A Congolese giant frog that grows to the size of a small hand would be a heart meal for any predator. But he avoids being eaten by birds, lizards, and snakes with a trick never seen anywhere else in the world: He looks and acts exactly like the Gabon viper, one of the most poisonous snakes in Central Africa.
Many animals imitate dangerous ones so they do not eat. Viceroy butterflies are colored like a toxic monarch, for example, and many harmless snakes imitate poisonous. But this is the first time a frog has been discovered to imitate a snake.
To make sure researchers don't see things, a team of herpetologists spend 10 years comparing dead frogs from museums to living frogs from 11 places across the Democratic Republic of the Congo to the deadly ash tree. First, the researchers noticed that the frog's body had a triangular shape similar to the head of a dropper (top, left and right respectively). Then they noticed a striking and constant color pattern: Just like the aubergine, the frog has two dark brown spots and a dark brown streak extending down the back. Finally, when the frog senses danger, it emits a long, low hissing noise, similar to the warning dryness that can drive a Gabuna's ashes before it strikes. Taken together, these similarities suggest that the frog is a near perfect mimicry for a speck, researchers write today in Journal of Natural History. Furthermore, given their close evolutionary history (both evolved between 4 million and 5 million years ago) and the fact that the frog only occurs in places where the ash is present, frogs and vultures are likely to develop together, the authors write.
The color and shape of the frog are not an exact match. But most predators probably avoid anything that looks like a snake – because a mistake can be deadly.