Population Dynamics of Sydney's Grey-headed Flying-fox

5 December 2006

Grey-Headed Flying-Fox

Mist-netting in Sydney's Royal Botanic Gardens Credit: University of Sydney

Dr Kerryn Parry-Jones, from the University of Sydney's School of Biological Sciences is conducting research over the summer months to track to movement of flying foxes around the city, in an attempt to add to our understanding of the species.

'Flying foxes are known to be highly mobile and are capable of dispersing pollen and seeds within a 30 km radius. Consequently, rather than simply feeding on plants, it is becoming increasingly clear that bats act as pollen vectors and seed carriers, thereby playing an important role in the natural forest ecosystems they inhabit,' said Dr Parry-Jones.

'However, the interaction between flying-foxes and their habitat is under threat due to an increase in landscape clearing, and with habitat loss and the relatively recent increase in the availability of native and exotic plants (providing year-round nectar supplies in urban areas), causing flying-foxes to move into urban areas,' she said.

Dr Parry-Jones and her team have found that Sydney's Grey Headed Flying Fox populations are prone to decline due to death of individuals on power lines, aerial wires and culling in orchards. This has a highly detrimental effect on the overall population as flying-foxes that have a relatively low reproductive rate (giving birth to a single young per year), and high maternal investment, characteristics indicative of long lived animals with low natural mortality rates.

'Our study aims at gaining information on the age structure of the Grey-Headed Flying Fox and to do this we are focusing on: accurately aging the dead animals that have been collected, and describing their age structure and demographics; and determining the impact of the causes of mortality on different sex- and age-classes,' said Dr Parry-Jones.

To date the team has aged 141 dead flying-foxes from the greater Sydney area (Bankstown and Canly Vale to Gosford and Wambina), as well as Singleton, Wingham Brush and Bellingen colonies.

Over the 2006/7 season the team will be catching animals from the permanent colony at the Royal Botanic Gardens Sydney using mist-nets suspended from poles in excess of 10m; extracting a tooth from each individual and determine their accurate age; describe the age structure of live population; and modelling the overall population demographics using the data from both the dead and live animals.

They will also be radio collaring flying-foxes from the Royal Botanic Gardens, Sydney to investigate their foraging behaviour and movements at this site and movements to other colony locations.

Source / Credit: University of Sydney