Amphibians

Foam-nest Frog

Chiromantis · also called foam-nest frog, foam-nest tree frog, grey foam-nest frog

Least Concern → carnivoreinsectivore Savanna & grassland Temperate grassland Temperate forest

A foam-nest frog solves the problem of raising young in a hot, drying landscape by not putting the eggs in the water at all. Instead, a group of frogs beats a mass of fluid and eggs into a stiff white froth on a branch over a pool. The crust bakes hard in the sun, the inside stays moist, and days later the tadpoles wriggle out of the bottom and drop straight into the water.

Overview

Foam-nest frogs are tree frogs that build frothy nests above water. The name covers the African grey foam-nest frogs (genus Chiromantis) of savanna and bushveld and the Asian whipping frogs (genus Polypedates) of forest and farmland — two separate lineages that hit on the same trick. They are nocturnal insect hunters.

The nest

A female climbs a branch or reed over a pool and, with several males clinging on, releases eggs and fluid that the frogs whip into meringue-like foam with their hind legs. The nest, 10–15 cm across, sets hard outside and stays wet inside. Several females often build onto the same nest, so one foam mass can hold many pairs’ eggs. When the tadpoles hatch, the crust breaks down and they fall into the water below.

Built for the heat

The grey foam-nest frog is one of the most heat- and drought-tolerant frogs known: it sits in full sun, turns chalky white to reflect heat, cuts skin water loss to near-reptile levels, and excretes uric acid paste instead of urine to save water. It waits out the dry season inactive in tree holes and under bark.

Status

Least Concern — the widespread species are common and readily use farm dams, troughs, and gardens. A few forest specialists with small ranges are of more concern.

Foam-nest Frog: common questions

How do foam-nest frogs make the foam?

The female produces a fluid along with her eggs, and the frogs whip this fluid into foam by kicking rapidly with their hind legs, much the way a cook beats egg whites into meringue. Proteins in the fluid trap air bubbles and stabilise them, so the foam holds its shape. The outside dries into a tough, crusty shell within hours, while the inside stays wet and cushiony around the eggs. The whole structure is built on a branch, reed, or rock face directly above water so that the tadpoles land in the pool when they emerge.

Why build a nest above the water instead of in it?

It keeps the eggs away from the many predators that hunt in the water itself, such as fish, aquatic insects, and other tadpoles, and it protects them from the low-oxygen, crowded, competitive conditions of a shrinking savanna pool. The foam guards against the other big risk, drying out, by holding moisture around the eggs and shielding them from direct sun. The tadpoles only enter the water once they have passed the safest part of development, which tips the odds in their favour.

Can foam-nest frogs really sit in full sun all day?

The African grey foam-nest frog can, and it is one of the most drought- and heat-hardy frogs known. It reduces water loss through its skin to a level far below that of a typical frog, close to that of a lizard, it turns pale, almost white, in bright light to reflect heat, and it converts its nitrogen waste into a paste of uric acid rather than watery urine, as reptiles and birds do, so it loses almost no water to excretion. This lets it rest exposed on branches through a hot African day.

Are the African and Asian foam-nest frogs related?

Only distantly. Both belong to the broad Old World tree frog group, but the African grey foam-nest frogs, genus Chiromantis, and the Asian whipping or foam-nest frogs, genus Polypedates and relatives, are separate lineages that independently evolved the same foam-nest breeding strategy. It is a good example of convergent evolution, where an effective solution to a shared problem, in this case protecting eggs in a hot climate with unreliable pools, arises more than once. Their nests, behaviour, and general appearance are strikingly alike despite the distance.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Chiromantis
Diet: A nocturnal ambush predator of insects and other small invertebrates, hunting in trees and shrubs and around lights near water, and able to go long periods without feeding through the dry season while it sits inactive in the open
The foam nest: To breed, a female climbs onto a branch or reed overhanging water and, while several males cling on, releases eggs and fluid that the frogs beat with their hind legs into a stiff meringue-like foam, forming a nest 10 to 15 centimetres across that hardens on the outside while staying moist within
A nursery on a branch: The eggs develop inside the foam for several days, protected from drying, from the sun, and from many predators, and when the tadpoles hatch the outer crust breaks down and they wriggle free and drop into the water below to continue growing
Built by a crowd: Several females often add to the same nest over a night or two, so a single large foam mass can contain the eggs of multiple pairs, and the trees over a good breeding pool can carry dozens of nests at once
Made for heat and drought: The grey foam-nest frog tolerates conditions that would kill most frogs, sitting fully exposed on a sunlit branch through the day, turning chalky white to reflect heat, cutting water loss through its skin to near reptile levels, and excreting waste as paste rather than watery urine to save water
Two frogs, one name: The name foam-nest frog is used both for the African grey foam-nest frogs of the genus Chiromantis and for the Asian whipping frogs of the genus Polypedates, which build very similar foam nests, an example of the same solution evolving twice in tree frogs on different continents
Waiting out the dry season: Through the long dry season foam-nest frogs become inactive, often in groups, sheltering in tree holes, under bark, or among leaves with a lowered metabolism, and they resume activity and breeding with the first heavy rains
Range: Sub-Saharan Africa for the genus Chiromantis, in savanna, bushveld, dry woodland, and forest edge near standing water, and South and Southeast Asia for the similar Polypedates whipping frogs, in forest, plantation, farmland, and gardens, in both cases wherever there are pools or dams with overhanging branches or reeds for nest-building.
Conservation status: Least Concern → ≈ The widespread foam-nest frogs are common and adaptable and are assessed as Least Concern. The grey foam-nest frog ranges across much of sub-Saharan Africa, readily uses farm dams, cattle troughs, garden ponds, and other artificial water, and often breeds around rural buildings, and the common Asian foam-nest species are similarly tolerant of disturbed and cultivated land. Local declines happen where breeding pools are lost or polluted or where the trees over water are cleared, and a few range-restricted foam-nest frogs in forest habitats are of greater concern, but the group as a whole is in no difficulty in the wild