in), its tail length averaging 217 mm (8.5 in) (Hooper 
1938), and its total weight, based on measurements of other subspecies, 
averaging about 227 g

[[Page 62277]]

(8 ounces), with marked seasonal variation (Williams et al. 1992). The 
riparian woodrat is predominantly gray and cinnamon above and whitish 
beneath, with white hindfeet. Neotoma fuscipes riparia is distinguished 
from other subspecies of N. fuscipes by size and coloration of the 
body, tail, ears, or feet, in addition to skull measurements and 
characteristics (Hooper 1938).
    The following information is taken from a number of studies on 
Neotoma fuscipes, including riparia and related subspecies. Mostly 
active at night, the woodrat's diet is diverse and mainly herbivorous, 
with leaves, fruits, terminal shoots of twigs, flowers, nuts, and fungi 
comprising the bulk of ingested material (Williams et al. 1992). 
Females have one to five litters per year with three to four young each 
time. Reproduction occurs in all months, with the fewest pregnancies in 
December and the most in February. The number of juveniles appearing 
outside the nest is greatest in July and least in January and February 
(Williams et al. 1992).
    The young are born in stick nest houses or lodges, which are 
located on the ground and measure 0.6 to 0.9 meters (m) (2 to 3 feet 
(ft)) high and 1.2 to 1.8 m (4 to 6 ft) in diameter. Most lodges are 
positioned over or against logs (Cook 1992, cited in Williams 1993). 
Unoccupied houses can persist for 20 to 30 years (Williams 1993). 
Unlike other subspecies, the riparian woodrat occasionally builds nests 
in cavities in trees and artificial wood duck nest boxes (Williams 
1986). Nest houses usually are occupied by single adults. Young seldom 
disperse far from their natal houses, and nest clusters occupied by 
related individuals tend to develop in favored habitats. Unlike males, 
females remain in or near natal areas throughout their life (Williams 
et al. 1992). At Caswell Memorial State Park, Williams (1993) reported 
a mean density of houses of 8.3 per ha (3.4 per ac), or 757 houses on 
91 ha (225 ac) of suitable habitat; occupancy of these houses was not 
verified.
    In a study of another subspecies of Neotoma fuscipes, Linsdale and 
Tevis (1951, cited in Williams et al. 1992) found that 70 percent of 
the population survived less than 1 year, 27 percent survived 2 years, 
and 3 percent survived 3 years or more. Williams et al. (1992) also 
cited a number of studies that indicated woodrats are highly responsive 
to habitat alteration, with populations fluctuating widely in response 
to a variety of perturbations such as fire, flood, drought, habitat 
modification, and browsing and trampling by ungulates.
    Historical localities for the riparian woodrat are distributed 
along the San Joaquin, Stanislaus, and Tuolumne rivers, and in Corral 
Hollow in San Joaquin, Stanislaus, and Merced counties (Hooper 1938, 
Williams 1986). This range is similar to the presumed historical range 
for the riparian brush rabbit. Thus, prior to the statewide reduction 
of riparian communities by nearly 90 percent (Katibah 1984), the 
riparian brush rabbit and woodrat probably occurred throughout the 
extensive riparian forests along major streams flowing onto the floor 
of the northern San Joaquin Valley.
    The only known population of the riparian woodrat occurs in, and 
immediately adjacent to, Caswell Memorial State Park, also the site of 
the only riparian brush rabbit population (Williams 1993). A woodrat 
population was reported during the early 1970s near the type locality 
at Vernalis, but the current status of the population is unknown (D. 
Williams 1986, pers. comm. 1994). The site of an old record at Corral 
Hollow, San Joaquin County, no longer supports suitable habitat (D. 
Williams, pers. comm. 1994). Cook (1992) estimated the Caswell Park 
population at 637 woodrats over 102 ha (250 ac) of habitat. Williams 
(1993) estimated a peak population at Caswell of 437 animals, based on 
mean density of 4.8 woodrats per ha on 91 ha (225 ac) of suitable 
habitat.
    Today, riparian forests of the lower San Joaquin River and its 
tributaries outside of Caswell Memorial State Park have nearly been 
eliminated. The remaining habitat is small, narrow forest patches 
confined within levees. These areas flood completely during major storm 
events. Because these forest remnants are small, isolated, and subject 
to periodic prolonged flooding (Williams and Basey 1986), their 
capability to support viable populations of these subspecies over the 
long-term is doubtful. Historic habitat and refugia from flooding in 
adjacent lands are now mainly cultivated fields, orchards, and 
vineyards, habitats unsuitable for these subspecies (Williams and Basey 
1986). Flooding, wildfire, predation, and other factors imperil their 
continued existence.

