Horny Marsupials' High Sex Drive May Be Driving Them Closer to Extinction

The males of an endangered marsupial species have such a high sex drive it might be killing them prematurely.

Male northern quolls prioritize having sex over sleeping, possibly leading to them dying up to four times faster than the females of the species, according to a study by researchers at Australia's University of the Sunshine Coast and University of Queensland published in the journal Royal Society Open Science on Wednesday.

"It seems that their drive is so strong that they forgo sleeping to spend more time searching for females," University of Sunshine Coast animal ecophysiologist and co-author of the paper, Christofer Clemente, said in a statement.

"The dangers of a lack of sleep are well documented in rodents, and many of the traits associated with sleep deprivation we see in male quolls, and not in females."

Northern quolls are an endangered species of marsupial around the size of a house cat. They are the smallest of the four Australian quoll species, only growing to a maximum body length of around 15 inches long. Cousins of more famous marsupials including kangaroos, koalas and wombats, the northern quoll population has been falling in recent decades.

This is due to a number of factors, including predation by feral cats, dingoes and foxes, as well as destruction of their habitat by fire and land clearing for livestock grazing or human development. The invasive cane toad in Australia is also a major threat to these marsupials, as they are often poisoned after eating or merely licking the toxic toads.

Female northern quolls can live for four years, compared to the males, who tend to only live to the age of one.

Researchers collected 42 days' worth of data on the movements of the quolls on Groote Eylandt, an island off the coast of Australia's Northern Territory. They found that males spent much less time than females sleeping and walked greater distances: some males walked up to 6.5 miles in a single night looking for females to mate with. Adjusted for stride length, that equates to around 25 miles per night for a human.

"Two males, who we named Moimoi and Cayless, moved for 10.4 kilometers [6.5 miles] and 9.4km [5.8 miles] in one night respectively," lead author and Ph.D. candidate at University of Sunshine Coast, Joshua Gaschk, said in a statement.

They also found that males spent only 7 percent of the time resting, whereas females rested for 24 percent of the time.

As a result of their lack of sleep, these males lose weight, become increasingly aggressive and appear to be more risk-prone, as well as becoming more susceptible to parasites. However, the exact cause of the males' early demise is unknown as of yet, as the researchers could not find any genetic condition that was killing more males than females. The researchers suspect that the leading cause for their shorter lifespans is their lack of sleep.

"Something is definitely causing their health to fail after just one season and we think it is linked to sleep deprivation," Clemente said.

"Sleep deprivation, and associated symptoms for a prolonged duration would make recuperation impossible and could explain the causes of death recorded in the males after breeding season," Gaschk agreed.

The quolls are the largest mammal known to use the strategy of semelparity, which involves investing all of its energy into just one breeding season. This is also seen in Pacific salmon, some species of squid and octopus, and some butterflies, cicadas, and mayflies. In spiders, semelparity is taken to the extremes by some species, where the female eats the male during or immediately after his one and only attempt at breeding.

Semelparity is also seen in a few land vertebrates, such as the gladiator frog, as well as a few lizard species such as Labord's chameleon. In mammals, all semelparity is found in the marsupial families Dasyuridae, of which quolls are a member, and Didelphidae, the opossums.

Despite their endangered status, there is nothing that researchers can do to slow the libido-driven decline of these cute creatures.

"We can't change what they're doing or I don't think it would be easy because they've been doing this for tens of thousands of years," Gaschk said.

It is possible that sleep deprivation may be a significant factor in the survival of other species of marsupial too.

"We want to determine if sleep deprivation is experienced by other family members, such as opossums, antechinus (marsupial mice) and Tasmanian Devils," Gaschk said.

"Virginian opossums (Didelphis virginiana) undergo a similar physiological change to other semelparous species but do not experience the die-off, while Tasmanian devils (Sacrophilus harrisii) experience a similar loss in condition and a reduced immunocompetence.

"If male quolls forgo sleep to the detriment of their survival, northern quolls become an excellent model species for the effects of sleep deprivation on body function."

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