Thermal biology and activity patterns of antechinus (Marsupialia) in relation to reproduction

Abstract

'Antechinus flavipes' and 'A. stuartii' are small dasyurid marsupial mammals known for their extreme phenomenon of complete male die-off after a brief mating period due to stress-related illness. Clearly, reproduction is a physiologically demanding process for these species, especially considering that in addition to male die-off, few female antechinus survive past weaning their first litter. Furthermore, the mating period in these species occurs in winter/early spring when conditions are still relatively poor and costly from a thermoregulatory point of view and thus meeting these high energetic costs can be difficult. In contrast to reproduction, torpor is an energy conserving mechanism used by many small animals, often when ambient temperatures are low and food is limited. Despite the potential adverse effects of torpor on reproduction and although torpor and reproduction show no temporal overlap in some rodent species, several other mammalian species have been observed to employ torpor when pregnant and lactating, and torpor also may be used in reproductive males. 'Antechinus flavipes' and 'A. stuartii' are known to extensively employ torpor throughout the year. However, work on torpor expression in these species has only been conducted in captivity and it is unknown whether antechinus are capable of employing torpor during reproductive periods. Therefore, I aimed to determine torpor and activity patterns of free-ranging antechinus and examine whether and how the reproductive status of an antechinus affects the prevalence of torpor. I also examined the influence of the main reproductive hormones, oestradiol and progesterone, on torpor use and activity patterns of female 'A. stuartii'. Using temperature-sensitive transmitters, body temperature of antechinus was measured.