The primate that uses its elongated middle finger to tap on wood and extract grubs is the aye-aye. Its scientific name is Daubentonia madagascariensis, and it is a nocturnal lemur found in Madagascar. The aye-aye’s unusual feeding technique is one of the most specialized behaviors among living primates.
It first taps on a tree trunk with its long middle finger to detect hollow spaces that may contain insect larvae. After locating prey, it gnaws through the wood with large, continuously growing incisors—more reminiscent of a rodent than a typical lemur. It then inserts the thin middle finger into the opening and hooks out the grub.
The aye-aye is sometimes mistaken for a rodent because of its teeth, large ears, and bushy tail, but it is a primate. It is also the world’s largest nocturnal primate. The long finger is not its only unusual adaptation: its ears help detect sounds inside wood, while its teeth and flexible fingers work together as a precise foraging toolkit.