Increasing the attractiveness of Waxtags® to possums (Trichosurus vulpecula) using visual and olfactory lures : a dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Science with Honours at Lincoln University

Abstract

Highly sensitive bait interference techniques are currently being investigated as alternatives for monitoring populations of the Australian brushtail possum (Trichosurus vulpecula) in New Zealand. One alternative, the Waxtag®, is a 40 cm² piece of isosceles-triangle shaped white sheet plastic, with a roughly 12 cc block of wax moulded at the sharpest point of the triangle. Possum presence is shown by bite marks on the wax. Waxtags® can potentially be used at greater sampling intensities than the currently used leg-hold traps, allowing for increased precision in population estimates, and greater potential to monitor small changes in residual possum densities following control operations. As Waxtags® require direct interaction by possums, making them more attractive to possums could increase tag sensitivity (to possum presence) particularly where possum populations have been reduced to very low numbers. During June 2004, field work was undertaken to determine if visual and olfactory lures increase the sensitivity of Waxtags® to possum presence in Eyrewell Forest, a multistage Pinus radiata plantation in North Canterbury, New Zealand. To field test the attractiveness of different lures, tags were treated with a visual flour blaze, an olfactory orange lure, flour blaze/orange lure combination, or no treatment. The number of tags bitten and proportion of wax removed from each tag, and from tag stations (consisting of five tags) was monitored over four days. Leg-hold trapping (using Victor No.1 leg-hold traps) was undertaken simultaneously to compare the sensitivity of the two monitoring methods, and to establish possum density within the plantation.

Visual (flour blaze) and olfactory (orange) lures increased the sensitivity of tag stations to possum presence in Eyrewell Forest. Possums were initially attracted to visual lures and lured tags were more palatable than unlured tags. Tag stations were more sensitive to possum presence than leg-hold traps but failed to identify artificially-induced reductions in possum density indicating tag stations are too sensitive when possum densities are high. The highest possum density found in Eyrewell Forest was 5/ha and is greater than any other published density in plantation forestry.