The alpine zone of New Zealand covers c. 30% of public conservation land and is home to a high diversity of endemic species. Predation by introduced stoats (Mustela erminea) is identified as a major threat to alpine fauna. However, a lack of biological information, such as what stoats eat in different settings, hinders efforts to focus control measures in time and space in order to achieve the greatest conservation gains. We used a biochemical tool, stable isotope analysis, to estimate stoat diet across three time-periods in the alpine zone of three national parks.
The eradication operations to remove stoats (Mustela erminea) from islands in Fiordland provided an opportunity to assess the diet of stoats in areas with no rodents or with only mice (Mus musculus) available as mammalian prey. The carcasses of stoats trapped on Chalky Island in 1999, Secretary Island and the adjacent mainland in 2005, and Resolution Island in 2008 were collected and their gut contents analysed. On rodent-free Chalky Island, most of the stoats had consumed birds, mostly passerines.
Studies of waterfowl productivity at the Pukepuke Lagoon Wildlife Management Reserve have shown high mortality amongst young ducklings. This has been found in other studies in which it has often been attributed to predation. (Evans and Wolfe 1967, Balser et al. 1968, Urban 1970, Schranck 1972). Areas of pasture, cut-over pine forest, and dunes outside the reserve were also included in the trapping area.
The influence of micro-habitat on stoat (Mustela erminea) and rat (Rattus rattus) capture success was explored using trapping data collected from large scale predator control operations at the Okarito and Moehau Kiwi (Apteryx spp.) sanctuaries. Generalised linear models were used to explore the relationship between micro-habitat predictors and predator kill trapping records from individual trap sites. Our results suggest that micro-habitat information can provide useful predictors of rat and stoat capture success.
Most research into the diet of stoats in New Zealand has been in low altitude valleys such as the Eglinton and Hollyford Valleys. Yet much of New Zealand’s national parks (e.g. Fiordland National Park) consist of many small montane valleys and alpine areas. This research identified the key prey species of stoats inhabiting such small montane valleys and alpine grasslands.
There are currently many attempts in New Zealand to restore native ecosystem functioning through the intensive control of introduced mammalian predators. One system that is faltering is bird pollination of endemic mistletoes (Peraxilla tetrapetala) by bellbirds (Anthornis melanura), apparently because of stoat (Mustela erminea) predation. We used a paired-catchment experiment in Nothofagus solandri var. cliffortioides forest at Craigieburn, central South Island, to measure whether stoat control could restore bellbird densities and mistletoe pollination.
Little is known about the movement of stoats in alpine grassland, where several species of native birds, reptiles and invertebrates are potentially at risk from predation. Radio-tracking, live trapping and tracking tunnel techniques were used to sample stoats in two adjacent habitats to determine whether the home range of stoats in beech forest valley floors extends into neighbouring alpine grasslands in the Ettrick Burn Valley, Fiordland.
To enhance the breeding success and survival of kaka (Nestor meridionalis) and mohua (Mohoua ochrocephala), we initiated stoat (Mustela erminea) control in the Eglinton Valley (13 000 ha), Fiordland, New Zealand using a single 40 km line of traps spaced 200 m apart with traps set continuously. This low intensity stoat control regime permitted successful kaka breeding and fledgling survival was high.
A simple deterministic accounting model was used to predict the rate at which a colonising stoat (Mustela erminea L.) population would reach specified sizes. The model was used to explore how the size and composition of the founder population, and the survival schedule to which it was exposed, influenced this rate. A function used in disease surveillance was modified to predict the number of tracking tunnels necessary to detect the presence of the colonising Population with a specified degree of confidence.
A single five night pulse of sodium monofluroacetate (0.15% 1080) applied in bait stations at two different spacing intervals, 100 and 200 m, along forestry roads in New Zealand beech forest, killed all four of the resident radio-tagged stoats (Mustela erminea) and all three of the resident radio- tagged wild house cats (Felis catus) by secondary poisoning. Gut contents of predators indicated that house mice (Mus musculus), ship rats (Rattus rattus) and bushtail possums (Trichosurus vulpecula) were important sources of the toxin.