Individual and population-level variability in diets of pallid bats (Antrozous pallidus)

Abstract

At 2 locations in California (coastal, Tocaloma; desert, Caliente), analysis of feces presented a significantly higher number of prey types for the diets of Antrozous pallidus than analysis of culled parts of prey. Analysis of diet by culled parts was biased toward larger, harder prey, and some softer, smaller prey were missed altogether. Observation of individuals feeding revealed that some bats ate prey without culling any parts, whereas others culled only the hardest and largest parts. Analysis of feces from tagged adult male pallid bats from Tocaloma (1993-1994) and Caliente (1994-1995) suggested that bats were generalists, but whereas diets of individuals at Caliente reflected the average diet for the group, none of the individuals at Tocaloma ate the average diet. Variation in the diets or A. pallidus reflects prey availability and individual foraging behavior. Tocaloma bats did not significantly change their diets throughout summer; Caliente bats did. Bats from Caliente and Tocaloma ate different prey than arthropods caught in pit traps, suggesting that bats in both populations were selective foragers. In captivity, hunting A. pallidus took flying and non-flying prey. Some flying prey were forced against a surface before capture, adding a novel dimension to the range of behavior involved in "gleaning".