Torpor during the reproductive season in a free-ranging subtropical bat, Nyctophilus bifax

During times of energetic stress many small mammals reduce their body temperature and metabolic rate, a state known as torpor. Whereas torpor is effective in energy conservation it also entails costs, such as reduced foetal development in pregnant females. Because it is currently not known how subtropical bats deal with energetic challenges during the reproductive season, the thermal biology of free-ranging non-reproductive male and pregnant female Nyctophilus bifax was examined during spring. Males entered torpor much more frequently than pregnant females. However, night time activity periods were similar in both sexes. My results show that even in the subtropics torpor is used regularly during the reproductive period in spring by non-reproductive male N. bifax to conserve energy, but is used rarely by pregnant females likely to prevent slowed foetal development.