Previous Federal Action

    Federal action on these two species began on September 18, 1985, 
when the Service published the Vertebrate Wildlife Notice of Review (50 
FR 37958), which included the riparian brush rabbit and riparian 
woodrat as category 2 candidate species. Category 2 candidates, a 
designation discontinued in a Notice of Review published by the Service 
on February 28, 1996 (61 FR 7596), were taxa for which information in 
possession of the Service indicated that proposing to list as 
endangered or threatened was possibly appropriate but for which 
conclusive data on biological vulnerability and threats were not 
currently available. In the January 6, 1989, Animal Notice of Review 
(54 FR 554), the Service elevated the riparian brush rabbit to a 
category 1 candidate species as a result of more intensive field work 
by Williams and Basey (1986) that identified only a single remaining 
population of this subspecies. Category 1 comprised taxa for which the 
Service currently had substantial information on biological 
vulnerability and threats to support proposals to list them as 
endangered or threatened species. The Service retained the riparian 
brush rabbit as a category 1 candidate and elevated the status of the 
riparian woodrat to category 1 in the November 21, 1991, Animal Notice 
of Review (56 FR 58804), based on a reevaluation of the information 
contained in the study conducted by Williams and Basey (1986). The 
November 15, 1994, Animal Notice of Review (59 FR 58987) included both 
subspecies in category 1. The February 28, 1996, combined Animal and 
Plant Notice of Review (61 FR 7596) included both subspecies as 
candidates.
    The processing of this proposed listing rule conforms with the 
Service's listing priority guidance for fiscal year 1997 published in 
the Federal Register on December 5, 1996 (61 FR 64475). The guidance 
clarifies the order in which the Service will process rulemakings 
following two related events, the lifting, on April 26, 1996, of the 
moratorium on final listings imposed on April 10, 1995 (Public Law 104-
6), and the restoration of significant funding for listing through 
passage of the omnibus budget reconciliation law on April 26, 1996, 
following severe funding constraints imposed by a number of continuing 
resolutions between November 1995 and April 1996. The guidance calls 
for giving highest priority to handling emergency situations (Tier 1) 
and second highest priority (Tier 2) to resolving the status of 
proposed listings. A lower priority is assigned to resolving the 
conservation status of candidate species and processing administrative 
findings on petitions to add species to the lists or reclassify species 
from threatened to endangered status (Tier 3). The lowest priority 
actions are in Tier 4, a category which includes processing critical 
habitat determinations, delistings, or other types of

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reclassifications. Processing of this proposed rule is a Tier 3 action.

Summary of Factors Affecting the Species

    Section 4 of the Endangered Species Act (16 U.S.C. 1533) and 
regulations (50 CFR part 424) promulgated to implement the listing 
provisions of the Act set forth the procedures for adding species to 
the Federal lists. A species may be determined to be an endangered or 
threatened species due to one or more of the five factors described in 
section 4(a)(1). These factors and their application to the riparian 
brush rabbit (Sylvilagus bachmani riparius) and the riparian woodrat 
(Neotoma fuscipes riparia) are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment 
of its Habitat or Range

