Tiny marsupials sacrifice sleep for sex during the breeding season

The dusky antechinus is a marsupial that resembles a shrew

Adam Fry / Alamy Stock Photo

Sleep is vital for almost all animals, but some male marsupials sacrifice their rest to find a partner and mate. Antechinus males give up 3 hours of sleep a night during their one-to-three-week breeding period before dying of exhaustion.

Antechinus are tiny, shrew-like creatures that can be found living along Australia’s east coast. The males live for about a year, so they have just one shot to mate with as many females as they can to pass on their genes.

Unsurprisingly then, breeding season is an intense period for these animals, with some mating for up to 14 hours a day, says Erika Zaid at La Trobe University in Melbourne.

“Reproducing is their biological priority,” she says. “But we wondered what was happening to their need for sleep.”

Zaid and her colleagues tracked the activity of 10 male and five female captive dusky antechinus (Antechinus swainsonii), kept in a naturalistic enclosure, by attaching accelerometers to their backs before and after the breeding season. They studied a further four males in the laboratory to monitor their brain activity and measure how much they slept.

They found that, on average, male antechinus increased their physical activity during the breeding season and slept 3 hours less per night. There were no noticeable changes in females.

The researchers also took blood samples from 38 wild agile antechinus (Antechinus agilis), a closely related species, before and during the breeding season. In both males and females, they found lower levels of oxalic acid, which is a sign of sleep loss, suggesting that both sexes may suffer from restricted sleep in the breeding season.

“The females are probably harassed by the males [in the wild], which keeps them awake,” says Zaid.

Erika Zaid holding a dusky antechinus

Francesca Leonard

Zaid said she was surprised that the males didn’t give up even more sleep during this period, especially as they will die at the end of it. “As we know, sleep is a really essential function,” she says. “So they can’t sacrifice all their sleep for reproducing.”

In the future, Zaid and her team hope to understand how male antechinus cope with sleep loss during such a physically intensive time and why exactly they die so soon after reproducing.

Antechinus may get some of their energy from cannibalism: other researchers recently reported seeing a dusky antechinus eating a dead animal of the same species during the breeding season.

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