Invasive rodents pose one of the biggest threats to island ecosystems globally. Reliable methods for detecting and monitoring rodent presence are essential for the effective conservation management of islands, but many detection devices fail to attract rodents when natural resources are abundant. Using a toolbox of detection methods is therefore key to detecting rodents as individual rodents vary in their susceptibility to detection devices.
A simple deterministic accounting model was used to predict the rate at which a colonising stoat (Mustela erminea L.) population would reach specified sizes. The model was used to explore how the size and composition of the founder population, and the survival schedule to which it was exposed, influenced this rate. A function used in disease surveillance was modified to predict the number of tracking tunnels necessary to detect the presence of the colonising Population with a specified degree of confidence.
In 2007 The Nature Conservancy (TNC) undertook an intensive ungulate control programme throughout three of its preserves on the Hawaiian islands of Maui and Moloka'i, with one aim being to reduce feral pig numbers to zero or near zero. The preserves were divided into manageable zones and over a 2 to 5 month period hunted from the ground with dogs in a series of up to four sweeps across the zones. More focussed hunting followed at sites with evidence of survivors. We used the data collected by the hunters to evaluate the efficacy of the control programme.
It is usually uncertain when to declare success and stop control in pest eradication operations that rely on successive reductions of the population. We used the data collected during a project to eradicate feral cats from San Nicolas Island, California to estimate both the number of cats remaining towards the end of the project, and the amount and type of surveillance effort required to declare successful eradication after the last known cat was removed.
A common question that arises when considering the results from a well-designed sampling programme for a rare or invasive species is: ‘Sampling has failed to detect a species that could have been present, so can we calculate the probability that it truly was absent during the sampling period?’ Noting that this invokes a Bayesian view of ‘probability’, which therefore must be accepted if the question is to be answered in the affirmative, we present a method of addressing it.
Translocation is an important tool in the conservation of New Zealand reptiles. Despite this, it is generally not known how Hoplodactylus geckos respond to being translocated, partly because they are difficult to monitor. In this opportunistic study, common geckos (H. maculatus) were captured from a site at Birdlings Flat (South Island, New Zealand) that was destined for destruction, and released in native coastal shrubland km away. Geckos were sampled monthly using pitfall traps and artificial retreats, with only the latter method yielding captures.