Advances in New Zealand mammalogy 1990–2000: Lagomorphs

Underaddressed animal-welfare issues in conservation

Much progress has been made toward assessing and improving animal welfare in conservation. However, several glaring knowledge gaps remain where animal-welfare concerns exist but animal-welfare studies have not been performed in politically sensitive contexts. Based on contemporary issues in Australia, we identified 4 topics that require more research: animal-welfare oversight for operations designated as management (as opposed to research); animal-welfare impacts of biological agents used to control invasive animals; welfare of animals hunted recreationally; and animal-welfare impacts associated with indigenous wildlife use. Animal-welfare science may be applied to these sensitive topics through simple quantitative studies (e.g., quantifying the frequency of adverse animal-welfare events). Several such studies have effectively addressed animal-welfare concerns in similarly contentious contexts, including feral camel (Camelus dromedarius) culling in Australia, recreational hunting in Scandinavia, and indigenous whale hunting in the United States. For discussions of animal welfare in conservation to be evidence-based, courageous research is required in the 4 key areas we identified.

Refining Operational Practice for Controlling Introduced European Rabbits on Agricultural Lands in New Zealand

European rabbits (Oryctolagus cuniculus) pose a major threat to agricultural production and conservation values in several countries. In New Zealand, population control via poisoning is a frontline method for limiting rabbit damage, with large areas commonly treated using the metabolic toxin sodium fluoroacetate (‘1080’) delivered in bait via aerial dispersal. However, this method is expensive and the high application rates of the active ingredient cause public antipathy towards it. To guide reductions in cost and toxin usage, we evaluated the economics and efficacy of rabbit control using an experimental approach of sowing 1080-bait in strips instead of the commonly-used broadcast sowing method (i.e. complete coverage). Over a 4-year period we studied aerial delivery of 0.02% 1080 on diced carrot bait over ~3500 ha of rabbit-prone land in the North and South islands. In each case, experimental sowing via strip patterns using 10–15 kg of bait per hectare was compared with the current best practice of aerial broadcast sowing at 30–35 kg/ha. Operational kill rates exceeded 87% in all but one case and averaged 93–94% across a total of 19 treatment replicates under comparable conditions; there was no statistical difference in overall efficacy observed between the two sowing methods. We project that strip-sowing could reduce by two thirds the amount of active 1080 applied per hectare in aerial control operations against rabbits, both reducing the non-target poisoning risk and promoting cost savings to farming operations. These results indicate that, similarly to the recently-highlighted benefits of adopting strip-sowing for poison control of introduced brushtail possums (Trichosurus vulpecula) in New Zealand, aerial strip-sowing of toxic bait could also be considered a best practice method for rabbit control in pest control policy.

The future biological control of pest populations of European rabbits, Oryctolagus cuniculus

European rabbits are exotic pests in Australia, New Zealand, parts of South America and Europe, and on many islands. Their abundance, and the damage they cause, might be reduced by the release of naturally occurring or genetically modified organisms (GMOs) that act as biological control agents (BCAs). Some promising pathogens and parasites of European rabbits and other lagomorphs are discussed, with special reference to those absent from Australia as an example of the range of necessary considerations in any given case. The possibility of introducing these already-known BCAs into areas where rabbits are pests warrants further investigation. The most cost-effective method for finding potentially useful but as-yet undiscovered BCAs would be to maintain a global watch on new diseases and pathologies in domestic rabbits. The absence of wild European rabbits from climatically suitable parts of North and South America and southern Africa may indicate the presence there of useful BCAs, although other explanations for their absence are possible. Until the non-target risks of deploying disseminating GMOs to control rabbits have been satisfactorily minimised, efforts to introduce BCAs into exotic rabbit populations should focus on naturally occurring organisms. The development of safe disseminating GMOs remains an important long-term goal, with the possible use of homing endonuclease genes warranting further investigation.

Animal welfare and ethical issues relevant to the humane control of vertebrate pests

Vertebrate pests and pest control impact on people, animals and the environment, so any ethical consideration of vertebrate pest control must incorporate the interests of all three. The necessity of intervention, whether it involves killing animals or not, must be properly evaluated. Justification for pest control is only tenable if all of the negative impacts (harms) on people, animals and the environment are minimised and all of the positive impacts (benefits) are maximised as far as can be feasibly achieved. In all cases, the most humane control methods possible must be used; we must actively seek ways to improve the humaneness of existing methods and to find new methods that are more humane. There are six major principles that guide the design and execution of ethically sound vertebrate pest control programmes. (1) The aims or benefits and the harms of each control programme must be clear. (2) Control must only be undertaken if the aims can be achieved. (3) The methods that most effectively achieve the aims of the control programme must be used. (4) The methods must be applied in the best possible way. (5) Whether or not each control programme actually achieved its precise aim must be assessed. (6) Once the desired aims or benefits have been achieved, steps must be taken to maintain the beneficial state. An ideal pest control method would be effective and easy to use, affordable, safe for human users and for people exposed to it, humane, specific to the target species or individuals, and safe for the environment. Although such a gold standard is difficult to achieve, we can only retain ethical credibility if we conscientiously strive to make incremental improvements towards that gold standard.