Humans tend to assume the opposable thumb is one of the things that sets us apart from the rest of the animal kingdom. It isn’t. A surprising range of animals with opposable thumbs use their own version of this grip to climb, forage, groom, and even strip bamboo down to the stalk.
Some of these species have a true opposable thumb built from the same bones humans use. Others have evolved a workaround called a pseudo-thumb, a modified wrist bone that mimics the same grasping function without being a true digit. Either way, the result is the same: a hand (or paw) that can wrap around a branch, pinch a piece of food, or hold a tool steady.
Key Insight: An opposable thumb is defined by movement, not just position. The digit has to flex, rotate, and touch the tips of the other fingers on the same hand for it to count as truly opposable.
Below are six animal groups that share this rare trait, along with what makes each one’s grip a little different from ours.
Koalas
The koala (Phascolarctos cinereus) has one of the more unusual hand layouts in the animal kingdom. Instead of a single thumb opposite four fingers like humans have, koalas have two opposable thumbs on each front paw, set against three regular fingers. According to the Bureau of Economic Geology’s EarthDate program, koalas have two opposable thumbs on each front paw and one opposable thumb on each rear paw for grasping food and maintaining their perches in trees.
That extra thumb isn’t a cosmetic quirk. Eucalyptus leaves are tough, fibrous, and low in nutrients, so koalas need a secure grip to stay balanced in the canopy while they feed for hours at a time. The same double-thumb setup on the hind paws helps them wedge themselves into branch forks so they can sleep without falling, a skill that matters given koalas spend most of their day resting.
Koalas also keep sharp claws on most digits, which work alongside their thumbs rather than in place of them. For a broader look at how claws and grip work together across the animal kingdom, the roundup of animals with claws covers several species that pair sharp digits with climbing skill.
Opossums
Opossums are marsupials, not primates, yet they carry one of the clearest examples of a true opposable digit outside the primate family. The Virginia opossum (Didelphis virginiana) has an opposable digit on its hind feet rather than its front paws. As Discover Wildlife notes, Virginia opossums have a fifth toe on their hind feet which acts as an opposable digit, helping them climb trees.
Unlike a human thumb, this digit has no claw, which actually improves its grip on smooth or narrow branches. Combined with a prehensile tail that can wrap around a branch for extra support, opossums are able to move through dense forest canopy with more control than most ground-dwelling mammals their size. This hind-foot thumb is also part of why opossums show up so often on lists of unusual North American wildlife, alongside other species covered in the guide to animals that start with O.
Pro Tip: Look for the opposable digit on an opossum’s back foot rather than its front paw. It’s easy to miss if you’re only checking the hands, since the front paws lack this feature entirely.
Old World Monkeys (Baboons and Macaques)
Old World monkeys, a group that includes baboons and macaques, have fully opposable thumbs that function much closer to the human version than the koala’s or opossum’s do. According to HowStuffWorks, Old World monkeys, such as baboons and macaques, have fully opposable thumbs that allow them to manipulate objects with precision, and these social animals use their hands to gather food, groom, and interact with other individuals in their groups.
The olive baboon (Papio anubis) uses this precision grip to pick seeds, insects, and small plants out of tight spaces while foraging on the ground and in trees. The rhesus macaque (Macaca mulatta) relies on a similar grip for grooming, a behavior that reinforces social bonds within its troop. That combination of manual dexterity and group memory for feeding sites and social relationships is part of why several primates also appear on lists covering animals with good memory.
Common Mistake: It’s easy to assume any animal with humanlike hands has an opposable thumb. Raccoons are a good counterexample. Research from A-Z Animals points out that raccoons use their hands to collect and wash food, but their hands do not have the same agility as those of primates because they lack a true opposable thumb.
Aye-Aye
The aye-aye (Daubentonia madagascariensis) is a nocturnal lemur from Madagascar known for oversized ears and teeth that never stop growing. Its hands are just as strange. The aye-aye’s actual thumb is not fully opposable, sitting in line with its other long, spindly fingers rather than rotating to meet them. Researchers writing for National Geographic explain that the aye-aye’s first finger, or thumb, is not fully opposable like in some other primates; it rather sits in line with the other digits.
