Nature watch: Primitive amphibians star in DoC promotion

By JOHN WALSBY

As the world's sole survivor of a particular reptile group from the age of dinosaurs, the tuatara is widely acknowledged as a very special creature.

But living fossils from other New Zealand animal groups deserve similar recognition, says Department of Conservation spokesman Ian Bradley. Most, including our four species of native frogs, pepeketua, are largely overlooked. But the department aims to raise the profile of these primitive amphibians in an awareness campaign launched at the Auckland Regional Council's Arataki visitor centre, in the Waitakeres.

It is hoped that this will lead to better protection for all surviving colonies and possibly to the discovery of a few more remnant populations in parts of the country where they have yet to be recorded.

The campaign is supported by a video and printed information revealing details of the lives and distribution of these secretive creatures and the threats to their existence. The video contains good footage of all four surviving native species.

Being small, well camouflaged and nocturnal, native frogs are hard to find but are easily distinguished from the more commonly encountered introduced frogs - all three from Australia - by their size, by having pupils that are round rather than slit shaped and in having no round, external eardrum behind the eye.

Unlike most frogs our native species do not have free-
swimming tadpoles. They complete the tadpole stage within their transparent eggs and emerge as walking juveniles that, in three of the species, are cared for by their fathers until they become independent.

From fossils and other preserved skeletal remains, it is known that until between 1000 and 2000 years ago New Zealand had at least seven different species of frog. Three are now extinct and the distribution range of the four survivors has shrunk dramatically.

Hamilton's frog is now found only on Stephens Island in Cook Strait where there are only about 300 individuals. The Maud Island frog was similarly restricted until some were recently transferred to another island for species security, and Archey's frog - our smallest at just 37mm long, smaller than the diameter of a golf ball - is only known from the Coromandel's forested peaks and one site near Te Kuiti.

The most widespread species, Hochstetter's frog, is found at several sites around the top half of the North Island. It appears to require wet conditions, for it is restricted to stream margins and seepages and is the only native frog with webbing between its toes.

New Zealand frogs are recognised as some of the most primitive in the world, and as their numbers are dwindling due to predation, habitat destruction or environmental contamination, it is important that any chance discoveries are reported to the nearest Department of Conservation office.