Questions & Answers

about the Grey-headed Flying-foxes at the Royal Botanic Gardens

>> Find out more about flying-foxes

Why does the Botanic Gardens Trust want to move the flying-fox colony?

Roosting flying-foxes are killing trees at the Royal Botanic Gardens. Thirteen trees have died since 1995 and 60 more are so damaged they are expected to die within the next three years.

For decades flying-foxes have visited the Gardens to feed, while trees were flowering or fruiting, then moving on. Damage to the trees began when large numbers of flying-foxes began to roost permanently in the Gardens. The Botanic Gardens Trust wants to discourage flying-foxes from roosting in the Gardens but not from feeding here. The Gardens and a permanent flying-fox camp cannot coexist. The trees will die and flying-foxes will leave the Gardens landscape degraded and then move on.

What type of damage do flying-foxes usually cause to trees/foliage etc.?

The weight and movement of large numbers of flying-foxes can break branches and strip trees of leaves and new shoots. This damage weakens the tree, and with continued pressure, may eventually result in its death. The damage caused by large numbers of flying-foxes living in the trees at the Royal Botanic Gardens is unsustainable.

Why are the Botanic Gardens so appealing to the Grey-headed Flying-foxes?

Flying-foxes have lost a lot of their natural roosting and feeding habitat through changes in land use. The Gardens provides habitat, conveniently located in relation to a reliable food source of mostly nectar and pollen of flowers, as well as fruits. Flying-foxes feed in the Gardens at night as well as roost during the day.

When did the flying-foxes first start coming to the Gardens?

The flying-foxes have set up camp in the Royal Botanic Gardens at various times since Governor Macquarie had the foresight to set aside this land for a world class botanic garden (they may have visited the area before European settlement, but the landscape and habitat were quite different). Large numbers are recorded for 1858, 1900, 1916 and 1920 - in those times, flying-foxes were culled, something we wouldn’t contemplate today.

There are then no records of significant numbers for nearly 70 years. In 1989, 200 took up residence, growing to a peak of 3200 in 1992. Other urban camps in Sydney have similarly fluctuated in size and location over the years, and the biggest concentration at the moment is at Gordon where camp size can reach more than 50,000 animals.

How many flying-foxes currently reside at the Gardens approx?

The numbers fluctuate in the thousands, but there are generally fewer flying-foxes here over winter. Current estimates are in the vicinity of 10,000-20,000. Fluctuations in numbers are believed to be related to local flowering and fruiting of known food trees in the area surrounding the camp - flying-foxes will follow their food sources for hundreds of kilometres, stopping off at various camps along the way.

What is the process the Botanic Gardens Trust must go through before it gets approval to relocate the flying-foxes?

Approval to relocate the flying-foxes is required under the NSW Threatened Species Conservation Act 1995 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. Before undertaking the noise disturbance relocation program a Section 91 Licence application must be approved by the Director General, Department of Environment & and Climate Change, and the proposal must also be approved by the Commonwealth Department of Environment, Water, Heritage & the Arts (NSW).

What parts of Sydney do you expect the flying-foxes will fly to and start roosting?

The Botanic Gardens Trust is in the process of identifying all existing flying-fox camps within a 50 kilometre distance of the Gardens, as well as any other potentially suitable new sites within 20 kilometres of the Gardens. The fly-out directions of the flying-foxes seem to mainly be to the south and east, with some flying north over Port Jackson.

The movements of the flying-foxes will be monitored after they leave the Royal Botanic Gardens to ensure they roost at appropriate sites. The Botanic Gardens Trust will actively seek feedback from local councils, rangers and the community about where the flying-foxes go following disturbance.

The Botanic Gardens Trust will work closely with those responsible for managing any potential sites.

Are the new areas the flying-foxes will move to in danger of being destroyed as well?

