Studying Australia’s Feisty Northern Quolls Requires Beef Chum and Backpacks
Scientists fitted the famously bitey marsupials with tiny accelerometers to learn their secrets.
Australia’s northern quoll is, by all accounts, an unpleasant animal. The carnivorous marsupial, Dasyurus hallucatus, lives in isolated pockets in the country’s north and, at first glance, might be mistaken for some kind of rat or other rodent—until you notice all those sharp teeth, similar to those of a cat. Like cats, northern quolls are highly skilled nocturnal hunters, nabbing mostly insects, but also the occasional small mammal, bird, or reptile. They have an outsized reputation for “being lively and pugnacious,” says University of Queensland marsupial expert Diana Fisher. For example, in a 2018 Functional Ecology paper on northern quoll biomechanics, including the animals’ impressive bite force, the authors observed that their subjects “readily bit down on anything close to their mouths.”
“We joke that they have ‘small man syndrome,’” says Joshua Gaschk, who studies animal movement at the University of the Sunshine Coast. Northern quolls are only about a foot long and max out at less than three pounds—the smallest of Australia’s four quoll species—but, says Gaschk, “They’re just an exceptionally vicious animal.”
Gaschk knows from experience: He and his colleagues decided to fit several northern quolls with tiny felt backpacks. “They did not enjoy it,” he says.
The backpacks carried accelerometers that collected information on how and when the quolls moved, including whether they were at rest or active. After retrieving as many of the backpacks as possible—it was “a bit of a struggle,” says Gaschk—and crunching the data, the team uncovered new clues to one of the northern quoll’s most unusual traits. But to get there, the scientists had to hike through the rugged bushland and rocky outcrops of Groote Eylandt, a large island off the coast of Australia’s Northern Territory, where daytime temps—even in winter, when the fieldwork was conducted—reached a sweltering 95 degrees Fahrenheit. The team endured biting ants, skin-shredding thorny plants, crocodiles, snakes, and packs of dingoes. And that was before they even reached their bitey, irritable subjects.
Understanding how the endangered northern quoll behaves in its environment may be key to learning how to stabilize their numbers—but the team discovered something else along the way. In a recent Royal Society Open Science paper, Gaschk and his coauthors quantified for the first time something that researchers had suspected about the males of the species: During mating season, they spend significantly less time resting than females. While females rested 24 percent of their day, males took it easy a mere eight percent of the time, and instead traveled considerable distances—sometimes several miles—looking for love. Essentially, male northern quolls live fast and furious, mating as often and with as many females as they can in a single season. And then, sleep-deprived and weak, they drop dead.
Northern quolls are among the handful of mammals that are semelparous, which means the males typically die after a single mating season, while the majority of females survive multiple mating seasons.
“Many other animals, such as salmon, octopuses, and spiders, use semelparity as their breeding strategy,” says Julie Old, a comparative immunology and mammal biology expert at Western Sydney University who was not involved with the new paper. Old works with red-tailed phascogales, an Australian marsupial that’s much smaller than the northern quoll and, as she notes, “truly semelparous.” While scientists doing long-term studies of northern quolls occasionally come across a male who survives to a second mating season, red-tailed phascogales are decidedly one-and-done.
Although semelparity in mammals is rare, Old says, “It’s just a different method of reproduction.” All or most of the males dying after mating may free up resources such as food and nesting sites for females and their offspring.
In semelparous species, success for males is not measured by longevity, but rather by the number of offspring. University of Queensland’s Fisher, who was not involved in the Groote Eylandt research but works closely with some of the paper’s coauthors, compares northern quolls with another semelparous, carnivorous marsupial: antechinus, a roughly rat-sized animal whose reproductive strategies have been extensively studied.
“Antechinus males try to out-mate other males rather than fighting,” Fisher says. As the antechinus males mate frantically day and night, their stress hormones and testosterone increase, they deplete their energy, their immune systems collapse, and they die from internal bleeding or infection. But, Fisher adds, “Males that die sooner are actually more successful.”
While, as Fisher notes, the new paper hints at similarities in how northern quolls and antechinus males “deplete their body reserves to gain a mating advantage,” its appears unlikely that the same thing is happening physiologically in both species. The spikes in stress hormones seen in antechinus males, for example, have not been observed in northern quolls. Instead, the quolls suffer symptoms similar to those experienced by rodents in sleep deprivation studies.
“I don’t think this gives us the full picture of what’s happening, but it definitely adds to the information,” Old says of the new paper. “We have so much more to learn.”
The new study offers promising leads for additional research, but it’s just one facet of Gaschk’s work. In fact, the quoll semelparity paper was almost an accident. “At heart, I’m an animal biomechanist,” he says. One particular area of interest is how prey moves in relation to predators. Having just completed a similar study on feral cats, he wanted to compare their movements to those of northern quolls, which are often hunted by the felines. Logistical issues delayed the planned fieldwork until the quolls’ mating season, however, which afforded the scientists an unexpected opportunity.
The Groote Eylandt research began with setting out dozens of traps, each baited with beef-flavored Chum, an Australian dog food brand. “That’s the thing the quolls love the most,” says Gaschk. He pauses, contemplative. “It’s not a great name.”
Once trapped, the animals were fitted with the small felt backpacks—carefully—and then released back into the wild. The team then tried to recatch the quolls using the same method; they recovered about half of the devices, each with hours or days of data, depending on how long it took to retrap the animal. About a dozen more minipacks fell off before they could be retrieved, though one was later found by a local in her backyard.
When fitting or removing the tiny packs, to avoid stressing the animals or getting bit, the team worked in pairs and kept the quolls’ faces covered as much as possible. “As soon as you cover their face, they’re like oh, I’m in a burrow, I’m okay, life’s good,” says Gaschk. He dodged being bitten during the fittings, but one northern quoll in the field gave him “a glancing bite” that he won’t soon forget: “It didn’t do much, but I felt it.”
Another team member was not so lucky: A quoll bit him on the hand, with a sharp tooth “punching a hole right through the fingernail,” Gaschk says.
Gaschk didn’t make it through the study unscathed, however. He recalls a particularly steep, rocky outcrop that was “a bit sketchy” climbing up, and very sketchy getting down while carrying two trapped quolls in thick, pillowcase-like bags. Gaschk slipped and landed on a young pandanus bush, which was full of sharp spines. “My hand was just shredded,” he says, recalling the pain of pulling out the embedded spines. “But I saved the animals. They didn’t get squished.”
Some of the traps were set near watering holes frequented by crocodiles, and, on more than one occasion, Gaschk and his trapping partner were stalked by small packs of dingoes. “One dingo is not a threat … but two or three of them are,” he says.
Aware of the various dangerous animals in the environment, “the biggest fright I got was in a dense bush area when I heard this thing, it sounded like someone driving a car through the bush,” Gaschk says. Crocodile? No. His smile turns sheepish. “It was just a big bandicoot,” he admits. The long-snouted marsupials reach lengths of only a couple feet, and, while they are omnivorous, they do not eat scientists.
Sometimes, however, the scientists helped themselves to the local wildlife. Gaschk recalls how some field sites on the island were densely wooded with eucalypt and melaleuca, others thick with tall grasses “absolutely filled with (biting) weaver ants.
“They stick onto you really well,” he adds. “They’ll be all over you when you’re out in the bush.… All of a sudden one’s creeped into a really soft spot, like under your armpit or in your groin, and starts nipping you and it really hurts.”
Gaschk pauses. “They taste like limes. I was munching on them as much as they were munching on me. Just as revenge.”
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