Rabbit control can induce toxic bait aversion in other pest species: Evidence and potential solutions

Abstract

Poisoning operations in habitats where several vertebrate pest species co-occur can induce sublethal dosing, and consequent bait aversion, in the less-susceptible species. We monitored a winter control for rabbits (Oryctolagus cuniculus) using 0.02% sodium monofluoroacetate (1080) carrot baits on North Canterbury farmland. An estimated 75% of brushtail possums (Trlchosurus vulpecula) in the area survived this control work and many of the survivors thereafter exhibited pronounced aversions to carrot bait. Our subsequent research identified two potential solutions to this problem. First, "prefeeding" possums with non-toxic bait prior to control can achieve a 10-fold reduction in the level of bait aversion among survivors. Second, replacing 1080 with slow-acting toxins such as cholecalciferol and brodifacoum can provide reasonably effective (70%) control of bait-shy possums. When these toxins are combined with a novel bait base (e.g., fruit paste) our control success was 100%. The relative costs and field practicalities of these alternatives have yet to be assessed.