A discussion paper on flying foxes and the implications for bush regeneration at their camp sites. By Dr Kristin den Exter, Billie Roberts, Angus Underwood, Dr Len Martin
Flying foxes are animals of extraordinary ecological and economic importance throughout forests of the tropics, playing an essential role as forest pollinators and seed dispersers (Fujita and Tuttle 1991). Flying foxes are considered a keystone species, that is a species “whose effect is large, and one that is disproportionately large relative to its abundance” (Power et al. 1996). Flying foxes are the original bush regenerator with enviable characteristics such as a big wingspan, and the ability to fly and forage over large distances, thereby pollinating and spreading the seed of numerous species, including rainforest species (e.g. Eby 1995).
Three species of mega bats (family: Pteropodidae) otherwise known as ‘flying foxes’ occur in the Big Scrub: the grey-headed flying fox (Pteropus poliocephalus), the black flying fox (Pteropus alecto), and the little red flying fox (Pteropus scapulatus) (see Figure 1). Whilst the black flying fox has expanded its range poleward (DECCW 2009) and the little red is highly nomadic and often occurring in great numbers, the grey-headed flying foxes numbers are in decline and this species is listed as vulnerable under the NSW Threatened Species Act 1995 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. The principle reason for this population decline is habitat loss, leading to restricted food supplies and a lack of suitable roosting sites (DECCW 2009). Clearly there is a role for human assisted bush regeneration to help address this problem; however, this may not always be a simple task.
The camps of flying foxes play a number of roles in the life histories of the animals and there is a growing awareness of the need to actively manage these sites to ensure the longevity of the vegetation and its suitability as roosting habitat, and to reduce conflict between flying foxes and humans. Although there are a number of sites that have a history of active management, these experiences have not been compiled and little information is available to guide others.
A recent forum in July 2010 in Brisbane was convened to discuss the management and restoration of flying-fox camps. The forum brought together over 80 people with an interested in camp management, focusing on maintenance and regeneration of camp vegetation. To build upon this recent forum, a panel was convened at this year’s Big Scrub Rainforest Day to discuss bush regeneration in flying fox camps within the Big Scrub region. The aim of this paper is to take these discussions even further. Specifically we examine how to conduct bush regeneration underneath flying foxes, particularly camps in small rainforest remnants, to reduce disturbance to the species and aid restoration of the vegetation communities.
Flying fox feeding and roosting habitat
Flying foxes commonly use forests and woodlands east of the escarpment in NSW and Qld as feeding habitat (Hall and Richards 2000). Current diet lists for the flying foxes contain over 100 species of trees and vines (e.g., Eby 1995).
Approximately half of the plants in their diet are fleshy fruits from subtropical and warm temperate rainforest. The balance are blossoms from a range of vegetation communities dominated by eucalypts, melaleucas and banksias. Flying foxes also use a range of introduced plants – most notably commercially grown fruits. Flying foxes travel up to 50 km per night to search for food, although typically this distance is less than 20 km (Eby 1991, Tidemann 1999). Flying foxes accommodate shifts in the volume and locations of food by migrating, often over large distances (Tidemann and Nelson 2004).
Flying foxes roost during the day in large communal roosts or camps. Numbers can range from a few hundred to over 50,000 (Ratcliffe 1932, Eby et al. 1999), and are driven by the amount of food resources in the surrounding area (Ratcliffe 1932, Parry-Jones and Augee 2001). Flying foxes exhibit strong fidelity to ‘traditional’ campsites, with some roosts being occupied for greater than 100 years.
Although flying foxes display a degree of flexibility in habitat choice, there are some key camp elements that are required (Ratcliffe 1932, Nelson 1965, Hall and Richards 2000, Parry-Jones and Augee 2001, Eby 2002, Peacock 2004, Roberts 2005, Snoyman 2008) for example:
- camps need to be positioned within nightly commuting distance (generally, less than 20 km) of sufficient food resources;
- camps are situated in the coastal lowlands;
- camps are commonly located in closed forest, Melaleuca swamps or stands of Casuarina and are generally found near rivers or creeks;
- camps occur in vegetation ranging from continuous forest to remnants as small as 1;
- typically a canopy height of at least 5 m;
- the microclimate characteristics of camps, such as temperature and humidity of sites, appear to be important.
There are eight known camps used by flying foxes within the Big Scrub region. When examining the characteristics of these camps (Table 1, page 14) it is notable that most occur in small remnant rainforest patches. The largest continuously occupied camp is Rotary Park at 12.8 ha and the smallest is Lumley Park at 2.2 ha. These small patches present challenges to bush regenerators, managers and flying foxes alike.
