On top of struggling for their own survival, New Zealand’s native frogs have an additional responsibility on their very little shoulders – being a barometer of forest health. Like other frogs around the world, our frogs are barometers of overall environmental health. That is because frogs breath through very sensitive skin and are more susceptible to disease, pollution and environmental changes. A decline in frog populations is usually an early signal of something awry in the environment – and potential threats to other animals, including people. But in New Zealand, three of our four remaining indigenous frogs are forest-dwellers – preferring shady, moist and undisturbed forests. Therefore, they also act as a measure of the health and distribution of our indigenous forest environments.
Fossil records show that our native frogs were spread throughout both the North and South Islands several thousand years ago. The four remaining species – Hochstetter’s frog, Archey’s frog, Hamilton’s frog and Maud Island frog – have declined significantly in range and numbers over the past one to two thousand years, as land has been cleared of forest and predators have been introduced. Apart from Hochstetter’s frog, which has a wider distribution, these frogs are now limited to one or two sites. Hamilton’s frog is the most critically endangered species – and one of the most endangered frogs in the world – with less than 300 individuals remaining.
Our native frogs are nocturnal and do not croak like their overseas cousins, so, combined with their small numbers, you are unlikely to encounter one on a bush-walk.
But it is not all bad news – scientists and wildlife specialists are engaged in some innovative initiatives to help preserve and monitor our frog populations. One of these is a joint project between the Department of Conservation and Auckland Zoo to establish an alternative population of Archey’s frogs. Watch a video about this initiative here.
[Photo above: Archey’s frog is our smallest native frog, growing up to 37mm long. It lives in misty, moist areas around 400m in altitude. It is now limited to Coromandel and one site in Waikato. Photo: Auckland Zoo.]