population

Ship rat (Rattus rattus) and mouse (Mus musculus) density and habitat use were estimated by snap trapping and tracking tunnels at Kaharoa in central North Island, New Zealand. Eighty-one ship rats were caught in an effective trapping area of 12.4 ha. Extinction trapping gave an estimated density of 6.7 rats ha(-1) (6.5-7.8 rats ha(-1), 95% confidence intervals). A linear relationship existed between ship rat trapping and tracking rates. Estimating the density of mice was impossible because trapping rates increased rather than decreased during the experiment.

We studied the ecology of a high-density population of stoats in Fiordland, New Zealand, in the summer and autumn of 1990-91 following a Nothofagus seeding in 1990. Results are compared with findings from the same area in 1991-92, a period of lower stoat density. In the high-density year, minimum home ranges (revealed by radio-tracking) of four females averaged 69 ha and those of three males 93 ha; range lengths averaged 1.3 km and 2.5 km respectively. Neither difference was statistically significant.

A 20-year capture-recapture study of alpine grasshoppers spanned three distinct sequences of abundance, featuring in turn dis-equilibrium, equilibrium and secondary cyclic equilibrium. This succession of population patterns in the most abundant species, Paprides nitidus, retained high stability between generations. It arose via superimposed life- cycle pathways and adaptive responses between grasshopper phenologies and their environmental constraints.

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.

New Zealand’s subantarctic Antipodes Islands are of international significance for breeding seabirds. However, penguin populations on the islands are declining. Uncertainty about the extent of this decline has been accentuated by a lack of accurate information on the population size and nest distribution of the penguin species, and the absence of an appropriate methodology for their long-term monitoring. We surveyed the nest abundance and distribution of eastern rockhopper penguins (Eudyptes filholi) and erect-crested penguins (E.