    Both the riparian brush rabbit and the riparian woodrat inhabit 
riparian forests, and each has been extirpated from all of its 
historical range except for a single population at Caswell Memorial 
State Park along the Stanislaus River. Katibah (1984) estimated that 
only 41,300 ha (102,000 ac) remain of an estimated 373,000 ha (921,600 
ac) of pre-settlement riparian forest in California's Central Valley, a 
reduction of 89 percent. Moreover, nearly one-half of the remaining 
forests are in a disturbed and/or degraded condition, and it is likely 
that the majority of the rest have been and continue to be heavily 
impacted by human activities. This elimination and modification of 
riparian forests along valley floor river systems was attributed to--
urban; commercial, and agricultural development; wood cutting; land 
reclamation and flood control activities; groundwater pumping; river 
channelization; dam construction; and water diversions (Katibah 1984).
    Several land use practices and related human activities have 
contributed to the decline of the riparian brush rabbit and riparian 
woodrat throughout their historical ranges. During the past 10 to 20 
years, cultivation has expanded along the floodplains of the main 
tributaries of the lower San Joaquin River system (Basey 1990). 
Increased habitat conversion to agricultural uses has resulted from the 
recent construction of the following dams on tributaries that 
individually and collectively altered the timing, frequency, duration, 
and intensity of flooding--Exchequer Dam on the Merced River, New 
Melones Dam on the Stanislaus River, and New Don Pedro Dam on the 
Tuolumne River. Before these dams and other flood control projects were 
constructed, much of the floodplain was livestock pasture (Basey 1990). 
Uneven topography on the floodplains provided escape areas for species 
because some land remained above most flood levels and contained 
patches of shrubs and trees for cover. Sites like these probably 
provided refuge from flooding for brush rabbits. Williams and Basey 
(1986) stated that, ``virtually all areas outside of flood control 
levees now have been cleared, leveled, and planted to orchards, 
vineyards, or annual row crops.'' Conversion from pasture to cultivated 
fields also eliminated hedge rows and other residual patches of cover 
that provided travel corridors and refuge sites for the two subspecies. 
The effects of catastrophic flooding are discussed further under factor 
E.
    Although brush clearing adversely affected the habitat of the 
riparian brush rabbit and riparian woodrat populations at Caswell State 
Park in the mid-1980s (Williams 1986), the State Park populations are 
no longer directly threatened by brush clearing, tree cutting, or the 
conversion of land to agricultural uses. Because the State Park harbors 
the only known populations of these species, these activities outside 
of the park do not pose a direct threat to either species. Such 
activities continue, however, to eliminate and fragment patches of 
remnant habitat within the historic range of these species.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    Overutilization is not known to be a problem for either species. 
However, the very small population at the remaining site makes the 
riparian brush rabbit vulnerable to extinction from recreational 
hunting and collection for scientific or other purposes. The brush 
rabbit (Sylvilagus bachmani) is designated as a resident small game 
species in California and is hunted from July 1 through January 30 with 
a daily bag limit of five animals (Williams and Basey 1986). Hunting 
regulations set by the California Fish and Game Commission do not 
distinguish the riparian brush rabbit from other subspecies of S. 
bachmani. Therefore, riparian brush rabbits that disperse beyond the 
boundaries of Caswell Memorial State Park (as they may, especially 
during times of flooding) face a potential threat of being hunted.

C. Disease or Predation

    All rabbits, including cottontails, are known to be susceptible to 
a variety of diseases that sometimes reach epidemic proportions. The 
small population size and restricted distribution of both the riparian 
brush rabbit and riparian woodrat increase their vulnerability to 
epidemic diseases, such as tularemia in the case of the brush rabbit 
(Williams 1988). However, the significance of the threat of disease to 
the riparian brush rabbit and riparian woodrat is not known.
    Coyotes, gray foxes, long-tailed weasels, raccoons, feral cats and 
dogs, hawks, and owls are known predators of brush rabbits as well as 
other small mammals, including woodrats (Williams 1988, Verner and Boss 
1980, Orr 1940). At currently depleted population levels, predation 
events could significantly affect the survival of these two subspecies.

D. The Inadequacy of Existing Regulatory Mechanisms

    Federal, State, and local laws and regulations have not proven 
adequate to curb habitat losses for the riparian brush rabbit and 
riparian woodrat. The National Environmental Policy Act (NEPA) and 
section 404 of the Clean Water Act (CWA) represent the primary Federal 
laws that potentially may afford some protection for these species. 
However, neither NEPA nor the CWA protect candidate species. Moreover, 
brush clearing, tree cutting, and the conversion to agricultural uses 
that are adversely affecting these species are generally unregulated at 
any level of government. For example, pursuant to 33 CFR 323.4, the 
U.S. Army Corps of Engineers (Corps) has promulgated regulations that 
exempt some farming, forestry, and maintenance activities from the 
regulatory requirements of section 404.
    Caswell Memorial State Park has a management plan for the riparian 
brush rabbit that provides some measure of protection to the 
population. This plan does not address the riparian woodrat. Despite 
the existence of a management plan, both the riparian brush rabbit and 
woodrat remain vulnerable to threats and hazards originating outside of 
the park (see factor E below).
    The California Environmental Quality Act (CEQA) requires a full 
public disclosure of the potential environmental impact of proposed 
projects. The public agency with primary authority or jurisdiction over 
the project is designated as the lead agency, and is responsible for 
conducting a review of the project and consulting with other agencies 
concerned with resources affected by the project. Section 15065 of the 
CEQA guidelines requires a finding of significance if a project has the 
potential to ``reduce the number or restrict the

