In the animal kingdom, reproduction can be a dangerous and peculiar game.

A small Australian marsupial known as the antechinus shot to fame after the discovery of two new species five years ago, when scientists revealed how males every mating season are, quite literally, killing themselves by having too much sex.

During the brief breeding period, males ferociously copulate with as many females as possible, in violent sessions that can last upwards of 14 hours – and, their bodies deteriorate as a result, the Daily Mail reports.

Scientists have warned that the black-tailed dusky antechinus and silver-headed antechinus are at risk, and now, the two have officially been placed on Australia's Endangered list.

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The two species were discovered in 2013, making a total of 15 antechinus species in Australia.

But, without help, they may be in danger of extinction.

"It is pretty rare to uncover new mammals in developed countries such as Australia," said Dr Andrew Baker from Queensland University of Technology.

"These two new species were discovered on misty mountain summits. They have likely retreated there as the climate has warmed, and there is now nowhere left for them to go.

"Australia has the worst mammal extinction rate anywhere on Earth. We must take action, so I am pleased the Australian Government has approved this listing and enshrined the protection of the antechinus, and a range of other species, in federal legislation.

"We can now turn the country's attention to the important job of saving these threatened species. If we take immediate action, hopefully in time we will see the antechinus removed from the endangered list."

The small animals face all sorts of risks in the wild, including climate change, habitat loss, and predation.

And, with their "suicidal" mating habits, they're a risk to themselves.

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After males reach sexual readiness, they stop making sperm – so, they must do all that they can to reproduce.

In these sex marathons, the males put all their energy into mating, causing the rest of their bodies to fall apart.

Testosterone and stress hormones soar, and his fur falls off, National Geographic reported after their discovery in 2013.

He also faces internal bleeding, and his immune system fails. All the while, he continues attempting to mate, before ultimately dying.

"These small marsupials have certainly courted a lot of attention for their mating habits," Dr Baker said.

"They are quite unique from that perspective, and we have been very fortunate to be able to capture some incredible vision of them in the wild."

The researcher is working on a book about the world's vanishing species, including these unusual marsupials.