Australian ‘mouse’ sacrifices sleep for sex

A small Australian mammal that foregoes sleep to have more sex during mating season is making scientists reconsider how much sleep is required for optimal performance.

La Trobe University experts in sleep science studied the way antechinus – a small shrew-like mammal that is prevalent in eastern Australia – adapts its sleeping behaviour and what impact the lack of sleep has on its behaviour.

Led by Erika Zaid, Graduate Researcher in Animal Plant and Soil Sciences, and Associate Professor John Lesku, Head of the Sleep Ecophysiology Group at La Trobe University, the study found male antechinus slept on average three hours less per night, every night, for three weeks during mating season, seemingly without affecting performance.

One male halved his sleep through the period, during which males compete through physical contest and sperm competition for access to as many females as possible to maximise reproductive success.

“In humans and other animals, restricting the normal amount of sleep leads to worse performance while awake; an effect that compounds night after night,” Ms Zaid said.

“The level of sleep loss in the antechinus would impair humans’ waking performance.”

Ms Zaid said what was unclear was whether the mammals were equally compromised but just accepting the physiological cost, or they are more resilient to the negative effects of sleep deprivation.

“Either they suffer but push on in order to secure paternity and pass their genes on, or they are resilient to the effects of chronic sleep restriction. In any case, they seem remarkably unlike how humans respond to even modest periods of extended wake,” Ms Zaid said.

“This remains an exciting mystery and perhaps the most important unanswered question in sleep research today.

“In the future it would be of value to directly investigate the functional consequences that sleep loss might have on breeding male antechinus, such as reduced immune function, brain plasticity and neurogenesis,” she said.

Ms Zaid said the antechinus did display some impacts after breeding season, including the development of skin lesions and fur loss that resembled physical changes in sleep-deprived rats. However, sleep loss may not be the cause of the male die-off.

In addition, eight of the 10 mammals studied became sterile, and two died at the same time, signalling a potential unknown trigger for simultaneous “programmed” death.

The study, Semelparous marsupials reduce sleep for sex, has been published in Current Biology.