Between November 2022 and February 2023, Te Papa Natural History interns Tobia Dale and Ben Carson assisted with the curation of three major donations of Aotearoa New Zealand pepeketua and mokomoko. In this fourth and final blog about their work, they highlight some very special frogs that they were privileged to work with.
Often referred to as living fossils, tail-wagging muscles, extra bones in their backs, and no eardrums are just a few of the features that make our native frogs so special. As part of the Phil Bishop acquisition, we got the chance to see all our native frogs and their closest cousin up close.
How many frogs live here?
New Zealand is home to some of the most unusual wildlife on the planet, and our amphibians are no exception. There are six living species of frog in New Zealand – three introduced species and three native species.
The southern bell frog (Ranoidea raniformis), green and golden bell frog (Ranoidea aurea), and the southern brown tree frog (Litoria ewingii) were all introduced from Australia and are most likely the frogs that we come across at local ponds or freshwater wetlands.
Aotearoa New Zealand’s own pepeketua are truly ancient members of our fauna, having diverged from other frogs nearly 200 million years ago. Because they split so long ago, they have retained ‘primitive’ traits which other frogs have lost.
The English, te reo Māori, and scientific names of our native frogs commemorate naturalists involved with their scientific discovery.
In the order that they were described, they are:
Hochstetter’s frog (poraka a Hochstetter, Leiopelma hochstetteri – 1861)
Hamilton’s frog (poraka a Hamiltoni, Leiopelma hamiltoni – 1919)
Archey’s frog (poraka a Archey, Leiopelma archeyi – 1942)
Recognising the true kiwi frogs from the Aussie imports
Our native frogs are very cryptic with no croak and perfect camouflage. They also only persist in fragmented populations in the North Island and Marlborough Sounds. As a result, native frogs are rarely encountered by members of the public.
They are much smaller than the two bell frog species, though all the introduced frog species pass through a small froglet stage soon after they metamorphose from tadpoles.
The easiest way to identify an introduced frog species is that they all have a prominent external eardrum – a disc of skin behind the eye. New Zealand native frogs don’t have eardrums and they don’t croak – though they sometimes give a panicked chirp when alarmed.
Unusual features of our endemic Aotearoa New Zealand frogs
In addition to being largely silent, Archey’s frogs and Hamilton’s frogs have unusual life histories compared to other frogs. They live terrestrially in damp forests, without the swimming tadpole stage typical of most frogs.
Both Archey’s frog and Hamilton’s frog carry young froglets on their backs until metamorphosis is completed. In contrast, Hochstetter’s frogs inhabit slow-running streams and shallow puddles and don’t carry their young.
Despite not having a swimming tadpole stage, our endemic frogs are unusual among frogs in retaining tail-wagging muscles even as adults. They also have an extra vertebra in their backbone. Both of these anatomical characters are shared with their nearest cousins, now living more than 10,000 km away.
A bizarre North American connection
One of the collections that we sorted through and registered for Te Papa was a research collection assembled by Professor Phil Bishop (1957–2021) of Otago University.
The Bishop collection included voucher specimens of the Rocky Mountain tailed frog (Ascaphus montanus). The tailed frogs of the American Northwest are considered the closest living relatives of Aotearoa New Zealand’s endemic frogs.
Check out this cool interactive phylogenetic tree to see how our native frogs and their cousin fit into the tree of life and how long ago they split from other frogs.
Like our native pepeketua, both Ascaphus species retain their tail-wagging muscles when adults. However, unlike our Leiopelma frogs, the North American species have a typical frog tadpole stage.
Ascaphus tadpoles have unusually large sucker-like mouths that they use to cling to rocks in cold, swift-flowing streams.
Te Papa did not previously hold specimens of Ascaphus. The two adults, two froglets, and five tadpoles of this unusual little frog are a welcome addition to the research collection.
Signing off
This is the fourth and final blog from our Natural History summer internship. We’ve thoroughly enjoyed working through the three acquisitions and learning how specimens are best preserved, and the value of good data for long-term research use. We have been very fortunate to handle some rare and unusual specimens, and to have the opportunity to share a few highlights with you! Check out our previous blogs here:
Related blogs
- Processing pickled pepeketua – how many frogs can you fit in a jar?
- Wanted dead or alive – Our Natural History interns’ work with Wellington lizards
- Searching for New Zealand’s first record of chytrid fungus
