Meeting Abstract

S10.2  Friday, Jan. 7  Hibernation and torpor in tropical and subtropical bats GEISER, Fritz*; STAWSKI, Clare; Univ. of New England, Armidale, Australia fgeiser@une.edu.au

Torpor, the most effective means for energy conservation available to endotherms, was traditionally viewed as a highly specific adaptation of a few high latitude, cold climate endotherms with no function in warm regions. It is now established that many diverse endotherms from low latitudes (0-30º), including species from tropical/subtropical regions, employ torpor. Use of torpor is especially important for bats because they are small, have a high energy expenditure when active, rely on a fluctuating food supply, and have a limited capacity for fat storage. Daily torpor is employed by several small nectarivorous/frugivorous megabats from the tropics and subtropics. Hibernation (a sequence of multiday torpor bouts) has been observed in subtropical tree-dwelling vespertilionids and cave-dwelling hipposiderids. Short bouts of torpor in summer (functionally different from daily torpor), interrupted by arousal and foraging, are common in tropical/subtropical insectivorous bats especially when ambient temperatures (Ta) are high or fluctuate, and even when insects are abundant. Interestingly and against predictions, these summer torpor episodes are most pronounced in subtropical long-eared bats in good body condition, suggesting that torpor is not only used for energy conservation, but also to minimize foraging requirements and thus exposure to predators. Risks of freezing are low in torpid tropical/subtropical bats; they therefore can afford to enter torpor in exposed sites and use daily fluctuations of Ta to minimise energetic costs of arousal from torpor. Other species select sites that are exposed to solar radiation to maximize passive rewarming from torpor. Although data especially from the field are still scarce, it is likely that torpor, which is effective in reducing energy and water requirements even under warm conditions, forms a crucial role in the long-term survival of a large number of small tropical and subtropical bats.