Scurrying along the dense brush of coastal woodlands and forests, the small, mouselike antechinus appears more unassuming than many of Australia’s marsupials. But for the three weeks of their breeding season, the males transform into absolute sex-obsessed lotharios.
“They have this super bizarre breeding system, which is quite common among flies and some fish, where the males live one year, have a single shot at securing all their reproductive success, and then they die,” said John Lesku, a zoologist at La Trobe University in Melbourne, Australia, who has spent a decade studying antechinuses.
So committed to the live fast, die young lifestyle, a male antechinus even forgoes one of the most essential biological needs: sleep. In a study published Thursday in the journal Current Biology, Dr. Lesku and his colleagues discovered these marsupials shave off, on average, three hours of sleep per night during their mating season, with some individuals forgoing even more.
Antechinuses engage in suicidal reproduction, a biological phenomenon called semelparity that has been observed in other marsupial species, like kalutas. Males are known to ramp up their physical activity during their mating season, but how their sleep quality changed — antechinuses typically sleep around 15 hours a day — remained elusive.
Trekking over to Great Otway National Park in the southwestern part of the state of Victoria, Dr. Lesku; a Ph.D. student, Erika Zaid; and other collaborators spent several years trapping two species of antechinus. In one study, the results of which were published in 2022, the researchers found that accelerometers tracking body movements were a good way to estimate sleep in antechinuses. They strapped the devices to the hefty necks of dusky antechinuses, which were housed in an enclosure within the park.
Agile antechinuses are far too small for an accelerometer. Instead, the researchers measured levels of oxalic acid, a metabolite associated with sleep loss, for some of the animals before, during and after the breeding season. Blood testosterone levels were also measured for both species.