Imagine you have sex with a man, who, after impregnating you, goes out into the night, climbing, jumping, galloping and bounding through the streets in search of other sex partners. Each day, he travels up to 35 kilometers.

When you meet him a few weeks later, you notice he's not doing very well. He has lost some hair and is thinner than when you first met him. He tells you he's only been sleeping one hour per night.

You are concerned, but he keeps at it. After leaving your apartment, he takes off on another 35km jaunt across the city, seeking new sex partners.

The cycle continues until one day, about a month later, you find out he is dead.

Sex drives male quolls to death

This is the story of how endangered male quolls — a sharp-toothed, rat-like marsupial native to Australia — reproduce. They are the largest mammal known to die within a single mating season, a reproductive process called semelparity.

Pacific salmon are also known to be semelparous, as well as some species of butterflies and octopus.

But their female counterparts don't experience this early death nearly as often. On average, female quolls survive around four mating seasons.

Researchers looking to understand this difference in lifespan set out to track the daily activity of the male and female sexes to see if the males were engaging in riskier behavior than the females. 

They fitted 13 northern quolls on the Australian island of Groote Eylandt with tiny backpacks containing a little speedometer-type device that tracked the animals' movements. In order to trap the quolls, the researchers baited them with dog food.

Their results were published in the journal Royal Society Open Science.

The researchers found that over the course of a day, some of the male quolls were traveling very far distances and resting much less than the females. Some of the male quolls traveled 10km in a day — the human equivalent is around 35km, author Christofer Clemente told DW in an email.

And they only rested an average of 7% of the day. That's about one hour.

The females, on the other hand, rested around 24% of the day — five hours — which Clemente said was normal.

This lack of sleep could be making the quolls more vulnerable to predator attacks, the researchers wrote, or could simply be causing death due to exhaustion.

What's the rush?

When quoll mating season starts, all females become receptive at the same time, and only for a very short period — around three weeks. During this period, the male quolls invest virtually all their time in breeding, said Clemente, in order to increase their reproductive output.

The study forms part of a larger investigation into animal movement and behavior.

Scientists hope to understand how movement is linked to habitat and animals' ability to escape predators.

"The quolls are of conservation significance, so if we can understand their movement, we might be better able to conserve this species," said Clemente.

Edited by: Zulfikar Abbany