Nocturnal Activity of Insectivorous Bats Relative to Temperature and Prey Availability in Tropical Queensland

Abstract

The flight activity of insectivorous bats from two high-altitude regions in coastal north Queensland was measured over three years at irregular intervals and at night temperatures ranging from 7.3 to 26.8°C. During the latter part of the study, potential insect prey were light-trapped from one of the study areas. For all but one of the 353 records of bats obtained in 166 surveys, ambient temperatures exceeded 15°C. The dry weights of light-trapped insects were significantly reduced when night minimum temperatures were below 16°C. This study shows that high-altitude areas in Australia's tropics have a bat activity pattern similar to that recorded in temperate areas, and that the drop in winter bat activity is presumably a response to the lack of insects caused by cool temperatures. The period between birth and weaning exhibited by many bat species coincides with that part of the year when minimum night temperatures exceed 15°C. Cognizance of this behavioural pattern is necessary in the study of bat communities in montane regions of Australia's tropics.