Many mammals, including primates, humans, opossums, and other tree-dwelling animals have opposable thumbs. This digit provides our hands with extra malleability and dexterity. Yet, there are so many different kinds of frogs that it may seem difficult to grasp if frogs are also on the list of animals that have opposable thumbs.
As a general rule, most frog species do not have opposable thumbs. However, many frogs in the Phyllomedusa family have opposable thumbs that function freely from the rest of their fingers, similar to a human hand. These frogs generally live in trees and are excellent climbers.
Frogs and toads in the order Anura have a well-conserved foot and hand morphology and usually have five-toed legs and four fingers on each hand. It is rare for an amphibian to have an opposable thumb since such thumbs are commonly found in mammals.
Read on to find out how certain frogsā feet are formed and adapted to suit different environments depending on the type of frog.
What Are Opposable Thumbs?
An opposable thumb is a digit on a hand that can adapt, flex, and rotate to bring the tip of the limb into opposition with the tips of any of the other digits. Humans have a relatively longer thumb compared to other primates.
Humans tend to have relatively longer thumbs compared to other primates because we have larger thumb muscles. Our thumbs are extremely useful in many regards, more than just for texting š
We use our thumbs to grasp, hold, carry, grip, pull, push, as well as for many other common and necessary actions in our everyday lives. When you think about it, it would be pretty hard to accomplish much without opposable thumbs.
Yet, not all frogs have opposable thumbs.
Which Frogs Have Opposable Thumbs?
Depending on the species, frogs use their hind legs to jump, swim, burrow underground, and even climb up vertical surfaces. Frog species that like to burrow and climb generally have their hind legs with toes that end in tubercles.
Most frog species, other than the Waxy Monkey Frog, do not have opposable thumbs. Their hind legs serve more significant functions like hopping, leaping, and swimming, compared to their shorter front legs.
- Tree Frogs: are adapted to climb vertical surfaces, such as trees, and have sticky pads on both their front and hind toes to improve their grip. However, generally, only frogs in the Phyllomedusa family have opposable thumbs.
- Toads: have claw-shaped digits that are instrumental in digging, burrowing, and removing dirt. Although they have thumb-like digits, they are not opposable.
- Aquatic Frogs: generally have hind legs with powerful muscles and webbed feet to help thrust them forward when jumping, leaping, and swimming. In water, frog species with webbed hind feet are better swimmers than those that do not have webbed feet. Yet they do not have opposable thumbs.
Therefore, most frogs do not have opposable thumbs. Typically, frogs are known to jump, hop and swim as a way to get around. However, some species of frogs walk around rather than hop. You will notice such species may have opposable thumbs.
Here is a list of frogs, the species and if they have opposable thumbs:
| Frog Species | Frog Type | Opposable Thumbs |
| Waxy Monkey Frog | Arboreal | Yes |
| Phyllomedusa Camba Tree Frogs | Arboreal | Yes |
| Tarsier Leaf Frog | Arboreal | Yes |
| Burmeister’s Leaf Frog | Arboreal | Yes |
| Red-Eyed Tree Frog | Arboreal | Yes |
| Grey Tree Frog | Arboreal | No |
| Spring Peeper | Arboreal | No |
| American Bullfrog | Aquatic | No |
| Green Frog | Aquatic | No |
| Northern Leopard Frogs | Aquatic | No |
| American Toad | Terrestrial | No |
| Colorado River Toad | Terrestrial | No |
The Phyllomedusa Camba Tree Frog is an excellent example of a frog that walks instead of hopping. The presence of an independent (opposable) thumb makes this possible. The forelimb of this frog is elongated and has a more significant muscle size. It also has a stronger and longer tendon with extended boney areas (CTNF).
This fifth digit has a greater abduction, allowing it to better grip surfaces. This enables Monkey Tree Frogs and Phyllomedusa Camba Tree Frogs to have a highly precise grip on narrow branches. Such precision can only be found elsewhere in primates. Frog species with opposable thumbs are extremely good climbers.
Benefits of Having An Opposable Thumb
An opposable thumb in amphibians is the only digit on their front limbs that can turn back and touch the tip of the other digits. This enables the front limbs of such frogs to have a refined grip on objects such as tree branches and other vertical surfaces.
Frogs that have prehensile limbs with opposable thumbs are perfectly adapted for grabbing and holding on to surfaces such as tree branches. They have long, slender limbs that have reduced terminal discs at the phalanges. Frogs with opposable thumbs are generally tree frogs since they need to climb.
Frogs with opposable thumbs can walk rather than leap and jump. Because of this walking mode of movement, the Waxy Tree Frog has a distinct lemuroid-like climbing manner. This makes it easier for them to survive and thrive in their tree habitats and it is from this walking as a way of moving that they got their nickname āMonkey Frogsā.
Waxy Monkey Tree Frogs are also able to spread lipids (wax) all over their skin via a series of incredibly dexterous movements. They have finer motor skills compared to other frog species thanks to their thumbs. Even though the thumb is not fully opposable like it is for humans, such fingers have made the monkey tree frog more dexterous than other amphibians.
Having opposable thumbs also make it possible for tree frogs to jump higher than average frogs. This is because no matter how high they jump, they have minimal risk of falling since they can grab onto branches. Some tree frogs, such as the Giant Monkey Tree Frog (Phylomedusa bicolor), can jump as high as 5 feet.
You may not have seen a frog using its limbs to feed itself since most suck up their prey with their long tongue. However, some arboreal frogs can use their forelimbs to bring food to their mouth with the help of their opposable thumbs and intricate rotation of their wrists.
Having an opposable thumb on the forelimb has also made it possible for such frogs to move across narrow passageways by way of walking and crawling rather than leaping and jumping. Having such a thumb has enabled them to close their hands and execute a grip to generate balance, crucial when moving on thin substrates.
Why Donāt All Frogs Have Opposable Thumbs?
Generally, frogs have not evolved to develop opposable thumbs due to the lack of need to grasp objects in order to survive as their main methods of locomotion consist of swimming, jumping, or digging. Most frogs with opposable thumbs are arboreal and require dexterous climbing.
Frogs have long been characterized by specialized morphology such as elongated ilia and hind limbs, all associated with hopping and leaping lifestyles. Over time, different lifestyles and environments influence a frogās evolution leading to species having unique modes of movement such as walking instead of hopping.
A frogās front limbs are generally shorter than their hind limbs and their primary purpose is usually to provide support during walking and sitting and absorb impact force when landing. However, arboreal frogs with opposable thumbs have more active front limbs. Such frogs have evolved to have fairly long forelimbs that are dexterous to help them groom and grasp branches.
More About Frog Anatomy
Therefore, most frogs do not have opposable thumbs, though there are some exceptions in the wild that have adapted to their unique lifestyle. Yet, interestingly, during the mating season, most male frog’s toes swell to improve their grip in amplexus. Their thumb is not opposable, but it is enlarged to better grip females in order to successfully reproduce during mating season.
Learn more about frog anatomy in the guides on our blog below:
Sources
Castanho, L. M. and de Luca I. M. S. (2001). ”Moulting behavior in leaf-frogs of the genus Phyllomedusa (Anura: hylidae).” Zoologischer Anzeiger, 240(1), 3-6.
Manzano, A., Abdala, V., and Herrel A. (2008). ”Morphology and function of the forelimb in arboreal frogs: specializations for grasping ability?” Journal of Anatomy , 214(3), 296-307.
Soliz, M., and Ponssa, M. L. (2016). ”Development and morphological variation of the axial and appendicular skeleton in Hylidae (Lissamphibia, Anura).” Journal of Morphology , 277(6), 786-813.
