Amphibians
Paedophryne Amauensis
Paedophryne amauensis · also called Amau frog, PNG dwarf frog
Paedophryne amauensis is a frog the length of a housefly. Discovered in the rainforest litter of Papua New Guinea and described in 2012, it is the smallest backboned animal ever found — small enough that a whole adult perches on a fingernail with room to spare.
Overview
Paedophryne amauensis lives only in the leaf litter of lowland and hill rainforest in eastern Papua New Guinea. Adults average 7.7 mm snout to vent. It is a mottled brown, cryptic against dead leaves, and it belongs to a genus of about seven New Guinea frogs all under 13 mm.
Life without water
It hunts mites and springtails — prey too small for most frogs — and lays its eggs in damp litter, where they develop directly into tiny froglets with no tadpole stage and no need for a pond. The permanently humid litter layer is what makes a frog this small possible.
Found by ear
Males call with a thin, high insect-like tick at 8–9 kHz. Researchers tracked the sound, then scooped up leaf litter and sorted through it to find the callers.
The cost of being tiny
Shrinking this far has trimmed the animal down: fewer vertebrae, reduced toes, a simplified skull. Even so, it can hop about 30 times its body length.
Status
The species is Not Evaluated. Its rainforest home appears intact, but its full range is unknown. A Brazilian flea toad reported in 2024 at around 7.1 mm may now hold the size record.
Paedophryne Amauensis: common questions
Is Paedophryne amauensis really the smallest animal with a backbone?
When it was described in 2012 it was, at an average of 7.7 mm, edging out a carp relative from Sumatran peat swamps that matures at around 7.9 mm. It held the title cleanly for over a decade. In 2024 a Brazilian flea toad in the genus Brachycephalus was reported with adult males averaging around 7.1 mm, which if confirmed by wider sampling would make that species the smallest. Either way, Paedophryne amauensis is at or very near the lower size limit for a vertebrate, and the two contenders are separated by fractions of a millimetre.
How does such a tiny frog survive?
By occupying a niche that larger animals cannot. At under 8 mm it hunts mites, springtails, and other minute invertebrates that are too small to be worthwhile prey for a normal frog but too fast or too armoured for many predatory insects. Living in the permanently damp tropical leaf litter solves the biggest problem a small amphibian faces, drying out, because the humidity there stays near saturation. Skipping the tadpole stage removes any need for ponds. The cost is fragility and a short list of trade-offs in the skeleton and sensory organs that come with being this small.
Why do frogs get so small in New Guinea?
New Guinea has an unusually rich leaf-litter fauna and, on many parts of the island, no native ground-dwelling mammals filling the small-insect-eater role that shrews and mice occupy elsewhere. Frogs appear to have radiated into that gap, and several unrelated New Guinea frog groups have independently evolved very small body sizes, with the genus Paedophryne taking it furthest. Extreme miniaturisation has evolved many times in frogs around the world, in the leaf litter of Brazil, Madagascar, the Seychelles, and Sri Lanka as well, wherever the conditions reward being tiny.
Has anyone kept one, or could you?
They are not in the pet trade and would be extraordinarily difficult to keep. An animal this small loses and gains water and heat almost instantly, needs a constant supply of live prey a millimetre or less across, and could not be handled without risk of injury. All study of the species has been done in the field or on a small number of preserved specimens. There is also no conservation reason to collect them; the sensible approach is to protect the rainforest litter they live in.