populations

Five herbivorous introduced mammals are sympatric in the central Southern Alps. All of these species have the potential to affect conservation values, yet the Department of Conservation at present monitors and mitigates the impacts of only one. We outline ecological arguments for multi-species management of sympatric herbivore pest impacts and use the two- species system of sympatric thar and chamois to highlight the need for multi-species management of the central Southern Alps alpine pest community.

Stoats were monitored by three methods through an aerial 1080 poisoning operation at Waimanoa, Pureora Forest in August 1997. Tracking rates and number of live captures were used as indices of abundance, and radio-transmitters were used to follow individual animals. All 13 stoats with radio-transmitters within the poisoned area died between 2-18 days after the operation. No mustelids were tracked or live-trapped after the operation for three months. Of the radio-tracked stoats that died, rat remains occurred in 67%, passerine birds in 17%, cave weta in 17% and possum in 8%.

Toxins, especially sodium monofluoroacetate (1080) and brodifacoum, are widely used throughout New Zealand for control of introduced mammals that are considered pests. This level of toxin use (not necessarily with these toxins) is unlikely to decline for at least 5-10 years. Ecological consequences derive both from mammal population reduction or eradication, and from using toxins as the control method.

Fuchsia (Fuchsia excorticata) has been heavily browsed and often killed by brushtail possums (Trichosurus vulpecula) in many New Zealand indigenous forests, but remains healthy at some sites despite long histories of possum occupation. To determine whether fuchsia varied genetically in its palatability to possums, material from six widely dispersed stands (provenances) was propagated, and leaf chemistry, leaf morphology, growth rate, and palatability to captive possums was compared.

The Intermediate Disturbance Hypothesis [IDH] and the Gradual Climate Change Hypothesis [GCC] offer intuitively appealing, verbal non-equilibrium explanations to species coexistence in competitive communities, but so far they lack a solid theoretical background and a proper experimental methodology. To make them testable and comparable on a solid methodological basis, they should be formulated as well-defined non- equilibrium community dynamical models.

Populations of ship rats (Rattus rattus), Norway rats (R. norvegicus), feral house mice (Mus musculus), stoats (Mustela erminea), weasels (M. nivalis), and ferrets (M. furo) were sampled with killtraps every three months from November 1982 to November 1987 in logged and unlogged native forest and in exotic plantations of various ages at Pureora Forest Park, central North Island. Mice (n=522 collected) were fewest in unlogged native forest, more abundant in road edge cutover forest, and most abundant in a young (5-10 year old) plantation.

This paper describes the impact of nine poison operations on ship rats in four areas (35 ha to 3200 ha) of North Island forest. Poisoning with 1080, brodifacoum, or pindone killed 87- 100% of rats, based on trapping and tracking-tunnel indices. Rat populations took 4-5 months to recover. Operations to protect nesting birds should therefore coincide with the onset of nesting and be rePeated each year, although not necessarily with the same methods.

We examined possum trapping data collected from 1945 to 1989 in the Pararaki catchment to assess whether there was any evidence for a major natural decline in possum numbers several decades after colonisation and whether the population has subsequently shown any long-term trend in abundance. The catchment was probably colonised by possums around 1915-20. We found evidence for a major decline (c. 80%) in possum numbers between 1945 and 1965. There was no significant trend in our trap catches from 1965 to 1976, but in 1977 there was a further abrupt decline.

Replacing native forests and grasslands with plantations, pastures and crops has resulted in both contraction of ranges and exploitation of modified habitats by native species, and both general and restricted dispersal of introduced species of soil fauna. Contraction is shown by native earthworms, land snails, ring nematodes and various arthropods, while the areas with changed land use suggest certain native insects are more numerous than 150 years ago. Damage to pastures by grass grub and porina show clearly how native species can exploit modified habitats.

The prevalence of infestation of the skulls of stoats with the parasitic nematode Skrjabingylus nasicola was previously described in a national survey by King and Moody (1982). Since then, more samples from Craigieburn Forest Park and from the Eglinton Valley, Fiordland, have been collected, and a method of determining the actual ages of adult stoats has been developed. The extended samples are here examined for a relationship between infestation and age, which could not previously be tested. Prevalence generally increases with age, significantly so at Craigieburn.