Who Wants Wallabies?

Forest and Bird, Issue 303, 1 February 2002, Page 32

Who Wants

Wallabies?

BASIL GRAEME

The damage possums do to our forests is well known but

finds

another Australian marsupial is also threatening forests and tussocklands.

here are so many introduced animals munching their way through our forests that we are inclined to forget wallabies. Yet wallabies are another browsing animal which, combined with deer and goat browsing, can totally suppress the regeneration and replacement of canopy

trees and so threaten the very existence of our native forests. While possums destroy foliage and can kill mature trees, it is the seedlings that hold the hope of forest regeneration. So wallabies, deer and goats which all eat these seedlings are ultimately a greater threat to native forest than possums.

t is 10 years since Forest ¢& Bird last profiled the threat of wallabies to our forests and tussocklands, and since then there have been changes — bringing both good and bad news. Because wallabies behave differently to deer and goats, their effects can be even more severe. Wallabies are sociable animals. They camp in a site. Around their camp they feed, not travelling too far, until their concentrated browsing has reduced the forest floor to bare earth and browsed moss. Even then they will stay around when food is so scarce that the falling leaves from the canopy become a large part of their diet. Experimental exclosure plots (fenced areas which keep the wallabies out) show a dramatic contrast between such ‘scorched earth’ outside and luxuriant forest within. Wallabies are remarkably fecund. A mother wallaby always has a spare embryo awaiting the departure of the joey from her pouch. Shift such a female wallaby and you shift three wallabies as a potential nucleus for a new population. Yet hunters have been known to use this method to establish new populations, to the extent that Landcare Research has drawn public attention to what has become a growing problem. Wallabies were deliberately released about 1870. Governor Sir George Grey introduced five wallaby species to Kawau Island in the Hauraki Gulf as part of his

efforts to establish animals from various parts of the world in his private hideaway. Bennett’s wallaby was introduced to South Canterbury. Subsequently, dama wallaby from Kawau Island were released in the forest beside Lake Tarawera. They thrived. Releases and escapes led to further populations of dama wallabies near Auckland at Waitakere. Rock wallabies were also released on Rangitoto and Motutapu Islands at the mouth of Auckland Harbour. The biggest population now is of dama wallabies, centred around Lake Tarawera. This population has grown and spread over 170,000 hectares of the Bay of Plenty and adjacent Waikato Region, with sightings peppered even further afield at Tokoroa, Tauranga and the Rangitaiki valley. In South Canterbury, Bennett’s wallaby occurs over 300,000 hectares in the hills and ranges around Waimate. Landcare Research has reported on other populations recently established. In New Zealand, the spread of wallabies is not principally by hopping. People shift wallaby R faster than wallaby disperse pane themselves. Although it is illegal to shift wallaby without a permit, a hunters, keen to have a handy new target, are known to deliberately release wallabies into Inver their local patch. Another source of dispersion is wildlife traders. Inexplicably, there are people who are licensed by the Director-General of Conservation to catch, move and hold wallaby for export. Several new wallaby populations have been established as a result of escapes in transit to or from a trader’s holding pen. So where is the good news in all this? The good news is that the Auckland Conservancy of the Department of Conservation, sponsored by the Auckland Rotary Club, has eradicated rock wallaby from Rangitoto and Motutapu Islands in recent years. Otago DoC has exterminated a small population of Bennett’s wallaby which became established at Quartz Creek, between Lakes Wanaka and Hawea. Environment Bay of Plenty has eliminated a wallaby population near Ngongataha and is working on another, thereby reducing the threat of wallaby spreading to the Mamaku forests. These successes demonstrate how Quartz C: mi i Stew: Islan

feasible it is to eradicate small, isolated groups of wallabies. Unfortunately most wallaby populations don’t fit this convenient model. The large, dispersed Bay of Plenty and Canterbury populations are a different kettle of fish. The spread of Bay of Plenty dama wallaby is a burden to Environment Waikato. Wallabies shifted by hunters are popping up as far afield as Tokoroa. To the south, only the imperfect barrier of the Rangitaiki River prevents the wallabies sighted there from bounding into Te Urewera National Park. A small population has crossed the Kaituna River, threatening the forests behind Tauranga. To manage the wallaby problem, the animal-pest manager of Environment Bay of Plenty, Dave Moore, is about to co-ordinate a joint strategy between his council, Environment Waikato and the

