ADORABLE BRAZILIAN FROGS CAN’T HEAR THEMSELVES SPEAK
Two species of tiny frogs, known as pumpkin toadlets, which live on the floor of Brazil’s Atlantic Forest, are unable to hear their own (and each other’s) cries, it has been discovered. This makes them the only two species known to have evolved in this way. The discovery was made by a team of scientists from Brazil, Denmark and the UK, led by Dr Sandra Goutte from Brazil’s Universidade Estadual de Campinas.
In order to find a mate, most frog species signal their presence to members of the opposite sex by calls, but making such calls consumes energy and can attract predators. The two species of pumpkin toadlet also make such calls, but laboratory testing at the University of Southern Denmark suggested they are unable to actually hear them, while anatomical studies at Cambridge University confirmed that the part of the ear that would normally detect the high frequencies involved is vestigial in the two species involved. In other words, like the human tailbone, it’s still there but no longer does anything.
Jakob Christensen-Dalsgaard from the University of Southern Denmark said: “We have never seen this before: these frogs make sounds that they cannot hear themselves.”
Goutte added: “One would think that if a signal is not perceived by its target audience, it would be lost through evolution.”
It’s thought that the calls have been retained because the bright orange toadlets have replace auditory with visual signalling, and that the throat-swelling that produces the call is now the way the toadlets attract a mate – with the resulting call now a mere by-product of this visual signal.
The pumpkin toadlets’ bright colours warn predators of their toxicity