Wherever the flying-foxes go, we will be entering into negotiations with the land managers to determine whether or not the site is an appropriate roosting site for the flying-foxes, and whether the site is physically able to sustain the flying-foxes. If it is determined that the new site is likely to sustain unacceptable levels of damage, then we will commit to moving the flying-foxes on to a more suitable location.

Many of the existing nearby camps are known to host fewer flying-foxes in winter (when the relocation will take place) than in summer, so there should be plenty of room for them to move into without overcrowding these sites. Once they have established a new winter roost, it is likely that the maximum number of flying-foxes at each site will not substantially change, even with the usual spring/summer immigration, as researchers believe that the number of flying-foxes in a camp is more closely related to the amount of food available near the site, rather than the amount of available roosting space in the site.

What do you plan to do to remove the flying-foxes from the Gardens?

The Botanic Gardens Trust’s flying-fox relocation proposal has largely been based on the successful 2003 Royal Botanic Gardens Melbourne's flying-fox relocation, when around 30,000 Grey-headed Flying-foxes were systematically disturbed out of the heritage listed Gardens using a variety of noises over a two week period. When the flying-foxes left the Gardens, they were followed-up to ensure that they did not stay roosting at any inappropriate sites, but were encouraged to stay in sites that were pre-determined as preferred sites. Most of the flying-foxes settled at Yarra Bend, where the Gardens supported the establishment of interpretive signage, pathways, and a viewing platform overlooking the new flying-fox camp site. A small colony also established at a new site in Geelong which has since been accepted by both the community and land managers. Throughout the relocation, there were no reports of any death or injury to a flying-fox as a result of the disturbance activities

Aren’t the situations different because the RBG Melbourne camp was a reasonably new camp (1985) at the edge of the flying-fox known distribution, whilst the Royal Botanic Gardens in Sydney is well known to be a long established camp with records of flying-foxes in the Gardens going back to the 1800s?

In Melbourne there were no major camps closer than East Gippsland while in Sydney there are camps within the normal nightly flying range of flying-foxes. The 1992-1997 experience in Sydney showed that the relocation can work here and at that time the flying-foxes seemed to join other nearby camps. Advice varies on whether the task will be easier or harder in Sydney but the previous experience confirms it can be achieved.

A successful relocation of flying-foxes has never been recorded in NSW. Does the Botanic Gardens Trust believe its relocation plan will work?

The relocation from Maclean Reserve in Northern NSW in 1999 was successful for a number of years but not long-lasting - it points to the importance for follow-up work to be committed to indefinitely.

The Botanic Gardens Trust’s disturbance program in the 1990s succeeded in keeping flying-fox numbers very low for around six years between 1992 and 1998. After this, the noise disturbance was stopped and the flying-fox numbers increased again.

Five years ago, the Melbourne relocation succeeded at moving the flying-foxes to suitable alternative locations, where they have been ever since, and have not attempted to return to the Gardens in any substantial numbers.

The 2009 Sydney relocation strategy is expected to succeed by using a variety of mobile, moderate, and mainly percussive noises to disturb the sleeping patterns of the flying-foxes throughout the day and then using a slightly higher level of similar disturbance to disperse them from the Gardens a little earlier than they would normally exit the Gardens at dusk. This will make the Royal Botanic Gardens less attractive as a roost site, and will encourage the flying-foxes to find an alternative site.

The Botanic Gardens Trust will commit to following up the flying-foxes after they have left the Gardens to ensure that they are moved on from any other inappropriate sites, until they reach a site that is both sustainable for the flying-foxes and acceptable to the community.

The Botanic Gardens Trust cannot guarantee that flying-foxes will never try to return to roost in Sydney’s Royal Botanic Gardens. However, the Botanic Gardens Trust has learnt from its previous noise disturbance program in the 1990s that the disturbance program may have to be reintroduced on an intermittent basis to prevent flying-foxes from re-establishing in large numbers.

Due to the significant value of the Royal Botanic Garden’s botanical collections, every effort will be made to ensure their long-term protection.

