reinvasion

Feral cats (Felis catus) have a negative impact on native biodiversity in New Zealand. As such, their populations require careful management and monitoring of the effectiveness of these management operations. We used camera traps to assess (1) effectiveness of an intensive cat control operation, and (2) the level of reinvasion six months later. Cat abundance was estimated on a pastoral property in Hawke’s Bay, North Island, New Zealand, subject to cat control using trapping and shooting.

Dispersal is a fundamentally important aspect of animal behaviour, but empirical data describing it are lacking for many species. Here, we report on a field study aimed at measuring post-weaning movement distances of juvenile ship rats (Rattus rattus) and their mother away from a known natal nest site in an area with low conspecific population density. The movement behaviour of invasive species at low density is of particular interest, as it can inform design of surveillance arrays to detect incursion into predator-free areas.

Invasive rats can be capable swimmers, able to cross substantial water channels of hundreds of metres to colonise islands. This dispersal capability puts at risk islands close enough to infested areas for rats to reach unassisted. When reinvasion rates are high, biosecurity surveillance on islands might be supported by source population control to prevent re-establishment. However, biosecurity surveillance can only detect reinvading rats when they arrive and the source of reinvading rats might remain unknown.