Chemical Cues, Hibernation and Reproduction in Female Short-Beaked Echidnas (Tachyglossus aculeatus setosus): Implications for Sexual Conflict

The short-beaked echidna (Tachyglossus aculeatus) is a highly seasonal, usually solitary monotreme, and Australia’s most widely distributed native mammal. Tasmanian echidnas hibernate for several months of the year and show sexual conflict around the timing of mating, as males locate and attempt to mate with hibernating females. The effect of hibernation on chemical cues in mammals is poorly understood, but is potentially important in this system, since reproduction and hibernation overlap, and males use odor to locate females. Furthermore, females mate with multiple males throughout pregnancy, suggesting males cannot distinguish between pregnant and non-pregnant females. We combined chemical analyses of cloacal secretions with data from external temperature loggers, urogenital smears and behavioral observations collected from 35 female echidnas in a wild population over 3 years, to investigate the effects of hibernation and reproductive status on odor cues and mating activity. Odor cues varied between years, individuals and euthermic and hibernating animals. There were no detectable changes in scent profile composition after females entered hibernation, suggesting females do not produce a new, attractive odor cue while hibernating. Reproductive females showed mating activity before, during and after fertilization, but no concurrent changes in chemical profiles. Odor cues do not seem to advertise pregnancy to conspecifics, which could encourage multi-male mating and confuse paternity among males. We suggest the observed patterns of olfactory communication and mating behavior in this species are a product of interrelationships between environmental, physiological and demographic conditions.