Grey-headed Flying-foxes (Pteropus poliocephalus) are native and endemic to Australia and the largest member of the flying-fox family. While there are other species of flying-fox in Sydney’s Botanical Gardens, the Grey-headed Flying-fox is the most common.
Grey-headed Flying-foxes are scheduled to be relocated from the Botanical Gardens in Sydney, Australia, because they are damaging trees and plants. Recently, a Federal Government ruling gave the Sydney Royal Botanical Gardens approval to use noise disturbance to relocate the bats to other camps around Sydney. This relocation is to begin in May 2011.
Why are Flying-foxes Attracted to Sydney’s Botanical Gardens?
Flying-foxes have been roosting in the Sydney Botanical Gardens for years, but they have been increasing in numbers. Originally the flying-foxes would just visit the gardens to feed, but now they are increasing in numbers and causing damage to plant life.
Flying-foxes are a protected species. Habitat loss is the main cause for their population decline and large colonies have taken up residence in Sydney’s Botanical Gardens. They are attracted to the food source the trees in the gardens provide, including fruits, nectar and pollen.
Why are Flying-foxes being Relocated from Sydney’s Botanical Gardens?
Over the years the number of flying-foxes in the gardens has increased to 22,000 (during summer of 2010). Though their numbers do fluctuate during the year depending on the flowering and fruiting of trees and times of mating, the large numbers mean the trees and plants are becoming damaged due to the bats movement and weight.
They strip leaves and break branches, weakening trees, which could result in tree death. Further damage is caused to the plants that live beneath the canopy, when the upper canopy suffers. The plants underneath are damaged, as they are unable to deal with the direct sunlight. The Flying-fox guano (excrement) also damages the leaves of certain plants.
How are Flying-foxes Being Relocated from Sydney’s Botanical Gardens?
Flying-foxes and other bats will be relocated using noise disturbance. From noon until 4pm, 10-minute intervals of unpleasant percussive noises will be played on the hour to discourage the bats from roosting. The noise will not be at a level that will frighten or harm the bats or any other wildlife that reside in the gardens (possums, birds), but simply to give the bats an unpleasant night’s sleep to encourage them to move on.
The relocation is scheduled to begin in May 2011 and go for 2-4 weeks in an attempt to encourage the bats to roost at other sites around Sydney that have been deemed suitable. This technique worked for the Melbourne Botanical Gardens in 2003 where bats relocated to other parts of Melbourne and even to Geelong (approximately 60km from Melbourne).
A spokesperson from the Humane Society has expressed concerns about the relocation having an impact on bat numbers and concern for whether they will all be able to find an alternative roosting place. There is also a chance that the bats will return after the noise has ceased, or the following season. If this happens, the plan is to re-try the noise disturbance strategy until it does work.
You may also be interested in reading Echolocation in Bats.
Resource and further reading:
Judge Rules Botanic Gardens can evict bat colony, Sydney morning Herald
Federal Government approval to relocate flying-fox camp, The Royal Botanic Gardens and Domain Trust
Roberta Goli - Roberta has a Bachelor of Science Degree (Zoology), has worked with animals for over 10 years and enjoys writing short stories and flash ...
