The aye-aye, a member of the lemur family, is a primate native to the island of Madagascar. This nocturnal creature was thought to have five fingers like most other animals. But new research has shown that aye-aye lemurs have a sixth finger.
The sixth finger
The discovery was made by a team of researchers at North Carolina State University. Researchers were looking at the tendon that leads to the creature’s hands when they noticed something strange. One of the tendons had branched out toward a smaller structure on the wrist. On close inspection using dissection digital imaging, the team discovered that the wrist structure is actually a thumb.
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“The pseudo thumb is definitely more than just a nub… It has both a bone and cartilaginous extension and three distinct muscles that move it. The pseudo thumb can wriggle in space and exert an amount of force equivalent to almost half the aye-aye’s body weight. So it would be quite useful for gripping,” Adam Hartstone-Rose, lead author of a paper, said to Phys.Org. Researchers checked the females and found that they too had these structures.
Aye-ayes are not unique in having a sixth finger. Some pandas have been identified as having an extra digit that helps them in gripping surfaces. A few species of moles have extra fingers that help them with digging. Researchers believe that aye-ayes may have developed the extra digit to compensate for their other fingers that tend to be specialized for certain tasks.
“The third or middle finger is the thinnest and can be moved independently, used by the aye-aye to tap the trees, to groom, and also to drink, moving water to the aye-aye’s mouth at a speed of 3 strokes per second. The fourth finger is the longest and is used by the aye-aye for feeding, particularly to scoop out the insect larvae from inside the tree,” according to IP Factly.
Aye-ayes are the biggest nocturnal primates in the world. Measuring up to two feet long, males of the species tend to grow to 5.9 pounds, while the females often weigh slightly less at 5.5 pounds. These creatures are the only known primates that use echolocation to find their way in the dark. Other creatures that use this technique include bats, whales, and dolphins. Females of the species can reproduce until they die, making them quite unique.
Despite these interesting facts about aye-ayes, they are seen as bad omens by the natives. “If an aye-aye is caught by someone who sees them as evil, the animal is killed on sight and hung so that the evil spirits can be carried off by travelers. Others believe that if an aye-aye points its middle finger at you, you have been marked for death. If an aye-aye appears in a village, it typically means that someone in that village is going to die and the only way to prevent that from happening is to kill the aye-aye,” according to Fact Animal.
The International Union for Conservation of Nature (IUCN) has classified aye-ayes as endangered creatures. Though several conservation efforts have been put in place, the population has been on a decline due to local superstitions and captive breeding programs. At present, IUCN estimates the aye-aye population to be around 1,000 to 10,000 individuals. These creatures were actually thought to be extinct in 1933 until they were rediscovered in 1957.