Amphibians
Water-holding Frog
Cyclorana platycephala · also called water-holding frog, flat-headed frog
The water-holding frog is the Australian desert’s answer to a water bottle. Before a drought, it drinks until it swells into a ball, buries itself deep in the clay, and wraps itself in a cocoon of its own shed skin — then waits, sometimes for years, until it rains again. Desert peoples knew exactly where to dig for one, and would squeeze the frog gently for a clean drink.
Overview
The water-holding frog lives across arid and semi-arid inland Australia, in claypans, floodplains, and temporary swamps. It is about 5–7 cm, squat, with a flattened head and upward-facing eyes, green to grey-brown. It hunts insects, tadpoles, and other frogs during the brief period when there is water.
Storing water
Before burrowing it takes in large amounts of water, filling its bladder and the loose spaces under its skin until it is rounded and swollen — carrying stored water equal to a big fraction of its body weight.
The cocoon
Buried up to a metre down, it sheds layer after layer of skin into a nearly waterproof envelope around its whole body, with only the nostrils open. Sealed in, it drops its metabolism and can stay dormant for several years, then dig out within hours of a heavy downpour.
A drink in the desert
Aboriginal peoples of the arid interior located buried water-holding frogs, dug them up, and gently pressed them to drink the clean stored water before releasing the animal — a survival technique recorded by early explorers.
Status
The water-holding frog is Least Concern, widespread and well buffered against drought by its burrowing and cocooning habits.
Water-holding Frog: common questions
How does the water-holding frog survive years of drought?
With a combination of storage, insulation, and shutdown. When rain fills a claypan, the frog drinks and absorbs as much water as it can, filling its bladder and the roomy lymph spaces beneath its skin until it is visibly swollen. It then digs backwards into the soft mud, sometimes down to a metre, and moults repeatedly without discarding the skin, building up a translucent, nearly airtight cocoon around itself. Sealed in, with only its nostrils in contact with the outside, it drops its heart rate and metabolism to a fraction of normal and lives off its stored water and body fat, sometimes for several years, until the next big rain triggers it to break out.
Did people really drink from these frogs?
Yes. Aboriginal peoples of arid Australia knew that water-holding frogs lay buried in certain kinds of ground and could be dug up in an emergency, and they would carefully press the frog so that it released the clean water held in its bladder into a container or straight into the mouth, then let the animal go. The water is essentially filtered and drinkable. Several nineteenth-century European explorers recorded being shown or told about the technique, and it is one of the better-known examples of detailed traditional knowledge of desert survival.
Is the water-holding frog the same as the desert rain frog?
No, they are different animals on opposite sides of the world. The desert rain frog is a small, round, aquatic-eyed frog of the Namib coast in southern Africa, famous for a squeaky distress call. The water-holding frog is an Australian species, larger, flat-headed, and adapted to the interior deserts. They are both burrowing frogs of dry country, and both are rounded when inflated, but they are not closely related and the water-holding frog's headline trait is its ability to store water and cocoon for years, which the desert rain frog does not do.
What happens when it finally rains?
A heavy rain event soaks down through the soil and softens the frog's cocoon, and within a matter of hours the frog rehydrates, sheds the cocoon, and digs its way to the surface. It then moves to the newly filled pools, feeds intensively on insects and other frogs' tadpoles, and joins in explosive breeding, with males calling and pairs laying eggs that must develop very fast before the water disappears again. The adults refill their water stores, fatten up, and, as the pools shrink, burrow back down to begin another period of waiting.