Diet and impacts of brushtail possum populations across an invasion front in South Westland, New Zealand

Impact of the irruptive fluctuation in abundance of brushtail possum populations since their initial colonisation was investigated in the forests of South Westland, New Zealand. Possum abundance, fecundity, and diet, the condition of common possum-palatable tree species, and the abundance of common forest birds were measured at three sites occupied by possums for c. 10, 20, and 30 years. Possum densities were highest at the site where possums had been present for c. 20 years.

Mistletoe (Tupeia antarctica) recovery and decline following possum control in a New Zealand forest

The condition of 79 plants of the loranthaceous mistletoe Tupeia antarcticain a podocarp-hardwood forest in the central North Island, New Zealand, was monitored over 4 years during a period of increasing possum density, following previous possum control. Mistletoe comprised 1.2% of total possum diet during the three years following possum control. Incidence of possum browse on mistletoe plants increased from 2.6% of plants when the trap-catch index of possum density was < 3%, to 75.9% of plants when trap-catch rates reached 4.6%.

Possum (Trichosurus vulpecula) densities and impacts on Fuchsia (Fuchsia excorticata) in south Westland, New Zealand

To assess the effect of possum browse on plant growth, an index of the amount of foliage on about 50 trees of Fuchsia excorticata and the number of trees that died or were completely defoliated was measured at five sites in South Westland over 5 years. This index was compared to possum density indices taken at each site each year. At one site, possums were reduced from a high density about 6 months before the final measurement. The degree of defoliation of fuchsia was significantly related to the density of possums at each site.

Diet of feral goats and feral pigs on Auckland Island, New Zealand

The diets of feral pigs and feral goats shot on the main Auckland Island in 1989 are described from analyses of stomach and rumen contents. Feral goats ate at least 50 species of plants, but only three, Metrosideros umbellata, Chionochloa antarctica, and Durvillea antarctica made up over 50% by dried weight of the food eaten. Feral pigs ate a mixed plant and animal diet, of which plants made up 61% of the diet, with the megaherb Anisotome antipoda being the largest dietary item at 38% by dried weight.

Vegetation on Goat-Free Islands in a Low-Alpine Lake, Paparoa Range, and Implications for Monitoring Goat Control Operations

Pronounced differences between the vegetation of four islands in a low-alpine lake compared to an adjacent mainland site are attributed to browsing by feral goats. The herbs Anisotome haastii and Ourisia macrocarpa are significantly more abundant on the islands, where they form tall herbfields. The grass Hierochloe recurvata and the shrub Gaultheria crassa were also more common on the islands, and were absent at the mainland study site.

Using five-minute bird counts to study magpie (Gymnorhina tibicen) impacts on other birds in New Zealand

We used five-minute bird counts to investigate whether introduced Australian magpies (Gymnorhina tibicen) influence the abundance of other birds in rural New Zealand. Over 3 years, magpies were removed from five c. 900-ha study blocks, one in each of Northland, Waikato, Bay of Plenty, Wellington and Southland. Birds were counted in both the treatment blocks and paired non-treatment blocks for the 3 years of removal and also 1 year before.