Cool Sex? Hibernation and Reproduction Overlap in the Echidna

Gemma Morrow,Stewart C Nicol

doi:10.1371/journal.pone.0006070

Abstract

During hibernation there is a slowing of all metabolic processes, and thus it is normally considered to be incompatible with reproduction. In Tasmania the egg-laying mammal, the echidna (Tachyglossus aculeatus) hibernates for several months before mating in mid-winter, and in previous studies we observed males with females that were still hibernating. We monitored the reproductive activity of radio-tracked echidnas by swabbing the reproductive tract for sperm while external temperature loggers provided information on the timing of hibernation. Additional information was provided by camera traps and ultrasound imaging. More than a third of the females found in mating groups were torpid, and the majority of these had mated. Some females re-entered deep torpor for extended periods after mating. Ultrasound examination showed a developing egg in the uterus of a female that had repeatedly re-entered torpor. The presence of fresh sperm in cloacal swabs taken from this female on three occasions after her presumed date of fertilization indicated she mated several times after being fertilized. The mating of males with torpid females is the result of extreme competition between promiscuous males, while re-entry into hibernation by pregnant females could improve the possibility of mating with a better quality male.

Highlights

Hibernation has been documented in species from a wide range of mammalian orders [1], and originally thought to be an adaptation to the cold, hibernation is considered to be an energy conserving strategy which different species employ in a range of ecological circumstances [2]
Hibernation is characterized by a reduction in body temperature (Tb) which typically falls to within 1uC of ambient, and a very substantial, but size dependent, reduction in metabolic rate [1]
Because metabolic processes are slowed during hibernation it is generally considered to be incompatible with reproduction: hibernation prevents spermatogenesis in males [3], slows fetal development, delays parturition [4] and inhibits lactation [5]

Summary

Introduction

Hibernation has been documented in species from a wide range of mammalian orders [1], and originally thought to be an adaptation to the cold, hibernation is considered to be an energy conserving strategy which different species employ in a range of ecological circumstances [2]. Kangaroo Island echidnas have been described as forming mating ‘‘trains’’ of up to 11 individuals with a period of competition between males and courtship lasting between 14–44 days [15].

Results

Conclusion