The role of non-toxic prefeed and postfeed in the development and maintenance of 1080 bait shyness in captive brushtail possums

Shyness to sodium monofluoroacetate (1080) in cereal bait can persist in su b-lethally poisoned possum (Trichosurus vulpecula) populations for at least 2 years. We investigated the use of non-toxic cereal 'prefeed' and 'postfe ed' as ways of inhibiting and overcoming such shyness. The postfeed result was also compared with changing to a non-cereal, gel-based 1080 bait. Prefe eding had a significant effect on the number of possums that became 'bait s hy' following an approximate LD20 1080 dose, with 97% of non-prefed possums developing an aversion to 1080 cereal bait compared with only 22% of prefe d possums. In contrast, postfeeding with cereal was relatively ineffective in reducing the number of 1080 bait-shy possums, with mortality of these po ssums being 30% compared with 0% of non-postfed possums. In contrast, the g el 1080 bait killed 64% of 1080 cereal bait-shy possums. These results sugg est that 1080 bait shyness can be markedly reduced by prefeeding non-toxic bait to possums prior to each control operation. However, this may not be t he most cost-effective control option, given the observed efficacy of follo w-up baiting with 1080 gel.