Watch how the Tungara does it.
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Reuters (screen capture)
Robo-Frog: Size doesn't matter, nor does the angelic quality of his voice: it's all about the coordination. Photo by Reuters (screen capture)

Just how does the tungara frog mate, anyway? Inquiring minds want to know and science was helpless to relieve their pain, until now. Enter Robo-Frog, which unfazed by the species' nocturalism, solved the riddles of the amphibians' courtship.

The Robo-Frog Romeo was the brainchild of American biologists Ryan Taylor and Michael Ryan, who programmed the metallic beast to do what they found impossible to do with a real frog in the steamy Panamanian jungles - test the tungara frog's courtship rituals.

Under normal conditions, the male emits a mating call, called "chucking" (not "croaking" – that's something else) to which the female responds.

Indeed the greenish girls eagerly responded to the sight of Romeo's vibrating throat, produced with the help of a mighty urinary catheter to replicate the throbbing vocal sac, and to his "mating calls," which were recorded from a real frog and piped through using remote-controlled speaker pipes.

So far so good: Robo-Frog successfully imitated the real male and the females responded. Terrific.

Then the researchers altered the timing of the robot's calls, losing the coordination with the sight element – the swelling throat. For the ladies, it was like a bucket of cold water. The magic was lost, and it couldn't be rekindled. The frog did not become a prince.

The conclusion is that successful courtship in the tungara frog depends on coordination of sight and sound – the throbbing throat and the vocal cords, say Taylor and Ryan.

It's just as well that science figured out how to make the male tungara look beautiful to his lady. The species' name in the local argot of Central America is sapito de pustulas, which means "pustulated toadlet".

When courtship succeeds, the male charmingly sits atop the female and mixes up the frog-nest goo she produces, to protect the delicate froggie eggs from the elements.

to do rhythmic mixing of a foam-producing solvent released by the female to generate a floating foam nest.[1] The foam nests are resistant bio-foams that protect the fertilized eggs from dehydration, sunlight, temperature, and potential pathogens until the tadpoles hatch. The nest degrades when the tadpoles leave after about four days, otherwise the nest can last for up to two weeks.