New Zealand Journal of Ecology (1982) 5: 36- 43

Field Acceptance of Non-Toxic and Toxic Baits by Populations of the Brushtail Possum (Trichosurus vulpecula Kerr)

Research Article
D. R. Morgan  
  1. Protection Forestry Division, Forest Research Institute, P.O. Box 31-011, Christchurch, New Zealand

In four populations of possums more than 94 % of animals accepted each of the three types of dye-marked, non-toxic bait. In a fifth trial, conducted in summer, only 68 % of the population accepted bait. This poor level of acceptance was attributed to the abundance of natural food available, as indicated by the good condition of the animals. In a trial with toxic bait approximately 25 % refused either to eat a lethal quantity of toxic bait or to eat any toxic bait at all, compared with 98 % acceptance in the non-toxic control trial.
Reasons for possums surviving poison operations include: sub-lethal poisoning as a result of encountering and eating sub-lethal baits, or by sampling baits followed by aversion to the taste of the poison; olfactory aversion to toxic bait; inadequate distribution of baits; and in— frequent visits by possums to the forest floor. The high acceptance rate of non-toxic bait types eliminates bait refusal as a major reason for operational failures, especially in winter.