New developments in vertebrate pest control technologies
Bait buckets used to sow 1080 baits from helicopters in a pest control operation in the Cascade Region, South Westland. Image - Grant Morriss.
‘Silver bullets’ and better mouse traps capture the imagination of pest managers, but while development of new technologies for effective pest control is one important aspect of Landcare Research’s science programme, pest control is much more complex than ‘new tools’ or ‘just killing animals’. This issue of Kararehe Kino provides a wider appreciation of the pest control technology initiatives being investigated by Landcare Research: initiatives that could ultimately contribute towards a ‘Predator-Free New Zealand’. However, all successful control technologies must not only kill individual animals but also function at the pest population level, the wider ecosystem level, and within existing social and regulatory frameworks. Consequently, spatial, temporal, and social factors influence the effective shyness of control programmes. No matter how smart a technology might be, control programmes will fail if they are not based on robust biological and ecological principles, don’t meet regulatory requirements, and are not acceptable to communities.
New Zealand’s current suite of lethal vertebrate pest control tools includes traps, toxins, firearms, and a biocontrol agent. Traps, toxins, and firearms have been available for several centuries, with some current technologies (e.g. leghold traps) still similar to their 18th century predecessors. Importantly though, traps and toxins and their best-practice application have improved significantly over the past 20–30 years through incremental improvements in their e.ectiveness, target specificity, residues (in the case of toxins), animal welfare impacts, and cost. There is room for further improvements, but ultimately cost will be the major constraint in using these technologies, particularly if managers seek to realise initiatives like predator-free New Zealand.
Going forward, development of ‘silver bullets’ and ‘step’ changes in pest control need to sit alongside incremental improvements in such technologies. One such potential step change, investigated over two decades, was fertility control of possums. Ways were found to make possums infertile, but the research foundered over oral delivery of the infertility agent. This failure does not mean, however, that searches for new biotechnologies should stop, but there does need to be an objective funding allocation process based on costs, benefits, and risks that provides optimal effort in both incremental improvements (often short–medium term) and step changes (long-term). Proposed benefits must be realistically discounted based on time to delivery and probability of success, which in turn must reflect the technological, social, regulatory and long-term funding risks. High risk projects need to be tempered by measured optimism from both researchers and funders. For example multinational agro-chemical and pharmaceutical companies invest huge sums of money in new product research, even though success rates are less than one in a hundred.
Increasingly, incremental improvements are being made to the application of tools, rather than to baits, toxins or traps per se. A good example of this is the use of global positioning systems (GPS) for more accurate aerial application of baits (Precision aerial sowing of baits for possum control) and for monitoring coverage of ground-based trapping and poisoning operations. Research-driven reductions in the sowing rates of 1080 bait (Nugent et al., Kararehe Kino Issue 14) have enabled significant reductions in costs, residues, and non-target risks (Improving baiting for rabbit control and minimising risks to non-target animals), and current research on bird repellents (Repellents to protect native birds from 1080 baits) will further reduce the risk to non-target species. Recent incremental product improvements include a simple modification of snap-back traps (Trapping stoats and ship rats – a low-cost option for their control), the adaptation of radio-frequency identification tags for assessing detection systems (Using radio frequency identification technology to measure possum interaction rates with traps), and the testing of sex pheromones as lures for pest animals (Sex pheromone attractants to improve the trapping and monitoring of mammal pests at low densities).
In terms of step changes, Landcare Research is using molecular biology techniques and genomics (identifying species receptors in animal bodies that provide lethal physiological control targets) to develop novel control tools that will be species-specific and humane. These approaches will provide either lethal tools (Developing species-selective novel control tools for pest control) or reduce the reproductive capacity of populations (Duckworth, Kararehe Kino Issue 14, and The Trojan Female Technique: a novel non-lethal approach for pest control). Additionally, new, more virulent strains of rabbit haemorrhagic disease (Duckworth, Kararehe Kino Issue 21) are being sought – in partnership with the Invasive Animals Cooperative Research Centre in Australia – to address the waning effectiveness of current strains and the possible resistance conferred by non-lethal strains of the virus in New Zealand.
Success in developing control tools, through both incremental and step changes, will assist managers of vertebrate pests to meet ongoing threats to native biodiversity and agricultural production. Management of vertebrate pests in New Zealand, at least in the short-to-medium term, will continue to rely on the suite of existing control tools, but research on novel tools must continue. Scaling up pest control will be a key requirement if New Zealanders embrace current initiatives to work towards a Predator-Free New Zealand. Incremental improvements must continue in parallel with the scoping, development and field application of new tools to provide the means to achieve that goal. Future advances will also require more cross-disciplinary research where biologists, engineers, geneticists, physiologists, pharmacologists, and social scientists work together to find novel solutions.