Boats dock off the coast of Santa Cruz Island in the Galapagos, Ecuador on April 15. Photos: AFP

Ecuadoran biologist Jorge Brito was trekking through the forest when he heard what he thought was the chirp of a cricket.

What he found changed a century of scientific belief.

"At first I thought it was some sort of cricket out there vocalizing, but then I paid attention" said Brito, from Ecuador's national biodiversity institute.

It was, in fact, a type of brown toad with rough skin called Rhinella festae that has a prominent nose and had been considered mute since it was first discovered 100 year ago.

"While it did not inflate its vocal sack, you could see a small flicker" on its chin, said Brito.

He caught it and took it to a laboratory to study with his colleague Diego Batallas.

"The first time I heard it, I said: 'Wow, that's not the sound of a toad, it's like a little bird,'" Batalla told AFP.

The toad, which measures with a range between 45 and 68 millimeters in length, lives in the mountainous Ecuadoran regions of Cutucu as well as Condor, extending over the border into the Amazonian region of Peru.

The discovery was first reported in February in Neotropical Biodiversity magazine, where Brito and Batallas described the sound made by the toad.

"It is the first time this unique song of the Rhinella festae has been recorded and it's surprising because it shouldn't sing," Batallas told AFP.

The toad does not have the vocal sack that allows most amphibians to amplify their calls so that they can be heard up to one kilometer away.

AFP