Frogs are vertebrates and belong to the class Amphibia. They are the only amphibians naturally occurring in New Zealand. All frogs have delicate, semi-permeable skin that allows them to absorb moisture and air from the surrounding environment.
In New Zealand, we originally had 7 species of native frog, but 3 are now extinct with only 4 native species remaining – Leiopelma hamiltoni (Hamilton’s frog), Leiopelma pakeka (Maud Island frog), Leiopelma archeyi (Archey’s frog) and Leiopelma hochstetteri (Hochstetter’s frog).
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The existence of each remaining species is threatened, with two species listed as endangered. They are very difficult to find in their natural environments.
There are also 3 introduced species, all from Australia. These are the brown tree frog, the southern bell frog and the green and golden bell frog.
Māori have 3 names for frogs – pepeke, peketua and pepeketua – which are variations on a theme and are applied to any frog in New Zealand.
Nature of science
Scientists follow strict rules for classifying and naming species. Classifications and names may change over time as new information comes to light. New species are often named after the person who first discovered or described them. For example, Hochstetter’s frog is named after the Austrian naturalist Christian Gottlieb Ferdinand von Hochstetter. Archey’s frog was named after Dr Gilbert Archey.
All our native frogs are endemic and belong to a single genus – Leiopelma.
Scientists believe that the ancestors of our native frogs colonised New Zealand over 80 million years ago, when it was still part of Gondwana. As a result, our native frogs have many unique features and life processes that are different to many other frogs:
- They don’t have an external eardrum. Although they can make chirping sounds, they don’t croak. Scientists think they use chemicals rather than sounds to communicate.
- They have round eyes instead of slits.
- They don’t develop a long tongue attached at the front like most other frogs. Their tongue is attached at the back, so they open their mouth and lunge forward to catch their prey.
- 3 of the 4 species live and breed on dry land. Even the more aquatic species – Hochstetter’s frog – can survive on dry land.
- The ones that live on dry land don’t have a free-swimming tadpole stage. The tadpole stage happens inside the egg, and the young hatch out as froglets.
- Our native frogs lay a few large eggs, and very few die before becoming froglets.
- After the female frog lays her eggs, they’re fertilised and then guarded by the male. Young frogs are carried around on their father’s back until they are mature enough to survive on their own.
Habitat and distribution
Fossil evidence suggests that, before human settlement, our native frogs were widespread. They have now disappeared entirely from the South Island. They are found only in the upper half of the North Island and on a couple of offshore islands. The table below shows their current known habitat and distribution.
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Stephens Island in the Marlborough Sounds.
Maud Island frog
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Maud Island in the Marlborough Sounds. A small population was translocated to Motuara Island in 1997.
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Coromandel Peninsula and Whareorino Forest, west of Te Kūiti.
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Numerous locations in the upper half of the North Island.
Threats to survival
Our remaining populations of native frogs are vulnerable to extinction. They face a number of threats including:
- introduced predators
- habitat loss
- competition with introduced frogs.
Save our frogs!
A number of New Zealand agencies, including universities, zoos and government departments, are working together to save our native frogs. The Department of Conservation administers the Native Frog Recovery Group and Native Frog Recovery Plan.
There are 2 main conservation strategies:
- Conserving frogs in the wild: Trying to save frogs in the wild involves protecting their natural habitat, removing predators and preventing the introduction of non-native frog species.
- Captive management: In captivity, scientists are working on best practice strategies for captive management, breeding techniques and treating frog diseases.
Translocation is a combination of the 2 strategies. This involves physically removing individuals from one population and moving them to an existing population or new habitat. Translocation can be very challenging. Scientists need to work out the right number of frogs to take, balance the number of males and females and transport them safely. They also need to be very careful that the new location is safe and not threatened by disease or mammalian predators.