What is the estimated cost of the Botanic Gardens Trust flying-fox noise disturbance relocation program?

After a few false starts, the operational part of the Melbourne relocation cost about $250,000 and our advice is that it will cost us about half that - a small price for even one of our heritage trees.

Even if higher than estimated, the cost of the project will be manageable within the Botanic Gardens Trust budget. It is expected volunteers will assist under staff supervision.

An assessment of the damage the flying-foxes cause to the trees will be made in financial terms, including the long-term repair of the Gardens, but we also need to consider the incredible heritage, scientific and aesthetic values of these trees.

In addition a critical cost consideration will be the monitoring, research and management support of existing and/or new camps where the flying-foxes may move to.

Will the noise disturbance program affect nearby residents and businesses?

Nearby residents and businesses are not expected to be affected by the noise disturbance program.

The noise disturbance program will be carried out according to EPA noise regulations. The City of Sydney will be consulted. Timely information will be provided to nearby residents and businesses via a letterbox drop, including a summary of the types of noises to be used.

What impact will the noise disturbance have on the welfare of the flying-foxes?

A noise disturbance program, if approved, will meet all requirements of the licence issued under the legislation that protects threatened species.

The noise disturbance program used by the Botanic Gardens Trust in the 1990s proved to be very successful with no injuries or deaths to flying-foxes being attributed to the disturbance program.

Timely information will be provided on the types of noises to be used to visitors, nearby residents of the Gardens and the Police.

Will the public access to flying-foxes roosting areas at Sydney’s Royal Botanic Gardens be affected?

Signage will be appropriately placed on the paths entering the roost areas advising of any restrictions. In addition, adequate access controls will be in place to keep members of the public away from roost areas during the disturbance activity.

What should I do if they move to my backyard?

A media communication campaign will alert local media about the disturbance activity, including providing information on ‘what to do if you find flying-foxes in your backyard’, such as not to interfere with flying-foxes and where to go for further information.

CALL CENTRE/WEB: A ‘Frequently Asked Question’ fact sheet will be made available at call centres which will reinforce key messages.

If flying-foxes are found in backyards and don’t move on after a short period of time people are advised to contact WIRES or Sydney Metropolitan Wildlife Services.

WIRES 13 000 WIRES or 1300 094 737
Sydney Wildlife: (02) 9413 4300

Are people at risk from diseases spread by flying-foxes such as the Lyssavirus?

The risk of a person catching any disease from a flying-fox is minimal; however the Australian Bat Lyssavirus is deadly to humans as well as bats, so it is important to take precautions. This disease is believed to be carried in a very small proportion of the flying-fox population, and can be transmitted to humans through a bite or a scratch. Flying-foxes are generally quite docile animals that do not scratch or bite people unless they are being handled. So the best precaution is to make no attempt at handling a flying-fox unless you are appropriately trained and vaccinated. If you find one in distress, call WIRES or Sydney Wildlife (contact numbers above).

Although, there is no known risk of disease transmission through flying-fox urine or faeces, basic hygiene/cleaning practices (washing any food preparation surfaces with an appropriate cleaning solution, and cleaning with water any walking surfaces that may present a slip hazard) are recommended in cases where flying-foxes leave behind a mess on your property.

The Botanic Gardens Trust can reassure people that although large numbers of flying-foxes have roosted at the Royal Botanic Gardens for almost 20 years there has never been any reported serious injuries caused by or diseases caught from these flying-foxes. However, it is important for the public to understand what should be done if they come into contact with flying-foxes, and we will continue to provide that information.

Why should the Botanic Gardens, and not others, be allowed to move the flying-foxes?

The Royal Botanic Gardens is applying for a Licence to relocate the camp in the same way that any other organisation would need to. The Gardens are one of our cultural and scientific icons. The Gardens were established in 1816 to study and grow Australian and overseas plants and, the landscape has been a public recreation precinct for almost 200 years. There is significant heritage value in the plants and landscape. Many trees were collected by pioneering botanists and explorers, some of the exotic trees were collected from wild habitats which no longer exist. Most of the trees and palms being damaged by the roosting flying-foxes are the oldest in the Gardens. If these trees are allowed to die an irreplaceable part of our heritage and culture will be lost.