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range of a rare or endangered plant or animal.'' Species that are 
eligible for listing as rare, threatened, or endangered but are not so 
listed are given the same protection as those species that are 
officially listed with the State. Once significant impacts are 
identified, the lead agency has the option to require mitigation for 
effects through changes in the project or to decide that overriding 
considerations make mitigation infeasible. In the latter case, projects 
may be approved that cause significant environmental damage, such as 
destruction of endangered species. Protection of listed species through 
CEQA is, therefore, at the discretion of the lead agency involved. The 
CEQA provides that when overriding social and economic considerations 
can be demonstrated, project proposals may go forward, even in cases 
where the continued existence of the species may be jeopardized, or 
where adverse impacts are not mitigated to the point of insignificance. 
Furthermore, proposed revisions to CEQA guidelines, if made final, may 
weaken protections for threatened, endangered, and other sensitive 
species.
    The California Endangered Species Act affords the riparian brush 
rabbit some conservation benefits. The animal was listed as an 
endangered species by the State of California in May 1994. Although 
this State law provides a measure of protection to the species, 
resulting in the formulation of mitigation measures to reduce or offset 
impacts for any projects proposed in riparian brush rabbit habitat, 
this law is not adequate to prevent the ongoing loss of riparian 
habitat. Many of the threats facing the riparian brush rabbit and the 
riparian woodrat (see factor E below) are not amenable to management 
without supplementing the depleted habitat base upon which these 
species depend. Moreover, State listing does not provide a nexus with 
Federal agencies, such as the Corps, that regulate flood control and 
other activities in waters of the United States.

E. Other Natural or Manmade Factors Affecting its Continued Existence

    Random events such as flooding or fire may be more critical than 
genetic considerations to the survival of species (Shaffer 1987, Gilpin 
1987). This is especially true for taxa, like the riparian brush rabbit 
and woodrat, that are represented by only one or a few small, isolated 
populations. In such cases, little or no possibility of recolonization 
exists if a chance environmental or human-caused catastrophe affects 
the population. Riparian habitat at Caswell State Park is confined 
entirely within river levees, and offers less habitat value for these 
subspecies during periods of high stream flow. This habitat is 
routinely flooded during the wet winter season. Major flooding likely 
drowns a significant portion of the populations, eliminates foraging 
habitat and shelter for prolonged periods, and exposes brush rabbits 
and woodrats to increased predation by concentrating the population on 
high ground and in areas with little or no cover. Only about 3.6 ha 
(8.9 ac) in five small areas of the 104.5 ha (258 ac) park showed 
regular use by brush rabbits in the summer of 1986 after floods in 
February and March of that year (Williams 1988).
    Williams (1986) found that riparian brush rabbits sometimes gain 
temporary shelter from floods by climbing trees, but he estimated that 
only 10 or fewer individual rabbits survived the severe winter flooding 
in 1985-86 (Williams 1988). Basey (1990) concluded, based on visual 
sightings and pellet surveys, that this same riparian brush rabbit 
population may have been reduced to fewer than 15 to 20 individuals 
during flooding in 1983.
    The floods of January 1997 left about 85 percent of Caswell 
Memorial State Park under 0.6-3.0 m (2-10 ft) or more of water in most 
areas for at least 2 weeks and, in lower areas, for as long as 7 weeks. 
During efforts in January to locate and potentially rescue stranded 
riparian brush rabbits, only a single rabbit pellet was found (D. 
Williams, in litt. 1997). In areas of the park searched visually in 
March 1997, no rabbits or pellets were found, although searchers did 
find two mounds containing fresh grass. Such mounds, or ``forms'' are 
typically made by rabbits. In April 1997, searchers found two rabbit 
fecal pellets, but no other sign of rabbits or woodrat activity. 
Trapping surveys were initiated in early May, well after flood waters 
had receded, in hopes that any surviving rabbits would be located. 
During 22 nights of trapping, no rabbits were caught, one rabbit was 
sighted, and at another location, fresh rabbit tracks were found (D. 
Williams, in litt. 1997). In comparison, during trapping efforts of 
similar intensity in January 1993, 41 brush rabbits were captured and 
several rabbits were sighted (D. Williams, in litt. 1997). A 
significant increase in brush rabbit sign was noted during surveys 
after May 30, 1997, including the finding of four separate groups of 
fecal pellets, two separate groups of dust baths with rabbit tracks, 
about a dozen rabbit runways, and one rabbit sighted by spotlight (P. 
Kelly, San Joaquin Valley Endangered Species Recovery Program, in litt. 
1997a, 1997b). Two sightings were also reported by park visitors (K. 
Graham, California Dept. of Parks and Recreation in Kelley, in litt. 
1997a).
    The riparian woodrat also is vulnerable to flooding, although its 
ability to nest in trees and wood duck nest boxes (Williams 1993) 
suggests some ability to avoid the negative effects of flooding. 
Nonetheless, the large majority of nests occur on the ground (Williams 
1993, pers. comm. 1994). After the January 1997 floods left Caswell 
Memorial State Park under 0.6-3.0 m (2-10 ft) of water for 2 to 7 
weeks, trapping and survey efforts in May 1997 resulted in capture of 
only eight woodrats (D. Williams, in litt. 1997). Trapping efforts of 
similar intensity in 1993 resulted in the capture of 57 woodrats (D. 
Williams, in litt. 1997). Severe flooding could eliminate the Caswell 
Memorial State Park populations of both the riparian brush rabbit and 
the riparian woodrat and result in the extinction of these subspecies.
    Flooding is also likely to increase competition between riparian 
brush rabbits and desert cottontails, a species that occurs in a wider 
range of habitats, including riparian zones, within the same geographic 
area (Basey 1990). Riparian brush rabbits cannot return to their home 
areas if displaced more than about 340 m (1,116 ft). Desert 
cottontails, in contrast, may return home when displaced as much as 4.8 
kilometers (3 miles). Therefore, if displaced by flooding more than 
about 340 m (1,116 ft) from their home areas, riparian brush rabbits 
may be stranded in habitats where desert cottontails have a competitive 
advantage.
    The number of individuals in the sole population of each subspecies 
is now sufficiently low that the effects of inbreeding may result in 
the expression of deleterious genes in the population (Gilpin 1987). 
Deleterious genes reduce individual fitness in various ways, the most 
typical being decreased survivorship of young. Small populations are 
also more at risk due to the effects of genetic drift, a decrease in 
genetic variation due to random changes in gene frequency from one 
generation to the next. This reduction of variability within a 
population limits the ability of that population to adapt to 
environmental changes.
    Although Caswell Memorial State Park provides protection to the 
riparian brush rabbit and the riparian woodrat against some threats, 
the park is also a recreational facility and consequently faces an 
increased threat of human-caused wildfires that may kill both the 
riparian brush rabbit and woodrat and destroy their habitat (Basey 
1990). The

