Scary little lemur has long teeth, a big brain and six fingers By Washington Post, adapted by Newsela staff on 11.07.19 Word Count 583 Level 570L

Image 1. An aye-aye, the Madagascan lemur with six fingers. Photo by: David Haring-Duke Lemur Center.

Madagascar is an island off of the continent of Africa. A strange creature lives there. It is called an aye-aye.

The aye-aye is a type of lemur, which is a primate. Humans and monkeys are primates, too.

The aye-aye has two large ears, like a bat. Its teeth never stop growing, like rodents. Its hands are especially weird. They have long, thin middle fingers. They tap this finger against rotten wood to sense if there are insects to eat.

Now, scientists have discovered something else odd. It turns out that aye-ayes have a tiny sixth finger that acts like a thumb. It sprouts from their palms. Researchers reported this in October in the American Journal of Physical Anthropology.

Aye-Ayes Are Sneaky Hunters

This article is available at 5 reading levels at https://newsela.com. Aye-ayes, like bats, depend on sounds. They sense how sounds bounce off of objects. This helps them to figure out where things are. They also have a huge brain. Their brains and good hearing mean they have a special skill. They can make maps in their heads of hollow spaces inside tree trunks. This helps them to hunt bugs. They love to eat bugs.

First, aye-ayes try to find a path of insect tunnels. Then they bite a hole in the wood. They put their slender middle fingers into that hole. Using a really long and creepy claw, they snatch the bugs out of the tunnels, Adam Hartstone-Rose said. He is a lemur expert. They can then drag the bugs to the surface and eat them.

Fewer Aye-Ayes In The Wild

Aye-ayes are very rare. Only about 30 captive aye-ayes live in the United States. Hartstone-Rose dissected aye-ayes from museums. He also studied some that died of natural causes and one that died in Madagascar.

There are fewer wild aye-ayes than ever, the International Union for Conservation of Nature says. The aye-aye population is decreasing.

Scientists Felt Something Weird

Hartstone-Rose and his team were tracing a special muscle in the aye-aye's body. It is called the abductor pollices longus. Humans have this muscle too. It allows us to stick out our thumbs.

They followed the aye-aye's muscle. A funny thing happened. A part of the muscle branched off to the aye-aye's palm, below the thumb. It is connected to a small nub of bone called the radial sesamoid. This is named after the sesame seed.

Humans do not have these bones on the thumb side of our hands. We have a similar bone on the pinkie-side. Trace the pinkie edge of your hand, palm-side-up. You can feel a similar bone. This is called the pisiform. It sits where your hand meets your wrist. That is a sesamoid bone. Our kneecaps are big sesamoid bones, too.

Extra Finger Has Some Scientists Scratching Their Heads

The bone nub, in the aye-aye, moves in three directions. It has its own fingerprint. The scientists examined six other specimens. All of the aye-ayes had the thumb-like finger.

Matt Borths studies fossils at the Duke Lemur Center. He wants to know more about how the aye- ayes use this thumb.

The long aye-aye fingers do not grasp things very well. The new thumb might have evolved to help. Evolution is the idea that animals and humans have changed over time. They change to fit their environments.

This article is available at 5 reading levels at https://newsela.com.