Sacramento Fish & Wildlife Office
Species Account
BUENA VISTA LAKE SHREW
(Sorex ornatus relictus)
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About usCLASSIFICATION: Federal Endangered Species (Federal Register 67:10101 (pdf); March 6, 2002)
CRITICAL HABITAT: Designated in Federal Register 70:3438 (pdf); January 24, 2005 (84 acres in Kern Co.)
RECOVERY PLAN: Recovery plan for the upland species of the San Joaquin Valley, California, September 30. 1998 (pdf)
DESCRIPTION
The Buena Vista Lake shrew (Sorex ornatus relictus) is one of nine subspecies of ornate shrew (Sorex ornatus) known to occur in California. Ornate shrews are primarily insectivorous (insect-eating) mammals that are the approximate size of a mouse. Shrews make up the family Soricidae.
Shrews have a long snout, tiny bead-like eyes, ears that are concealed, or nearly concealed, by soft fur, and five toes on each foot. They are active day or night. When they are not sleeping, they are searching for food, namely insects and other small invertebrates. Shrews eat more than their own weight each day to avoid starvation and maintain their body weight at high rates of metabolism. The specific feeding and foraging habits of the Buena Vista Lake shrew are unknown.
The Buena Vista Lake shrew's back is predominantly black with a buffy-brown speckling pattern, its sides are more buffy-brown than the upper surface, and its underside is smoke-gray. The tail is faintly bicolor and blackens toward the end both above and below. The Buena Vista Lake shrew grows to around 4 inches in total length, including a tail of about 1.5 inch. Adults weigh 0.14-0.27 ounce.
Little is known about the reproduction or demography of this subspecies. It lives in dense vegetation around the perimeter of marshes, lakes or sloughs. The breeding season may begin in autumn and end in May or June. Up to two litters of four to six young are produced per year.
DISTRIBUTION
The Buena Vista Lake shrew formerly occupied the marshlands of the San Joaquin Valley and the Tulare Basin. Its range has become much restricted due to the loss of lakes and sloughs in the area. It has been recorded from the Kern Lake Preserve area and the Kern National Wildlife Refuge. Current distribution is unknown but likely to be very restricted due to the loss of habitat.
THREATS:
Loss and fragmentation of habitat seem to be the main causes of decline of the Buena Vista Lake shrew. Conversion of historical range to agricultural land has sharply reduced the available habitat. The Kern Lake Preserve was formerly managed by the Nature Conservancy, but has now reverted to private management.
The only known population of Buena Vista Lake shrews is vulnerable to the risks associated with small, restricted populations. Impacts to species populations that can lead to extinction include the loss or alteration of essential elements, such as habitat or food, the introduction of limiting factors into the environment, such as poison or predators, and catastrophic random changes or environmental perturbations, such as floods, droughts or disease.
REFERENCES FOR ADDITIONAL INFORMATION
Brown, N.L. C. D. Johnson, and D.F. Williams. Endangered Species Recovery Program Species Account.
U.S. Fish and Wildlife Service. 1998. Recovery plan for the upland species of the San Joaquin Valley, California, September 30. 1998 (pdf). Region 1, Portland, OR.
U.S. Fish and Wildlife Service. 2002. Endangered and threatened wildlife and plants; Endangered Status for the Buena Vista Lake Shrew (Sorex Ornatus Relictus) (text) (pdf). Federal Register 67:10101-10113.
