Dying for sex: endangered male quolls may be mating themselves to death instead of sleeping, scientists say | Endangered species
Male northern quolls appear to be sacrificing sleep for sex, a behavior that may be responsible for their early death, a new study of endangered marsupials suggests.
Australian scientists have investigated why northern quoll males 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 carnivorous marsupials on Groet Eylandt, off the coast of the Northern Territory, the researchers found that lack of rest during the breeding season could contribute to the massive annual death of males.
Critically endangered on the Australian mainland, northern quolls are the largest mammal known to exhibit sibling, a breeding strategy in which an organism dies after it reproduces for the first time. Males can weigh up to 600 g and grow to the size of a small domestic cat.
The researchers tracked northern quolls for 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 only about 8% of the time, while females rested three times as long (24% of the time). The team received data from seven men and six women.
Male quolls also spent more time in motion. The two men, whom the researchers named Moimoi and Keyless, covered 10.4 km and 9.4 km, respectively, in one night, which they estimate is the equivalent of 35 to 40 km of walking for a human.
“Males put all that energy into… looking for females because that’s how they maximize their reproductive capacity.. But they just don’t rest in between,” said Dr. Christopher Clemente, co-author of the study and senior lecturer in animal ecophysiology at the University of Southern California.
Because they measured time spent at rest, the researchers can’t say with certainty whether sleep deprivation is the culprit, but they believe it explains the gradual deterioration and eventual death of the men.
This “may explain why males die after the breeding season (for example, they become easy prey, cannot avoid collisions, or die of exhaustion),” they wrote.
“By the end of the breeding season, these quollies look terrible,” Clemente said. “They start losing their hair, they can’t groom themselves effectively, they lose weight and… they also fight each other all the time.”
Previous research has shown that sleep-deprived rodents experience similar problems.
In mammals, semelparity is rare and is known to occur only in some marsupials, including the antechinus, a genus of mouse-like native animals whose males experience a cortisol spike after breeding, leading to organ destruction.
Male northern quolls do not show the same hormonal changes as antechinus.
Other semi-breeders include the Pacific salmon, whose males and females die after swimming upstream to spawn in their birthplace, and some species of octopus.
Dr. Vera Weisbecker, an associate professor of evolutionary biology at Flinders University who was not involved in the study, described semelpary as “a really extreme mode of reproduction” that yielded interesting evolutionary discoveries.
“[Natural] selection is easier to see in something that reproduces very, very quickly,” she said. “And when you have semi-fertile species where the males are constantly dying out, that means we can expect evolution to work easier.”
Weisbecker added that the northern quoll has an unusually wide distribution 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 separate groups of animals that survive on their own, but they are separated by very large gaps,” Weisbecker said.
The Groote Eylandt study is part of a larger study of quoll behavior and predator-prey interactions that Clemente hopes can help with conservation management planning.
