A hairy frog with fur? And sharp, cat-like claws? Either might sound improbable, and Africa’s hairy frog Trichobatrachus robustus is certainly stranger than fiction.
How big is the hairy frog?
The hairy frog (Trichobatrachus robustus) is a medium to large-sized frog, around 10cm long, that looks superficially very much like many other frogs for most of the year.
Where does the hairy frog live?
The hairy frog lives in and around the fast-flowing rivers and streams of tropical central Africa.
Why is the hairy frog hairy?
This frog is hairy during the mating season, when the male develops a thick bristle-like fringe along his flanks and thighs. This is actually a mass of thin strands of skin replete with blood vessels, and is a temporary organ that may boost breathing ability in times of need.
After the female has laid her eggs and the male has fertilised them, she hops out of the water and the male remains guarding the clutch of spawn, which is stuck to a submerged rock. Until the tadpoles hatch, he effectively becomes aquatic. The fast-flowing water means he needs to hunker down to avoid being swept away, so with trips to the surface to breathe out of the question, skin-breathing makes total sense.
So why aren't all frogs hairy?
The reason hairy frogs have claws and need to be hairy, while many other (just as aquatic) species don’t, may be down to the increased oxygen demands caused by their aquatic grappling matches.
Do hairy frogs have claws?
This frog has another clever survival trick. With the flex of a foot muscle, it can produce an arsenal of sharp, curved claws that snap out of its toes like switchblades. These thorn-shaped toe bones rapidly pivot when triggered, sending the pointed tip slicing through the frog’s skin and transforming its feet into formidable weapons. A few violent kicks can lacerate a foe and draw blood from an unsuspecting biologist. People in Cameroon, who hunt these frogs for food, use spears and machetes to avoid handling them.
What are its claws made from?
What’s weirder still is that these are not analogous to mammal claws at all – there is no keratin here. These claws are comprised of the broken ends of the frog’s toe bones. Inside each toe of its rear foot, the last bone is attached to an anchor bone at the very tip of the toe. When needs must, it contracts muscles and tendons attached to the underside of this last bone, causing it to break away from the anchor bone and then swing downwards, puncturing and bursting through the skin.
So it breaks its own bones?
If you think this sounds pretty drastic and damaging, don’t worry. Another frog superpower is regeneration. When the claws are no longer needed, they are pulled back up and into place, and the tendons, muscles and skin heal and reset, ready for the next breeding season.
