1. We're related to aye-ayes
It's a guarantee that no member of your family is as odd looking as the aye-aye, and yet they're a very, very distant cousin of ours. The endangered species is classified as a lemur, but even lemurs may think the aye-aye is the weirdest cousin of all. As a lemur, it's a member of the primate family along with chimpanzees, gorillas and yes, humans. That means like it or not, this odd fellow is part of the family!
2. The aye-aye is the only primate that uses echolocation
Echolocation is the ability to use sound to locate an object by listening to the sound waves after they bounce off an object. The aye-aye uses this method to locate insect larvae inside the branches and trunks of trees.
Using a particularly long middle finger, it taps the tree and listens. When it locates a larvae, it rips away the wood and uses the elongated finger to fish out the food.
The behavior is called "percussive foraging" and the aye-aye is not just the only primate to use echolocation but also the only known mammal to use its fingers to echolocate food.
3. Aye-ayes are thought to be evil spirits (but of course they aren't)
Aye-ayes are cute in their own weird way when they're in the light. But who wouldn't be a bit freaked out coming across one of these wide-eyed animals in the middle of the jungle at night? So it's no wonder that people living where aye-ayes have traditionally considered them to be bad spirits.
According to National Geographic, "Many people native to Madagascar consider the aye-aye an omen of ill luck. For this reason they often have been killed on sight. Such hunting, coupled with habitat destruction, have put aye-aye populations at-risk. Today they are protected by law."
4. Scientists used to think the aye-aye was a rodent
It took a while before researchers placed the aye-aye in the primate family. Before that, the aye-aye's appearance as well as its continuously growing incisor teeth — which is characteristic of rodents — caused it to be classified in the order Rodentia. Now, this creature is known to be a highly specialized lemur.
5. They have 'pseudothumbs'
Researchers from North Carolina State University found that aye-ayes have a tiny extra structure that could help them grasp objects and grip branches as they move through trees. These "pseudothumbs" are tucked near each wrist and have a bone, cartilage and three distinct muscles that move it, as well as their own fingerprints.
"The aye-aye has the craziest hand of any primate," says lead author Adam Hartstone-Rose, associate professor of biological sciences, in a statement. "Their fingers have evolved to be extremely specialized — so specialized, in fact, that they aren't much help when it comes to moving through trees. When you watch them move, it looks like a strange lemur walking on spiders."
Hartstone-Rose and his team were the first to document the extra digit.
"It’s rather mysterious that no one had noticed the finger before, but this could be because it is mostly embedded in the fleshy part of the hand and therefore easy to miss," he writes in The Conversation. "It could also be that the long fingers are so distracting that anatomists just never noticed this small structure."
Editor's note: This story has been updated with new information since it was published in May 2017.