The influence of lunar phase on indirect indices of activity for the Common Brushtail Possum (Trichosurus vulpecula) on Banks Peninsula, New Zealand : Masters thesis submitted to the Faculty of Biology, Georg-August-Universität Göttingen in partial fulfilment of the requirements for the intergrated bi-national Masters degree at Georg-August-Universität Göttingen, Germany and Lincoln University, New Zealand

Abstract

The brushtail possum, Trichosurus vulpecula is an introduced nocturnal marsupial no larger than a house cat. First arriving in 1848, it was intended to bring a profitable fur industry to New Zealand. This proved unsuccessful and many trappers, not understanding the consequences of their actions, released them into surrounding forests. Possum were highly successful in the New Zealand landscape and have become a major vertebrate pest species. Possum not only threaten the native plants and animals (through direct predation) of New Zealand, but also the agricultural industry, as they are vectors of bovine tuberculosis (Tb). The Department of Conservation (DOC), Animal Health Board (AHB) and various regional and district councils spend an estimated $72 million annually on possum control. This clearly highlights the significant threat they pose and the need for an effective and well thought-out control program. Being mindful of periods during the month when possum activity is highest can aid in the assurance of successful trapping and poisoning efforts. There are limited studies on possum ecology and even fewer on how they respond to lunar illumination and seasonal changes. Prior to the current study, no published information existed that studied the effects of lunar phase on the activity patterns of the possum during winter months. Monitoring new-and-full moon phases over a four-month period included the use of WaxTags® and camera traps, which measured activity at three different habitat types including 1) exotic-and-native scrub, 2) pine plantation and 3) mixed-hardwood-andbroadleaf forest. It was predicted that possum foraging behaviour would vary during the moon phases. According to previous research on small nocturnal mammals, they substantially reduce their activity under moonlit nights, exhibiting a behaviour known as lunar phobia. This includes reducing use of open space, spending less time foraging and reducing vocalizations and movement. This anti-predator tactic is a common behaviour amongst small mammals. The results of the current study show that possum foraging behaviour does in fact vary during the moon phases however, they are more active during the full moon, exhibiting lunar philia, an uncommon behaviour among potential prey species. This could be due to lack of the possum’s natural predators in New Zealand. Another interesting result from the current study is that possum activity significantly decreased during the new moon (less illuminated) phase in forested sites (with canopy) compared to scrubland habitats. Less exposure from daily ambient light coupled with canopy cover provided unfavourable conditions for possum during this study. My results indicate that the behaviour of common brushtail possum in New Zealand is influenced by changing lunar phases and as such, timing must be considered when carrying out future possum control operations.