An assessment of visual lures for the possum Trichosurus vulpecula : a dissertation submitted in partial fulfilment of the requirements for the degree of Master of Applied Science at Lincoln University

Abstract

The successful use of traps and bait stations for possum monitoring and control is largely reliant on the interaction of the possum with the traps and bait stations. Increasing the efficiency of these methods could be achieved with visual lures that attract a higher proportion of possums.

WaxTags® are a recently-developed device for estimating possum abundance. Each WaxTag® consists of a 40 cm² piece of isosceles-triangle shaped sheet plastic, with a 12 cc block of wax moulded to the sharpest point of the triangle. Possums are attracted to the tag, and their presence is recorded by bite marks on the wax.

WaxTags® of 5 different colours, (white, luminescent, UV enhanced, blue and black) were deployed along lines within Eyrewell forest, a pine plantation in North Canterbury. The number of tags bitten by possums was recorded over 14 days.

Colour appeared to have an effect on possum preference. The ·highest proportion of tags bitten were white with a luminescent pigment. There were significantly more luminescent tags bitten than any of the other four colours (P<0.05). The observed possum preference for luminescent-coloured WaxTags provides new information that colour could be used to increase the attractiveness of monitoring devices, bait stations and traps for possum management.

In addition to assessing colour, an exploration was made of the issue of contagion, where a possum could bite more than one WaxTag®, potentially biasing abundance estimates. WaxTags® were deployed in stations of five tags, in a cruciform arrangement, with a central tag, and the other four tags spaced evenly around the central tag, at a distance of 10 m. Stations were placed at 100 m intervals from neighbouring stations. Contagion within stations is likely to have occurred. The mean number of tags bitten per station increased over 14 days and there were no obvious patterns of biting of several neighbouring stations. The spacing of 100 m, therefore, appeared to negate the occurrence of contagion.

The proportion of wax bitten on each tag was assessed also. Luminescent tags had the highest proportion bitten. This was significantly different (P<0.05) from all test colours except white. This finding suggested that if toxicants to control possums were incorporated into WaxTags®, luminescent tags could potentially deliver a larger dose of toxin compared to the other tags tested.

In conclusion, luminescent-coloured lures are more likely to attract possums and have a larger proportion of wax bitten by possums than white, blue, UV or black. Incorporating this colour in traps and bait stations is likely to increase their capture and kill rates. Spacing WaxTag® stations 100 m apart will reduce and potentially negate the influence of contagion.