Meeting Abstract

73.1  Saturday, Jan. 5  Population Structure and Life History of Western Pond Turtles, Actinemys marmorata, in Lentic Habitats in the Trinity River Basin, CA SLOAN, L.M.*; MARKS, S.B; Humboldt State University; Humboldt State University lmsloan@alaska.edu

As populations of a species decline, an understanding of the regional variation in population health can aid in focusing conservation efforts. Over the past century Western Pond Turtle (Actinemys marmorata) populations have declined throughout much of their range (Baja California through Washington) as a result of habitat loss, overexploitation, introduced species, and water course alterations. The Trinity River, in northwestern California, has been modified from its natural state by damming and flow regulations; these alterations have decreased river quality for turtles. We investigated the health of Western Pond Turtle populations in alternative, lentic habitats adjacent to the Trinity River and its tributaries using four indicators of population health: 1) age structure, 2) size structure, 3) adult size, and 4) growth rate of young turtles. Of six lentic habitats sampled, four were biased towards large, old turtles. These habitats had prolific Bullfrog populations, while the other two sites lacked Bullfrogs. Given that Bullfrogs will eat hatchling turtles, it appears that Bullfrogs are inhibiting turtle recruitment. The same four lentic habitats also had turtles with faster growth rates and larger adult sizes, likely a result of warmer water temperatures. Overall, conservation efforts should focus on creating or preserving ephemeral lentic habitats that dry in late summer; turtles and native anurans do not require permanent water, but Bullfrog larvae usually take two years to metamorphose.