Gambelia sila

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA SQUAMATA CROTAPHYTIDAE

Scientific Name: Gambelia sila
Species Authority: (Stejneger, 1890)
Common Name(s):
English Blunt-nosed Leopard Lizard, San Joaquin Leopard Lizard
Synonym(s):
Gambelia silus (Stejneger, 1890) [orth. error]
Taxonomic Notes: Gambelia sila was previously placed in the genus Crotaphytus. Except in recent literature, the spelling of the specific name usually has been given as "silus". See Jennings (1995) for an explanation of the spelling change. An isolated population of putative hybrid (G. sila x G. wislizenii) origin has been reported in the Cuyama River drainage system southwest of the southern end of the San Joaquin Valley; apparently hybrids are no longer extant, as a result of habitat loss and local extirpation (Jennings 1995).

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(ii,iii,iv,v)c(iv) ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Hammerson, G.A.
Reviewer(s): Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)
Justification:
Listed as Endangered, because: its area of occupancy is less than 500 kmĀ²; its distribution is severely fragmented, and there is continuing decline in its area of occupancy, in the extent and quality of its habitat, in the number of locations, and in the number of mature individuals; and because there are extreme fluctuations in the number of mature individuals.
History:
1996 Endangered
1996 Endangered
1994 Endangered (Groombridge 1994)
1990 Endangered (IUCN 1990)
1988 Endangered (IUCN Conservation Monitoring Centre 1988)
1986 Endangered (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description:This species is endemic to California in the United States. The historical range encompassed the San Joaquin Valley and adjacent foothills of southern California, from Stanislaus County to extreme northern Santa Barbara and Ventura counties, at elevations below 800 m (2,600 feet) (Jennings 1995, USFWS 1998). The currently known occupied range includes scattered parcels of undeveloped land on the floor of the San Joaquin Valley and in the foothills of the Coast Range (see USFWS 1998 for further details). In the northern part of the San Joaquin Valley, Blunt-nosed Leopard Lizards have been found in the Firebaugh and Madera Essential Habitat Areas (Williams 1990). Other northern locations include the Ciervo, Tumey, and Panoche Hills, Anticline Ridge, Pleasant Valley, and the Lone Tree, Sandy Mush Road, Whitesbridge, Horse Pasture, and Kettleman Hills Essential Habitat Areas. In the southern San Joaquin Valley, known extant populations exists in the following locations: Pixley National Wildlife Refuge, Liberty Farm, Allensworth, Kern National Wildlife Refuge, Antelope Plain, Buttonwillow, Elk Hills, and Tupman Essential Habitat Areas; on the Carrizo and Elkhorn Plains; north of Bakersfield around Poso Creek; in western Kern County in the area around the towns of Maricopa, McKittrick, and Taft; at the Kern Front oil field; at the base of the Tehachapi Mountains on Tejon Ranch; and just west of the California Aqueduct on the Tejon and San Emizdio Ranches (USFWS 1998). The species is presumed to be extant in the upper Cuyama Valley (USFWS 1998). The distribution approaches that of Gambelia wislizenii in the Cuyama Valley drainage, where wislizenii occurs above 1,100 m and sila occurs below 790 m (see McGuire 1996).
Countries:
Native:
United States (California)
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: There are not many more than a few dozen distinct populations. The total population size is unknown but probably includes more than 1,000 adults. The species had been eliminated from 94% of the original range since the mid-1800s (Jennings 1995). Populations fluctuate greatly with environmental conditions, so determination of the trend in abundance is difficult. However, the extent of occurrence and area of occupancy have probably continued to decrease.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This species inhabits semi-arid grasslands, alkali flats, low foothills, canyon floors, large washes, and arroyos, usually on sandy, gravelly, or loamy substrate, sometimes on hardpan. It is common where there are abundant rodent burrows, and rare or absent in dense vegetation or tall grass. Habitats in order of decreasing favourability: 1) clump grass and saltbush grassland, with sandy soil, 2) washes with brush, in grassland, with sandy soil, 3) alkali flats, with saltbush in sandy or gravelly soil, and 4) grassland with hardpan soil. See Warrick et al. (1998) for additional habitat information. This lizard cannot survive on lands under cultivation (it may use edges adjacent to suitable habitat); repopulation of an area after tilling ends requires at least 10 years. It basks on kangaroo rat mounds and often seeks cover at the base of shrubs, in the burrows of small mammals, or in rock piles. Adults may excavate shallow burrows for shelter but depend on deeper burrows of rodents for hibernation (and egg laying). Eggs typically are laid in an abandoned rodent burrow, at a depth of about 50 cm (US Fish and Wildlife Service 1980).
Systems: Terrestrial