To compensate, aye-ayes evolved something no other primate has: a sixth digit. A 2019 study covered by Science News found that the extra digit, a nubby little pseudothumb made of bone and cartilage, can move in three directions and carries its own distinctive fingerprint. This pseudothumb sits near the wrist and gives the aye-aye a grip its overly specialized fingers can no longer provide on their own.
Key Insight: The aye-aye’s pseudothumb was the first accessory digit ever documented in a primate, described in a 2019 paper in the American Journal of Physical Anthropology.
The aye-aye’s enormous eyes, built for hunting insects in total darkness, are almost as famous as its hands. Readers curious about other species with oversized eyes for low-light living can find more examples in the guide to animals with big eyes.
Great Apes (Chimpanzees, Bonobos, Orangutans, Gorillas)
Great apes have thumbs closest to our own in structure and use, which makes sense given how closely related we are. The International Fund for Animal Welfare notes that chimpanzees, bonobos, orangutans, and gorillas are our closest genetic relatives, and their thumbs prove important for survival and fitting in with social groups, as they use them to swing between branches, groom each other, and use sticks as tools.
The chimpanzee (Pan troglodytes) and its close relative the bonobo (Pan paniscus) both use their thumbs to strip leaves from twigs, a behavior researchers have documented as a form of tool preparation. The orangutan (Pongo pygmaeus) relies on its grip for a slower, more deliberate style of climbing through the forest canopy of Borneo and Sumatra, where individuals can live for several decades. That kind of longevity is part of why great apes frequently appear alongside other long-lived species covered in the list of animals with the longest lifespan.
The gorilla (Gorilla beringei) rounds out the group with a hand built more for strength than fine manipulation, though it still uses its opposable thumb to select and handle specific plants while feeding. Gorillas share this letter with several other notable species featured in the guide to animals that start with G.
| Animal Group | Thumb Type | Location | Primary Use |
|---|---|---|---|
| Koala | True opposable (double thumb) | Front and rear paws | Gripping branches, holding leaves |
| Opossum | True opposable | Hind feet only | Climbing, tree navigation |
| Old World monkeys | Fully opposable | Hands | Foraging, grooming, precision grip |
| Aye-aye | Pseudo-opposable (sixth digit) | Wrist/hand | Grasping branches and small objects |
| Great apes | Fully opposable | Hands | Tool use, climbing, grooming |
| Giant panda | Pseudo-opposable (sesamoid bone) | Forepaws | Stripping and gripping bamboo |
Giant Pandas (Pseudo-Opposable Thumb)
The giant panda (Ailuropoda melanoleuca) is a bear, not a primate, so its thumb didn’t evolve the same way the others on this list did. Instead of a true digit, pandas have a pseudo-thumb formed from an enlarged wrist bone. Writing for National Geographic, researchers explain that a similar scenario likely happened with the giant panda, which is well known for having a sixth digit, also called a pseudo-thumb, and the ancestor of these bears, like other ursines, had digits in a single line, allowing them to walk on the ground.
That single-line hand arrangement works fine for walking, but it’s a poor tool for handling bamboo, which makes up the vast majority of a giant panda’s diet. Science News reports that other species also have pseudothumbs, including giant pandas, which use their sixth digits to grasp bamboo stalks. The pseudo-thumb lets a panda hold a stalk steady with one paw while stripping leaves and bark with its teeth, a feeding strategy that would be far more difficult with a standard bear paw.
Giant pandas share their name’s first letter with a number of other distinctive species profiled in the guide to animals that start with P.
Across mammals, marsupials, and even a lemur with an entirely separate evolutionary path, the opposable thumb keeps reappearing wherever climbing, grasping, or precision feeding gives an animal a real survival advantage. Some species built a true thumb from the same bones humans use. Others, like the aye-aye and giant panda, found a workaround that does the same job through an entirely different bone. Either way, the pattern points to the same conclusion: when a good grip pays off, evolution tends to find a way to build one.