The Hairy Frog Has Retractable Claws Made of Bone

Hairy frogs develop hair-like structures on the sides of their bodies, but these aren’t real hairs. They’re actually tough strands of skin with short ridges, found only on the breeding male during the mating season.

These strands act like external gills, increasing surface area to absorb oxygen from water—a helpful trait when males guard egg masses in oxygen-poor environments.

This adaptation is especially useful in the frog’s aquatic stage. Breeding males often remain with the eggs for an extended period, even as water currents in fast-flowing rivers threaten to wash them away. The better grip and oxygen absorption from these structures help them survive.

The hairy frog’s nickname comes from its retractable claws, made of bone. Inside each toe tip of the frog’s hind foot lies a small bony nodule just under the skin.. When attacked, the frog intentionally breaks the nodule loose and pushes the sharpened bones through its own skin.

Possessing retractable or erectile claws gives hair frogs a brutal but effective defense.

The claws are not keratin like in cats; they’re made from the frog’s own bones. Because of this, they can’t retract passively. They remain extended until the damaged tissue heals.

Some scientists speculate this weaponry evolved to give frogs a better grip during territorial disputes or when clinging to slippery surfaces.

Each claw sits on the inner surface of the frog’s toe and is sharpened like a horned tooth. The claw connects to the bone via a nodule connection, forming a natural hinge.

When the claw is extended, the bony nodule remains embedded in the toe pad, anchoring the bone and preventing it from tearing completely out of the toe.

The retraction mechanism is still under study. Researchers from the American Museum of Natural History and other scientist news services are exploring whether these claws evolved solely for defense or if they assist with mobility in rough environments.

These claws give new meaning to the idea of natural weaponry. Unlike many species that develop external tools, the hairy frog turns its own bones into weapons.

Trichobatrachus robustus typically breeds during the rainy season. Males stay close to egg masses, guarding them from predators. They rely on their tough skin and somewhat hair-like structures to remain oxygenated and safe.

This frog species is most commonly found in Cameroon but has a large range across parts of Central Africa. It’s typically considered semiaquatic, with adults feeding on insects, worms, and other small invertebrates.

Frogs fall into various categories based on breeding behavior, and the hairy frog is notable for its parental investment. The male's commitment to guarding eggs adds an extra layer to its survival story.

Due to its unusual biology, the hairy frog has caught the attention of the wild animal trade. Collectors seek it for exotic pet markets and as specimens for scientific institutions.

The hairy frog is classified as Least Concern on the IUCN Red List, but it faces threats from rainforest habitat loss and unsustainable harvesting for food and the pet trade.

Local communities (for example, the Bakossi people of Cameroon) traditionally believe that eating these frogs can help childless couples conceive, leading to additional hunting pressure on the species.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.