Endangered and Threatened Wildlife and Plants; Reopening of the Comment Period on the Proposed Endangered Status of the Sierra Nevada Distinct Population Segment of the California Bighorn Sheep

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AF59

Endangered and Threatened Wildlife and Plants; Reopening of the

Comment Period on the Proposed Endangered Status of the Sierra Nevada

Distinct Population Segment of the California Bighorn Sheep

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; notice of reopening of comment period.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), pursuant to

the Endangered Species Act of 1973, as amended (Act), provide notice of

the reopening of the comment period for the proposed endangered status

for the Sierra Nevada distinct population segment of California bighorn

sheep (Ovis canadensis californiana). The comment period has been

reopened in response to a request from the Foundation for North

American Wild Sheep and to conduct a peer review of the proposed rule.

DATES: Comments from all interested parties must be received by October

15, 1999.

ADDRESSES: Written comments, materials, data, and reports concerning

this proposal should be sent to the Supervisor, Ventura Fish and

Wildlife Office, 2493 Portola Road, Suite B, Ventura, California 93003.

Comments and materials received will be available for public

inspection, by appointment, during normal business hours, at the above

address.

FOR FURTHER INFORMATION CONTACT: Carl Benz, at the address listed above

(telephone 805/644-1766; facsimile 805/644-3958).

SUPPLEMENTARY INFORMATION:

Background

The bighorn sheep (Ovis canadensis) is a large mammal (family

Bovidae) originally described by Shaw in 1804 (Wilson and Reeder 1993).

Several subspecies of bighorn sheep have been recognized on the basis

of geography and differences in skull measurements (Cowan 1940;

Buechner 1960). These

[[Page 52758]]

subspecies of bighorn sheep, as described in these early works, include

O.c. cremnobates (Peninsular bighorn sheep), O.c. nelsoni (Nelson

bighorn sheep), O.c. mexicana (Mexican bighorn sheep), O.c. weemsi

(Weems bighorn sheep), O.c. californiana (California bighorn sheep),

and O.c. canadensis (Rocky Mountain bighorn sheep). However, recent

genetic studies question the validity of some of these subspecies and

suggest a need to re-evaluate overall bighorn sheep taxonomy. For

example, Sierra Nevada bighorn sheep appear to be more closely related

to desert bighorn sheep than the O.c. californiana found in British

Columbia (Ramey 1991, 1993). Regardless, the Sierra Nevada bighorn

sheep meets our criteria for consideration as a distinct vertebrate

population segment (as discussed below) and are treated as such in this

final rule.

The historical range of the Sierra Nevada bighorn sheep (Ovis

canadensis californiana) includes the eastern slope of the Sierra

Nevada, and, for at least one subpopulation, a portion of the western

slope, from Sonora Pass in Mono County south to Walker Pass in Kern

County, a total distance of about 346 kilometers (km) (215 miles (mi))

(Jones 1950; Wehauser 1979, 1980). By the turn of the century, about 10

out of 20 subpopulations survived. The number dropped to five

subpopulations at mid-century, and down to two subpopulations in the

1970s, near Mount Baxter and Mount Williamson in Inyo County (Wehauser

1979). Currently, five subpopulations of Sierra Nevada bighorn sheep

occur at Lee Vining Canyon, Wheeler Crest, Mount Baxter, Mount

Williamson, and Mount Langley in Mono and Inyo Counties, three of which

have been reintroduced using sheep obtained from the Mount Baxter

subpopulation from 1979 to 1986 (Wehausen et al. 1987).

The Sierra Nevada bighorn sheep is similar in appearance to other

desert associated bighorn sheep. The species' pelage shows a great deal

of color variation, ranging from almost white to fairly dark brown,

with a white rump. Males and females have permanent horns; the horns

are massive and coiled in males, and are smaller and not coiled in

females (Jones 1950; Buechner 1960). As the animals age, their horns

become rough and scarred with age, and will vary in color from

yellowish-brown to dark brown. In comparison to many other desert

bighorn sheep, the horns of the Sierra Nevada bighorn sheep are

generally more divergent as they coil out from the base (Wehausen

1983). Adult male sheep stand up to a meter (m) (3 feet (ft)) tall at

the shoulder; males weigh up to 99 kilograms (kg) (220 pounds (lbs))

and females 63 kg (140 lbs) (Buechner 1960).