Bush regeneration in Big Scrub flying fox roosts
A number of issues require consideration when undertaking bush regeneration in flying-fox roost sites, for example the timing of works, and the paradox of weeds as habitat and weeds as threats to vegetation community structure and health. Patch size is a major consideration when determining the appropriate course of action. Many bush regenerators are of the view that bush regeneration needs to occur in continuously occupied camps because of the increased weed infestation that invariably occurs with flying fox occupation. The effects of continuous occupation of flying foxes in very small patches are well known. For instance roosting in small patches causes damage to the canopy, letting in extra light, and there is also thought to be an increase in available nutrients. This disturbance leads to favourable conditions for the invasion by many weeds species, some of which are introduced by flying foxes.
In Rotary Park (a newly established camp) regenerators have documented the invasion of a new suite of weeds, possibly brought in by flying foxes including giant devil’s fig, seedling of seeded bananas, cockspur, guava, cocos palm, Alexandra palms etc (Rosemary Joseph pers comm. 2010).
At Lumley Park, flying foxes are estimated to have had a significant impact on canopy health in approximately half the site. The extra light, nutrient and weeds make restoration of this already small patch more difficult. However, the lower and mid layers of the forest have recovered well despite continuous use by flying foxes with a substantial revegetation effort (Darren Bailey pers comm. 2010).
Addressing the influx of new weeds may mean that greater resources are required for weed control than just at maintenance level (Heidi Lunn, pers comm. 2010).
In terms of flying-fox habitat, weeds may prove allies where core vegetation is already under pressure from roosting flying foxes. Flying foxes will roost in weed species, as they show no selection preferences for tree species (Roberts 2005). For example in Rotary Park, flying foxes have been observed roosting in mature large-leaved privets (Rosemary Josephs pers comm. 2010). Lower stratum weeds even morning glory, are known to be used during heat events. There are numerous examples of places where understory weeds have been removed and the habitat made unsuitable for flying foxes.
If weeds are left in core remnant vegetation then the viability and ongoing succession of the community is likely to be affected. From the bush regeneration perspective, the long-term sustainability of the vegetation patch can only be achieved through weed control of the understorey weeds.
So how do we accommodate the dual goals of restoring Big Scrub remnants with sustainable flying fox roosts? Can we maintain and create flying-fox habitat without the help of weeds? Is it a matter of allowing (some) weeds to stay in some places but not others? The questions are complex and often hotly contested, with or without the added complexity of flying foxes.
When discussing this amongst practitioners it is clear that many now consider it unwise to be advocating a sudden and total removal of all weed species unless the site warrants it. There are many reasons for the staged, gradual and strategic removal of weed species; flying-fox habitat requirements are just another consideration to take into account for some sites. Opportunities arise over the longer time frame when continuously occupied camps are “abandoned” for a short period of time. It is at these times that bush regeneration work that could not be done under occupation can be acted on. The key is to have the resources to be able to act at that time. This may currently be the case for Lismore’s Currie Park.
In larger patches it appears that neither the weed nor canopy health issues are quite as critical. For example, at Booyong flying foxes’ impact on the site is considered to be minimal, due to the large remnant size, small flying-fox population and the fact the core roosting area shifts through time. Flying foxes are thought to still bring in cocos palm, devil’s fig and white passionflower to this site but according to bush regenerators the level is manageable (Darren Bailey pers comm. 2010). So it seems logical that if the issues are lessened in the larger remnants we look to increase the patch size of our smaller sites, but the question is how, especially when many of these remnants have confined boundaries.
The topic of how to increase the size of the smaller remnants provided for an interesting discussion between the panel and the audience at Big Scrub Day, including actively planting non-rainforest species, for example fast growing eucalypts, in areas within existing reserve boundaries, but away from core remnant vegetation, and even allowing the weeds to take their course, thereby providing the kind of vegetation structure required for flying fox roosts (i.e., emergent trees about a dense understorey).
This issue becomes more complex when considering most of the Big Scrub remnants are Endangered Ecological Communities and contain a range of threatened plant species. Whatever the management approach is it must consider the conservation of the range of species that are threatened in the area.
Whether the goal is to manage human/flying fox conflicts or to increase vegetation resilience to flying fox roosting, there is consensus that we need to look at expanding the current sites. Some bush regenerators estimate that in the Big Scrub region it may only take 10-20 years, depending on the site, maintenance regimes, and species selection, for plantings to be utilised by flying foxes. Large scale planting of rainforest trees has already been shown to provide habitat for flying foxes at Fernleigh. Planting of mixed species rainforest trees along a riparian strip has been ongoing at a site managed by Mark Dunphy since 1991, and has created an area that has been used as a roost site for up to 500 Black flying foxes (Angus Underwood pers. obs. 2009). The flying foxes are regularly present at the site, which is around 100 m wide, roosting in remnant trees at the top of a gully, as well as the surrounding emergent planted trees including cudgerie, hoop pine and blue quandong.
