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

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

osal 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

od 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)

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

ion 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

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

(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

) 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

es (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

heir

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

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

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

Summary of Factors Affecting the Species

sing 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

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)

ity 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

fore 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

gricultural 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)

remia 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

on 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

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

solated

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

rush 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)

ur 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

ndividual 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

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

h 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

ans 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

he 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 . .

ce 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

n 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

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

n 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

FR 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;

es, 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;

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;

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.

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

ulation

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.

egulation 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