4 Department of Ecology, Montana State University,
Bozeman, USA
* Correspondence author:
tamika.lunn@griffithuni.edu.au
Abstract
- Fruit bats (Family: Pteropodidae) are animals of great ecological and
economic importance, yet their populations are threatened by ongoing
habitat loss and human persecution. A lack of ecological knowledge for
the vast majority of Pteropodid bat species presents additional
challenges for their conservation and management.
- In Australia, populations of flying-fox species (Genus:Pteropus) are declining and management approaches are highly
contentious. Australian flying-fox roosts are exposed to management
regimes involving habitat modification, either through human-wildlife
conflict management policies, or vegetation restoration programs.
Details on the fine-scale roosting ecology of flying-foxes are not
sufficiently known to provide evidence-based guidance for these
regimes and the impact on flying-foxes of these habitat modifications
is poorly understood.
- We seek to identify and test
commonly
held understandings about the roosting ecology of Australian
flying-foxes to inform practical recommendations and guide and refine
management practices at flying-fox roosts.
- We identify 31 statements relevant to understanding of flying-fox
roosting structure, and synthesise these in the context of existing
literature. We then contribute contemporary data on the fine-scale
roosting structure of flying-fox species in south-eastern Queensland
and north-eastern New South Wales, presenting a 13-month dataset from
2,522 spatially referenced roost trees across eight sites.
- We show evidence of sympatry and indirect competition between species,
including spatial segregation of black and grey-headed flying-foxes
within roosts and seasonal displacement of both species by little red
flying-foxes. We demonstrate roost-specific annual trends in occupancy
and abundance and provide updated demographic information including
the spatial and temporal distributions of males and females within
roosts.
- Insights from our systematic and quantitative study will be important
to guide evidence-based recommendations on restoration and management
and will be crucial for the implementation of priority recovery
actions for the preservation of these species into the future.
Keywords : Pteropodidae; fruit bat; camp; habitat; management;
conservation
Introduction
Fruit bats (Family: Pteropodidae) are animals of extraordinary
ecological and economic importance (Fujita & Tuttle 1991). As long
distance seed dispersers and pollinators, fruit bats play a crucial role
in the maintenance and regeneration of forest ecosystems (Shiltonet al. 1999; Hodgkison et al. 2003; Oleksy, Racey & Jones
2015). Moreover, fruit bats are responsible for the propagation of at
least 289 plant species, 186 of which have economic value, making fruit
bats important contributors to the sustainability of human livelihoods
(Fujita & Tuttle 1991). Despite their importance, many fruit bat
species are in severe decline. Half are listed as near threatened to
extinct according to the IUCN (88 of the 177 species with sufficient
data) (IUCN 2020), with human persecution and habitat loss identified as
two of the largest threats imposed on these species (Jenkins et
al. 2007; Acharya, Bumrungsri & Racey 2011; Andrianaivoariveloet al. 2011; IUCN 2020). While measures have been taken in some
countries to reverse this
trend
– including increased legislative protection (Eby & Lunney 2002b;
Thiriet 2010; Aziz et al. 2016) and community awareness campaigns
(Carroll & Feistner 1996; Trewhella et al. 2005; Anthony,
Tatayah & De Chazal 2018) – conservation and management efforts for
the majority of these species remain hindered by an enduring absence of
ecological knowledge (Fujita & Tuttle 1991; Mickleburgh, Hutson &
Racey 2002) and ongoing conflict with humans (Aziz et al. 2016;
Currey et al. 2018).
These same conservation challenges persist for Australian flying-foxes
(Genus: Pteropus ) despite improved levels of protection.
Indiscriminate and widespread persecution and killing of flying-foxes
were persistent until the ~1990’s (Ratcliffe 1931;
Fujita & Tuttle 1991; Hall 2002). Species listed as threatened are now
afforded national protection under the Environment Protection and
Biodiversity Conservation Act 1999 (EPBC Act) (Department of Agriculture
Water and the Environment 1999) and other species are protected from
harm under state-level native species legislations (Department of
Environment and Primary Industries State Government of Victoria 1988;
Queensland Government 1992; New South Wales Government 2016). However,
loss and degradation of roosting habitat continues to pose a substantial
threat, and management of these species must additionally balance
conservation outcomes with negative public perception and human-wildlife
conflict (e.g. BBC News Australia 2017; Kohut 2017; Welle 2021).
