Small mustelids in New Zealand: invasion ecology in a different world

This chapter reviews the ecology of the three species of small mustelids introduced into New Zealand: the ferret (Mustela furo), the stoat (M. erminea) and the weasel (M. nivalis), for biological control of rabbits. New Zealand offers a mosaic of environments totally different from those in which the three species evolved, including a diminishing array of endemic fauna especially vulnerable to mammalian predators. Mustelids in New Zealand display significant adaptive flexibility in diet, habitat selection, co-existence, dispersal, body size, population biology and predatory impact, with results contrasting with those observable in their northern-hemisphere ancestors. These evolutionary and ecological responses by mustelids to new opportunities are of considerable interest to evolutionary ecologists, especially those interested in competition and predator-prey relationships. Likewise, the need to protect New Zealand’s native fauna has stimulated extensive research on alternative options for mitigating the effects of invasive predators, applicable to pest management problems in other countries.

Comparison of ranging behaviour in a multi-species complex of free-ranging hosts of bovine tuberculosis in relation to their use as disease sentinels

SUMMARYSentinel species are increasingly used by disease managers to detect and monitor the prevalence of zoonotic diseases in wildlife populations. Characterizing home-range movements of sentinel hosts is thus important for developing improved disease surveillance methods, especially in systems where multiple host species co-exist. We studied ranging activity of major hosts of bovine tuberculosis (TB) in an upland habitat of New Zealand: we compared home-range coverage by ferrets (Mustela furo), wild deer (Cervus elaphus), feral pigs (Sus scrofa), brushtail possums (Trichosurus vulpecula) and free-ranging farmed cattle (Bos taurus). We also report in detail the proportional utilization of a seasonal (4-monthly) range area for the latter four species. Possums covered the smallest home range (<30 ha), ferrets covered ∼100 ha, pigs ∼4 km2, deer and cattle both >30 km2. For any given weekly period, cattle, deer and pigs were shown to utilize 37–45% of their estimated 4-month range, while possums utilized 62% during any weekly period and 85% during any monthly period of their estimated 4-month range. We suggest that present means for estimating TB detection kernels, based on long-term range size estimates for possums and sentinel species, probably overstate the true local surveillance coverage per individual.

A New Experimental Infection Model in Ferrets Based on AerosolisedMycobacterium bovis

There is significant interest in developing vaccines to control bovine tuberculosis, especially in wildlife species where this disease continues to persist in reservoir species such as the European Badger (Meles meles). However, gaining access to populations of badgers (protected under UK law) is problematic and not always possible. In this study, a new infection model has been developed in ferrets (Mustela furo), a species which is closely related to the badger. Groups of ferrets were infected using a Madison infection chamber and were examined postmortem for the presence of tuberculous lesions and to provide tissue samples for confirmation ofMycobacterium bovisby culture. An infectious dose was defined, that establishes infection within the lungs and associated lymph nodes with subsequent spread to the mesentery lymph nodes. This model, which emphasises respiratory tract infection, will be used to evaluate vaccines for the control of bovine tuberculosis in wildlife species.