ZME Science
No Result
View All Result
ZME Science
No Result
View All Result
ZME Science

Home → Environment → Animals

‘Cursed’ yet adorable aye-aye has a sixth ‘pseudothumb’

The aye-aye is the craziest primate out there -- and it just got a lot more interesting.

Tibi PuiubyTibi Puiu
October 22, 2019
in Animals, Biology, News
A A
Share on FacebookShare on TwitterSubmit to Reddit

Exclusively found in the north-eastern parts of Madagascar, the aye-aye (Daubentonia madagascariensis) is a dark-brown or black primate, distinguished by a bushy squirrel-like tail that is larger than its body, bat-like ears, and an over-sized, slender middle finger. But although the species has been known to science since the mid-1800s, scientists have just now discovered that the aye-aye has a sixth digit — a tiny pseudothumb that likely helps the creature grip branches.

The aye-aye uses its exaggeratedly long middle finger to forage for food, typically insects lying within hollow branches. The primate first uses its keen ears to listen for the activity of unsuspecting grub, after which it uses its rodent-like incisors to gnaw through the bark of the branch to make an opening for its middle finger, which is slender enough to nudge right through the hollow tree branch. The finger has a ball-and-socket joint, similar to a human shoulder, which allows a fantastic degree of motion. At the tip of the finger, the aye-aye has a hooked nail that can snag and drag out prey.

Unfortunately for our adorable-looking aye-aye, humans on the island don’t think of it too fondly. Its bizarre appearance is frightening to the locals, and its eery call doesn’t help too much in this regard. According to ancient Malagasy legends, the aye-aye is considered a symbol of death. The natives believe if an aye-aye ever points its middle finger at you, then death will surely soon befall. For this reason, the poor aye-ayes are often killed on sight by superstitious locals. Due to this persecution, as well as habitat loss, the aye-aye is listed as critically endangered, with experts estimating fewer than 1,000 individuals left in the wild. Perhaps that middle finger is rightfully called for.

The aye-aye’s newly found pseudothumb. Credit: Adam Hartstone-Rose.

New anatomical insights, however, are making things more complicated. According to a new study led by Adam Hartstone-Rose, a biologist at North Carolina State University, the aye-aye actually has six digits, which means there’s no actual middle finger. Take that!

“The aye-aye has the craziest hand of any primate,” says Adam Hartstone-Rose, associate professor of biological sciences at NC State. “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.”

The reason why it hasn’t been found thus far has to do with the pseudothumb’s anatomy. The bone itself is very small, whereas the rest of the finger is mainly made of cartilage and muscle, which doesn’t show up on X-rays.

The researchers found the tiny thumb by accident while they were employing dissection digital imaging techniques on six aye-ayes. They noticed that one of the hand tendons split from the base of the thumb, heading towards a wrist bone called the radial sesamoid (humans don’t have it).

“Using these digital techniques allows us to visualize these structures in three dimensions, and to understand the organization of the muscles which provide movement to the digit,” says Dickinson, who built the digital model of the anatomy and is co-first author of the paper.

“The pseudothumb is definitely more than just a nub,” Hartstone-Rose says. “It has both a bone and cartilaginous extension and three distinct muscles that move it. The pseudothumb 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.”

According to the researchers, the aye-aye’s elongated middle finger gymnastics doesn’t allow for a very good grip on branches. Like the panda, which also has a pseudothumb, the aye-aye likely uses this extra digit to grasp branches. Besides the aye-aye and pandas, moles also have six digits, which they employ to move more dirt.

RelatedPosts

Fossil Friday: bird encased in amber has an unique, “extreme” toe
Violence might be deeply embedded in our genes, study finds
Our early ancestors first metabolized alcohol 10 million years ago, a find that helps shape primate evolution
30 million years ago, a group of monkeys sailed from Africa to South America

“Other species, like the panda bear, have developed the same extra digit to aid in gripping because the standard bear paw is too generalized to allow the dexterity necessary for grasping,” Hartstone-Rose says. “And moles and some extinct swimming reptiles have added extra digits to widen the hand for more efficient digging or swimming. In this case, the aye-aye’s hand is so specialized for foraging an extra digit for mobility became necessary.

