Animals are covered in various foul-smelling fluids to keep them cool. Humans sweat, kangaroos spit, and some birds urinate on themselves to survive the heat. As it turns out, echidnas do something cuter—though perhaps just as sticky (and a little gross)—to beat the heat.
spiny insectivore Blow your nose bubbles to stay coolthe researchers reported on January 18 in Biology Letters。 The air bubbles burst to keep critters’ noses moist. As it evaporates, this moisture draws heat away from the blood-filled sinuses in the echidna’s beak, helping cool the animal’s blood.
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Short-beaked Echidna (Ratchet Moss) Looks a bit like a hedgehog, but is actually a monotreme — egg-laying mammals endemic to Australia and New Guinea (Serial Number: 11/18/16). Previous laboratory studies have shown that temperatures above 35°C (95°F) should kill echidnas. But the echidna doesn’t seem to have gotten the memo. They’re ubiquitous in everything from tropical rainforests to deserts to snow-capped mountain peaks, leaving scientists with a physiological conundrum.
Mammals evaporate water to stay cool when temperatures exceed their body temperature, says Christine Cooper, an environmental physiologist at Curtin University in Perth, Australia. “Many mammals do this by licking, sweating or panting,” she said. “It’s believed that echidnas can’t do that.” But the critters have been known to spit out snot bubbles when the weather gets hot.
So Cooper and Philip Withers, an environmental physiologist at the University of Western Australia in Perth, armed with thermal imaging cameras and telephoto lenses, drive through Western Australia’s nature reserves once a month, continuously One year photographing echidnas.
In infrared light, the warmest parts of the echidna’s spiny body glow orange, yellow, and white. But the video shows their noses as dark purple spots that stay cool as the water in the snot bubbles evaporates. Echidnas also likely radiate heat through their abdomens and legs, and their spikes act as insulators, the researchers report.
“It’s very exciting to find a way to do this in the field,” says Stewart Nicol, a physiological ecologist at the University of Tasmania in Hobart, Australia, who was not involved in the study. “You can learn about the animals and see how they respond to their normal environment.” The next step, he said, is to quantify how much heat the echidna loses through its nose and other body parts.
Monotremes diverged from other mammals 250 to 160 million years ago because Pangaea breaks up (Serial Number: 3/8/15). So “they have a lot of features that are considered primitive,” Cooper said. “Understanding how they do thermoregulation can give us insight into how thermoregulation … may have evolved in mammals.”