The current and historical habitat of the Sierra Nevada bighorn

sheep is almost entirely on public land managed by the U.S. Forest

Service, Bureau of Land Management, and National Park Service. The

Sierra Nevada is located along the eastern boundary of California, and

peaks vary in elevation from 1825 to 2425 m (6000 to 8000 ft)) in the

north, to over 4300 m (14,000 ft) in the south adjacent to Owens

Valley, and then drop rapidly in elevation in the southern extreme end

of the range (Wehausen 1980).

Sierra Nevada bighorn sheep inhabit the alpine and subalpine zones

during the summer, using open slopes where the land is rough, rocky,

sparsely vegetated and characterized by steep slopes and canyons

(Wehausen 1980; Sierra Nevada Bighorn Sheep Interagency Advisory Group

(Advisory Group) 1997). Most of these sheep live between 3,050 and

4,270 m (10,000 and 14,000 ft) in elevation in summer (John Wehausen,

University of California, White Mountain Research Station, pers. comm.

1999). In winter, they occupy high, windswept ridges, or migrate to the

lower elevation sagebrush-steppe habitat as low as 1,460 m (4,800 ft)

to escape deep winter snows and find more nutritious forage. Bighorn

sheep tend to exhibit a preference for south-facing slopes in the

winter (Wehausen 1980). Lambing areas are on safe precipitous rocky

slopes. They prefer open terrain where they are better able to see

predators. For these reasons, forests and thick brush usually are

avoided if possible (J. Wehausen, pers. comm. 1999).

Bighorn sheep are primarily diurnal, and their daily activity show

some predictable patterns that consists of feeding and resting periods

(Jones 1950). Bighorn sheep are inherently grazers; however, they may

browse woody vegetation when it is growing and very nutritious. They

are opportunistic feeders selecting the most nutritious diet from what

is available.

Sierra Nevada bighorn sheep are gregarious, with group size and

composition varying with gender and from season to season. Spatial

segregation of males and females occurs outside the mating season, with

males more than two years old living apart from females and younger

males for most of the year (Jones 1950; Cowan and Geist 1971; Wehausen

1980). Ewes generally remain in the same band into which they were born

(Cowan and Geist 1971). During the winter, Sierra Nevada bighorn sheep

concentrate in those areas suitable for wintering, preferably Great

Basin habitat (sagebrush steppe) at the very base of the eastern

escarpment.

All five subpopulations of this species are threatened by mountain

lion (Puma concolor) predation, disease, and random, naturally-

occurring events.

We published an emergency rule to list the Sierra Nevada distinct

population segment of California bighorn sheep as endangered on April

20, 1999 (64 FR 19300), as well as a proposed rule to list the species

as endangered on that same date (64 FR 19333). The original comment

period closed on June 21, 1999. In a memo dated June 16, 1999, the

Foundation for North American Wild Sheep requested that the comment

period be extended to allow us to consider additional information

regarding the Sierra Nevada bighorn sheep. In addition, we will also

conduct a peer review of this proposal and solicit the opinions of

three appropriate and independent specialists regarding the data,

assumptions, and supportive information presented for the Sierra Nevada

bighorn sheep, per our Interagency Cooperative Policy for Peer Review

in Endangered Species Act Activities (59 FR 34270).

References Cited

A complete list of references cited in this rule is available upon

request from the Ventura Fish and Wildlife Office of the U.S. Fish and

Wildlife Service (see ADDRESSES section).

Author

The primary author of this notice is Barbara Behan of the Regional

Office, U.S. Fish and Wildlife Service, 911 N.E. 11th Avenue, Portland,

Oregon 97232-4181 (telephone 503/231-6131).

Authority

The authority of this action is the Endangered Species Act of 1973,

as amended (16 U.S.C. 1531 et seq.).

Dated: September 24, 1999.

Elizabeth H. Stevens,

Acting Manager, California/Nevada Operations Office, Fish and Wildlife

Service.

[FR Doc. 99-25466 Filed 9-29-99; 8:45 am]

BILLING CODE 4310-55-P