They look like a cross between a hedgehog, porcupine and anteater, but echidnas are a different sort of creature entirely. They're actually the only surviving members — along with the platypus — of an ancient clade of animals called monotremes, or egg-laying mammals.
Researchers are still learning new things about these weird but charismatic little beasts. Case in point, they've just discovered a secret superpower that echidnas possess that gives the animals the remarkable ability to survive wildfires, and the skill might help explain why mammals were somehow able to live through the asteroid that killed the dinosaurs, reports the BBC.
The ability was first recognized in 2013, after a catastrophic fire swept across Warrumbungle National Park in eastern Australia, which many of these creatures call home. Julia Nowack, a researcher based at the University of New England in New South Wales at the time, noticed that while most wildlife was devastated by the fire, the area's population of echidnas seemed as robust as ever.
How did echidnas escape the blaze? To investigate, Nowack and her colleagues took advantage of a controlled burn being conducted in a region known to host a small population of echidnas in Western Australia. The echidnas were trapped and implanted with small temperature loggers, along with GPS trackers that were glued to the spines on the animals' backs.
Researchers followed the echidnas for about a month before and after the blaze. What they found was nothing short of remarkable. The animals did not attempt to flee the fire. Rather, they simply went to bed and slept through it.
Echidnas are known to be capable of a type of hibernation called torpor, whereby they lower their metabolism, and thus lower their body temperature as well. The adaptation allows them to conserve energy in times of scarcity, but how does it help them to survive fire?
First, it should be noted that echidnas don't just collapse into torpor out in the open. They pick somewhere safe and hidden, such as a hollowed tree log or underground burrow, to snooze away in. These natural shelters certainly play a part in helping protect them from fire, but shelter alone is not enough of a protectant — a fire can turn such burrows into an oven in a hurry.
Researchers believe that the lowered body temperature that occurs during torpor protects the animals from increased heat. It actually makes them mildly fire-retardant.
"After the fire, the body temperature of the echidnas in the fire areas was on average lower than the body temperature in the control groups," said Nowack.
But ice cold body temperatures aren't the only fire-saving benefit of torpor states; torpor also allows echidnas to sleep through the times of scarcity that follow major bushfires. That is, echidnas might be able to survive a wildfire, but other critters cannot. So torpor also allows echidnas to save energy until their insect food returns.
In fact, researchers even suspect that states of torpor might have been what allowed mammals to survive the asteroid impact that wiped the dinosaurs off the planet. Echidnas do represent an ancient line of mammals, after all. And many scientists believe that torpor was a far more common trait in ancient mammals than it is today.
"In fact, a state of torpor is also employed by other winners of the [extinction event that killed the dinosaurs], including turtles and crocodiles," explained palaeontologist Tyler Lyson of the Denver Museum of Nature and Science in Colorado.
The ability to fall into states of prolonged sleep might not sound like much of a superpower on first blush. But the ability to survive fire, charred Earth and asteroid impacts? It's enough to make certain you never think of the echidna in the same way ever again.