[[Page 62280]]

brushy areas most vulnerable to fire are important habitat for brush 
rabbits and woodrats (Basey 1990). Between 1975 and 1987, 10 wildfires 
were reported within the park. After a large area burned in 1981, no 
evidence of brush rabbits was found in the area (Basey 1990). The 
extent to which recreational activities, such as vehicular and 
pedestrian traffic, dogs, etc., also may affect habitat quality is 
unknown.
    The Service has carefully assessed the best scientific and 
commercial information available regarding the past, present, and 
future threats faced by these subspecies in determining to propose this 
rule. Based on this evaluation, the preferred action is to list the 
riparian brush rabbit (Sylvilagus bachmani riparius) and the riparian 
woodrat (Neotoma fuscipes riparia) as endangered. The single, small 
population of each of these two taxa render them vulnerable to a wide 
array of threats. Increases in human population and pressures 
associated with urban development, as well as the inadequacy of 
existing regulatory mechanisms have led to a significant loss of 
historic habitat and reduced these subspecies to the brink of 
extinction. Both subspecies currently face threats from floods, 
wildfires, and predation. Riparian forests, the habitat type upon which 
the riparian brush rabbit and woodrat depend, are so depleted along the 
San Joaquin River system that all habitat remnants outside of Caswell 
Memorial State Park are too small and isolated to support viable 
populations of these animals. Thus, even if the few remaining 
unsurveyed tracts of habitat do harbor these subspecies, the status of 
the riparian brush rabbit and woodrat would not change and listing of 
these taxa as endangered would be warranted.

