endemic to a single state or province

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (<100-250 square km (less than about 40-100 square miles)) Historical range probably included the extensive riaprian forests along major streams flowing onto the floor of the northern San Joaquin Valley, California (USFWS 2000). Currently known only from Caswell Memorial State Park; apparently extirpated from the Sacramento-San Joaquin Delta and from most of riparian zone along the lower San Joaquin River and its tributaries; surveys conducted in all potential habitat along the Merced, San Joaquin, Stanislaus, and Tuolumne rivers failed to locate any additional populations (Williams 1988).

Historic Range:
U.S.A. (CA)

Lectotype for Sylvilagus bachmani bachmani
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Unknown;
Preparation: Skin; Skull
Collector(s): W. Trowbridge
Year Collected: 1853
Locality: Near San Francisco, Monterey County, California, United States, North America

Comments: Riparian forest with a dense shrub layer; dense thickets (e.g., wild rose, willows, blackberries) close to the San Joaquin River (Orr 1940).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 5

Comments: One known occurrence.

1 - 1000 individuals

Comments: Recent peak population estimates range from 170 to 608 individuals over an area of 198 acres (Williams 1993). After the 1997 flood, only one individual has been trapped (USFWS 2000).

United States

Rounded National Status Rank: N1 - Critically Imperiled

Rounded Global Status Rank: T1 - Critically Imperiled

Reasons: One very small population exists in remnant riparian forest habitat in the San Joaquin Valley, California; negatively impacted by ongoing riparian habitat destruction.

Current Listing Status Summary

Status: Endangered
Date Listed: 02/23/2000
Lead Region:   California/Nevada Region (Region 8) 
Where Listed:


Population detail:

Population location: entire
Listing status: E

For most current information and documents related to the conservation status and management of Sylvilagus bachmani riparius , see its USFWS Species Profile

Global Short Term Trend: Relatively stable (=10% change)

Comments: Flooding in January 1997 inundated 80% of Caswell Memorial State Park for three weeks, and few captures or sighting have been made in subsequent surveys (USFWS 2000).

Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species

Comments: Has been negatively impacted by habitat destruction; probably over 90% of the historical habitat has been destroyed as a result of agricultural activities, urbanization, and flood control activities. These impacts are ongoing. The narrow remaining riparian habitat, confined between the river and a levee, provides few if any refuges during winter flooding, probably exposing the population to catastrophic mortality through drowning, reducing the availability of foraging habitat, and exposing the population to increased predation when rabbits are forced into areas with little cover. The level of threat posed by disease or predators is unknown. Grazing by livestock in the riparian zone outside the state park is contributing to the elimination and degradation of rabbit habitat. The use of rodenticides inside and outside the park, and brush-destroying fires, are additional threats. Widespread urban development is rapidly reducing the potential for habitat restoration. Vulnerable to the usual threats posed by small population size.

Management Requirements: See "Draft recovery plan for upland species of the San Joaquin Valley, California," available in September 1997 (U.S. Fish and Wildlife Service, Sacramento, California; 916-979-2725).

Global Protection: Few (1-3) occurrences appropriately protected and managed

Comments: All currently occupied habitat is in Caswell Memorial State Park, but in general there is inadequate protection of riparian habitat in the region (due, for example, to farming/forestry/maintenance exemptions from section 404 of the CWA).

Needs: Protect the population in Caswell Memorial State Park. Promote the protection and restoration of riparian vegetation.