Department of Conservation. This is a real step forward. One objective, tentatively identified by Mr Moore, is to clear the boundary with the Waikato Regional Council to make its investment in wallaby control and eradication more effective. ay of eile "We need to walk the wallabies nd Waikato lapier back to the centre, but how do we deal with the sparse Gisborne | numbers of wallaby spread over extensive areas?’ he asks and, answering himself, muses, ‘It looks as if we have to invest in a programme that will clean out all the pests over some 170 000 hectares.’ So, in the Bay of Plenty and Waikato, serious thought is being given to a regional plan to prevent wallaby spread. The same problems apply with the population of Bennett’s wallaby. These wallabies are spread over 300,000 hectares in the Hunter Hills, Two Thumb Range, and the Kirkliston and Grampian Mountains. Just as for the Bay of Plenty, a co-ordinated and substantial investment will be required to clear such a large area. As in the Bay of Plenty too, shooters have spread them further afield, to Mt Oxford in North Canterbury, and the Godley Valley at the head of Lake Tekapo. These small populations need to be eradicated quickly. We don’t need wallaby as well as thar, chamois and deer in the South Island high-country. That Waimate District has adopted this wallaby as their local logo — as bizarre as adopting a ferret or a possum — suggests that a lot of education about wallaby is needed in the South Island. Fortunately, there is another discrete population which can be readily tackled. Kawau Island is one of the most underrecognised wildlife habitats in the country. This island, in the Hauraki Gulf off Warkworth, is already forested and

free of ferrets, stoats, weasels and hedgehogs. As a consequence the island still manages to sustain a tiny population of kiwi, brown teal and 80 percent of the remaining gene pool of critically threatened North Island weka. The forests are dominated by kanuka, with a coastal fringe of pohutukawa, some pine trees and a few native canopy trees. Yet so severe is wallaby browsing that all the palatable native seedlings are eaten, leaving arum lilies, monkey apple and silver tree fern to colonise the sparse understorey. The soil is thin and there is scarcely any of the duff and humus needed by the soil invertebrates on which the weka depend. Weka have already died out on Kawau Island once before, probably because of droughtinduced starvation. Getting rid of the wallabies is critical to the enhancement of Kawau Island’s wildlife. There is now a strong groundswell of support from Kawau residents who want their island to become wallabyfree and a haven for threatened species. Local attitudes have changed over the last 10 years, due largely to the advocacy of land owner, Ray Weaver. Ray drives the Pohutukawa Trust, whose mission is to protect and restore the island’s pohutakawa trees. The Trust now has the eradication of wallabies in its sights. In Ray’s words: "The Trust has "beavered away for the past 10 years and voted with their wallets ($43,000) and their actions for real conservation on Kawau. A constant wildcard, played whenever wallaby eradication is sought, is the threatened status of some of the island’s wallaby species back home in Australia. Parma wallaby were once thought to be extinct in Australia and Kawau Island stock were captured and exported to create new populations. The parma wallaby is now much more secure as a result of these exports and from subsequent discoveries of surviving populations in their native realm. For years rock wallabies were also exported from Kawau Island to zoos worldwide, and now an Australian academic is calling for more to be collected for captive breeding to supplement a gene pool bred in the Blue Mountains. This is no excuse to delay the eradication of wallaby from Kawau Island, however. As Ray Weaver says: "We are no longer prepared to see our island turned into a desert just because

the Australians are tardy at taking what they want. The stage is now set for a co-operative effort between the Department of Conservation, the Auckland Regional Council’s animal-pest team and the local Trust. A critical role for the Department is to clear its own reserve land first, and to ensure that it holds a population of the Kawau weka in secure pens for re-release after wallabies have been poisoned on the rest of the island.

The key players in tackling the wallaby problem are the Minister of Conservation and the Department of Conservation. Wallaby are a noxious animal under the Wild Animal Control Act which they administer. The good news is that we have a real Minister of Conservation in the Hon. Sandra Lee, a former member of Forest and Bird’s executive with a track record of active conservation in the Auckland region. For 2002 she is promoting, as a key output from her department, halting the spread of wallabies and the elimination of discrete populations. At last the wallabies are going to be recognised and treated as the threat that they are to our biodiversity. a

BASIL GRAEME

was formerly

a field officer with Forest and Bird in the central North Island, and is now a member of the national executive.