As the Planet Warms, Australia’s Numbats Are at Risk of Overheating

The endangered, squirrel-sized marsupials forage for termites during the day—but they can become too hot after just ten minutes in direct sunlight, according to new research

Small striped marsupial on the ground
Researchers studied roughly 50 numbats over the course of a year. Curtin University

Numbats—small, endangered marsupials that live in Australia—are at risk of overheating amid global warming, a new study finds.

These striped mammals forage for termites, their primary food source, when the insects are most active during the day. But because termites aren’t a very hearty meal, numbats must eat a lot of them to survive—and they need to conserve energy where possible.

For example, the animals have evolved special fur that traps the warmth of the midday sun, instead of spending energy to generate more body heat. Now, however, as global temperatures rise, scientists say this trait is getting numbats in trouble.

In some conditions, numbats can overheat within ten minutes of being in direct sunlight, according to a new paper published this month in the Journal of Experimental Biology. And even if they manage to find a bit of shade to cool off for a few moments, that might not be enough. Heat radiating from the ground—even in shade—may be too much for the pouched creatures.

Numbats are endangered, with an estimated 2,700 individuals living in the wild, according to the Australian Broadcasting Corporation’s Peter de Kruijff. Though they used to roam throughout southern Australia, their numbers have declined because of habitat loss and the proliferation of invasive predator species, such as cats and foxes. Today, just two known groups live in nature preserves in Western Australia.

Conservationists have been trying to help the squirrel-sized creatures rebound by relocating some of them to protected areas across their native range in South Australia, Western Australia and New South Wales. However, because those regions are getting hotter amid human-caused climate change, that may not be a viable long-term solution, according to the researchers.

Thermal vision shows endangered numbats feel the heat of warming climate

To find out how numbats are faring, the team spent 12 months in 2020 and 2021 driving around their known habitats in Western Australia.

When they spotted a numbat, they used a thermal imaging camera to film the animal and record its body surface temperature. With a portable weather station, they recorded data at the location of each sighting, including humidity, air temperature and wind speed. Then, they developed a computer model to estimate how the local weather conditions would affect the animals’ internal temperatures, writes New Scientist’s Christa Lesté-Lasserre. All told, they captured 50 videos of numbats in the wild.

The numbats began overheating once their body temperatures reached roughly 104 degrees Fahrenheit (40 degrees Celsius). And that could occur in as little as ten minutes with air and ground temperatures as low as 73 degrees Fahrenheit (23 degrees Celsius), depending on humidity, wind and other factors.

As the climate changes, some animals are adapting their schedules to become active during the coolest parts of the day. However, numbats can’t follow suit, because they have poor night vision and aren’t strong enough to break into the mounds where termites retreat each evening. Being out and about at night also puts them at a greater risk of being eaten by predators, according to a Journal of Experimental Biology article accompanying the new paper.

Already, numbats appear to be foraging earlier in the morning and later in the evening during the summer months. But if global temperatures continue to rise, “the windows for foraging will get narrower and narrower,” says study co-author Christine Cooper, an environmental biologist at Australia’s Curtin University, to the Australian Broadcasting Corporation.

One lingering question is how limited foraging hours would potentially affect the numbats’ health and reproduction. In the future, scientists may want to consider this relationship so they can “draw more direct associations between how hot the animal gets and its ability to survive,” says Eric Riddell, a biologist at the University of North Carolina at Chapel Hill who was not involved in the research, to Science News’ Jake Buehler.

The study’s findings have practical implications for efforts to protect numbats. To give the marsupials the best chance of surviving amid the warming climate, conservationists should consider relocating them to cooler areas with plenty of shade, researchers say.

“Understanding how the numbat responds to and manages heat is essential to understanding its ecology and has particular relevance for the future conservation and management of the species in the face of global warming,” says Cooper in a statement.

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