invasive species

Evaluation of remote cameras for monitoring multiple invasive mammals in New Zealand

Numerous conservation projects in New Zealand aim to reduce populations of invasive mammalian predators to facilitate the recovery of native species. However, results of control efforts are often uncertain due to insufficient monitoring. Remote cameras have the potential to monitor multiple species of invasive mammals. To determine the efficiency of cameras as a multi-species monitoring tool, we compared the detection rates of remote cameras and tracking tunnels over 4 non-consecutive days across 40 sites in Wellington.

Conserving biodiversity in New Zealand’s lowland landscapes: does forest cover or pest control have a greater effect on native birds?

Effective biodiversity conservation in lowland New Zealand requires an understanding of the relative benefits of managing impacts of native forest loss versus controlling invasive species. We used bird count data from 195 locations across mainland northern New Zealand to examine how the abundance and richness of native forest birds varied across wide gradients of native forest cover (c. 0–100%) and intensity of invasive species control (‘eradication’, ‘high-intensity rat and possum’, ‘low-intensity rat and possum’, ‘periodic possum’ and ‘none’).

A comparison of horizontal versus vertical camera placement to detect feral cats and mustelids

Invasive predators are a threat to biodiversity in New Zealand. However, they are often difficult to monitor because of the animals’ cryptic, mobile behaviour and low densities. Camera traps are increasingly being used to monitor wildlife, but until recently have been used mainly for large species. We aimed to determine the optimal camera alignment (horizontal or vertical) for detecting feral cats (Felis catus) and mustelids (Mustela furo, M. erminea and M. nivalis). We deployed 20 pairs of cameras, each pair with one horizontal and one vertical camera.

Home range and population density of black rats (Rattus rattus) on a seabird island: a case for a marine subsidised effect?

Rodents on islands are known to exhibit differing spatial ecology than is seen in mainland habitats and in the case of invasive rats this may affect their impacts on native species. Ship rats’ (Rattus rattus) home range size and population densities were measured on Big South Cape Island/Taukihepa, an island with a dense seabird colony, near South-west Stewart Island. Home ranges for both male and female rats were much smaller than had been recorded for virtually all sites in New Zealand.

Using home-range data to optimise the control of invasive animals

Invasive species have been identified by the Convention on Biological Diversity as a significant threat to biodiversity. Conservation managers often lack tools for addressing uncertainty about the control intensity required to achieve cost-effective management of invasive species. We describe a modelling approach for informing the spacing of control-device lines given the availability of home-range data. To demonstrate its utility, we used data on stoats (Mustela erminea), an introduced mammalian predator responsible for the decline of endemic birds in New Zealand.

Short-term influence of snow cover on movements and habitat use by brushtail possums (Trichosurus vulpecula)

Climatic events affect the behaviour and ecology of many mammal species (e.g. activity, body condition, home range sizes or predation risk within others). We investigated short-term changes in movements, activity and habitat use of brushtail possums (Trichosurus vulpecula) in response to two major snowfall events in a grassland ecosystem in the southern South Island of New Zealand during winter of 2011. Global positioning system collars were deployed on 21 possums.

Causes and consequences of ground disturbance by feral pigs (Sus scrofa) in a lowland New Zealand conifer–angiosperm forest

The ecological impacts of feral pigs (Sus scrofa) are of concern in many places around the world. One noticeable impact is soil disturbance, although the causes and consequences are often unclear. We measured the effect of ground disturbance by feral pigs on seedling recruitment and soil ecology over 25 months on a forested riparian terrace at Waitutu, south Fiordland, New Zealand, and assessed the diet of pigs from the area from stomach contents of animals shot by hunters. Foraging by feral pigs for below-ground food disturbed between 7.4% and 12.4% of the soil.

Optimisation of a microsatellite panel for the individual identification of brushtail possums using low template DNA

The Australian brushtail possum Trichosurus vulpecula is a pervasive marsupial pest of New Zealand. Impacting on the native flora and fauna and the nation’s livestock industry as a vector of bovine tuberculosis, T. vulpecula is a priority for control and eventual eradication. Possum control at present relies on conventional trapping and poisoning methods. Efficient allocation of control depends on accurate quantification of abundance, which could be achieved with the implementation of non-invasive sampling schemes.

Impacts of invasive house mice on post-release survival of translocated lizards

Invasive house mice (Mus musculus) have detrimental effects on biodiversity, but their impacts can be difficult to detect and are often unquantified. We measured their effects on survival of a translocated population of an endangered lizard in New Zealand. Twelve captive-reared Otago skinks (Oligosoma otagense) were translocated to a 0.3-ha area of grassland/shrubland cleared of invasive mammals and surrounded by a mammal-resistant fence. Sixteen more skinks were released 2 years later but this was followed by an incursion of mice for c. 160 days.

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