Amphibians
Archey's Frog
Leiopelma archeyi · also called archey's frog
Archey’s frog is a tiny brown frog from the forests of northern New Zealand, and it is one of the most ancient frogs on Earth. Its body plan has barely changed since the Jurassic. It has no eardrum and does not croak, it skips the tadpole stage entirely, and after the eggs hatch the father carries the froglets around on his back.
Overview
Archey’s frog lives in damp native forest on the Coromandel Peninsula and at one site near Te Kūiti, on New Zealand’s North Island, among leaf litter, moss, and rocks — usually well away from open water. It is only 31–37 mm long, brown or green, warty, and unwebbed. It hunts springtails and mites at night, and lacking a projectile tongue it simply lunges and grabs prey with its jaws.
An ancient lineage
It is one of a few surviving species of Leiopelma, a group that branched off very early and then changed little. It keeps features the ancestors of frogs had and all other living frogs lost: small tail-wagging muscles (though it has no tail), an extra vertebra, round pupils, and no eardrum or loud call — communicating only in faint close-range squeaks.
Reproduction on land
There is no swimming tadpole. The eggs are laid in a moist, hidden spot; the embryos develop inside the capsule; and the froglets hatch fully formed and climb onto the male’s back, where he carries and guards them.
Status
Archey’s frog is Critically Endangered. One population crashed by about 88 percent between 1996 and 2001, linked to the fungal disease chytridiomycosis, and it also faces introduced predators and habitat damage. Because it represents so much unique evolutionary history and is so threatened, it ranks at or near the top of the global list of evolutionarily distinct, endangered amphibians. Conservation work includes predator control, monitoring, disease precautions, and a captive insurance population.
Archey's Frog: common questions
Why is Archey's frog called a living fossil?
Because the living animal is anatomically very close to frogs that lived alongside the dinosaurs. Archey's frog belongs to Leiopelma, a lineage that separated from all other frogs very early and then changed little. It keeps several features that the ancestors of frogs are thought to have had and that every other living frog has lost or modified, including small muscles that would wag a tail if it had one, an extra vertebra, a particular way of moving that involves belly-flopping rather than long jumps, and the lack of an eardrum and a loud call. Studying it gives biologists a window into what early frogs were like.
How do Archey's frogs reproduce without a tadpole stage?
They practise direct development on land. Instead of laying eggs in water that hatch into swimming tadpoles, the female lays a small clutch of large eggs in a damp, hidden place such as under a log or stone. The embryos develop fully inside the egg capsule, passing through a tadpole-like phase internally, and hatch as tiny four-legged froglets rather than as larvae. The male then takes over care, letting the froglets climb onto his back and carrying them around, which keeps them moist and protected until they are independent. This strategy frees the frog from any need for ponds or streams.
Why did Archey's frog become Critically Endangered?
The sharpest blow was disease. Between 1996 and 2001 one of the main populations, on the Coromandel Peninsula, fell by roughly 88 percent, a collapse linked to chytridiomycosis, the fungal disease that has devastated amphibians worldwide. On top of that, the frog has a naturally tiny range, and it faces predation by introduced rats, stoats, and possums, damage to its forest floor habitat by feral pigs and goats, and historically the threat of mining on the Coromandel. Its small size, low reproductive output, and dependence on cool, damp, undisturbed forest leave it little margin.
What is being done to protect Archey's frog?
Conservation work in New Zealand includes intensive predator control at the key sites, close population monitoring, disease research and hygiene protocols for anyone entering frog habitat, and the establishment of a captive breeding and research population as an insurance against loss in the wild. There have also been translocations to create additional secure populations. Because the species carries so much unique evolutionary history, it is treated as a high priority, and it is often used as a flagship for the conservation of New Zealand's other ancient, vulnerable native frogs.