Echidnas blow snot bubbles to say cool

Echidnas rely on snot bubbles and belly flops to keep themselves cool in the searing Australian heat, researchers have found.

The furry and spiky pointy-beaked critters don't perform the usual behaviours animals rely on to avoid overheating.

Sweating is out of the question because they don't have the right glands. Nor do they pant or lick themselves, but they do have a secret weapon.

It turns out they blow snot bubbles to cool a pool of blood at the top of their elongated beaks.

They also perform belly flops on cool surfaces, allowing the escape of heat when their spineless tummies make contact with patches of shady ground or hollowed-out logs, and their legs also let heat escape.

Dr Christine Cooper, from Curtin University, has used thermal vision of wild echidnas, taken southwest of Perth, to unpack how they exchange heat with their environment.

"Echidnas are not supposed to be very tolerant to high temperatures and that's pretty unusual for a species that lives all over the Australian continent," she says.

"So we have suspected for a long time that they're much more tolerant than what the early lab data suggests. And that raises the question of how do they deal with these higher temperatures when they don't pant or lick or sweat."

One novel approach is snot bubbles.

"They blow mucus bubbles out of their nose and they burst and wet the tip of their snout," she says.

"That means evaporation can cool the big pool of blood that's just under the skin at the tip of their nose. When we looked at the temperature of their snouts it was really quite cold."

They can also use their bellies and legs, which lack insulating spines, to flop down on or press against cool surfaces and shed body heat that way.

Dr Cooper says it's important to understand how echidnas tolerate heat, as the world's climate warms.

"The next thing we need to do is some thermal modelling to see how important these thermal windows are for heat dissipation, and where their thermal limits might lie.

"We can then calculate do they have to spend 10 minutes in the sun before they overheat, or can they spend an hour in the sun at different conditions and how might that change their foraging duration and that sort of thing."

The research has been published in the journal Biology Letters.