Models were developed to examine the efficacy of immunocontraception as an alternative control method for pest rabbits. The models simulated the dynamics of rabbit populations structured by age and sex, and helped identify the benefits of an integrated pest management strategy that includes immunocontraception and lethal control. Virally vectored immunocontraception (VVIC) using a sterilising myxoma virus reduced the long-term density of rabbits. However, our models indicated that the efficacy of VVIC is much less than using lethal methods of management currently available (e.g.
Changes in vegetation from 1990 to 2000 were examined at 10 high country localities, representing four grassland types: fescue tussock (Festuca novae-zelandiae), snow tussock (Chionochloa rigida), red tussock (C. rubra), and silver tussock (Poa cita). At each locality, three treatments were established: ambient sheep+rabbit grazing, rabbit grazing only, and no grazing. The mutivariate methods of classification and ordination were used on individual-quadrat cover data to define vegetation states and to examine transitions between them over time.
Plastic bait stations were trialled to assess their usefulness as a rabbit control tool. Non-toxic cereal baits were applied at two 171 ha Mackenzie Basin sites, at one site in stations and at the other site spread directly on the ground. Bait-take at each site was measured. Rhodamine-dyed baits were also used to determine the proportion of rabbits at each site that took bait. Bait-take, and the proportion of shot rabbits with stomachs containing dye, were both significantly lower (P ² 0.0001) at the bait station site.
Norway rats (Rattus norvegicus) were present on Whale Island (Moutohora), Bay of Plenty, New Zealand between about 1920 and 1987. During 1969-1971 they reduced by less than 10-35 % the breeding success of grey-faced petrels (Pterodroma macroptera gouldi), by eating unattended eggs and killing young or weak chicks. Rabbits (Oryctolagus cuniculus), introduced to Moutohora (240 ha surface area) in about 1968, multiplied rapidly to reach a density of up to 375 individuals/ha by early 1973.
Assays for the toxin sodium monofluoroacetate (compound 1080) were undertaken on arthropods collected from toxic baits after a brushtail possum (Trichosorus vulpecula) control operation in Nothofagus forest in central North Island, New Zealand. The 1080 concentrations measured (mean 57 mu g per g, max 130 mu g per g) are considerably higher than those reported by other researchers who collected arthropods randomly after control operations.
Vertebrate pest control operations using toxic baits can have unintended consequences for nontarget species. some of which may themselves be pests. Learned avoidance behaviour (termed 'aversion') can be induced by sublethal dosing, which can arise when species with high and low susceptibilities to a toxin co- exist in the same area. In such cases the less-susceptible species (e.g., possums Trichosurus vulpecula) may be sublethally poisoned by control work targeting the more- susceptible species (e.g., rabbits Oryctolagus cuniculus).
Aerial poisoning using Talon(R) 7-20 baits (active ingredient 20 ppm brodifacoum) was carried out on Motuihe Island, Hauraki Gulf, during the winter of 1997. The operation aimed to eradicate Norway rats (Rattus norvegicus) and house mice (iMus musculus) and to reduce rabbit (Oryctolagus cuniculus) numbers significantly. We studied the diet of feral house cats (Felis earns) before the operation, then monitored the impact of the operation on them to determine whether secondary brodifacoum poisoning caused a reduction in their numbers.
Predation of yellow-eyed penguin (Megadyptes antipodes) chicks may be reduced by removing stock around penguin breeding sites because long grass may reduce lagomorph abundance and hence small mammal predators. This study tests this hypothesis in the South Island, New Zealand. The abundance of lagomorph faeces (mainly rabbit Oryctolagus cuniculus, but some European hare Lepus europaeus) was used as an index of relative abundance of lagomorphs at 16 penguin breeding sites in winter 1991 and 37 sites in 1992/93.
The density of rabbits (Oryctolagus cuniculus) in the modified tussock grasslands of the Mackenzie Basin, South Island, New Zealand, in August-September 1991 was determined within 26 I-ha quadrats spread over 1000 ha. The area was poisoned with 1080- carrot baits and dead and live rabbits counted. The overall kill rate was 93%. Wide variability in rabbit densities amongst the quadrats was correlated with burrow density, but vegetation was not a significant predictor of rabbit numbers. High density quadrats were not all spatially clumped together.
Rabbits are serious economic and environmental pests in New Zealand's semi arid lands, yet there is surprisingly little quantitative information about their grazing impacts. This paper describes the shortterm gains in pasture yield following protection from rabbit grazing in a rabbit-prone, dry tussock grassland community in Central Otago. During the four most productive plant growing months of 1994 (September to December), a six-fold increase in pasture yield was observed after protection from rabbit grazing (139 kg dry weight ha(-1) with rabbits cf. 853 kg DW ha(-1) without rabbits).