Some male marsupials have quite the end-of-life experience: They "mate themselves to death," explains the lead author of a new study in the journal PNAS. Researchers found that in some insect-eating species, the males buck themselves up for one grand finale, then mate with as many partners as possible in sessions that last up to 14 hours, reports the BBC. And then, all pooped out, they die. That kind of behavior—called suicidal reproduction, or semelparity—is more common with creatures such as fish or spiders, but it's rare in mammals, notes LiveScience.
Scientists first observed the trait in marsupials years ago, but the new study fills in some details and suggests a reason to explain it: These "suicidal" males try to win the reproduction sweepstakes first by creating high-quality sperm (they even have larger testes than their non-suicidal peers) and then by making sure their sperm is delivered to as many females as possible. During the marathon mating sessions, they expend themselves so thoroughly that their muscles break down to provide needed energy. The ultimate winners: Lady marsupials. "Females are all for this," the lead scientist tells National Geographic, "because they get the best fathers for their young by mating promiscuously and letting the best sperm win." (Read more marsupials stories.)