New Zealand has four frog species that are endemic – found only in New Zealand. There were three other endemic species, but they have become extinct since humans arrived. A further three species from Australia have formed self-perpetuating populations.
Frogs are known as pekeketua or pepeketua in Māori.
Features of New Zealand endemic frogs
New Zealand endemic frogs are among the world's most ancient. Their ancestors were carried by continental drift from the supercontinent of Gondwana millions of years ago. In a family of their own (Leiopelmatidae), they differ from most other frogs in many respects:
- They have no eardrums.
- They have no vocal sac and do not call or croak, although they make quiet squeaks when disturbed.
- They catch insects with their mouth, not with a long tongue.
- They lay small numbers of large yolky eggs in moist places, but not in water.
- Tadpoles grow inside the egg and hatch as tailed froglets – there is no free-swimming tadpole stage.
Spine and muscles
All the New Zealand native frogs have an extra vertebra, and unlike modern vertebrates their vertebrae are concave at both ends. They have long pieces of cartilage in the abdominal muscles. Although the adults have no tail, they have tail-wagging muscles (called caudalipuboischiotibialis muscles).
They share some of these features with ancient fossil frogs as old as 135 million years, and with one other living primitive family (Ascaphidae) in the American Rockies.
The primitive native frogs swim using alternate legs – like a dog paddle instead of a frog kick. Because their head moves from side to side, this is less energy-efficient than the swimming style of modern frogs.
Distribution of endemic frogs
Two species – Hochstetter’s frog (Leiopelma hochstetteri) and Archey’s frog (L. archeyi) – occur in the North Island. The other two, the Maud Island frog (L. pakeka) and Hamilton’s frog (L. hamiltoni), are restricted to Maud Island in the Marlborough Sounds and Stephens Island in Cook Strait respectively, apart from recent transfers to other suitable islands for back-up populations. There is the intriguing possibility that a South Island frog may yet be found.
Of the three extinct species described by Trevor Worthy in 1987, remains of Leiopelma markhami have been found in the North and South islands. L. waitomoensis is known only from the North Island and L. auroraensis from a single cave in the South Island. L. waitomoensis was a large, robust frog, almost twice the length of any endemic frog alive today, and presumably many times heavier.