Landholder participation in regional-scale control of invasive predators: an adaptable landscape model

Control of invasive predators is necessary for the conservation of many endemic species. Invasive predator management tends to focus on priority sites, which often comprise only a small fraction of the impacted area. Landscape-scale ecological recovery requires threatening processes to be managed not only in these priority areas, but also in the matrix between them. However, wide-scale control of invasive species can be logistically, economically and socially challenging. We developed a spatially explicit model to estimate the effects of varying levels of landholder participation in landscape-scale programs to control invasive predators. We demonstrate the use of this model with a case study from the North Island of New Zealand in which the results of predator control are projected over a 6 year period. Under various scenarios for landholder participation, we estimated how the participation rate, and size and location of non-participating properties, would influence effectiveness of predator trapping. We also modelled how trap deployment could be adjusted to limit reinvasion from non-participating properties. Under all modelled scenarios, predator populations remained below pre-control levels throughout the 6 years. Non-participation by owners of small properties (<= 25 ha) had a negligible effect on the efficacy of predator control. If owners of large properties (> 800 ha) failed to participate, reinvasion by predators from these properties reduced the efficacy of control; however, this could be largely offset by placing additional traps on the nearest participating properties. Predator control will thus be effective even if some landholders choose not to participate. Our model can be readily adapted to other invasive species and landscapes worldwide.