The mercury is set to rise as Australia edges out of a wet weather cycle and back to hot and dry conditions.
While humans turn to fans, sprinklers, ice baths and a spot of shade to cool the blood, new research from Curtin University has found Western Australian short-beaked echidnas control their body temperature through built-in air-conditioning vents and blowing bubbles out of their nose.
“Echidnas were supposed to be really intolerant to high temperatures, but we observed them out and about at two degrees higher than expected,” lead author of the study Dr Christine Cooper told Crikey.
What’s their secret?
Using infrared thermal technology and portable weather stations to map and record 124 echidnas in WA’s Dryandra Woodland and Boyagin Nature Reserve for 34 days across 2020 and 2021 (data was pulled for each of the 12 months), the research team found the mammals relied on two types of bodily “windows” — thermal and evaporative — to turn their internal heat down and/or up.
Thermal windows (not unique to echidnas) are two-way ventilation shafts that adjust in line with external heat conditions. It’s a state-of-the-art split system that Cooper calls “flexible insulation”.
These vents are positioned on ventral (meaning under their belly), inside leg and mid-spine areas and are remote-controlled by movement. In short: all the echidna has to do to get a little more airflow is to get limber and change its position. They roll into a ball to keep the heat in (cover the vents) and stretch their spines (expose the vents) to let heat out.
Evaporative windows are comparatively wet systems (again, not unique to echidnas) designed to cool the blood and dissipate heat. The most popular evaporative pastime among animals is to urinate on themselves or lick their arms, but the WA echidnas were found to cool, calm and collect themselves by blowing bubbles of mucus out their nose to wet their snout.
Cooper said these wet and dry avenues for heat loss are particularly important given echidnas do not (and cannot) pant, lick or sweat. Although all run-of-the-mill human habits, they’re not common to most animals. Sweating, for example, requires sweat glands, which many animals don’t have.
It’s not yet known whether these thermal and evaporative windows are shared by all species of echidnas given their function is contingent on climate.
Compare the hot-dwelling northern echidnas to the Tasmanian residents that go about their business in considerably colder conditions. These echidnas are equipped with spines and fur and were always thought to be better insulated in cooler climates as a result. But Cooper said spines — and only spines — function just as well in the cold and far better in the heat, making the WA echidnas well placed to deal with rising temperatures on account of climate change and weather systems.
The Bureau of Meteorology released its latest climate driver update yesterday, confirming the La Niña system that has plagued the east and north-east of Australia with excessive rain for the past three years, is easing. It anticipates a return to neutral come April and a caveated swing in the direction of El Niño by June. The annual autumn predictability barrier makes it difficult for climatologists to get a clear read on what’s in store for weather.
The scientific consensus is however clear that hot and dry conditions are on the cards in coming years. Cooper said the inevitability of higher temperatures made it imperative to understand how Australian animals behave, cope and adapt in heat.
“We have identified areas that function, now we need to determine how much of an echidna’s thermal body heat is dissipating,” she said. “Is it 5 or 50% of their heat load? From there, we can calculate the heat conditions that echidnas can tolerate.”
Cooper wants to know how long it takes an echidna to warm up when they’re out in the sun, how long until they must move and hide in the shade, and how long until they have to burrow underground.
These questions relate to overall foraging time, the extent to which heat will impact on the daily ritual of the mammals, and whether a little bubble can keep the echidna out of trouble.
