Thermal physiology of a reproductive female marsupial, 'Antechinus flavipes'

Abstract

Reproduction is an energetically costly, but necessary, process for animals. Small mammals in particular are at a disadvantage as they experience high heat losses to their environment, substantially increasing their energetic costs. However, many small mammals save energy by using torpor, a reduction in metabolic rate and body temperature (Tb). 'Antechinus flavipes' is a small dasyurid marsupial endemic to Australia that uses torpor during adverse conditions. Females usually produce only one litter in their life. In our study, we aimed to quantify the thermal physiology of reproductive female A. flavipes held under natural ambient conditions in an outdoor aviary, and also under stable conditions indoors, during gestation, parturition and lactation. Throughout gestation, 'A. flavipes' displayed similar variations in torpor use and Tb to reproductively unsuccessful females (did not produce young). Torpor use increased with decreasing ambient temperature in the outdoor aviary and ceased when held under stable ambient conditions indoors. Interestingly, during parturition/early lactation, Tb was tightly controlled and daily Tb variation decreased by ≥2.3°C in comparison to all other reproductive states. Additionally, daily Tb variations during lactation were slightly smaller than those of gestating and reproductively unsuccessful females; however, this conclusion is only preliminary. Our results reveal that the flexibility of the thermal physiology of female 'A. flavipes' is important throughout the reproductive period, except during parturition/early lactation when a stable Tb is likely beneficial to the early stages of development.