This Marsupial Has Marathon Sex Until It Goes Blind and Drops Dead

When antechinus makes eyes, run. Something terrible is about to happen around you.

In the forests of Australia, every year just before spring, there erupts a sexual frenzy unlike any other on Earth. It’s bigger than an ultra-romantic Neil Diamond concert, bigger even than spring break in Cancun. Here a tiny hyperactive marsupial called antechinus sprints around mating almost non-stop for an exhausting three weeks, with single romps lasting as long as 14 straight hours.

Males relentlessly bound from partner to partner, as massive hormone releases in their bodies cause their immune systems to crash and their fur to fall out. They bleed internally. Some males even go blind, yet still stumble around the leaf litter hoping for one last tryst. In a few short weeks, every single male lies dead, leaving the females to raise their offspring. And so it seems that in perpetually dangerous Australia, even the sex can kill you.

For these three weeks of sexual kamikaze, antechinus males are concerned with nothing–absolutely nothing–other than mating with as many females as they possibly can. Ecologist Andrew Baker of Australia’s Queensland University of Technology, who studies these critters’ astonishing habits, has even picked up a copulating pair, who ignored him entirely and went about their business in his hands. “It’s pretty frenzied,” said Baker. “There’s no courtship or anything like that. The males basically just grab the females and go for it.”

Driving males to such feats are astronomical levels of testosterone. Think of an MMA fight wrapped in an Insane Clown Posse concert wrapped in the Insane Clown Posse playing during an MMA fight. While the hormone mobilizes all the sugars in the antechinus’ body so it doesn’t need to feed for the three-week orgy, it also glitches the mechanism responsible for regulating the production of cortisol, a stress hormone that in small amounts results in bursts of energy and higher pain tolerances.

With runaway levels of cortisol, though, the males’ bodies literally begin to fall apart. Bone density plummets and blood-sugar levels go nuts. Their immune systems essentially degrade to worthlessness, as open sores form and never heal. Of course, females are also quite stressed during all of this, but they don’t produce anywhere near the same levels of testosterone, so their cortisol regulation remains normal.

The whole affair is one of nature’s most striking manifestations of the true meaning of life: At a very basic level, all critters, including you and me, are on this planet to pass along their genes, even if it means an early demise. Antechinus males, after all, were only born after the previous year’s mating season. Not a single one reaches 12 months old, while females live up to three years.

And while it may not seem like anything other than strange hedonism, the males, with their mass suicide, in a way help guarantee the success of the offspring they’ll never get to enlighten with what would have been a truly epic sex talk. (You see, son, when a man loves a woman very much, it’s not long before he goes blind and dies.)

“It’s all geared toward the young being born when spring starts,” said Baker, “so there will be a big flush of insects in spring. The female will give birth to the young and then she’ll have plenty of food available because the population has been halved, because all the males are dead.”

In the eight to 12 weeks leading up to the mating season, though, males are taking more than their fair share of food, scurrying around frantically and hoovering up insects. “They’re spending all of their time building up food and fat stores,” said Baker, “because they know they’re going to need it across that intensive mating block.”

Plus, the more weight you pack on, the more energy you can devote to producing sperm, which males store in enormous quantities before the mating season begins. Bigger males will also beat out smaller ones for the right to mate–Baker has found individuals that are twice the weight of others (MMA enthusiasts, obviously).

In the end, though, females find themselves alone in a forest of dead males, carrying an incredible amount of sperm from perhaps dozens of different potential fathers. But this seems to be problematic for one of evolution’s most basic principles: sexual selection. Typically, females pick only the most fit of males, so they can better guarantee offspring with strong genetics. But antechinus ladies aren’t exactly picky–it’s not like they roll up to a sperm bank and studiously flip through catalogs of donors. So aren’t they inevitably stuck with sub-par sperm?

Well, sure, she’s carrying sperm from smaller, less fit males. But larger males produce more sperm, boosting the chance that theirs will win out in the fertilization game. And obviously, with that many partners the competition is fierce. Indeed, a single brood will consist of young from several different fathers.

She’ll actually give birth to up to three times as many young as she has teats. This, too, is where good genes from their fathers benefit the diminutive, barely developed young. “They haven’t got much going for them except for a really strong mouth and sucking mechanism and some little hands and arms to crawl their way up,” said Baker. “They’ll crawl up and attach to a teat and then once all the teats are occupied all the other extras that were born will die within an hour or two.”

As a marsupial, antechinus gives birth to highly underdeveloped jelly beans.

So right from birth, natural selection favors only the strongest young from the strongest fathers. The ones that survive settle into a kind of pouch, though it’s nowhere near as luxurious as a baby kangaroo’s digs. This is more of a depression in the lower abdomen, with raised and slightly enclosed walls, where the young hole up even while the mother hunts.

And the female must feed ravenously, for milk production in marsupials is extremely energy-intensive. In placentals, most of the energy in rearing young is spent in utero, as you mothers out there can attest (that’s not to say that significant energy isn’t eventually spent on the uniquely human duties of keeping kids from tumbling down stairs and eating crayons). “But marsupials are born small and immature,” said Baker, “and most of the energy is driven toward milk production. So when she’s producing milk for the growing young, it’s an incredible imposition on her energetics.”

Read more at Wired Science