Thermoregulatory strategies in the heat varies among Australian insectivorous bats

Despite the threat of global warming, few studies have investigated inter- and intra-specific thermoregulatory variation in bats at high temperatures. Those from Europe and Africa suggest that individuals from warmer roosts tolerate higher temperatures than those from comparatively cooler roosts. However, because comparable data are lacking, it remains unclear whether these patterns apply more generally. We predicted that bats occupying cooler roosts (e.g., tree-cavities) would initiate evaporative cooling at lower air temperatures compared to those from warmer roosts (e.g., bark). We also predicted that, compared to males, females would: (a) have higher heat tolerance limits, and (b) be more conservative with water due to their warmer roost preferences during the breeding season. We conducted flow-through respirometry experiments in an Australian semi-arid ecosystem to make inter-specific comparisons of males from five bat species (Chalinolobus gouldii, Vespadelus vulturnus, Nyctophilus geoffroyi, N. corbeni, and Ozimops petersi), and intra-specific thermoregulatory patterns within C. gouldii, V. vulturnus and N. geoffroyi. Our results indicate that both inter and intra-specifically, the use of warmer, thermally unbuffered roosts is positively correlated with higher heat tolerance limits and greater evaporative cooling capacities. Understanding this variation can improve conservation decisions in ecosystems under the greatest threat of global warming.