Possum (Trichosurus vulpecula) responses and preferences to novel objects in their environment

Abstract

The Australian brushtail possum (Trichosurus vulpecula Kerr 1792) is a major conservation and agricultural pest in New Zealand, and is currently a focus of much research to improve control efficacy. Traps and toxins stored within bait stations are used to control possums in ground-based operations, yet few studies have investigated the influence of trap componentry and design on possum behavioural responses towards them. This thesis describes pen and field research examining possum preferences in five main areas of research which include: testing possum attractiveness towards different colours, control device entrance geometry preferences, trap size entrance openings preferences, trap material attractiveness and trap orientation preferences. This information will be used to assist in designing and developing new, re-setting, permanent-set kill traps for the sustained control of possums in native forests or farmlands currently being developed at Lincoln University. Captive possum preferences were recorded within laboratory pens via four-way cafeteria tests and analysed using multinomial log-linear models and Akaike Information Criterion. Black was the preferred colour (followed by Blue, Yellow and White) by both possum genders and weight classes (i.e. <2.5 kg). Possums expressed a preference for the more ‘open’ Square trap geometry shape (followed by the shapes Key, Diamond and Triangle), although this may be confounded with size. Possums chose the largest trap entrance size (120 mm diameter) over the smaller sized entranceways (100, 80 & 70 mm respectively). The test subjects expressed no preference towards the trialled materials (Wood, Plastic, Corflute & Metal), however, possums interacted with novel devices with the orientation “Timms” (i.e. straight front entrance) at significantly higher levels than any other design (“Warrior” i.e. angled front, “Henry”; i.e. vertical up entrance and “box”; i.e vertical down entrance). The captive possum trials did succeed in quantifying possum preferences towards novel device designs, however, the field trials did not provide sufficient interactions to be included in the preference experiments, but did allow non-target (rodent and weka) bait take from novel possum control devices to be examined and discussed. In conclusion, improving ground based possum control devices relies on increasing possum encounters and subsequent interactions with control devices. This research identified that black devices, with open, easily assessable entranceways and claw holds for front limb grip, could increase possum/device interactions over control devices currently being employed for possum control.