When considering expanding roost habitat it would also be useful to know more about which tree species are more resilient to flying fox roosting, or indeed may respond to flying fox presence. It is critical to any such endeavours that the resources currently allocated for core vegetation work must not be redirected, as this work is essential to the long-term sustainability of the vegetation community. More resources are required to assist in the expansion of the vegetation structure required for flying-fox roosts, and we argue here that continuously occupied, maternity roosts in small remnants should be the priority.
In our view the best practice management approach for bush regeneration under continuously occupied flying fox roosts would be to:
- make an assessment of the impacts to flying foxes of vegetation structure change that may occur as a result of bush regeneration before undertaking any works; and
- taking a staged approach to any weed removal.
As well as the staged removal of weeds a number of other strategies can be employed to minimise the impact of bush regeneration on roosting flying foxes, including the timing of works (preferably between May-July), eliminating the use of machinery and camp monitoring.
Firstly, let’s look at the timing of works. Working in the breeding season is an obvious issue that needs to be considered. Other than hoping and waiting for the site to be ‘abandoned’ (discussed above) there are some other options:
- not to carry out works under active flying-fox maternity roosts during the breeding season;
- not to carry out works within a reasonable distance of active flying fox maternity roosts during the breeding season;
- to continue only necessary works and to do this as quietly as possible with continual monitoring for signs of disturbance/distress.
Whilst it might seem an obvious course of action to go with options 1 or 2 these may present problems for some practitioners working on core vegetation weed control within continuously occupied maternity roosts. As with many protocols it may not be that a one-size-fits-all approach will work, so any guidelines need to allow for some flexibility and feedback with regards to site context. Critical breeding and maternity season (Sept-March) is also prime weed control season. Canopy and roost height can also be variable, for example Booyong has a high canopy compared with many camps in coastal swamp forests, and disturbance levels can be lower under some higher roosting camps. So in some cases perhaps option 3 is the practical way to go.
In any case, if work is required directly under a camp this should be carried out in a way to minimise the impacts on the camp. Work teams should be small in size and noise level and time within camp should be kept to a minimum.
Using powered or noisy machinery is not such a complex issue. Machinery such as chainsaws, brushcutters and generators that are likely to disturb flying foxes should not be used in and around occupied camps, particularly during the breeding times. Hand tools are preferred, but we reiterate that an assessment be made of the impacts to flying foxes of vegetation structure change before undertaking such activities, that a staged approach be taken to any weed removal and that no disturbance should be made to trees that flying foxes are roosting in.
Whatever the course of action taken, it is important to be able to monitor what is happening in the flying foxes’ camp in terms of behaviour etc as well as what is happening with respect to canopy and weeds.
It is important that bush regenerators working in flying fox camps know what to look for, for example to know what constitutes normal behaviour and what constitutes ‘disturbance’ or ‘distress’. This may involve bringing in ecologists to talk with bush regeneration teams. The recent initiative by Byron Shire Council is one example which involved flying-fox ecologist Billie Roberts presenting two free seminars on flying-fox ecology to both council staff and members of the public. In addition to this a set of guidelines have been developed for bush regenerators working in and around flying fox camps; this aims to minimise both the impacts on flying-fox camps and the OH&S risks on workers.
Finally let’s turn to what bush regenerators can do to minimise the OH&S risks. A site OH&S risk assessment should be undertaken to determine the appropriate level of personal protective equipment required. It is currently the practice of some to wearouter layer of clothes (at least an overshirt) while working under flying foxes. If workers find injured or sick flying foxes local wildlife carers should be contacted immediately. Workers should not touch or handle flying foxes. If a worker is bitten or scratched wash the wound thoroughly with soap and water for at least 5 minutes and inform a doctor immediately.
The authors welcome feedback and response to this article. As we see it, the conversation has just begun.
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Acknowledgements: Thanks to Rosemary Josephs, Darren Bailey and Heidi Lunn for providing comments on those tricky questions of bush regeneration in flying-fox colonies; thanks to Peggy Eby, Billie Roberts and Liz Gould for the Flying Fox Forum and to Lib Ruytenberg (WIRES Northern Rivers) for her comments on flying-fox behaviour.
Comments and observations on this conversation paper are being actively sought. Feedback can be directed to: Kristin den Exter
c/- School of Environmental Science & Management
Southern Cross University
PO Box 157, East Lismore NSW 2480
Or to the editor:
www.tweed.nsw.gov.au/BushFutures and click on Regeneration near Flying-Fox Camps under Project Outcomes to open a pdf document.