What is the scientific value of the tree collection?

The tree collection at Royal Botanic Gardens Sydney is of exceptional heritage significance (it is one of the great tree collections of the world) and also has scientific significance because of the rarity of some species or their association with scientific work in the Gardens.

Professor David Mabberley, in his contribution to the Conservation Management Plan for the Royal Botanic Gardens, identifies the collection of kauris and the only known mature specimen, apparently anywhere in the world, of the palm, Pritchardia maideniana, as ‘trees’ of international scientific and conservational significance. The Kauris, in particular, have been greatly effected by the flying-foxes and some significant specimens (including a specimen from the critical ‘type collection’ of Agathis moorei) have been killed already.

Several fungal species have been discovered and described from palms in the Palm Grove so these specimens become what we call ‘type localities’ - important scientific reference points.

There are also many other trees which are difficult to collect or may be rare in the wild today and provide representative specimens for scientific study by scientists at the Botanic Gardens Trust and elsewhere.

For the study of plant taxonomy and classification (systematics), in particular, the living collections are a rich resource. Plants grow in similar conditions, their life cycle can be observed, their DNA extracted, their variability in form documented, and so on. Much of the recent research on plant evolution and new DNA bar-coding techniques has relied on samples from botanic garden collections. Several of the kauri pines, as well as trees in the Proteaceae family, were sampled - these trees are carefully documented on our database and from known wild origins. Our Tree Waratah, for example, was used for DNA extraction, dissection of flowers and studies of wood anatomy, all part of a worldwide study of the family Proteaceae.

As additional examples, a bamboo-like plant, Joinvillea, growing in the Palm Grove has been used to study floral development in a study with the Jodrell Laboratory at Royal Botanic Gardens Kew. The Brown Silky Oak on the edge of the Palm Grove was used for chromosome counts in some research done by one of the Trust scientists.

There are 48 species of wild-collected palms that are available for scientific study or conservation. A number of these are rare in cultivation - e.g. Ceroxylon alpinum, Howea belmoreana X forsteriana, Jubaeopsis caffra, Polyandrococos pectinatus - and our New Caledonian palms are particularly valued by the Palm and Cycad Societies of Australia.

Aren’t there other ways of minimising damage rather than moving the flying-foxes out of the Gardens?

Over a number of years the Botanic Gardens Trust has trialled a number of other techniques to minimise damage from roosting flying-foxes. Plastic bags have been tied to branches; mirrors were used to reflect light into trees; sirens and fire alarms were rung; mesh bags of toilet deodorant blocks were hung among leaves; recorded flying-fox distress calls were played; containers of rock carbide were placed high in the tree canopies; a high intensity strobe light was focused on affected trees; containers of raw bullock liver were placed on branches; a synthesised sound on the same wavelength as a street sweeper was introduced; plastic pythons were placed on branches; dog whistles were blown; 'shu-roo’, an ultrasonic device, was trialled and a product named D-Ter applied to leaves. None of these techniques deterred the flying-foxes from roosting and the size of the camp continued to increase.

If the flying-foxes are protected, how can you move them from the Gardens without causing them harm?

The Grey-headed Flying-fox is listed as a vulnerable species in NSW and nationally. In 1992 the Botanic Gardens Trust successfully used noise to discourage flying-foxes from roosting. Numbers in the Gardens were reduced from around 3000 to less than 100 and the population remained low for six years without any detected impact on the population as a whole. The Royal Botanic Gardens in Melbourne were also successful using noise to move flying-foxes to a more suitable location without any harm to the animals and with the support of animal welfare and conservation groups. The Royal Botanic Gardens in Sydney will use a similar model, overseen by a steering committee including a range of experts and key stakeholder groups.

