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NATURAL HISTORY

BUENA VISTA LAKE ORNATE SHREW } Sorex ornatus relictus
FAMILY: Soricidae

The Buena Vista Lake ornate shrew is one of nine subspecies of ornate shrew occurring in the United States, and one of eight in California. Its lower-elevation wetland habitat is entirely surrounded by that of the Southern California ornate shrew. Though introgression between the two subspecies has not been documented, the latter has hybridized with the Suisun Marsh ornate shrew.

DESCRIPTION: The shrew is about five inches long, including tail, and weighs as much as a quarter (0.14 ounces). It has small, beady eyes, a long snout, five toes on each foot, and a scaly tail covered with very short hair. Its ears are visible but covered in hair. Its upper side is covered in black fur with brown spots and its underside is smoky gray.

HABITAT: The Buena Vista Lake ornate shrew occurs in moist areas with a dense riparian understory and a well-developed overstory. The moisture and vegetative cover in such habitats support abundant and diverse populations of shrew prey species.

RANGE: The Buena Vista Lake ornate shrew is endemic to the southern Tulare Basin in California. Its exact historic range is not known because most of its habitat was destroyed before it was discovered in 1932. It is presumed to have occurred throughout the 957,000 acres of wetlands and riparian areas that once surrounded Tulare, Buena Vista, Kern, and Goose Lakes. Today only four tiny populations are known at Gator Pond (within the former Kern Lake Preserve), Kern National Wildlife Refuge, Cole Levee Ecological Preserve, and the Kern Fan recharge area.
MIGRATION: The species does not migrate.

BREEDING: Breeding season begins in February or March and ends with the onset of the dry season in May or June. Females give birth to two litters of four to six young per year.

LIFE CYCLE: The Buena Vista Lake ornate shrew likely lives less than a year. It appears to be solitary except during the breeding season.

FEEDING: Like all shrews, the Buena Vista Lake ornate shrew has an amazing metabolic rate, eating more than its own weight in aquatic and terrestrial insects and other invertebrates each day. To meet its nutritional needs, it hunts around the clock. The vast quantities of plant consumers and pollinators eaten by shrews contribute to the unique structure and successional patterns of wetland ecosystems. In addition to insects, shrews eat slugs, spiders, centipedes, snails, and earthworms.

THREATS: Water diversion, agricultural expansion, pesticide spraying, selenium poisoning, and drought continue to threaten the shrew.

POPULATION TREND: Historic population numbers are not known, but 1999 surveys found seven shrews in Kern National Wildlife Refuge, nine in Cole Levee Ecological Preserve, and five along the Kern Fan. Twenty-five individuals, comprising the largest known population, have been seen in a small pond without guaranteed water flow called Gator Lake.

Photo © B. Moose Peterson