Rainforest frogs have evolved to wave instead of croak to attract females as waterfalls are too loud

A Ghost Glass Frog sat patiently on a leaf branch in the coastal rainforest of northwestern Ecuador

Credit: David Weiller/WENN

Rainforest frogs have evolved to replace croaking with waving to attract females because waterfalls are too loud, a study has found.

Glass frogs belonging to the Sachatamia orejuela species choose habitats located deep in the Amazon rainforest in Ecuador because they can blend in to the mossy surroundings and avoid predators.

However the croaking of the frogs is often drowned out by the background noise of rushing water, even when they are in close proximity to their potential mates.

The amphibians have now evolved and developed new techniques in an attempt to attract females, with individual frogs raising their hand above their body while bobbing their head.

This is the first time that waving has been spotted in place of the traditional mating call, researchers from the University of California found.

The frogs did not maintain their habit of waving during the entire observation period, which was attributed to the amount of energy that the gesture uses up.

Different species of frog in the Borneo and Indian jungles have previously been spotted dancing as part of their mating rituals, but this was in addition to vocalisations rather than as a replacement.

“A handful of other frog species around the world use visual signaling, in addition to high-pitched calls, to communicate in really loud environments,” said lead researcher Rebecca Brunner, a conservation biologist.

“What’s interesting is that these species are not closely related to each other, which means that these behaviours likely evolved independently, but in response to similar environments — a concept called convergent evolution.”

Ms Brunner said that she hopes the findings will draw attention to the vast diversity of species that inhabit the Amazon.

“One of the best things about fieldwork is that nature is always full of surprises, you never know what discoveries you may happen upon,” Ms Brunner said.

The evolution from croaking with waving can create an added danger of its own to male frogs, the researchers also discovered.

“Presumably visual cues also increase predation risk, although their habitats are incredibly slippery and hard to access,” they wrote.

The findings were published in the journal Biology.