The flying-foxes have been in the Gardens for years, why move them now?

There are records of flying-foxes in the Gardens as early as the 1850s. In 1990 there were only 200 but numbers had increased to more than 3000 by 1992. The Botanic Gardens Trust used noise to discourage roosting and the permanent population reduced to fewer than 100 flying-foxes for much of the time up until 1998, when the numbers rose once again to more than 3000. Since then, the colony has continued to grow in size, and now approximately 20,000 flying-foxes are permanently roosting in the Gardens. Damage is severe and widespread in the Palm Grove and among the rainforest trees, with more than 300 trees (10 per cent of the collection) being affected. Thirteen trees have died since 1995 and up to 60 more are so damaged they are expected to die within the next three years. Sydney tree expert, Judy Fakes, has advised us that heritage trees in the Palm Grove will continue to die unless we do something now.

Can’t the Gardens plant more trees and provide a habitat for the flying-foxes?

The landscape of the Royal Botanic Gardens itself is considered to be of heritage importance and the composition and design of the Royal Botanic Gardens is carefully planned to maintain its heritage value. The landscape design, plant content and variety has the primary purpose of providing key plant related messages through landscape displays and the use of interpretative information. For educational and aesthetic purposes, many plantings are grouped according to their scientific, geographical, evolutionary, aesthetic and horticulture history and values. Any new plantings take a long time to mature, and with many of our most significant tree specimens now dying, we do not have time to wait. Our thematic plantings may not even suit the requirements of a flying-fox colony, even when they have matured, as they are designed with the purpose of maintaining the heritage, plant science, and aesthetic values of the Gardens in line with our Conservation Management Plan, rather than recreating habitat for wildlife.

Why don’t you just net the heritage trees to keep them out, like farmers do?

In orchards trees are a uniform height (usually no more than 5 m) and planted in straight rows. In the Royal Botanic Gardens netting would need to accommodate the tallest affected trees which are 30 m tall and would have to cover the entire Palm Grove as the trees and palms form a single canopy. Netting would be very expensive and some people may consider it inappropriate to the look of the Gardens. In addition, unless the netting were to cover the entire Palm Grove as well as adjoining garden beds where the flying-foxes are roosting, it is likely that the flying-foxes would simply move from the netted areas into the un-netted areas of the Gardens. The Botanic Gardens Trust wants to save the heritage trees and safely relocate the flying-foxes to an appropriate habitat. Unlike mobile disturbance, netting would not be able to direct the flying-foxes to any particular locations once they had left the Gardens.

There may be some interim measures taken to protect the most significant trees including trial netting where possible before the relocation begins in May 2009. The public will be kept informed about these measures.

Will you just be moving the problem somewhere else?

The Trust intends to relocate the flying-foxes to one or more locations where the habitat is suitable and sustainable, the land use is appropriate, and they are accepted by the local community and relevant land managers. The Trust has committed to moving the flying-foxes on from any inappropriate locations for as long as is permitted under the relevant licences. The best outcome would be for the camp to disperse into existing campsites within the Sydney basin and beyond, without overcrowding any one campsite.

What will you do if you there is no suitable place for the camp to relocate to?

There are a number of other camps currently established in the Sydney region and previous experience has shown that they can be relocated in this area without resulting in the establishment of inappropriate campsites. We will ensure that their movements are closely monitored to see that they either join other established camps or establish a new camp in an appropriate sustainable location.

What will you do if the flying-foxes go to new areas where they are unsafe or unwanted?

We will be ready to work with land managers and support disturbance to move them on from unsuitable locations to suitable ones - this was done successfully when flying-foxes were relocated from the Royal Botanic Gardens Melbourne.

How can you be sure the flying-foxes won’t just come back next season? Is this a permanent solution?

