SEASONAL-VARIATION IN USE OF CAVES BY THE ENDANGERED OZARK BIG-EARED BAT (CORYNORHINUS-TOWNSENDII-INGENS) IN OKLAHOMA

We searched 19 caves, including known maternity roosts and hibernacula , in Adair and Delaware counties, Oklahoma, for the federally endanger ed Ozark big-eared bat (Corynorhinus townsendii ingens) on eight occas ions in 1989 and 1990. The same caves, and usually the same roost site s within caves, were used during summers as maternity roosts and durin g winters as hibernacula. An additional cave was used by large numbers of big-eared bats (>120 individuals) during spring and autumn of both years; this cave may serve as a transient roost and swarming site. At least one Ozark big-eared bat was found in 17 of 19 caves during one of the eight surveys; none was found in two caves during any survey. N umbers of bats using hibernacula varied markedly among November, Decem ber and February surveys, and we infer that Ozark big-eared bats were active during winter. Because big-eared bats move among hibernacula, a ccurate estimates of winter populations based on a single survey may n ot be possible.