Daily torpor and thermoregulation in antechinus (Marsupialia): influence of body mass, season, development, reproduction, and sex.

Season and body mass influence torpor in mammals. However, the effects of the two factors are often difficult to distinguish because body mass in many species changes with season. The present study attempted to separate seasonal and body mass related alterations of torpor. Adult female Antechinus stuartii and A. flavipes (Marsupialia), which were about half the size of males of the respective species, showed longer and deeper torpor than males. When the two species were compared, torpor in A. stuartii, the smaller species, was more pronounced than in A. flavipes. Juveniles of both species had lower body temperatures and longer torpor durations than adults. Torpor was most pronounced in juvenile males during summer; in winter, when males had grown to adult size, the use of torpor was reduced. Seasonal changes in torpor of adults were not distinct. These results suggest that the influence of body mass on torpor in these Antechinus species is stronger than that of season.