One of the quirkiest of all mammals, the egg-laying echidna of Australia, has been found to employ an appropriately eccentric method of cooling off in the heat, according to research published in Biology Letters.
“Short-beaked echidnas have the broadest distribution of any mammal in Australia,” says Christine Cooper who led the new research. “They’re all over the place, from alpine areas through to the deserts and the tropics.”
Past experiments in the laboratory have suggested that echidnas cannot survive air temperatures above 35°C.
“Heat exchange is much more complex in the wild than in the lab where the air temperature is kept constant by design,” says Cooper.
“Echidnas live in areas where they must be dealing with these high temperatures. In fact, people have measured the temperatures in logs where echidnas are sleeping and it’s over 40ºC. The question is how they are doing that.”
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Echidnas are unable to sweat. But Cooper’s research shows that they blow bubbles through their nose, which moisten it when they pop.
“They have a large blood sinus at the tip of their nose, so when the water evaporates, that should cool the blood in the sinus,” she says.
“I had a PhD student who was studying echidna physiology and behaviour. She noticed that at higher temperatures they were blowing more bubbles. Then we had the opportunity to use thermal imaging technology out in the wild to see if their noses really are cold. And yes, they really are.”
Main image: Researchers made their discovery about echidnas while carrying out other measurements. © Jamie Lamb/elusive-images.co.uk/Getty