Critical Habitat

    Critical habitat is defined in section 3 of the Act as: (i) the 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection and; (ii) specific areas outside the 
geographical area occupied by a species at the time it is listed, upon 
a determination that such areas are essential for the conservation of 
the species. ``Conservation'' means the use of all methods and 
procedures needed to bring the species to the point at which listing 
under the Act is no longer necessary.
    Section 4(a)(3) of the Act, as amended, and implementing 
regulations (50 CFR 424.12) require that, to the maximum extent prudent 
and determinable, the Secretary designate critical habitat at the time 
the species is determined to be endangered or threatened. Service 
regulations (50 CFR 424.12(a)) state that critical habitat is not 
determinable if information sufficient to perform required analyses of 
the impacts of the designation is lacking or if the biological needs of 
the species are not sufficiently known to permit identification of an 
area as critical habitat. Section 4(b)(2) of the Act requires the 
Service to consider economic and other relevant impacts of designating 
a particular area as critical habitat on the basis of the best 
scientific data available. The Secretary may exclude any area from 
critical habitat if he determines that the detriments of such exclusion 
outweigh the conservation benefits, unless to do such would result in 
the extinction of the species. Service regulations (50 CFR 
424.12(a)(1)) state that designation of critical habitat is not prudent 
when one or both of the following situations exist--(1) The species is 
threatened by taking or other human activity, and identification of 
critical habitat can be expected to increase the degree of threat to 
the species, or (2) such designation of critical habitat would not be 
beneficial to the species.
    The Service finds that the designation of critical habitat for the 
riparian brush rabbit and riparian woodrat is not prudent because such 
designation would not provide any additional benefit to the two species 
beyond that conferred by listing them as endangered species. The basis 
for these conclusions, including the factors considered in weighing the 
benefits against the detriments of designation, is explained below.
    As discussed above, the sole site currently occupied by the 
riparian brush rabbit and the riparian woodrat is within Caswell 
Memorial State Park, and no other currently suitable habitat for these 
species is known to exist within their historical ranges (Basey 1990). 
State Park designation provides protection to the natural resources of 
the park, such as through hunting prohibitions, and facilitates 
appropriate resource management. This protection would not be increased 
through critical habitat designation.
    A high potential for Federal involvement exists because of the 
flood control activities of the Corps and water regulation activities 
of the U.S. Bureau of Reclamation (BOR). Section 7 of the Act requires 
that Federal agencies refrain jeopardizing the continued existence of a 
listed species and from contributing to the destruction or adverse 
modification of critical habitat. However, implementing regulations (50 
CFR part 402) define ``jeopardize the continued existence of'' and 
``destruction or adverse modification of'' in virtually identical 
terms. Jeopardize the continued existence of means to engage in an 
action ``that reasonably would be expected . . . to reduce appreciably 
the likelihood of both the survival and recovery of a listed species.'' 
Destruction or adverse modification means an ``alteration that 
appreciably diminishes the value of critical habitat for both the 
survival and recovery of a listed species.'' Common to both definitions 
is an appreciable detrimental effect on both survival and recovery of a 
listed species, in the case of critical habitat by reducing the value 
of the habitat so designated. In this case, because each species exists 
as a single, small population, it is even clearer that any activity 
that would destroy or adversely modify their habitat would also likely 
jeopardize their continued existence. For this reason, designation of 
critical habitat provides no benefit beyond that conferred by listing.

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
activities. Recognition through listing results in public awareness and 
conservation actions by Federal, State, and local agencies, private 
organizations, and individuals. The Act provides for possible land 
acquisition and cooperation with the States and requires that recovery 
actions be carried out for all listed species. The protection required 
of Federal agencies and the prohibitions against taking and harm are 
discussed, in part, below.
    Section 7(a) of the Act requires Federal agencies to evaluate their 
actions with respect to any species that is proposed or listed as 
endangered or threatened and with respect to its critical habitat, if 
any is being designated. Regulations that implement this interagency 
cooperation provision of the Act are codified at 50 CFR part 402. 
Section 7(a)(4) of the Act requires Federal agencies to confer with the 
Service on any action that is likely to jeopardize the continued 
existence of a species proposed for listing or result in destruction or 
adverse modification of proposed critical habitat. If a species is 
listed, section 7(a)(2) requires Federal

