More sex thanks to less sleep: these mice have clear priorities

To have more time for sex during the mating season, male broad-footed possums sometimes sacrifice several hours of sleep per night. This is the conclusion of an international study published on Thursday in the journal Current Biology.

The movements and sleep of Swainson’s and gray marsupial mice (Antechinus swainsonii and A. agilis), which are found only in Australia, were measured. According to the researchers, this is the first study to provide direct evidence for this type of sleep restriction in a land mammal.

“Using a combination of techniques, we showed that males sleep less during the mating season,” said lead author Erika Zaid from La Trobe University in Melbourne, Australia. One man even cut his sleep by half.

“In humans and other animals, a reduction in the normal amount of sleep leads to poorer performance when awake – an effect that increases night after night. And yet the broad-footed possums did just that: They slept three hours less per night, every night, for three weeks.” Sleep time remained unchanged in women.

For the small marsupials, it’s a trade-off between sleep and reproduction, which is likely due to strong sexual selection, as the research shows: male broad-footed marsupials experience only one mating season, after which they die. This rare reproductive strategy is also called semelparity. During their first and only mating season, males compete to have contact with as many females as possible to maximize their chances of successful reproduction, the study authors said.

“It’s actually a bit surprising that the animals don’t sacrifice more sleep during the mating season, because they’re going to die soon anyway,” says Zaid. “This way, a large part of their sleep is preserved, which emphasizes the basic functions of sleep.”

According to the research, it remains unclear why the males die after the three-week mating period, at only about a year of age. The lack of sleep is probably not a decisive cause; animals with less sleep were no worse off than animals with more sleep. (sda/dpa)