Kiwi Conservation Kids to Search for Hochstetters Frog on Maungatautari

Story By Leigh Marshall and Julie Milne of www.maungatrust.org

This Sunday a group of Kiwi Conservation Kids will head up to Maungatautari with DoC Ecologist Leigh Marshall in search of the endangered Hochstetters frog. They will have their work cut out for them though, as a native frog, Hochstetters does not croak (it does not have a vocal sac) and their green brown warty skin makes them extremely well camouflaged along the splash zone of streams where they live.

The group will search a stream on Bill Garlands property and in doing so will actually begin the baseline research required to determine the presence of Hochstetters on Maungatautari. Ms Marshall believes that the introduction of rats and stoats have contributed to the decline of the frog and while she admits that there is a slim chance of finding Hochstetters on Maungatautari now, a pest proof fenced Maungatautari would be an ideal, safe environment for our native frog to thrive.

New Zealands native frogs are some of our most ancient native species, having lived in our forests alongside the tuatara and the kiwi for millions of years. Our native frogs are also some of the most primitive frogs in the world, having changed very little in the last 70 million years. Unlike most frogs in the world, New Zealands native frogs do not have a free-swimming tadpole stage and the eggs hatch directly into little froglets (young frogs with tails). They also have no vocal sac, meaning that they can't croak, and probably rely on smells to communicate instead. As well as four species of native frogs, New Zealand has three species of frogs that have been introduced from Australia. So now you know that if you hear a frog croak, it must be an immigrant!

Hochstetters frogs are the most abundant and widespread of our native frog species. They are also the only one of the native frogs that are semi-aquatic and need to live close to streams. The other three species, Archeys, Maud Island and Hamiltons frogs all spend their entire life on land. Hochstetters frogs grow up to 48 mm long and their green-brown warty skin makes them extremely well-camouflaged in the small forest stream beds where they live. The frogs spend most of their time under shelter in the splash zone of streams, but their partially webbed hind feet mean they can also swim well.

Like many of our native species, Hochstetters frogs have declined since human settlement and are now only found in some of the forests in the upper half of the North Island. In the Waikato, Hochstetters are found in the Kaimai, Coromandel and Rangitoto Ranges. Just why Hochstetters are not present in the remnant forests of the Waikato Basin is not well understood. However, it is highly likely they were once present in the streams of mountains like Pirongia and Maungatautari.

The loss of Hochstetters frogs from some areas is probably due to a combination of many factors, such as habitat destruction, introduced animals and environmental change. Many forests have been cleared, but even where forest remains, the Hochstetters frogs are still being threatened. Introduced predators, such as rats and stoats are known to prey directly on native frogs and may also compete with the frogs for their invertebrate meals. Other introduced animals, such as feral goats, eat out the smaller plants of the forest and can dry up the moist habitats the frogs need or cause increased erosion and silting up of frog streams.

Without introduced predators and pests, Maungatautari is likely to be a safe home for Hochstetters frogs. Once the under-storey has regenerated, the small streams that run down the mountain will provide nice damp spots for the frogs and ample invertebrates for them to eat. The Maungatautari Ecological Island Trust is currently assessing the possibilities for reintroducing Hochstetters frogs to the mountain as part of the overall plan to restore the mountain ecosystems back to their original state of health and vitality. Hochstetters frogs have not before been translocated, however translocations of the more threatened native frog species in the Marlborough Sounds have been highly successful. If Hochstetters frogs are to be reintroduced to the mountain, the first step will be to make sure that the species is not already there.

Maungatautari Trust Website: www.maungatrust.org