[[Page 62281]]

agencies to insure that activities they authorize, fund, or carry out 
are not likely to jeopardize the continued existence of the species or 
to destroy or adversely modify its critical habitat. If a Federal 
action may affect a listed species or its critical habitat, the 
responsible Federal agency must enter into formal consultation with the 
Service.
    Federal actions that may require conference or consultation with 
the Service include the funding or authorization by the Corps of levee 
and channel maintenance projects along the lower San Joaquin River and 
its tributaries and the operation of upstream dams by the Corps and the 
BOR.
    Listing the riparian brush rabbit and riparian woodrat as 
endangered species would also provide for the development of a recovery 
plan (or plans) for the taxa. Such a plan would establish a framework 
for State, Federal, and local governmental efforts to coordinate 
conservation planning for these animals. The plan would set recovery 
priorities and estimate costs of various tasks necessary to accomplish 
them. The plan also would describe site specific management actions 
necessary to achieve conservation and survival of these subspecies.
    The Act and implementing regulations set forth a series of general 
prohibitions and exceptions that apply to all endangered wildlife. 
These prohibitions, codified at 50 CFR 17.21, in part, make it illegal 
for any person subject to the jurisdiction of the United States to take 
(includes harass, harm, pursue, hunt, shoot, wound, kill, trap, 
capture, collect; or to attempt any of these), import or export, ship 
in interstate commerce in the course of commercial activity, or sell or 
offer for sale in interstate or foreign commerce any such species. It 
also is illegal to possess, sell, deliver, carry, transport, or ship 
any such wildlife that has been taken illegally. Certain exceptions 
apply to agents of the Service and State conservation agencies.
    Permits may be issued to carry out otherwise prohibited activities 
involving endangered wildlife under certain circumstances. Regulations 
governing permits are codified at 50 CFR 17.22 and 17.23. Such permits 
are available for scientific purposes, to enhance the propagation or 
survival of the species, and/or for incidental take in connection with 
otherwise lawful activities. Under some circumstances, permits may be 
issued for a specified period for species in trade in order to relieve 
undue economic hardship that would be suffered if such relief were not 
available.
    It is the policy of the Service, published in the Federal Register 
on July 1, 1994 (59 FR 34272), to identify to the maximum extent 
practicable at the time a species is listed those activities that would 
or would not constitute a violation of section 9 of the Act. The intent 
of this policy is to increase public awareness of the effect of this 
listing on proposed and ongoing activities within the range of the two 
species. The Service believes that, based on the best available 
information, the following actions will not result in a violation of 
section 9:
    (1) Possession of legally acquired riparian brush rabbits and 
riparian woodrats;
    (2) Light to moderate livestock grazing in riparian brush rabbit 
and riparian woodrat habitat that prevents or minimizes the 
encroachment of invasive plant species and does not significantly 
reduce shrub cover;
    (3) Federally approved projects, such as those involving the 
discharge of fill material, draining, ditching, tiling, pond 
construction, stream channelization or diversion, or alteration of 
surface or ground water into or out of riparian areas (i.e., due to 
roads, impoundments, discharge pipes, stormwater detention basins, 
etc.), when conducted in accordance with any reasonable and prudent 
measures given by the Service in accordance with section 7 of the Act.
    Activities that the Service believes could potentially harm the 
riparian brush rabbit and the riparian woodrat and result in ``take'' 
include, but are not limited to:
    (1) Unauthorized collecting or handling of the species;
    (2) Unauthorized destruction/alteration of occupied habitat of the 
riparian brush rabbit or riparian woodrat through the discharge of fill 
material, draining, ditching, tiling, pond construction, stream 
channelization or diversion, or the alteration of surface or ground 
water flow into or out of riparian habitat of these two species (i.e., 
due to the construction/installation of roads, impoundments, discharge 
pipes, stormwater detention basins, etc.);
    (3) Any activity constituting a violation of discharge permits 
which results in death of or injury to riparian brush rabbits or 
riparian woodrats or which results in degradation of their occupied 
habitat;
    (4) Burning, cutting, or mowing of riparian vegetation which 
results in death of or injury to riparian brush rabbits or riparian 
woodrats or which results in degradation of their occupied habitat;
    (5) Application of pesticides in violation of label restrictions 
which results in death of or injury to riparian brush rabbits or 
riparian woodrats;
    (6) Discharging or dumping toxic chemicals, silt, or other 
pollutants (i.e., sewage, oil, or gasoline) which results in death of 
or injury to riparian brush rabbits or riparian woodrats;
    (7) Interstate and foreign commerce (commerce across State lines 
and international boundaries) and import/export (as discussed earlier 
in this section) without prior obtainment of an endangered species 
permit. (Permits to conduct these activities are available for purposes 
of scientific research and enhancement of propagation or survival of 
the species.)
    Questions regarding whether specific activities will constitute a 
violation of section 9 should be directed to the Field Supervisor of 
the Service's Sacramento Field Office (see ADDRESSES section). Requests 
for copies of the regulations concerning listed wildlife and general 
inquiries regarding prohibitions and permits may be addressed to the 
U.S. Fish and Wildlife Service, Ecological Services, Endangered Species 
Permits, 911 N.E. 11th Avenue, Portland, Oregon, 97232-4181 (telephone 
503/231-2063; facsimile 503/231-6243).

