Layla Nelson
February 1, 2023
Male northern marsupials appear to sacrifice sleep in favor of sex, a behavior that may account for their early deaths, new research on the endangered marsupials suggests.
Australian scientists have investigated why male northern quolls typically mate to death after one season, while females of the species breed once but live up to four years.
By tracking the activity of the carnivorous marsupials on Groote Eylandt, off the coast of the Northern Territory, researchers found that a lack of rest during the breeding season can contribute to the annual mass die-off of males.
Critically endangered in mainland Australia, northern quolls are the largest mammals known to exhibit semelparity, a breeding strategy in which an organism dies after it has reproduced for the first time. Males can weigh up to 600g and reach the size of a small domestic cat.
The researchers tracked the northern quolls during the seven weeks of the breeding season using accelerometers contained in miniature felt rucksacks.
Their study, published in the Royal Society Open Science journal, found that male quolls only rested about 8% of the time, while females rested three times as long (24% of the time). The team collected data from seven men and six women.
The male quolls also spent more time on the move. Two men, whom the researchers named Moimoi and Cayless, walked 10.4 km and 9.4 km, respectively, in one night — the human equivalent of walking about 35 to 40 km, they estimate.
“The males put all that energy into… finding the females, because that’s how they maximize their reproductive output. But they just don’t rest in between,” said Dr. Christofer Clemente, co-author of the study and senior lecturer in animal ecophysiology at USC.
Because they measured rest periods, the researchers cannot say with certainty whether sleep deprivation is the cause, but they believe it would be responsible for the men’s gradual deterioration and eventual death.
It “might explain the causes of death found in the males after the breeding season (e.g., becoming easy prey, unable to avoid collisions, or dying of exhaustion),” they wrote.
“At the end of the breeding season, these quolls look just awful,” Clemente said. “They start shedding their fur, they can’t groom themselves efficiently, they lose weight and … they also fight with each other all the time.”
Previous research has shown that sleep-deprived rodents exhibit similar problems.
In mammals, semelparity is rare and known only in some marsupials, including the Antechinus, a genus of mouse-like native animals whose males experience a post-breeding cortisol spike that leads to organ degradation.
Male northern quolls do not show the same hormonal changes as the antechinus.
Other semelparous animals include the Pacific salmon, whose males and females die after swimming upstream to spawn at their birthplace, and some species of squid.
Related: Unusual sightings of ‘devil birds’ over Melbourne raise migration mysteries for researchers
Dr. Vera Weisbecker, an associate professor of evolutionary biology at Flinders University who was not involved in the research, described semelparity as “a really extreme mode of reproduction” that produced interesting evolutionary insights.
“[Natural] The selection is easier to see in something that reproduces very, very quickly,” she said. “And if you have a semelparous species where the males are constantly dying off, that means we can expect evolution to be more easily at work.”
Weisbecker added that the northern quoll had an unusually wide range, ranging from Queensland and the northern parts of the country to the Pilbara region of Western Australia.
However, the animals are threatened by cane toad poisoning, competition from invasive predators, and habitat fragmentation.
“We have individual groups of animals that survive on their own, but they’re separated by really big gaps,” Weisbecker said.
Groote Eylandt’s study is part of broader research into quoll behavior and predator-prey interactions, which Clemente hopes can inform conservation management planning.
Male northern marsupials appear to sacrifice sleep in favor of sex, a behavior that may account for their early deaths, new research on the endangered marsupials suggests.
Australian scientists have investigated why male northern quolls typically mate to death after one season, while females of the species breed once but live up to four years.
By tracking the activity of the carnivorous marsupials on Groote Eylandt, off the coast of the Northern Territory, researchers found that a lack of rest during the breeding season can contribute to the annual mass die-off of males.
Critically endangered in mainland Australia, northern quolls are the largest mammals known to exhibit semelparity, a breeding strategy in which an organism dies after it has reproduced for the first time. Males can weigh up to 600g and reach the size of a small domestic cat.
Read Also: Sex and no sleep can kill endangered quolls
The researchers tracked the northern quolls during the seven weeks of the breeding season using accelerometers contained in miniature felt rucksacks.
Their study, published in the Royal Society Open Science journal, found that male quolls only rested about 8% of the time, while females rested three times as long (24% of the time). The team collected data from seven men and six women.
The male quolls also spent more time on the move. Two men, whom the researchers named Moimoi and Cayless, walked 10.4 km and 9.4 km, respectively, in one night — the human equivalent of walking about 35 to 40 km, they estimate.
“The males put all that energy into… finding the females, because that’s how they maximize their reproductive output. But they just don’t rest in between,” said Dr. Christofer Clemente, co-author of the study and senior lecturer in animal ecophysiology at USC.
Because they measured rest periods, the researchers cannot say with certainty whether sleep deprivation is the cause, but they believe it would be responsible for the men’s gradual deterioration and eventual death.
It “might explain the causes of death found in the males after the breeding season (e.g., becoming easy prey, unable to avoid collisions, or dying of exhaustion),” they wrote.
“At the end of the breeding season, these quolls look just awful,” Clemente said. “They start shedding their fur, they can’t groom themselves efficiently, they lose weight and … they also fight with each other all the time.”
Previous research has shown that sleep-deprived rodents exhibit similar problems.
In mammals, semelparity is rare and known only in some marsupials, including the Antechinus, a genus of mouse-like native animals whose males experience a post-breeding cortisol spike that leads to organ degradation.
Male northern quolls do not show the same hormonal changes as the antechinus.
Other semelparous animals include the Pacific salmon, whose males and females die after swimming upstream to spawn at their birthplace, and some species of squid.
Related: Unusual sightings of ‘devil birds’ over Melbourne raise migration mysteries for researchers
Dr. Vera Weisbecker, an associate professor of evolutionary biology at Flinders University who was not involved in the research, described semelparity as “a really extreme mode of reproduction” that produced interesting evolutionary insights.
“[Natural] The selection is easier to see in something that reproduces very, very quickly,” she said. “And if you have a semelparous species where the males are constantly dying off, that means we can expect evolution to be more easily at work.”
Weisbecker added that the northern quoll had an unusually wide range, ranging from Queensland and the northern parts of the country to the Pilbara region of Western Australia.
However, the animals are threatened by cane toad poisoning, competition from invasive predators, and habitat fragmentation.
“We have individual groups of animals that survive on their own, but they’re separated by really big gaps,” Weisbecker said.
Groote Eylandt’s study is part of broader research into quoll behavior and predator-prey interactions, which Clemente hopes can inform conservation management planning.
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