A major challenge for these species is that policies for conservation
and conflict management are often in direct contrast. The
identification, management and protection of roosting habitat are listed
as priority recovery actions for the Vulnerable
grey-headed flying-fox
(Pteropus poliocephalus ) and Endangered spectacled flying-fox
(P. conspicillatus ) (Commonwealth of Australia 2017a). Yet in
direct contrast, roost management policies and guidelines that aim to
reduce human-wildlife conflict often promote removal of roost trees to
create perimeter buffers between the roost and private properties, which
can exceed 50 meters in some cases (State of NSW and Office of
Environment and Heritage 2018). In more extreme cases, flying-fox roost
management permits can be granted to disturb, drive away or destroy
flying-fox roosts entirely (Mo et al. 2020a; Mo et al.2020b).
Management challenges in Australia are being further compounded by an
emerging and accelerating trend of urbanisation of flying-fox roost
sites, and fragmentation of roost populations (Williams et al.2006; Tait et al. 2014). Roost structures are transitioning from
large roosts that are seasonally occupied by nomadic individuals into
smaller, continuously occupied roosts in urban areas (Van der Reeet al. 2006; Eby et al in review). This fragmentation, or
fissioning, of roost populations has been attributed to environmental
change, both land clearing of winter flowering native species in
south-eastern Australia (Eby et al. 1999) and the concurrent
increase in availability of exotic winter food resources in urban areas
(Parry‐Jones & Augee 2001; Williams et al. 2006). As a
consequence, increasing numbers of roosts have formed near residential
housing, particularly in metropolitan areas like Sydney, the Gold Coast
and Brisbane, despite overall population declines (Tait et al.2014). These urban roosts often develop into sites of ongoing conflict
with neighbours (Commonwealth of Australia 2017b) and
there has been growing demand to
reduce the impact of roosts on local communities through active
management of flying-fox camps (Currey et al. 2018). Similar
changes with fragmentation and urbanisation have been observed elsewhere
(Hahn et al. 2014a; Hahn et al. 2014b; Peel et al.2017) suggesting that this occurrence is likely representative of other
systems across the range of Pteropodids.
A second major challenge for management of these species is that
systematically informed, baseline ecological knowledge is limited, so
the impact and effectiveness of efforts to contribute to either
conservation (roost restoration) or conflict (roost modification) goals
are unknown. Roosting requirements of these species are not well
understood (Commonwealth of Australia 2017a) beyond broad scale trends
in roosting patterns (e.g. Tidemann et al. 1999; Vardon &
Tidemann 1999), migration (Eby 1991; Eby et al. 1999) and studies
on sociality and behaviour (Nelson 1965b; Welbergen 2005; Klose et
al. 2009). Detailed (fine-scale) spatio-temporal patterns in animal
density and tree-use remain unquantified (Commonwealth of Australia
2017a), and knowledge on
historical usage patterns (e.g. Ratcliffe 1931; Nelson 1965b; Tidemannet al. 1999; Vardon & Tidemann 1999) may be inconsistent with
current usage patterns. This lack of detailed information is of
particular concern, as current conservation strategies that aim to
identify, protect and restore important roosting habitat, and practices
for managing conflict, are necessarily founded on observations that may
not fully reflect the habitat requirements of the animals. In this
context, the number of flying-fox roosts exposed to programs of
vegetation modification is increasing rapidly in Australia, yet the
potential impact of modifications to roosting habitat on flying-foxes is
largely unknown. More information
is needed to provide baseline ecological data in this time of rapid
ecological change, and to guide and support vegetation management
practices and decision-making criteria to provide a realistic
representation of the roosting habitat needs and preferences of
flying-foxes. Systematic and comprehensive examination of multiple
species in Australia may also help identify whether generalities exist
among Pteropodids, and guide understanding in systems where more limited
data and resources are available.
In this paper, we seek to identify and evaluate commonly held
understandings about the roosting ecology of Australian flying-foxes,
focusing on species on the Australian mainland. We first review ‘grey
literature’ (management, recovery and restoration plans or reports
published by state government and local groups) to identify commonly
held understandings concerning flying-fox roosting structure. We then
review the existing empirical literature, to critically evaluate the
extent of empirical support for these statements and highlight gaps in
empirical evidence. Lastly,
we
utilise high resolution spatial mapping techniques and monthly field
observations to systematically and quantitatively document spatial and
intra-annual temporal patterns in flying-fox roost and tree use in
south-east Queensland and north-east New South Wales. This approach
allows us to highlight where quantitative information on flying-fox
roosting has been missing, and where updated information may be
required. Our new dataset is the first to capture fine-scale spatial and
temporal dynamics of flying-fox roost use in a structured, repeatable
design, and provides baseline
information in a time of rapid ecological change. Such systematic and
quantitative study will be
important for informing evidence-based recommendations to guide
vegetation modification practices and improve roost management
strategies for flying-fox conservation. This will be crucial for
implementation of effective habitat restoration projects, to
successfully balance the management of these threatened, contentious and
urbanising wildlife, and to guide comparable approaches in other
Pteropodid species across their range.
Methods