invasive predators

Cats (Felis catus) are among the most damaging invasive predators in the world, and their impacts in Aotearoa New Zealand (NZ) are particularly severe. However, unlike the invasive predators that are targeted for eradication under the Predator Free NZ initiative, cats are also highly valued by people and therefore will likely remain widespread in NZ for the foreseeable future. This raises the question of how to manage the impacts of cats, which include predation, competition, and disease affecting native species, livestock, and humans.

Conservation programmes in New Zealand often suppress populations of a single invasive predator for the benefit of threatened avifauna. However, the establishment of whole guilds of invasive species has created complex competitor and predator-prey relationships, including some well-described trophic cascades. Trap networks designed to target stoats (Mustela erminea) are poorly optimised to supress a population of weasels (M. nivalis), and may contribute to periodic spikes in weasel numbers due to decreased interspecific competition and aggression.

Invasive predator control to protect native fauna usually takes place in native habitat. We investigated the effects of predator control across 6000 ha of multi-tenure, pastoral landscape in Hawke’s Bay, North Island, New Zealand. Since 2011, low-cost predator control has been conducted using a network of kill traps for mustelids (Mustela spp.), and live trapping for feral cats (Felis catus). Although not deliberately targeted, other invasive mammals (particularly hedgehogs Erinaceus europaeus) were also trapped.