Welcome to another fortnightly edition of Freaky Frog Friday! This time, we’ll be taking a brief look at the hairy frog from central and western Africa. As you can see from the taxidermied museum specimen above, this frog is named after the thick, shaggy ‘fur’ that grows across the flanks and thighs of the males during the breeding season. However, this is not true hair (which is possessed only by mammals); instead, they are hair-like projections, or papillae, which are used like external gills to extract dissolved oxygen from the water. All frogs can breathe through their skin, provided it is wet, and the papillae serve to increase the hairy frog’s normal surface area, which in turn increases oxygen intake.
But why do only the males have this ‘hair’ – and only during the breeding season? The reason is thought to be because males stay with their underwater egg broods for an extended period of time after they have been laid by the females. The papillae allow the males to absorb enough oxygen while submerged so that they don’t even need to temporarily leave their eggs to snatch a gulp of air from the surface.
But the hairy frog’s most noteworthy features are surely its retractable claws. Unlike true claws, these are made out of bone rather than keratin, and they are usually found beneath the frog’s skin. If this bizarre amphibian feels threatened, special muscles contract and force these bones out through the frog’s toe pads like switchblades. Small but hooked, the razor-edged bone shards can then be used to slash at any attacker. In fact, they’re so effective that local people in Cameroon often hunt the hairy frog with machetes or long spears to avoid being injured.
This type of behaviour has not been studied extensively and many mysteries still surround it. However, it is thought that the bones slide back into the body of the frog once the threat has subsided, and the damaged tissue heals quickly. With its retractable claws, the sideburn-like growths on its body, and accelerated healing abilities, the hairy frog can be seen as the ‘Wolverine’ of the amphibian world.
In the next Freaky Frogs article, as we get closer to Christmas, we’ll be looking at a frog that can survive being frozen solid – the wood frog.