Thermal physiology and seasonal energetics of eastern bent-winged bats

Abstract

Winter hibernation is a crucial component of the life-history of many insectivorous bats, yet very little is known about the thermal physiology or hibernation ecology of any Australian cave-roosting species. The cave-roosting eastern bent-winged bat (Miniopterus orianae oceanensis) occurs throughout eastern Australia and forms large congregation into a limited set of winter hibernacula. Disturbance or damage to winter roosts or adjacent foraging sites could have large ramifications for the regions' populations and understanding of roost behaviour and habitat requirements is paramount for the conservation of this species. Additionally, Australia's cave-roosting species are predicted to be exposed to the threat of White-nose syndrome and a greater understanding of the species winter ecology is needed to determine the disease' potential impacts on winter survival rates. In this project, we studied the thermal physiology and energetics of Eastern Bent-winged Bats at the Jenolan Caves Karst Reserve in Central NSW. Using temperature-sensitive radio telemetry, we assessed thermoregulation patterns of roosting bats in the wild and bat detectors were used to determine the seasonal variance in nightly activity. In addition, we monitored seasonal changes in body mass by periodically capturing individuals through harp trapping post-sunset. Eastern bent-winged bats were found to use torpor in both the summer and winter with winter bouts lasting up to 12 days in duration and summer torpor patterns being significantly impacted by nightly foraging potential. During winter, body mass for males and females increased by 20.5% and 37.5% of their pre-winter mass respectively and bat activity decreased during the middle of winter when bats were observed to use prolonged torpor. Eastern bent-winged bats' hibernation season and torpor bout duration was shorter than previously observed in many North American species that show high mortality from WNS. Due to more frequent arousal and winter foraging opportunities, eastern bent-winged bats are thus predicted to show reduced levels of mortality from WNS, however a greater understanding of thermal biology, and in particular metabolic rate and water loss when exposed to low air temperatures, and regional variance in winter ecology is needed to determine potential impacts of WNS for the species.

Date of Award	2018
Original language	English