Behaviour-manipulating parasites as adjuncts to vertebrate pest control

Invasive vertebrates damage native biota and agricultural productivity worldwide. Under many circumstances sustained control is limited by cost and effectiveness. Here we model the utility of a novel adjunct to vertebrate pest management; specifically, the potential that behaviour-manipulating parasites could be employed to improve control efficacy. We suggest that through its well documented effects on reducing neophobia in rats, using pre-baiting to establish Toxoplasma gondii infection in ship (black) rat (Rattus rattus) populations could appreciably either increase the efficacy of control operations or reduce the effort required to meet control thresholds for the benefit of biodiversity protection in New Zealand. For example, our model predicts that 70% T. gondii prevalence would reduce the effort required to maintain rat populations in beech dominated forests below a threshold for conservation benefit of 40 per 100ha, in three-yearly trapping sessions with traps at one per hectare, down to 50 nights trapping from 76 for an infection-free population. This is the first such assessment of its kind, with implications beyond this specific context. First, rodents are not only conservation pests globally, but their control is frequently necessary for both food security and human health. Second, T. gondii infects most of all warm-blooded animals, and thus its behaviour-manipulating effects may have utility for the control of other vertebrate pest species. Finally, other behaviour-manipulating parasites could potentially also be put to the use explored here.