A rare species that is a pest

The Grey-headed Flying-fox (Pteropus poliocephalus) is a large fruit bat which feeds on nectar, pollen and fleshy fruit.  It is a nomadic species which will travel long distances in search of food which it forages for at night.  During the day it will congregate in semi-permanent colonies, called camps, which can comprise thousands of individuals.  The species has been widely recorded in Victoria but most of the sightings represent individuals or small groups of animals that are passing through in search of food.  There are two major sites for colonies in Victoria, one is in East Gippsland in two rainforest gullies north-east of Mallacoota and the other is on the banks of the Yarra River, a few kilometres east of Melbourne.  The Grey-headed Flying-fox has been classified as vulnerable in Victoria, vulnerable in Australia (EPBC) and it has been listed under the Flora and Fauna Guarantee Act (FFG) and is classified as vulnerable world-wide by the IUCN.

Grey-headed Flying-foxes, from NSW, were probably visiting Victoria on foraging expeditions long before European settlement.  Our earliest records date back to the 1880s and there have been regular sightings almost every year since.  The two rainforest gullies in far East Gippsland have, for a long time, been annual autumn-winter camps for the bats and until relatively recently they represented the only colonies in Victoria.

During the 1980s, however, a small population of flying-foxes found its way to the Royal Botanic Gardens (RBG) in Melbourne where the animals would roost in the gardens' rainforest gully by day and fly off to feed on fruit (often figs) and nectar from surrounding gardens and parks by night.  Initially this was a great tourist feature of the gardens and was also considered to be of some scientific interest as the RBG colony was the most southerly in the world.  Unfortunately the tourist value began to decline as the colony grew in size over the next two decades to almost 20,000 animals.  Exciting as this was from a scientific and conservation standpoint the RBG management was faced with a serious problem of dealing with the damage to the gardens flora by so many large animals.

Pteropus poliocephalus - Grey-headed Flying-fox : Vulnerable in Victoria : Vulnerable in Australia
Grey-headed Flying-fox
© Paul Gullan/Viridans Images 

When animals threaten valuable assets it has become common practice to demonise them, label them as pests and then to implement eradication measures.  In the first instance, in 2001, this was the approach of the RBG.  The director of the gardens likened the bats to a disease which needed to be eradicated and he said that culling was the only effective method available.  He dismissed proposals for a program of irritating noises to persuade the bats to leave the gardens as being unlikely to succeed.  When arguments were put to the Victorian Government that the bats were threatened across the country and that the RBG population was a significant refuge, the response from the Government was cool.  The Minister for Environment and Conservation had recently rejected a recommendation from the Scientific Advisory Committee (SAC) of the FFG to list the Grey-headed Flying-fox.  Consequently there were no impediments to the eradication program and plans were made for the bats to be culled using methods that included shooting.

The culling began sometime in early 2001 but was halted in the middle of that year amid criticism from conservation groups, ecologists and the Federal Minister for Conservation.  In December of 2001 the Grey-headed Flying-fox was listed as vulnerable under the federal EPBC Act and the following year the Victorian Minister accepted advice from the SAC to list the species under the FFG.  Now that the bat was protected by two layers of legislation the RBG needed to find a less confrontational method to free the gardens of flying foxes, and while it was looking the population increased to nearly 30,000. 

Fortunately, an idea, promoted earlier, to use a form of bat noise-pollution, was ready to hand and during 2003 it was applied, with a range of empirical modifications, with outstanding success.   By the end of 2003 all of the flying-foxes had left the gardens and a large proportion of them had relocated to Yarra Bend Park, about 4 km north-east of the gardens, in a narrow band of woodland on the banks of the Yarra River.  It seems to be close to a perfect solution.  The animals are in what appears to be a more natural environment with native and near-native vegetation and fresh water.  The area is an established park and management plans are now in place to secure the species long-term survival.  Meanwhile the RBG can approach the process of restoration without the need to compete with 30,000 restless frugivores and half a tonne of bat droppings each day. 

© Paul Gullan, Viridans Biological Databases