Honours research into the impact that a decline in bogong moth has on mountain pygmy possums

Claire Hutton is a new honours student at at La Trobe University studying with Dr Dean Heinze and Dr John Morgan. Below, Claire has written about her project and motivations for working in the alps.

My interest in the alps originates from two different aspects. Firstly, from a great appreciation for the beauty of mountains. And secondly, from the belief that the management of alpine environments should balance tourist access and the preservation of its ecosystems. My honours project focuses on two major species which rely on the perseverance of Australia’s unique montane conditions: bogong moth and mountain pygmy possum.

Bogong moth migrate in large numbers to the peaks of the Snowy Mountains and the Victorian Alps, including the Bogong High Plains and Mount Buller, every spring. This, in itself, delivers a huge influx of prey to many species, such as mountain pygmy possum. These possums need to gain sufficient weight in the space of only a few months to carry them through their winter hibernation. Traditionally, they do this by capitalising on the extensive bogong moth availability, particularly in October and November; therefore these possums are believed to be dependent on the bogong moth. Over the last two summer, however, there have been anecdotal reports indicating a crash in bogong moth population, raising concern over the impact this decline could have on mountain pygmy possum, among other species.

This study aims to determine both the abundance of bogong moth and the composition of mountain pygmy possum diet, specifically the proportion of bogong moth to other carnivorous and herbivorous prey in faecal samples. This will give insight into the degree of specialisation of these species’ predator prey relationship.

Data collection will take place through field surveys at Mount Little Higginbotham and Mount Buller across the coming snow free season. Specifically, collections will be monthly from October to February capturing the traditional peak in bogong moth alpine population in Spring and allowing for comparisons across early and late summer. Environmental moth abundance will be measured using light traps; diet composition will be assessed through scat collection from possum trapping and subsequent laboratory analysis.

This research may find that moths are not arriving in large numbers. This may reflect the recent drought or agricultural changes in their lowland breeding grounds. This may lead to a reduced proportion of bogong moth being consumed. This study will be able to determine if other arthropods are predated upon in lieu, given that alternative species are available. However, there may be significant impacts on possum health and reproduction if bogong moth cannot be substituted with species which are both available in high numbers and rich in energy.

This study will contribute to records of bogong moth populations as there is currently very limited published data. It will also highlight an additional, potential threat to mountain pygmy possum and the importance of maintaining these ecosystems for supporting the species comprising them.

– Claire Hutton