Story at a glance
- The aye-aye, a strange looking type of lemur, is now the world’s only six-fingered primate.
- Scientists discovered a hidden pseudo-thumb that the animals use to grasp branches in their native Madagascar. They may have evolved the extra thumb to compensate for incredibly specialized fingers they use to hunt for bugs.
- Aye-ayes are endangered, largely due to habitat loss from logging and agriculture.
A bug-eyed, bat-eared Madagascan lemur called an aye-aye is now the world’s only six-fingered primate, according to new research.
Finger is being a little generous, the extra digit looks more like an ambitious callous, but “it’s more than just a nub,” study co-author Adam Hartstone-Rose of North Carolina State University said in a release. In fact, the extra digit works like an extra thumb, complete with its own bones, cartilage, a trio of surprisingly strong muscles and even its own fingerprint.
The bonus “pseudo-thumb” is thought to have evolved to help the aye-aye grip branches and climb through the treetops it calls home. Giant pandas also have a pseudo-thumb that serves a similar purpose: helping them grab bamboo stalks.
The aye-aye may have needed to beef up its grip strength as the rest of its fingers morphed into spindly, highly specialized tools for the nocturnal primate’s unique hunting strategy: tap foraging.
When the aye-aye finds a choice log it uses its incomprehensibly long third finger to tap around the rotten wood. With its ghoulish face pressed against the wood to listen close, the aye-aye uses the subtle changes in the sound of each tap to find the insects hiding inside. With a set of teeth that never stop growing, like a rodent, the six-fingered nocturne bites a hole in the wood and uses the same freaky finger to pick out the bugs.
Future research into this unusual primate may look to catch them using their pseudo-thumbs in the wild. But scientists may need to move quickly — the aye-aye is endangered and quickly losing its habitat to agriculture and logging.
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