“Some other primate species have reduced digits to aid in locomotion. The aye-aye is the first primate to dial digits up in the hand rather than dial them down. And it’s amazing that it’s been there the whole time, in this strangest of all primates, but no one has noticed it until now.”

The findings were described in the American Journal of Physical Anthropology.

Tags: aye ayefingerprimate

ShareTweetShare
Tibi Puiu

Tibi Puiu

Tibi is a science journalist and co-founder of ZME Science. He writes mainly about emerging tech, physics, climate, and space. In his spare time, Tibi likes to make weird music on his computer and groom felines. He has a B.Sc in mechanical engineering and an M.Sc in renewable energy systems.

Related Posts

Animals

Scientists Uncover the Secret Dance Moves of Gibbons — And It’s Like Nothing You’ve Seen

byTibi Puiu
7 months ago
News

The last primate that lived in North America shouldn’t have existed. Now scientists know what happened

byTibi Puiu
1 year ago
Animals

We’ve discovered a new, adorable species in Myanmar — it’s already on the brink of extinction

byAlexandru Micu
5 years ago
Anthropology

30 million years ago, a group of monkeys sailed from Africa to South America

byMihai Andrei
5 years ago

Recent news

The Best Archaeopteryx Fossil Ever Found Just Showed It Could Fly

May 14, 2025

Earliest Reptile Footprints Found By Amateur Paleontologist in 355-Million-Year-Old Rock Push Back the Dawn of Land Animals

May 14, 2025

A Massive Brain Study Reveals the Hidden Work Your Mind Does While You Read

May 14, 2025
  • About
  • Advertise
  • Editorial Policy
  • Privacy Policy and Terms of Use
  • How we review products
  • Contact

© 2007-2025 ZME Science - Not exactly rocket science. All Rights Reserved.

No Result
View All Result
  • Science News
  • Environment
  • Health
  • Space
  • Future
  • Features
    • Natural Sciences
    • Physics
      • Matter and Energy
      • Quantum Mechanics
      • Thermodynamics
    • Chemistry
      • Periodic Table
      • Applied Chemistry
      • Materials
      • Physical Chemistry
    • Biology
      • Anatomy
      • Biochemistry
      • Ecology
      • Genetics
      • Microbiology
      • Plants and Fungi
    • Geology and Paleontology
      • Planet Earth
      • Earth Dynamics
      • Rocks and Minerals
      • Volcanoes
      • Dinosaurs
      • Fossils
    • Animals
      • Mammals
      • Birds
      • Fish
      • Amphibians
      • Reptiles
      • Invertebrates
      • Pets
      • Conservation
      • Animal facts
    • Climate and Weather
      • Climate change
      • Weather and atmosphere
    • Health
      • Drugs
      • Diseases and Conditions
      • Human Body
      • Mind and Brain
      • Food and Nutrition
      • Wellness
    • History and Humanities
      • Anthropology
      • Archaeology
      • History
      • Economics
      • People
      • Sociology
    • Space & Astronomy
      • The Solar System
      • Sun
      • The Moon
      • Planets
      • Asteroids, meteors & comets
      • Astronomy
      • Astrophysics
      • Cosmology
      • Exoplanets & Alien Life
      • Spaceflight and Exploration
    • Technology
      • Computer Science & IT
      • Engineering
      • Inventions
      • Sustainability
      • Renewable Energy
      • Green Living
    • Culture
    • Resources
  • Videos
  • Reviews
  • About Us
    • About
    • The Team
    • Advertise
    • Contribute
    • Editorial policy
    • Privacy Policy
    • Contact

© 2007-2025 ZME Science - Not exactly rocket science. All Rights Reserved.