Dying for sex: endangered male quolls may be mating themselves to death instead of sleeping, scientists say
Male northern quolls seem to sacrifice sleep in favour of having sex, behaviour that might be responsible for their early deaths, suggests new research into the endangered marsupials.
Australian scientists have investigated why male northern quolls usually mate themselves to death after one season, while females of the species reproduce once but live up to four years.
Tracking the activity of the carnivorous marsupials on Groote Eylandt, off the Northern Territory coast, the researchers found a lack of rest during the breeding season may contribute to the mass yearly die-off of males.
Northern quolls, which are endangered on the Australian mainland, are the largest mammals known to exhibit semelparity, a breeding strategy in which an organism dies after it reproduces for the first time. Males can weigh up to 600g, and grow to the size of a small domestic cat.
Researchers tracked northern quolls during seven weeks of the breeding season, using accelerometers contained in miniature felt backpacks.
Their study, published in the journal Royal Society Open Science, found that male quolls rested for only about 8% of the time, while females spent three times as long (24% of the time) resting. The team retrieved data from seven males and six females.
The male quolls also spent more time on the move. Two males the researchers named Moimoi and Cayless travelled 10.4km and 9.4km respectively in one night – the human equivalent of walking around 35 to 40km, they estimate.
“The males are investing all this energy into … looking for the females, because that’s how they maximise their reproductive output. But they’re just not resting in between,” said Dr Christofer Clemente, study co-author and a senior lecturer in animal ecophysiology at USC.
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Because they measured time spent resting, the researchers cannot say for certain whether sleep deprivation is the culprit, but they believe it would account for the gradual deterioration and eventual die-off of males.
It “could explain the causes of death recorded in the males after breeding season (eg they become easy prey, unable to avoid collisions, or die from exhaustion),” they wrote.
“By the end of the breeding season, these quolls just look terrible,” Clemente said. “They start to lose their fur, they start to not be able to groom themselves efficiently, they lose weight and … they’re constantly fighting with each other as well.”
Previousresearch has shown that sleep-deprived rodents exhibit similar problems.
In mammals, semelparity is rare and only known to occur in some marsupials, including the antechinus, a genus of mice-like native animals whose males experience a cortisol spike after breeding that results in organ breakdown.
Male northern quolls do not show the same hormonal changes as the antechinus.
Other semelparous animals include Pacific salmon, whose males and females die after swimming upstream to spawn at their birthplace, and some species of octopus.
Dr Vera Weisbecker, an associate professor in evolutionary biology at Flinders University, who was not involved in the research, described semelparity as “a really extreme mode of reproduction” that yielded interesting evolutionary insights.
“[Natural] selection is easier to see in something that reproduces really, really quickly,” she said. “And when you have a semelparous species where the males constantly die off, that means we can expect to see evolution at work more easily.”
Weisbecker added that the northern quoll had an unusually large distribution, ranging from Queensland and the northern parts of the country to the Pilbara region in Western Australia.
However, the animals are threatened by cane toad poisoning, competition with invasive predators and habitat fragmentation.
“We have individual groups of animals that survive on their own but they’re separated by really large gaps,” Weisbecker said.
The Groote Eylandt study forms part of broader research into quoll behaviour and predator-prey interactions, which Clemente hopes may inform conservation management planning.