Seasonality of torpor and thermoregulation in three dasyurid marsupials

Summary Seasonal variation in the pattern of torpor and temperature regulation was investigated in the closely related arid zone dasyurid marsupialsSminthopsis crassicaudata (17 g),S. macroura (24 g), andDasyuroides byrnei (120 g). The tendency to enter torpor was greater, torpor commenced earlier, torpor duration was longer, and body temperatures (T_b) were lower inSminthopsis spp. than inD. byrnei. The minimum mass-specific rate of oxygen consumption () of torpid animals was similar among the three species despite the differences in minimumT_b. The mass-specific oxygen consumption of normothermic animals was reduced during winter when compared with the summer values in all species, but there was no seasonal variation in normothermicT_b in any species. The tendency to enter torpor was incrased during winter. TorpidSminthopsis spp. had lower values ofT_b and during winter than during summer;D. byrnei did not show seasonal changes in these variables. These results suggest that seasonal changes in the pattern of thermoregulation and torpor in small dasyurids may be more distinct than in larger species.Abbreviations RMR resting metabolic rate - BMR basal metabolic rate