PLASTICITY OF ENERGETICS IN BLOSSOM BATS (PTEROPODIDAE) - IMPACT ON DISTRIBUTION

Blossom bats, Macroglossus minimus and Syconycteris australis, from Ne w Guinean lowland rainforests usually enter torpor at low ambient temp eratures (11-29 degrees C). Torpid individuals maintain a 2-5 degrees C differential of body temperature above ambient temperature. Individu als from highlands, however, regulate body temperature at 36-37 degree s C at ambient temperatures as low as 13 degrees C. A third species, M elonycteris melanops, exhibits imprecise temperature regulation, but r arely enters torpor. Basal rates of metabolism for lowland populations of the three species are low compared to the mammalian standard, wher eas highland and subtropical S. australis and highland M. minimus have basal rates near expected values. Thermal conductances of blossom bat s are lower than the mammalian standard, except in subtropical S. aust ralis. The variation in basal rates of metabolism in nectarivorous bat s correlates with body size and effectiveness of thermoregulation. M. minimus and S. australis have large geographic distributions, ability to cross narrow oceanic water gaps, and sufficient plasticity in energ etics to meet demands imposed by environments including small oceanic islands, disturbed successional forests, and primary lowland and monta ne rain forests.