Public Comments Solicited

    The Service intends that any final action resulting from this 
proposal will be as accurate and as effective as possible. Therefore, 
comments or suggestions from the public, other concerned governmental 
agencies, the scientific community, industry, or any other interested 
party concerning this proposed rule are hereby solicited. The Service 
will also comply with its policy on peer review, published on July 1, 
1994 (59 FR 34270), in the processing of this proposed rule. Comments 
particularly are sought concerning:
    (1) Biological, commercial trade, or other relevant data concerning 
any threat (or lack thereof) to these species;
    (2) The location of any additional populations of these species and 
the reasons why any habitat should or should not be determined to be 
critical habitat as provided by section 4 of the Act;
    (3) Additional information concerning the range, distribution, and 
population size of these species;
    (4) Current or planned activities in the subject area and their 
possible impacts on these species; and,
    (5) Information on biological considerations, land ownership, 
habitat restoration potential, flood control constraints, and other 
factors that may lead to a critical habitat determination.

[[Page 62282]]

    Final promulgation of the regulations for these species will take 
into consideration the comments and any additional information received 
by the Service, and such communications may lead to a final regulation 
that differs from this proposal.
    The Act provides for one or more public hearings on this proposal, 
if requested. Requests must be received within 45 days of the date of 
publication of the proposal in the Federal Register. Such requests must 
be made in writing and be addressed to the Field Supervisor, Sacramento 
Field Office (see ADDRESSES section).

National Environmental Policy Act

    The Fish and Wildlife Service has determined that Environmental 
Assessments and Environmental Impact Statements, as defined under the 
authority of the National Environmental Policy Act of 1969, need not be 
prepared in connection with regulations adopted pursuant to section 
4(a) of the Endangered Species Act of 1973, as amended. A notice 
outlining the Service's reasons for this determination was published in 
the Federal Register on October 25, 1983 (48 FR 49244).

Required Determinations

    The Service has examined this regulation under the Paperwork 
Reduction Act of 1995 and found it to contain no information collection 
requirements.

References Cited

    A complete list of all references cited herein, as well as others, 
is available from the Field Supervisor, Sacramento Field Office (see 
ADDRESSES section).
    Authors. The primary authors of this proposed rule are Peter 
Sorensen and Diane Windham, U.S. Fish and Wildlife Service, Sacramento 
Field Office (see ADDRESSES section), telephone 916/979-2725.

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, Transportation.

Proposed Regulation Promulgation

    Accordingly, the Service hereby proposes to amend part 17, 
subchapter B of chapter I, title 50 of the Code of Federal Regulations, 
as set forth below:

PART 17--[AMENDED]

    1. The authority citation for Part 17 continues to read as follows:

    Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C. 
4201-4245; Pub. L. 99-625, 100 Stat. 3500, unless otherwise noted.

    2. Section 17.11(h) is amended by adding the following, in 
alphabetical order under MAMMALS, to the List of Endangered and 
Threatened Wildlife:


Sec. 17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------
                        Species                                                    Vertebrate                                                           
--------------------------------------------------------                        population where                                  Critical     Special  
                                                            Historic range       endangered or         Status      When listed    habitat       rules   
           Common name                Scientific name                              threatened                                                           
--------------------------------------------------------------------------------------------------------------------------------------------------------
             Mammals                                                                                                                                    
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
Rabbit, riparian brush...........  Sylvilagus bachmani   U.S.A. (CA)........  Entire.............  E               ...........           NA           NA
                                    riparius.                                                                                                           
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
Woodrat, riparian (San Joaquin     Neotoma fuscipes      U.S.A. (CA)........  Entire.............  E               ...........           NA           NA
 Valley).                           riparia.                                                                                                            
                                                                                                                                                        
                   *                  *                  *                  *                  *                  *                  *                  
                                                                                                                                                        
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Dated: October 30, 1997.
Jamie Rappaport Clark,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 97-30553 Filed 11-20-97; 8:45 am]
BILLING CODE 4310-55-P