Foam nest frogs

Text: Ranger Pieter van Wyk

Days of overcast and wet conditions on MalaMala Game Reserve have now given way to clear blue skies. The wind has died down and the smell of rain has faded like a distant memory. It almost feels like we’ve entered into a calmer world but any sense of emptiness is an illusion. On the contrary in fact, the bush has been rejuvenated and frogs in particular, have been busy.

It’s quite common during our summer months to come across conspicuous balls of white foam suspended on branches over water. These slimy and frothy, almost extraterrestrial structures, are the product of perhaps the most promiscuous vertebrate on the planet: the female Foam Nest Frog (Chiromantis xerampelina). Before laying her eggs the mating female secretes a fluid, which is then churned up by the hind legs of the mating pair. The couple’s privacy is short-lived as several males (as many as 12!) will enter the fray and jostle for a spot next to the female. When she releases a batch of eggs they are fertilized by her mating partner as well as the other nearby males. As the eggs are laid all the males will help churn them into the foam. From time to time the female will leave the nest to rehydrate herself in the water below before returning, normally to a different partner. This ordeal carries on throughout the night. The following day’s sunlight will harden the nest’s outer surface. After roughly five days the developing tadpoles break out and fall into the water below where they will complete their metamorphosis.

Why do they go through all this trouble? It simply increases their offspring’s’ chances of survival. Starting life above the water means that they are out of the grasps of their aquatic predators. The nest also functions as an insulator, allowing the eggs to develop at an even temperature.

There are more than 5000 species of frogs and toad on earth, coming in all shapes and sizes.

“Frogs are truly fascinating. You may not have thought much about them and they don’t necessarily grab the headlines, but there’s more to frogs than you might suppose.” ~ Sir David Attenborough.