The nursery frog is Australia’s smallest – and sweetest


Bec Crew


Bec Crew

Bec Crew is a Sydney-based science communicator with a love for weird and wonderful animals. From strange behaviours and special adaptations to newly discovered species and the researchers who find them, her topics celebrate how alien yet relatable so many of the creatures that live amongst us can be.
By Bec Crew 16 May 2022
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Everything about the nursery frog is adorable. This tiny frog, which is barely more than a few centimetres long, is named for the fastidious care it gives to its offspring.

Unlike most amphibians, which abandon their eggs as soon as they’re laid, nursery frog males run a sweet little froggie daycare for its unhatched babies, keeping them warm, moist and safe under a rock, log or pile of leaf litter.

What’s strange about nursery frog offspring is that it bypasses the tadpole stage altogether – a characteristic that likely comes from laying its eggs on the land. The eggs, which will never touch the water, are coated in a thin string of clear jelly, which helps tie them all together.

From the egg stage, nursery frog offspring transition right through to froglet form. As you can see in the image above, which shows an ornate nursery froglet (Cophixalus ornatus) from Possum Valley in Queensland, this means hatching with fully formed legs and a tail, which it will eventually lose.

Nursery frogs belong to the genus Cophixalus. There are more than 60 known species, found in parts of Indonesia, New Guinea and Queensland, Australia.

The dainty nursery frog (Cophixalus exiguus), which grows to just 16-19mm, is thought to be Australia’s smallest frog. It’s found in a tiny area of northern Queensland, just south of Cooktown. 

Also known as the scanty frog, this species goes to great lengths to find a mate, scaling trees to a height of 1.5m in order for its calls to travel further.

For comparison, the smallest frog in the world is Paedophryne amauensis, from Papua New Guinea. Discovered in 2012, this minuscule amphibian grows to just 7.7mm, on average.

The fact that the nursery frog takes such good care of its eggs means that it doesn’t have to lay that many. Compared to other frog species, which can lay thousands of eggs in the water due to extremely high rates of predation and other threats, nursery frogs can lay fewer than 20 eggs at a time, confident that, with the right care, most of them will survive long enough to hatch.

Nursery frogs join a small number of amphibians that take extra special care of their young. The Surinam toad from South America, for example, incubates its eggs in little holes sunk into its back.

Darwin’s frog, from Chile and Argentina, is a mouth-brooder – it takes its offspring into its mouth and incubates them in its vocal sac.

And then there’s the poison dart frog from tropical Central and South America, which actually transports its tadpoles on its back to cups of rainwater created by bromeliad plants:

Find out more about the fascinating world of frog parenting.