Trends in Abundance of Hibernating Bats in a Karst Region of the Southern Great Plains

Abstract

We analyzed temporal variation in abundance of hibernating bats from long-term records (1965-2004) in gypsum caves of the Red Hills of Kansas and Oklahoma, a region lying at peripheries of geographic ranges of four species of bats. Nonparametric correlation analyses were used to evaluate variation in abundances of five species among 12 hibernacula. Townsend's big-eared bat (Corynorhinus townsendii) showed no significant change in abundance among most of its hibernacula, but exhibited one increase and one decrease in abundance in two hibernacula. The cave myotis (Myotis velifer) displayed increasing abundance in some hibernacula (27% of hibernacula, n 5 3) and one decrease (9% of hibernacula, n 5 1). The tri-colored bat (Perimyotis subflavus) exhibited increasing abundance in 60% (n 5 6) of its hibernacula. The pallid bat (Antrozous pallidus) and big brown bat (Eptesicus fuscus) exhibited no statistically significant change in size of population in any hibernaculum, although the pallid bat occurred infrequently and in low numbers (#11 individuals) in the hibernaculum where it was detected. The changes in abundance we detected may reflect range expansions of some species (e.g., tri-colored bat) or changes in qualities of hibernacula or other aspects of habitats, but underlying mechanisms are unknown.