Ship rats (Rattus rattus) were removed from sites on Pearl Island, southern Stewart Island, in 2004 and 2005, to test whether they excluded Pacific rats (R. exulans) or Norway rats (R. norvegicus) or both from podocarp-broadleaf forest. As predators can influence habitat use in rodents, Pearl Island was selected because no mammalian predators of rodents are present. Rats were trapped in two other habitats to clarify rat distribution on the island and to obtain samples for stable isotope investigation of food partitioning within habitats.
The relative abundance of ship rats (Rattus rattus), Norway rats (R. norvegicus), and Pacific rats (R. exulans), was measured in four vegetation types on Stewart Island/Rakiura, over six consecutive seasons. Ship rats were found in all four vegetation types and dominated in podocarp-broadleaf forest and riparian shrubland. Norway rats were most common in subalpine shrubland and Pacific rats dominated in manuka (Leptospermum scoparium) shrubland. Analysis of micro-habitat affinities for the three species showed that ship rats were habitat generalists.
Introduced rodents and possums in New Zealand eat flowers, fruits, seeds and seedlings, but little is known about their impact on forest regeneration. We investigated seedling establishment in exclosures with mesh of two different sizes to exclude (1) possums and (2) possums and rats, at two mainland forest sites (beechpodocarpbroadleaved and second-growth broadleavedpodocarp) near Dunedin. We recorded all new woody seedlings that established over the next 2 years.
Stoat (Mustela erminea) density was estimated by live-trapping in a South Island Nothofagus forest, New Zealand, at 8-9 (Jan/Feb 1996) and 15-16 (Aug/Sep 1996) month intervals after significant beech seedfall in autumn 1995. Absolute densities were 4.2 stoats per km² (2.9-7.7 stoats per km², 95% confidence intervals) in Jan;Feb 1996 and 2.5 stoats per km² (2.1-3.5 stoats per km²) in Aug/Sep 1996. Trappability of stoats increased in the latter sampling period, probably because mice (Mus musculus) had become extremely scarce.
The objective of this study was to quantify the population dynamics, morphological characteristics, and diet of rodents on Rangitoto Island (Hauraki Gulf, New Zealand) to provide information for the future development of an eradication strategy. An aerial 1080 operation to eradicate possums and wallabies was carried out two months after the study began. The effects of this operation on rodent population dynamics are discussed. Both ship rats (Rattus rattus) and mice (Mus musculus) were trapped on Rangitoto Island over a 15 month period.
Home range dimensions and habitat use by ship rats (Rattus rattus) at Puketi, a kauri (Agathis australis) forest in Northland, were examined by live capture and radio-tracking over five weeks in September and October 1993. Home ranges of six females and five males averaged 0.86 ha in area and 174 m in length, with no significant difference in range area or length between males and females. There was substantial overlap in ranges between and within sexes.
The abundance and diet of stoats (Mustela erminea) were compared before and after an aerial 1080-poison operation for possums (Trichosurus vulpecula) in a New Zealand podocarp- hardwood forest. Poisoning dramatically reduced ship rat (Rattus rattus) abundance. Although rats were the main prey item of stoats before the poisoning, stoat abundance was unaffected by the operation and there was a change in stoats' diet from rats to birds. The conservation benefits and risks of undertaking such operations are not clear.