1080-induced bait aversions in wild possums: influence of bait characteristics and prevalence

The current experiment aimed to determine the proportion of wild-caught pos sums from previously poisoned and non-poisoned populations that developed a versions to 1080 baits. In addition, we aimed to identify the bait characte ristics mediating the ongoing aversions. In an initial test, animals from a reas previously exposed to a 1080 control-operation avoided 1080 baits (60- 80%), whereas few naive animals (0-20%) avoided these baits. The baits comp rised a green-dyed, cinnamon-lured cereal loaded with 0.08% 1080. As a resu lt of the exposure to the toxic baits, over 80% of the naive animals subseq uently developed aversions to those baits. Sixty-nine of these averse anima ls were allocated to one of 16 bait-treatment groups in a factorial design balanced for population, sex, age and bodyweight. Each bait was characteris ed by four factors: (a) presence or absence of 1080, (b) presence or absenc e of green dye, (c) lure type (cinnamon or orange), and (d) bait type (No. 7 or carrot). The presence or absence of 1080 or green dye did not influenc e the degree of bait avoidance. Lure type had a significant effect on consu mption, with 53% of possums avoiding an orange bait compared with 73% for c innamon baits. Bait type also had a significant effect on avoidance rates, with carrot baits being avoided by 42% of possums compared with 83% for No. 7 baits. Changing the bait type would appear to hold the greatest promise for overcoming aversions by possums to cereal bait.