Mesopredator and competitor release can lead to population increases of invasive house mice (Mus musculus) after larger introduced mammals are controlled or eradicated. In New Zealand, mammal-resistant fences have enabled multi-species mammal eradications in order to protect indigenous species. When house mice are the only mammals remaining in these biodiversity sanctuaries, they may reach a high population density, with potential consequences for their indigenous prey.
Forty computer-simulated populations were analysed to derive formulae for estimating density of populations from a set of distances from sample points to the nearest member, from that member to its neighbour and from that neighbour to its nearest neighbour. Distances may be truncated or unlimited.
Pathological consequences of the blood-sucking mite Ornithonyssus bursa vary between species, with its impact ranging from no measurable effect, to significant blood loss and chick mortality. In New Zealand, where several bird species are known to be parasitised by O.bursa, the effect of this mite on host fitness is unclear, as few studies have been carried out. During a three-year study of the North Island robin Petroica longipes on Tiritiri Matangi Island, the prevalence of O.
Percentage non-toxic bait interference is currently used by local authorities to monitor brushtail possum control operations but the validity of the method has not been established. Two models have been proposed to estimate an index of possum density (possums per bait) from a log-transformation of percentage bait interference. In two trials, percentage bait interference and the density index derived from percentage bait interference using the Bamford (1970) model usually increased from night to night.
Feral horses (Equus caballus L.) occupy 64 000 ha of montane- subalpine tussock grassland in the south-western Kaimanawa Mountains, an area zoned for military training. Since 1979, the population has increased at 16.7% per annum, reaching 1102 in 1990. The most extensive habitat, red tussock (Chionochloa rubra) grassland, was variably affected by horses; tussocks in restricted mesic sites were heavily grazed and mostly eliminated, but those in extensive xeric grasslands showed little impact.
Records of official deer control operations in the Kaweka Range between 1958 and 1988 have been used to describe the pattern of official hunting, to indicate changes in hunting efficiency, and to show trends in the proportions of sika and red deer in sympatric populations. The pattern of hunting largely reflected wild animal control priorities, and to some extent the resources available.
In late 1986 an official deer hunting regime in the Murchison Mountains, Fiordland, was compared with two commerical aerial hunting regimes in the adjacent Stuart Mountains by measuring the density of deer faecal pellet groups. Overall densities in the Stuart Mountains were twice those in the Murchison Mountains. Official hunting appeared to be more effective than commercial hunting at reducing and controlling deer densities in heavily forested catchments, but not in catchments with less extensive forest cover.
Seven feral pigs (Sus scrofa), radio-tracked in relatively undisturbed rough pasture and forest near Murchison, New Zealand, for periods of 18-186 days, occupied home ranges of 28-209 ha. The immature pigs were significantly more active and had significantly larger home ranges than the adults, particularly adult females. The pigs were mainly nocturnal but they varied individually. The frequency of grazing and the rooting up of pasture and bracken (Pteridium esculentum) varied seasonally.
Deer density indices were estimated in 1969, 1975, and 1984 in the core of the Wapiti Area of Fiordland National Park. Between 1969 and 1984, density above timberline was reduced to near zero by commercial airborne hunting, with smaller decreases in the forest. Overall density declined by 81%. An estimated 2007± 385 deer were present in the 850 km2 survey area in 1984, with an average density in the forest of 3.47±0.66/km2. The highest densities remained in the most completely forested sub-area (Catseye).
Adele (87 ha) and Fisherman (3.6 ha) Islands lie 800 m and 1100 m, respectively, offshore in Tasman Bay, Nelson. Both are covered predominantly in native forest and scrub. There are mice (Mus musculus) on Adele Island but no rodents on Fisherman Island. Both islands are within swimming range of stoats (Mustela erminea) which have colonised Adele Island and occasionally visit Fisherman Island, 700 m distant.