资源环境科技发展态势分析平台

Many tropical endotherms are already confronted by ambient temperatures (T-a) close to their body temperature (T-b) and risk severe hyperthermia due to global warming. Tropical fruit bats play a vital role in the ecosystem and their absence could have dire consequences for ecosystem health. Many fruit bats have exposed roosting habits that increase their vulnerability to heat stress. We investigated the thermoregulatory capacity of wild caught lesser dog-faced fruit bats Cynopterus brachyotis from the Island of Borneo; a heterothermic 32 g foliage-roosting generalist bat. We determined the effect of T-a (21-36 degrees C) on metabolism, T-b and evaporative cooling. We also measured the T-a and relative humidity (RH) at capture sites. The bats displayed a seemingly narrow thermoneutral zone of 30 +/- 1 degrees C, a basal metabolic rate of 5.60 +/- 0.26 W kg(-1) (1.01 +/- 0.05 ml O-2 g(-1) h(-1)) and a normothermic T-b of 32.5 +/- 0.3 degrees C; all much lower than expected. Evaporative cooling was only effective at T-a <= 31 degrees C, above which heat storage became apparent. Bats typically entered torpor at T-a < 25 degrees C and thermoconformed (i.e. allowed their T-b to fluctuate with T-a) at T-a > 32 degrees C. The microclimate at capture sites remained cool (T-a = 24-25 degrees C) and humid (RH > 90%). Our study supports the argument that tropical endotherms are susceptible to hyperthermia due to their low T-b. Further, we discuss the potential advantage of heterothermy in coping with short-term heatwaves. However, the future of these bats, and likely other low T-b species, depends primarily on their thermally buffered habitats, and decisive conservation action is required to protect thermal refugia.