Plasticity of Energetics in Blossom Bats (Pteropodidae): Impact on Distribution

Abstract

Blossom bats, Macroglossus minimus and Syconycteris australis , from New Guinean lowland rainforests usually enter torpor at low ambient temperatures (11–29°C). Torpid individuals maintain a 2–5°C differential of body temperature above ambient temperature. Individuals from highlands, however, regulate body temperature at 36–37°C at ambient temperatures as low as 13°C. A third species, Melonycteris melanops , exhibits imprecise temperature regulation, but rarely enters torpor. Basal rates of metabolism for lowland populations of the three species are low compared to the mammalian standard, whereas highland and subtropical S. australis and highland M. minimus have basal rates near expected values. Thermal conductances of blossom bats are lower than the mammalian standard, except in subtropical S. australis . The variation in basal rates of metabolism in nec-tarivorous bats 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 energetics to meet demands imposed by environments including small oceanic islands, disturbed successional forests, and primary lowland and montane rain forests.