Lemurs of Madagascar: Surviving on an Island of Change
The Uncommon Aye-Aye: An Interview with Eleanor Sterling
The dozens of diverse lemur species on Madagascar are a motley crew. Still, none look and act quite like the aye-aye. In fact, this lemur is considered one of the world's strangest animals altogether. Just ask Eleanor Sterling: she's a conservation biologist, the director of the Museum's Center for Biodiversity and Conservation, and one of the world's few experts on the aye-aye.
An aye-aye on Nosy Mangabe, a small island and nature preserve in Antongil Bay, Madagascar. Being nocturnal canopy-dwellers, aye-ayes are notoriously difficult to photograph in the wild. Note the animal's special elongated middle digit.
What makes the aye-aye so strange?
First off, it’s got continuously growing front teeth like a rodent. It has a really thin middle finger that is mostly tendon and bone. A protective film also covers its eye when it is gnawing wood and bits are flying everywhere. These features are not found in any other lemur nor any other primate, even. Most animals have behavioral characteristics that allow them to adapt well to their environment, but very few animals have such extreme morphological changes in body form and shape.
How do those adaptations help it survive?
Its features make it exquisitely well suited to acquire food, including insect larvae. Larvae live inside chambers in tree trunks and branches. The aye-aye taps along a branch with its funny finger and listens carefully with its large ears. It echolocates where larvae might be, opens up the chamber with its teeth, then sticks a finger in and pulls one out.
I’ve seen aye-ayes eat really big, chunky larvae just like a child eating an ice cream cone. First it bites the little head off and spits out the mouth parts—those are hard to digest. The insect’s insides then drip down the aye-aye’s fingers, so the animal runs it tongue around its hand to lick the juicy parts up fast.
Sounds tasty.
Well, larvae are high in both fat and protein, so they’re good for both quick and long-term energy. And if you can gain access to hard-to-acquire, “structurally defended” food sources like larvae with your specialized adaptations, you don’t have a lot of competition from other animals.
An aye-aye in captivity at the Duke University Primate Center in North Carolina.
So does that mean the aye-aye is smarter than other lemurs?
Not necessarily. The finger is certainly very advanced in its manipulative abilities. It has incredible flexibility—aye-ayes can move it 360 degrees around the joint with the hand. Interestingly, the aye-aye has an enormous brain for its body size compared to that of other lemur species. The mechanics of its manipulative operations and the sophisticated echolocating ears might explain the size of the brain.
Why else does the aye-aye look like it does?
It has dark fur and big bright eyes because it lives in a dark rain forest. It is well specialized for nocturnal living. The eyes are designed to pick up any available light, even on a night with very little moonlight, and reflect it to discern the smallest changes in the environment. Aye-ayes also have very acute senses of smell and hearing.
How did you become so well acquainted with these animals?
I lived on a little island off the coast of Madagascar called Nosy Mangabe for about two years studying aye-ayes for my doctoral thesis. I conducted the first long-term study of the animal, following single aye-ayes through the night to figure out exactly what they do, whom they meet, and how they interact with each other. Only a few researchers have studied aye-ayes in the wild since, as field conditions are very difficult. You have to put a radio telemetry collar on the animal to track it—a very expensive, difficult, and time-consuming project—then follow the aye-aye for the life of that collar, which can be months. It’s only after following individuals through the seasons that you get a sense for how they live their lives.