Threats [top]

Major Threat(s): Its distribution and abundance have been greatly reduced, and populations are now severely fragmented, due primarily to loss of habitat to urbanization, water development projects, and agricultural development; intensive mineral development, off-road vehicle activity, pesticide application (for ground squirrels), overgrazing, and flooding also have been detrimental (USFWS 1998). Thick cover of non-native grasses degrades the habitat in some years and locations (Germano and Williams 2005). These lizards use mammal burrows for shelter, so activities that compact soil or crush burrows should be avoided. Habitat disturbance, destruction, and fragmentation continue as the greatest threats to Blunt-nosed Leopard Lizard populations (USFWS 1998).

Conservation Actions [top]

Conservation Actions: Surveys of known and potential habitat should attempt to determine the presence and abundance of blunt-nosed leopard lizards throughout the range (USFWS 1998). An effort should be made to determine appropriate habitat management and compatible land uses (USFWS 1998). Remaining populations on public and private land should be protected, as should additional suitable habitat for the species (see Recovery Plan, USFWS 1998). It occurs in a number of protected areas.

Bibliography [top]

Baillie, J. and Groombridge, B. (eds). 1996. 1996 IUCN Red List of Threatened Animals. pp. 378. International Union for Conservation of Nature, Gland, Switzerland and Cambridge, UK.

Germano, D.J. and Williams, D.F. 2005. Population ecology of blunt-nosed leopard lizards in high elevation foothill habitat. Journal of Herpetology 39: 1-18.

Groombridge, B. (ed.). 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 1990. 1990 IUCN Red List of Threatened Animals. Gland, Switzerland and Cambridge, UK.

IUCN. 2007. 2007 IUCN Red List of Threatened Species. Available at: www.iucnredlist.org. (Accessed: 12th September 2007).

IUCN Conservation Monitoring Centre. 1986. 1986 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN Conservation Monitoring Centre. 1988. 1988 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

Jennings, M.R. 1995. Gambelia sila. Catalogue of American Amphibians and Reptiles 612: 1-4.

Jennings, M.R. and Hayes, M.P. 1994. Amphibian and reptile species of special concern in California. Final Report submitted to the California Department of Fish and Game, Inland Fisheries Division, Rancho Cordova. Contract No. 8023. 255 pp.

McGuire, J.A. 1996. Phylogenetic systematics of crotaphytid lizards (Reptilia: Iguania: Crotaphytidae). Bulletin of Carnegie Museum of Natural History 32: 1-143.

Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians. Third Edition. Houghton Mifflin Company, Boston, Massachusetts.

U.S. Fish and Wildlife Service (USFWS). 1980. Selected vertebrate endangered species of the seacoast of the United States - Blunt-nosed leopard lizard. FWS/OBS-80/01.2, Slidell.

U.S. Fish and Wildlife Service (USFWS). 1998. Recovery plan for upland species of the San Joaquin Valley, California. U.S. Fish and Wildlife Service, Portland, Oregon.

Warrick, G.D., Kat, T.T. and Rose, B.R. 1998. Microhabitat use and home range characteristics of blunt-nosed leopard lizards. Journal of Herpetology 32: 183-191.

Williams, D.F 1990. Assessment of potential habitat for the blunt-nosed leopard lizard and San Joaquin kit fox in western Madera County, California. US Fish and Wildlife Service, Endangered Species Office, Sacramento, California.


Citation: Hammerson, G.A. 2007. Gambelia sila. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 22 August 2014.
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