If the initial disturbance is successful at relocating the flying-foxes from the Gardens, we plan to continually monitor the trees and recommence noise disturbance at the first sign of any further roosting by the flying-foxes in the Gardens in order to prevent the numbers from building up to unsustainable levels again.

Will the damaged trees regenerate or is it too late?

Approximately 60 trees have been severely damaged, 40 of which are unlikely to survive. Nine of these trees are damaged to the point where survival is uncertain, while the remainder should start to recover once the stress from the roosting flying-foxes has been removed, although these trees may never regain the same condition that they had prior to roosting.

How loud will the noise be? Will it disturb people too?

Numerous different sounds will be used with varying noise levels depending on the reactions of the flying-foxes. We intend to begin the program using noise levels similar to those produced during every-day work in the Gardens, by equipment such as chainsaws, hedge trimmers, tractors and bobcats. This noise, although common in the Gardens, will be produced more frequently than usual throughout the program, and the noise will be aimed at the roosting flying-foxes. If different noise types are not eliciting the desired reaction of the flying-foxes, the noise level may be raised slightly in order to increase the effectiveness of the disturbance. However, in the Melbourne experience, the noise levels were actually able to be lowered after a while, as the flying-foxes became sensitised to the disturbance, so that much lower noise levels were able to disturb them. Throughout the relocation program, we will be closely consulting with nearby residents and local councils at each site of disturbance to ensure that any disturbance to people is minimal. Initially, the disturbance will take place throughout the day and just prior to dusk. If the flying-foxes need to be prevented from roosting in a particular inappropriate site, some low level disturbance may be required during the pre-dawn hours, but this will only be done if the land owner/manager/resident is agreeable, and if it is permitted by the Department of Environment & Climate Change (DECC) licence conditions.

Will the noise affect other wildlife in the gardens? Will it drive away the birds as well?

Wildlife such as ibises and possums share the Palm Grove with the flying-foxes. Wildlife that is active in the Gardens during the day move to other parts of the Gardens to avoid the noise of chainsaws, hedge trimmers, tractors, bobcats and a range of noise created by staff and visitors, later returning when the area is quiet. Brushtail possums, which are extremely common in the Gardens, will be asleep in their hollows during the day, and are more likely to hide from the noise than try to run away. The flying-foxes are active at night so the noise disturbance is designed to interrupt their sleep cycle during the day, thus making the Gardens an unattractive place to roost.

How long will the relocation take?

The noise disturbance program is planned to start in May 2009. It is estimated that a concerted disturbance effort will take between two and four weeks to remove all the flying-foxes from the Gardens. We’ll then maintain a look out for any inappropriate camps establishing in the Sydney Metropolitan region, so that we can move them on towards the preferred sites. For the welfare of the flying-foxes, we do not intend to continue the relocation disturbance beyond the end of July 2009, when the females will be getting heavily pregnant and thus more vulnerable to stress. However, we do plan to maintain an ongoing vigil to prevent new camps settling in the Gardens for as long as is necessary. We’ll encourage them to feed on our fruit and flowers (nectar and pollen) but not to roost here.

How will the Gardens encourage flying-foxes to feed but not roost?

Noise disturbance will not be conducted at all during the night-time foraging period. This will allow the flying-foxes freedom to feed wherever they choose.

When will the relocation take place?

Flying-fox experts, veterinary scientists and conservationists on our steering committee have agreed that between May and July is the optimum time to avoid interrupting the flying-foxes’ mating season, separating mothers from their dependent young, or stressing heavily pregnant females.

Who are the experts?

Our steering committee consists of representatives of the RSPCA, NSW Wildlife Council, NSW Department of Environment and Climate Change, NSW Wildlife Council, Ku-ring-gai Bat Conservation Society, Ku-ring-gai Council, The Cabramatta Creek Flying-fox Committee, Fairfield City Council, Sydney University (including biologists specialising in flying-foxes) the Botanic Gardens Trust, Friends of The Gardens, and the Royal Botanic Gardens Melbourne.