of a thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science Implications of prefeeding for the development of bait aversions in brushtail possums (Trichosurus vulpecula) by Zane N. Moss The first cage trial determined the effects of prefeeding on aversion development. Three treatment groups received for 7 days either i) no prefeed ii) plain prefeed, or iii) dyed and lured prefeed baits. Each possum then ingested a sub-lethal 1080 bait. Seven days later, the possums were tested for development of an aversion towards a 1080 bait, a prefeed bait, and a prefeed bait containing brodifacoum. Most (96%) non-prefed possums became averse to the 1080 bait, compared with only 55% and 9% of the two prefed groups.Similarly, over 90% of the non-prefed possums were averse to prefeed and brodifacoum baits, compared to <15% of the prefed possums. The trial also showed that novelty has an influence on possums' aversion development; as prefeed and toxic baits became more similar (i.e. the more cues shared), fewer prefed possums were able to distinguish between the two after sub-lethal poisoning and so few developed aversions.The second cage trial examined the influence of bait cues and prefeeding duration on possums' development of aversion. Three main treatment groups received either i) dyed, ii) cinnamon lured, or iii) dyed and lured prefeed baits, for either 1 or 7 days.iii Mter sub-lethal poisoning possums were tested for aversion towards a 1080 bait and a prefeed bait. Once again the influence of familiarity was apparent, with only 34% averse to the toxic bait, significantly less than for non-prefed possums (cf. trial one). Dye seemed to provide relatively weak cues linking prefeed and toxic bait, with 7 days prefeeding required to inhibit aversion development. In contrast, cinnamon appeared to provide relatively strong olfactory and/or taste cues linking prefeed and toxic baits, with one exposure to cinnamon lured prefeed sufficient to inhibit aversion development. As in the first trial, most of the possums that developed aversion to the toxic bait did not generalise this aversion to the prefeed bait. Some possums were seemingly able to detect 0.08% 1080, despite it being' masked' with cinnamon oil.The field trial aimed to validate results of the cage trials and to examine whether possums preferentially associate certain cues with poisoning. Two treatment groups received either cinnamon lured baits, or apples, for 3 weeks. Mter sub-lethal poisoning possums were tested for aversion towards a non-toxic prefeed bait, a dyed non-toxic bait, a toxic bait, and a dyed toxic bait, all of which contained cinnamon. Once again most non-prefed possums developed generalised aversions, avoiding all cereal baits. In contrast, prefed possums consumed familiar prefeed baits, but avoided all other baits. This demonstrated that possums could detect both dye and 1080 in a cinnamon-lured bait. This result also suggests that extended prefeeding may enable possums to distinguish between prefeed a...

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