4 Department of Ecology, Montana State University, Bozeman, USA
* Correspondence author: tamika.lunn@griffithuni.edu.au

Abstract

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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