HANOVER, N.H., Jan. 17 (UPI) -- The aye-aye, a lemur on Madagascar, heats up its unusually long finger when using it to search for dinner, scientist say.
The world's largest nocturnal primate taps its specialized middle finger -- long and very thin, less than half the width of its other digits -- on tree trunks to find nutritious beetle larvae living beneath the bark.
Studying thermal images of the aye-aye's digits, researchers at Dartmouth University found the longer digit was usually colder than the others but warmed up by almost 10 degrees F when the animal was foraging for food.
"It was striking to see how much cooler the third digit was while not in use and how quickly it warmed to [match] the other digits when engaged in an active foraging task," researcher Gillian Moritz told the BBC.
In order to sense vibrations of beetle larvae through tree bark, "the long digit is packed with sensitive nerve endings," she said.
Those specialist sense receptors likely mean using the digit as a tapping tool is very costly in terms of energy.
"Like any delicate instrument, it is probably best deactivated when not in use," Moritz said.
Aye-ayes, listed as near threatened by the International Union for Conservation of Nature, are the only primates known to have this strange adaptation.
