New Zealand Journal of Zoology abstracts

Editorial

New Zealand Journal of Zoology

The New Zealand Journal of Zoology is proud to publish this Special Issue to mark the 3rd International Wildlife Management Congress in Christchurch, in December 2003.

The holding of this important congress in New Zealand has offered a large group of scientists from overseas the chance to see at first hand the range of unique problems in wildlife management we have in this country, and, even more important, some of the innovative solutions we are developing to deal with them. At the same time, New Zealand authors have an unprecedented opportunity to bring their work to the attention of a wide international audience, and conversely, to learn from overseas experience. This special issue was therefore designed to facilitate that two-way communication.

The normal range of subject matter covered by the New Zealand Journal of Zoology is very wide, but it does publish extensively in various aspects of pest control. The conference is huge and covers many topics, so to make a cohesive special issue, we had to pick one. Various aspects of pest control will be prominent in the congress sessions, so we chose that as a theme relevant to the normal scope of the journal.

The six reviews in this special issue were all individually invited by the Scientific Editor, and are arranged into three sections. The first covers the very large questions of strategy and ethics as applied to management of introduced mammals in New Zealand. John Parkes and Elaine Murphy summarise the complex legal, scientific, organisational, and social issues that arise when 25 different mammalian species have to be managed by several interacting government agencies and NGOs operating under a cumulative and changeable system of legislation. Understandably, agreement on some important issues is hard to attain, and the costs are immense. One of the most intensely argued debates concerns the recreational hunting of deer, chamois, and tahr. These species still provide hunters with sporting quarry in magnificent surroundings matched in very few other places in the world, yet conservation managers have declared all introduced ungulates as pests to be slaughtered from helicopters. Recreational hunting is a long-established part of New Zealand culture, and many hunters consider that the largest present threat to their sport is an official conservation policy that no longer supports the idea of separate recreational hunting areas especially managed for game populations. But, in a thoughtful and well-argued review, John Eggleston and his co-authors challenge our traditional assumptions about hunting, and the extent to which philosophical ideas about ethics and animal welfare apply to it and, by implication, to animal control generally.

The second and third sections offer detailed accounts of case studies in management of one particular group of introduced mammals, the small mustelid and rodent predators. The authors and subjects were chosen in order to illustrate important advances in understanding and planning wildlife management in New Zealand and overseas. They describe the problems faced by managers dealing with, first, some key introduced predators in New Zealand (especially rats, cats, and stoats), and second, a comparable species in the United Kingdom, the American mink. The hope is that such comparisons might be useful in helping managers in different places to see how they can learn from and help each other. The authors of these four papers were therefore asked to review a series of real management operations in their own contexts, describing the reasons why management was needed, the technology employed (especially if new), the economic, legal and ethical requirements, the biological problems, the results both for the target species and for the ecosystem, the costs, the public response, and whether and why the operation was judged a success or a failure.

In the New Zealand section, David Towns and Keith Broome trace the history of rat eradications on New Zealand offshore islands, both by trapping and ground-based bait stations and by aerial distribution of toxic baits. Rats are ubiquitous and damaging predators on islands all around the world, and New Zealand has been at the forefront in developing achievable technologies to eradicate them. The size and complexity of offshore islands that can now feasibly be cleared of rats has rapidly accelerated over the last decade, with wonderful consequences for the critically threatened native species that can live nowhere else. On the main islands of the New Zealand archipelago, the challenges are different but just as important. New Zealand has developed a series of "mainland islands" as a way of extending the benefits of effective protection from ground predators to habitats not well represented on islands and more accessible to the public. Craig Gillies and his team describe predator control operations and their outcomes in Trounson Kauri Park, one of the smaller and most precisely monitored of the mainland islands. Unlike offshore islands, which can usually be cleared in a one-off operation and thereafter remain free, pests removed from mainland islands are constantly being replaced. The costs of the unremitting war against the invaders are very high, and a single predator that escapes attention can undo months of patient labour. Nevertheless, at Trounson, the million dollars (NZ) spent over the first 6 years has achieved the minimum necessary increase in the survival of chicks of the New Zealand iconic bird, the brown kiwi, and many New Zealanders will consider that money well spent.

The international section concentrates on describing the impact and control of the American mink, a mustelid carnivore that has invaded large areas of Britain and Europe but, fortunately, not New Zealand. We do, however, have another widespread introduced mustelid of similar size, shape, and generalist tastes in native fauna, the feral domestic ferret. European and New Zealand conservation managers therefore face similar problems, but in very different circumstances. The toxic baits that New Zealanders can use at Trounson and on offshore islands are prohibited in the European Union (EU), where control is done entirely by live-trapping and shooting. On the other hand, monitoring of predator density before and after control work, preferably by non-lethal means that do not affect the population being monitored, is needed everywhere. Monitoring techniques applicable to predators the size of ferrets and mink are well advanced in New Zealand, and could in time help maximise the efficiency of control operations against mink in the EU.

The editorial and production team at the Royal Society of New Zealand, publisher of the New Zealand Journal of Zoology, welcome all delegates to the 3rd International Wildlife Congress, and offer this special issue to inform and stimulate your thinking about the management of invasive mammals in New Zealand and overseas.

C. M. King
Scientific Editor

Acknowledgments

I am grateful to the Royal Society of New Zealand for supporting the concept of the special issue, in principle and financially, and to all the invited authors who managed to submit their contributions more or less promptly. Several other authors who were invited but could not oblige in time may still be able to add to the discussion via a future regular issue.

A radiotagged brown kiwi cradled in the arms of Landcare Research scientist John McLennan, at his study area in the Urewera National Park. McLennan's work underpinned the population modelling that determined the minimum level of juvenile recruitment required to maintain populations of kiwi in mainland islands. Gillies et al. (pp. 399-420) illustrate the costs of the intensive predator control needed to meet that target at Trounson Kauri Park, Northland. Photo C. M. King

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