Frog Week 05
21 October, 2005
As Kermit would say, "It's not easy being green", or in the case of New Zealand native frogs, it's not easy being brown and green in a world full of disease, pesticides, predators and shrinking habitats. In common with frogs around the world, the ancient and unique species of this country are suffering population declines. Frog Week 2005, which takes place between October 24 and 30, is designed to raise awareness of New Zealand frogs, and of the hazards that threaten the survival of these special animals.
Scientists, including members of the Department of Conservation (DOC) Frog Recovery Group, are seeking help from the public. DOC Recovery Group member, Dr Rhys Burns said today, that because it is not known exactly how the various threats to native frogs are causing population decline, the most urgent requirement is for information to help build a picture of what is happening in New Zealand species.
"New Zealand originally had seven frog species spread throughout the country, but three became extinct following the arrival of humans and pests like rats. Of the four remaining species, only two are still found on the mainland. There are also three introduced species of frog in New Zealand, and we are interested in hearing about these because it is possible that they may transmit disease or directly compete with native frogs," Mr Burns said.
Introduced from Australia in the 19th century, brown tree frogs, green and golden bell frogs and southern bell frogs differ from New Zealand species, with the Aussie imports being larger and noisier than their kiwi counterparts. DOC staff are keen to hear of any reports of sick or dead frogs. More than most animals, frogs are sensitive to disease, pollution, poisons and environmental changes as they absorb so much through their very sensitive skin. A recent concern has been the spread of chytrid fungus, which has caused the extinction of some frog species in Australia. The impact of chytrid on New Zealand frogs is not yet known, although scientists are very concerned about a recent dramatic population decline in Archey's frogs which are only found on the Coromandel Peninsula and in one site west of Te Kuiti.
Hochstetter's frogs are the most widespread New Zealand species. They live in forests south of Whangarei down as far as East Cape, which is a stronghold for the species. As it is not known how chytrid fungus or any potential diseases may spread from one population to another, observing good hygiene practices is another way people can help frogs. The Recovery Group recommends that people who are likely to be walking through a known frog area, thoroughly clean tramping gear between sites.
It is also important for people to report to MAF any sightings of unusual frogs that may have been accidentally imported amongst freight or cargo. Exotic species may be carrying diseases or could eat native frogs. Protection of riparian margins, the strips of land bordering waterways, is another way people can protect frog habitat. Frogs are unable to live in silted up streams and well-managed streamside vegetation provides a healthy environment for a wide variety of plants and animals. Herbicides and pesticides may be lethal to frogs, so spraying of stream areas is not recommended.
All native New Zealand frogs are protected species so it is illegal to capture or keep them. However, the introduced species make good pets that may live for fifteen years or more. It is important that frogs are not moved around the country and that if they are released back into the wild, they must be returned to the pond from which they were originally taken. This will limit the spread of diseases caused by the chytrid fungus, carried by over 30% of introduced frogs, but harmless to humans.
"As major predators of insects, frogs play an important role in food chains. Because of their semi-permeable skin, they are very sensitive to pollutants and environmental stresses. They can be used as an early warning system on the quality of the environment and potential threats to other species, including humans.
"New Zealand frog species are very unusual and are thought to be similar to the common ancestor of all modern frogs. They are part of what makes this country unique. It was people who introduced the many threats that have destroyed three frog species and left the remaining four in a very vulnerable situation. We are just asking that people help us redress the balance and provide information to protect the native frogs that we still have," Dr Burns said.
Archey's and Hochstetter's frogs are the two native species still found on the New Zealand mainland. Both are mainly brown, some with blotches of green and in the case of Archey's, patterns of orange, red and black. Native frogs are small, well-camouflaged and nocturnal. Archey's frogs live in shady, moist forests and Hochstetter's are semi-aquatic, living on stream edges. New Zealand frogs do not have loud calls, but can make faint squeaks when harassed. The two other native species are Hamilton's frog, found only on Stephens Island and Maud Island frog found on Maud Island.
Threats to frogs world wide include, habitat destruction, pollution, climate change, UV radiation, predators, disease, overexploitation (collection as a food source, particularly in Asia for export to Europe, USA and Africa) and the multi-million dollar pet trade.