invertebrates

The advent of mammal-resistant fences has allowed multi-species eradications of mammals from ecosanctuaries on the New Zealand mainland. However, maintaining eradication of house mice (Mus musculus) has proven difficult, and at some fenced reserves they are the only exotic mammal present and reach a high population density. Over 5 years we examined the impacts of mice alone on biodiversity at Sanctuary Mountain Maungatautari by comparing forest blocks with relatively high and low numbers of mice.

Urbanisation causes fragmentation of natural habitats, which results in loss of biodiversity, while promoting an environment that can facilitate invasive species. However, forest fragments are an important refuge for native species and therefore understanding and mitigating threats in fragments is critical.

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.

Areas of indigenous forest in urban and rural areas are often the last remaining examples of lowland ecosystems that were once extensive before human settlement. Conserving the indigenous invertebrate species in these remnants requires knowledge of how many taxa are functionally isolated and how many are capable of dispersing to, and persisting in, forest restoration sites and the surrounding matrix.

While invasive rats are demonstrably inimical to indigenous vertebrate species, there has not been unequivocal evidence of benefit to invertebrate communities from management of these invasive mammals in New Zealand forest systems. The present study examined the response of land snail communities to intensive management of ship and Norway rats by sampling paired rainforest blocks, one block of which had been subject to intensive management of rats, while the other block had been without management of invasive rats and thus subject to ambient rodent infestations.

Plant–invertebrate mutualisms involve the production of food and/or shelter by plants to co-opt invertebrate groups in order to either prevent herbivore or pathogen damage or facilitate seed dispersal. Plant structures and the provision of food are relatively expensive, and a reactive plant response to attack may reduce those costs provided the fitness benefit of the mutualism is maintained.

Natural regeneration on waste rock was investigated at the old Wangaloa coal mine, south-east Otago. A 450-m long waste rock stack had been created 40–50 years ago, and has had little anthropogenic intervention since. The stack is made up of a gradient of three main waste rock types, defined as ‘silt-rich’, ‘mixed’, and ‘quartz-rich’, which reflect different proportions of loess siltstone and quartz gravel conglomerate. Plant species assemblages were quantified in four 5-m² quadrats in each waste rock type.

Control of one pest species may permit increases in abundance of other pests, thereby reducing the overall net benefit from pest control. We provide evidence that control of introduced possums (Trichosurus vulpecula) may increase ship rat (Rattus rattus) abundance in some New Zealand native forests. Ship rat abundance in a podocarp–hardwood forest was assessed using simple interference indices over 14 years (1990–2004) that included two aerial possum-poisoning operations (1994, 2000).