Animals cover themselves in all kinds of insipid fluids to keep cool. Sweaty men, spitting forms, and some birds melt into themselves on hot days. It turns out that echidnas have a lot of cute — though perhaps just as tough (and slightly icky) — heat to beat.
Spiny insectivores remain chilled by blown rock bubbles, researchers report January 18 in Biology literature. Pop the bubbles, having wet nose critters. By exhaling this fluid, heat is drawn from the blood sac in the echidna’s beak, helping to cool the animal’s blood.
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short-nosed echidnas (Tachyglossus aculeatus) a bit like a hedgehog, but they are really monotremes – egg-laying mammals unique to Australia and New Guinea (SN: 11/18/16). Previous lab studies have shown that temperatures above 35° Celsius (95° Fahrenheit) should kill echidnas. But the echidnas do not seem to have reached the monument. They live everywhere from the tropics in the rain in the deserts to the snow peaks, leaving a physiological puzzle.
Mammals exhale water to cool themselves when temperatures climb above their body temperatures, says world physiologist Christine Cooper of Curtin University in Perth, Australia. Lots of moms do that either by licking, sweating, or panting, he says. “It wasn’t believed to make echidnas.” But the critters are known to snot bubbles when it gets hot.
So armed with a camera and a telephoto lens, physiologist Cooper and environmental physiologist Philip Withers of the University of Western Australia in Perth pushed through nature reserves in Western Australia once a year to move the echidnas.
In the infrared, the spiny bodies of the echidnas’ hottest parts glowed in oranges, yellows, and whites. But I see that the tips of the noses are exposed to the purple blossoms, the cool moisture has disappeared from the nostrils. Echidnas can also lose heat through their bellies and legs, the researchers report, while the spikes can act as an insulator.
“Finding a way to do this in the field is quite exciting,” says physiologist Stewart Nicol of the University of Tasmania in Hobart, Australia, who was not involved in the study. “You can understand animals and see how they respond to a normal environment.” The next step, he says, is to quantify how much heat echidnas really lose through their noses and other body parts.
Monotremes split evolutionary paths with other mammals between 250 million and 160 million years ago as the supercontinent Pangea broke up.SN: 3/8/15). So they have all the conditions that are considered primitive, says Cooper. “Understanding how thermoregulates might give us ideas about how thermal regulation…could evolve in mammals.”
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