Jamie MacKay

Testing island biosecurity systems for invasive rats.

Rats continue to invade rat-free islands around the world, and it remains difficult to successfully intercept them before they establish populations. Successful biosecurity methods should intercept rats rapidly, before they can establish a population. Current island biosecurity practice employs techniques used for high-density rat eradication, assuming that they will be equally effective on low-density invaders. However, such approaches are often untested. Adult male Norway rats (Rattus norvegicus) were individually released onto forested rat-free islands in New Zealand to test methods of detecting and eliminating a single invader. Only half the rats released were caught within a two-week timeframe, although the mean time to interception was just under 14 days. Permanent island biosecurity surveillance systems performed better than contingency responses. Success rates were higher on islands where complete coverage could be obtained, although surveillance systems using multiple devices eventually detected most invading rats. For some rats a change of methods was necessary. Single invading rats left a rat-free island despite the presence of excessive natural food resources. With surveillance systems comprising an array of tested island biosecurity devices, and where necessary a contingency response using alternative methods, it should be possible to maintain islands as rat-free even when they have a high reinvasion rate.

Exploratory behaviour of colonizing rats in novel environments.

The immediate movement and behaviour of individuals arriving in novel environments influence long-term survival and population establishment. Studies have previously investigated exploratory behaviour in novel laboratory environments, but never during colonization of natural systems. Experimentally releasing and monitoring animals would allow testing of laboratory and computer-simulation hypotheses. We sequentially released and tracked three adult male brown rats, Rattus norvegicus, on a rat-free island, monitoring their movements hourly for 3 weeks to test laboratory and simulation-generated hypotheses of how animals explore and move in novel environments. We found that (1) individual movements are apparently random; (2) range size increases most rapidly in the first week after arrival; (3) range size is larger than for individuals at high density; (4) movement is mediated by central place foraging behaviour. These findings contradict laboratory hypotheses of nonrandom exploration but support simulation search strategy hypotheses. Random movement and increased ranges at low density have implications for understanding animal colonization dynamics and intercepting invasive species arriving at new locations.

Innovative developments for long‐term mammalian pest control

BACKGROUND Invasive mammalian pests have inflicted substantial environmental and economic damage on a worldwide scale. RESULTS Over the last 30 years there has been minimal innovation in the development of new control tools. The development of new vertebrate pesticides, for example, has been largely restricted due to the costly and time-consuming processes associated with testing and registration. CONCLUSION In this article we discuss recent progress and trends in a number of areas of research aimed to achieve long-term population suppression or eradication of mammalian pest species. The examples discussed here are emerging from research being conducted in New Zealand, where invasive mammalian pests are one of the greatest threats facing the national environment and economy.

What can the geographic distribution of mtDNA haplotypes tell us about the invasion of New Zealand by house mice Mus musculus

We mapped the distribution and diversity of mitochondrial D-loop haplotypes among 502 New Zealand house mice (Mus musculus). By widespread sampling from 74 sites, we identified 14 new haplotypes. We used Bayesian phylogenetic reconstructions to estimate the genetic relationships between the New Zealand representatives of Mus musculus domesticus (all six known clades) and M. m. castaneus (clade HG2), and mice from other locales. We defined four distinct geographic regions of New Zealand with differing haplotype diversity indices. Our Results suggest (a) two independent pre-1840 invasions by mice of different origin (domesticus clade E and castaneus clade HG2) at opposite ends of the country; (b) multiple later invasions by domesticus clades E and F accompanying the post-1840 development of New Zealand port facilities in the central regions, plus limited local incursions by domesticus clades A, B, C and D1; (c) a separate invasion of Chatham I. by castaneus clade HG2; (d) previously undescribed New Zealand haplotypes, potentially the products of localised indigenous mutation, and (e) hybridisation between different lineages.

Increasing possum interaction rates with chew cards using new formulation lures

ABSTRACT Measuring the frequency at which brushtail possums (Trichosurus vulpecula) interact with chew cards is a cost efficient way to identify the presence of possums, particularly when at low densities following population reductions. The effectiveness of a new combined olfactory and visual lure, Lure-itTM Spray and Blaze (LISB, Connovation Ltd), was evaluated against the standard flour/icing sugar lure (FIS). A total of 154 alternately lured chew cards were set in a 50 m × 50 m grid over 48 ha of regenerating forest. Possums were detected by 41.0%, 62.1% and 70.5% of chew cards baited with FIS, aniseed laced LISB and cinnamon laced LISB cards, respectively. LISB lures scented with cinnamon or aniseed were significantly more likely to detect possums than FIS lures (odds ratios 3.42 and 2.36, respectively). There was no such difference between cinnamon or aniseed scented lures. Lure-it Spray and Blaze has the potential to increase possum detection rates during surveillance operations.