Predator control on farmland for biodiversity conservation: a case study from Hawke’s Bay, New Zealand

Invasive predator control to protect native fauna usually takes place in native habitat. We investigated the effects of predator control across 6000 ha of multi-tenure, pastoral landscape in Hawke’s Bay, North Island, New Zealand. Since 2011, low-cost predator control has been conducted using a network of kill traps for mustelids (Mustela spp.), and live trapping for feral cats (Felis catus). Although not deliberately targeted, other invasive mammals (particularly hedgehogs Erinaceus europaeus) were also trapped. We monitored predators and native prey in the predator-removal area and an adjacent non-treatment area. Predator populations were monitored using large tracking tunnels, which also detected native lizards. Invertebrates were monitored using artificial shelters (weta houses). Occupancy modelling showed that site use by cats and hedgehogs was significantly lower in the predator-removal area than in the non-treatment area. Site use by mustelids also appeared to be lower in the treatment area, although sample sizes were too small to allow firm conclusions. Site use by invasive rats (Rattus spp.) was higher in the treatment area, while that of house mice (Mus musculus) showed no difference between treatments. There was evidence of positive responses of some native biodiversity, with site use by native lizards increasing significantly in the treatment area, but not in the non-treatment area. Counts of native cockroaches were higher in the treatment area, but other invertebrates were detected in similar numbers in both areas. Our results show that low-cost predator control in a pastoral landscape can reduce invasive predator populations, with apparent benefits for some, but not all, native fauna.