Activity patterns of bats at house roosts near Adelaide

Abstract

Activity patterns of bats in rural areas near Adelaide (South Australia) were monitored systematically at one roost (holding Mormopterus planiceps) and episodically at two others (holding Chalinolobus morio and Nyctophilus geoffroyi) from March 1999 to March 2001. Bats were active from about late August to mid May, and left roosts each night about half an hour after sunset. Exit times were 15 min (mean) for M. planiceps (66 nights), 27-40 min for C. morio (4 nights) and 13-20 min for N. geoffroyi (3 nights), with significant correlation between numbers of M. planiceps exiting and sunset temperatures. M. planiceps were active near the roost before midnight, with very little activity after midnight. C. morio were active near the roost over the whole of some evenings. Most N. geoffroyi activity near the roost was recorded as bats returned just before sunrise and as they left after sunset, with low activity near the roost overnight. Temperatures were logged hourly in two roosts, and exceeded 40°C on some days. Visual observations showed that C. morio were sometimes located in different positions in the roost, and that they vacated the house roost over winter.