Lit+Review

=Lit Review=

The western pond turtle (//Clemmys marmorata//) formally ranged from northwest British Columbia to northern Baja, California. It is a small turtle, with few distinct markings and a relatively low carapace. While there are thought to be many genetic variations of the western pond turtle, two subspecies are recognized: the northwestern variety (//Clemmys marmorata marmorata//), ranging from San Francisco to eastern Nevada, and the southwestern variety (//Clemmys marmorata pallida//), ranging from south of San Francisco throughout coastal and central California. Sweet Springs Nature Preserve in Los Osos, California is host to the southwestern pond turtle. Due to the similarities in species, habitat, and problems with population decline, analysis of the entire //Clemmys maramorata// species provides a more in depth understanding of the problem, and possible solutions. The pond in Sweet Springs Nature Preserve is a suitable habitat for the southwestern pond turtle, although some issues exist preventing it from being ideal. Lovich writes that “optimal habitat seems to be characterized by the presence of adequate emergent basking sites, emergent vegetation, and the presence of suitable refugia in the form of undercut banks, submerged vegetation, mud, rocks and logs (Holland, 1994).” While there are many of these characteristics at Sweet Springs, there is a severe lack of sunlight reaching the pond due to overhanging eucalyptus trees shading the area. In addition, the pedestrian trails in the area may limit the necessary habitat for the species, as “the availability of suitable terrestrial shelter sites is necessary to provide protection from predators and thermal extremes,” (Lovich, 1999). Nests are usually located along pond margins, but may be over 100m away from the water on hillsides or 2 km downstream if suitable nesting areas are not available. Typical nests of the species are in open, grassy areas with southern exposure (Holland, 1994). Population decline of the western pond turtle has been sudden, and steep. In 1960, southern California hosted 87 known localities of the species, by 1970, this was reduced to 57. In 1987, 53population locations were identified, but only 10 were thought to contain reproductively viable populations (Brattstrom, 1988; Brattstrom and Messer, 1988). In 1992, the Fish and Wildlife Service stated “The greatest single threat to this species is habitat destruction. Over 90 percent of the wetland habitats within the historic range of the species in California alone have been eliminated due to agricultural development, flood control and water diversion projects, and urbanization.” Other threats include invasion of exotic pests and non-native turtles such as the red-eared sliders and painted turtles. These animals out compete the native western pond turtle for food and habitat. Predation from bullfrogs, especially from birth until full maturity, has been shown to limit population of the species (Overtree and Collings, 1997).
 * The Southwestern Pond Turtle**

Sources Brattstrom, B. H. 1988. Habitat destruction on California with special reference to //Clemmys marmorata//: a perspective. pp. 13-24. //In:// H. F. DeLisle, P. R. Brown, B. Kaufman and B. M. McGurty (eds.), Proceedings of the Conference on California Herpetology. Southwestern Herpetological Society, Van Nuys, California.

Brattstrom, B.H. and D.F. Messer. 1988. Current status of the southwestern pond turtle, Clemmys marmorata pallida, in southern California. Final Report for California Department of Fish and Game, Contract C-2044. 47 pp. + xii.

Fish and Wildlife Service. 1992. Endangered and threatened wildlife and plants; 90-day finding and commencement of status reviews for a petition to list the western pond turtle and California red-legged frog. Fed. Reg. 57:45761-45762.

Holland, D.C. 1994. The western pond turtle: habitat and history. U.S. Department of Energy, Bonneville Power Administration, Portland, Oregon. 11 chapters + appendices.

Lovich, Jeff. Western Pond Turtle. Rep. United States Geological Survey, UC Davis, 1999. 

Overtree, L.; Collings, G. 1997. Western pond turtles in the Kern Valley region. The Tortuga Gazette 33:1-2.