"The most unusual feature of the aye-aye is its extremely narrow middle finger, which it uses to tap on trees to find grubs under the bark. The aye-aye listens for echoes to find hollow areas in the trees, a method called percussive foraging. Once an individual has found a hollow part of a tree, it gnaws into the bark and uses its middle finger to hunt for grubs and insects inside the tree. The aye-aye's finger is a remarkably specific adaptation, allowing it to fill a small ecological niche!"

Weird & Wonderful Creatures: The Aye-Aye 

"The aye-aye (Daubentonia madagascariensis) is a highly unusual lemuriform primate that has evolved a dentition similar to that of rodents: it possesses large, ever-growing incisors which it uses to strip the bark from trees in order to feed on wood-boring beetle larvae."

Convergent Evolution