The development of strategies for management of the flying-fox colony at the Royal Botanic Gardens, Sydney
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G. C. Richards, 2002. "The development of strategies for management of the flying-fox colony at the Royal Botanic Gardens, Sydney", Managing the Grey-headed Flying-fox: As a Threatened Species in NSW, Peggy Eby, Daniel Lunney
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This paper summarises 12 months of research at the Royal Botanic Gardens in Sydney to manage a permanent camp of Grey-headed Flying-foxes Pteropus poliocephalus that had encamped in an area of culturally significant trees. New and innovative methods came to light from these studies.
Numbers of flying-foxes vary at this site from 1000 - 6000, but data also show that there was always a core group that remained in the site. This indicated that deterrence methods should focus upon the location of the core group, but because the site is a traditional maternity camp, one constraint to testing methods of deterrence was the presence of non-flying young during summer.
Three methods were trialled, including sonic deterrence with a Phoenix Wailer (a crop protection system), olfactory deterrence with python excrement, and taste aversion with prawn paste. Trials with the Phoenix Bat Wailer (operating only from dawn for two hours) successfully removed flying-foxes from groups of heritage trees. Noise levels from the Phoenix Wailer were within the ambient range of the Sydney CBD. The fixation of males to territories on branches was a significant research outcome, and has led to new trials on branch removal as a method to relocate colonies.
Deterrence of bats roosting within isolated trees involved the use of python excrement and fermented prawn paste. Pythons, which reside in camps in the tropics, are a major predator of flying-foxes, and it was suspected that bats may keep their distance from pythons by olfactory cues. Python excrement that was wrapped in mesh and tied to branches used by dominant males was tested against controls with soil and leaves. The bags with the excrement initially created a buffer zone free of flying foxes, whereas the controls had no effect. However, as the aroma declined in intensity, the buffer zone reduced. This method was not pursued because of logistical issues, but it revealed the potential for further research into a synthetic compound that could be sprayed on tree branches.
Prawn paste, when sprayed by hand directly onto bats, had an immediate effect. Delivery of the prawn paste using a commercial irrigation system was then trialled in a single tree with excellent results, but required repetition through the day to keep trees completely free of bats. However, this trial has led to new research into automation methods.
Of relevance to the fruit industry as well as managers of flying-fox camps, is that (apart from the sonic deterrence) none of these new ideas would have been tested without the support of research funding that was specifically allocated to the problem.