Are any an­i­mals un­able to hear their own calls?

BBC Wildlife Magazine - - Q&a - Liz Kalaugher

AYes. Sci­en­tists study­ing two species of pump­kin toadlet, a tiny frog found in the cloud-forests of Brazil, dis­cov­ered that the males call at fre­quen­cies that they, and the fe­males they hope to at­tract, can’t hear.

Frogs nor­mally have a mid­dle ear con­tain­ing a bone that trans­mits sound vi­bra­tions from the eardrum to the flu­id­filled in­ner ear, where hair cells de­tect move­ment of the liq­uid and send elec­tri­cal sig­nals to the frog’s brain. Pump­kin frogs, how­ever, lack this mid­dle ear, and as such are de­fined as ‘ear­less’.

Though they are still able to de­tect some fre­quen­cies, trans­mit­ted to their in­ner ear via body­parts such as the lungs, mouth or skull, the toadlets can’t sense fre­quen­cies above 1 kHz, even though the males call at 3.7–5.7 kHz. It’s the only known ex­am­ple of a species not be­ing able to hear its own mat­ing call. Fe­males may in­stead pick up on the vi­su­als of the call, such as the male’s bulging vo­cal sac. Mak­ing a noise may ap­pear to put this frog at risk of pre­da­tion for no gain, but his brightly coloured toxic skin may pro­tect him.

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