Aye-Aye Gives World the Highly Elongated Finger

My mother used to tell me I’m a unique snowflake, and also that this is my last warning to stop monkeying with the damn thermostat. But let’s face it, I’m not unique. You’re not either. We’re all born largely the same animal. And while we have these pretty sweet brains, even outside of our species we’re quite closely related to other primates — sharing, for example, 96 percent of our genetic material with chimpanzees.

But in the forests of Madagascar, aye-aye mothers are also telling their children that they’re unique snowflakes, and other than their kids not literally being snowflakes, they’re absolutely right. No other creature on this planet comes close to the extraordinary aye-aye. It has the bushy tail of a squirrel, the ears and teeth of a rat, and the extremely elongated, super-thin, swiveling middle finger of … well, just the aye-aye.

Indeed, scientists initially thought it was a rodent. We now recognize the aye-aye as a primate — specifically, a kind of lemur — and have granted the species not only its own genus, but its own entire taxonomic family. This might sound lonely, but consider that we humans are forced to share a family with gorillas, chimps, and orangutans, which are all kinda like that embarrassing cousin you have who doesn’t shower and who sometimes climbs the Empire State Building and yells at biplanes. So maybe the aye-aye is alright with being alone.

While the aye-aye is no King Kong-esque menace, Malagasy superstition has painted it as a Grim Reaper of sorts. Legend goes that if an aye-aye points at you with its elongated middle finger, you’re marked for impending death, and the only path to salvation is to slaughter the defenseless animal. But it’s this finger that stands as one of the more remarkable adaptations in the animal kingdom.

As the nocturnal aye-aye slinks through the forest canopy, it rapidly taps its elongated digit on hollow branches and bamboo stalks, with the idea of agitating hidden grubs and listening for their movement, according conservation geneticist Ed Louis of the Madagascar Biodiversity and Biogeography Project at Omaha’s Henry Doorly Zoo. When it likes what it hears, it uses incredibly tough teeth to tear into the larva’s hiding place.

“They have these huge lower incisors that are fused together, that actually grow continuously throughout their lifetime, just like in rodents,” Louis said. “And they use these teeth to chew through bamboo or wood, things like that, and in captivity they’ve been known to chew through concrete cinder blocks.” So it’s a bit like Clint Eastwood in Escape From Alcatraz, only with more biting.

Once the hole in the bamboo is opened up, the aye-aye uses its middle digit to feel around for the grub, hooking it with a long nail. “Our fingers, we have these hinge joints, so we can go up and down, but that’s pretty much it,” said Louis. “But the [aye-aye’s] middle finger is actually a ball and socket, so it actually can sort of swivel like our shoulder,” granting it far more dexterity to reach its prey.

In and of itself this is an amazing technique, but it’s all the more fascinating to consider that chimps and orangutans arrived at a similar solution for gathering termites and ants — only they’re using tools in the form of sticks, jamming them into mounds to extract the insects. Aye-ayes just evolved with a tool in hand, perhaps finding the use of sticks undignified. And with such an asset they have assumed the niche that a grub-hunting woodpecker would fill elsewhere around the world.

But the aye-aye is not entirely alone in its brilliant adaptations. Thousands of miles away in Australia and New Guinea, the striped possum employs the same mode of hunting, called percussive foraging. It too has an elongated probing digit, though instead of using its middle finger the striped possum uses its ring finger (which the fashion-challenged creature would probably just call a fourth finger). It also has similar chompers for gnawing through wood. The two creatures arriving at almost identical adaptations is a great example of what’s known as convergent evolution: Where there’s a problem, unrelated species can independently develop the same fix.

For all its evolutionary triumphs, though, the aye-aye is now endangered due to, if you can believe it, human meddling. Beyond loss of habitat and getting killed just for pointing at the wrong guy, aye-ayes are often attacked by dogs, because they are unafraid to descend from the trees and trot through the human settlements in their massive territories, which are around 6 square kilometers, according to Louis. He and his team even tracked one animal traveling 25 kilometers in just four days.

Read more at Wired Science