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.