ROSALIND Park’s grey-headed flying foxes could be here for a long time, if the Royal Botanic Gardens in Sydney’s 20-year bat problem is anything to go by.The gardens were given approval in May by then federal environment minister Peter Garrett for the Botanic Gardens Trust to evict a colony of up to 22,000 threatened grey-headed flying foxes, which have killed 18 mature trees and threaten 300 more.Botanic Garden’s Trust executive director Tim Entwisle said the camp of flying foxes arrived at the gardens in 1990 and for the first few years there was only low level disturbance.He said the numbers slowly increased from 3000 to almost 6000 and in the past three to four years the numbers grew to 20,000.Dr Entwisle said it took three years to get approval from the state and federal government for the flying foxes to be relocated. He said the main concern was the animals roosting in the trees causing defoliation.“A lot of big, old mature trees have been killed,” he said.“It wasn’t unusual for them to be in Sydney, but it was for the numbers to increase and for them to kill the trees.”In May next year the trust will blast the bats with loud industrial noise, such as motors and banging, following success using the same method at Melbourne’s Royal Botanic Gardens.The approval comes with strict conditions, including supervision by an independent observer group with expertise in animal biology.The operation can be carried out only outside the flying fox breeding season, and the trust must make sure the colony relocates to an appropriate site. Eureka Wildlife Shelter officer Steve Boyes said there was no need to consider moving the flying foxes on.“They’re being checked regularly and they are moving on,” he said.“They have been here a bit longer than expected, but let them stay as long as it takes.”The City of Greater Bendigo said it would wait until April before it considered moving the flying foxes. The number of flying foxes has dropped from 30,000 eight weeks ago to between four and five thousand.Sign the Bendigo Advertiser's Ban the Bats campaign and have your say.