Final comments and implications for roost management
State-level management guidelines, including the Flying-fox Camp
Management Policy (State of NSW and Office of Environment and Heritage
2018) and the Flying-fox Roost Management Guideline (State of
Queensland Department of Environment and Science 2020) outline several
camp-based management approaches that involve the modification or
removal of vegetation within roost sites. ‘Routine camp management
actions’ include the removal of tree branches or whole trees, weed
removal, trimming of understorey vegetation, and minor habitat
augmentation. The aim of such actions are often to encourage roosting in
alternative areas of the roost (e.g. Geolink 2010; EcoLogical 2014), or
to increase the sustainability of existing roosting habitat for
flying-foxes (e.g. Ku-ring-gai Council 2018). These actions are
considered to be low impact activities (Department of Environment and
Science 2020b) and do not require referral under the EPCB act
(Commonwealth of Australia 2015), however these actions may considerably
alter the structure of roost vegetation and decrease the suitability of
a roost as habitat (Ku-ring-gai Council 2018). For example, the removal
of mature weed vines in the canopy and midstory, as well as the clearing
of understory, can reduce the structural complexity of roost vegetation.
This may have immediate and direct effects on roosting flying-foxes, and
may accidently cause bats to disperse or adjust use of roost trees in
ways contradictory to conflict management. This may also have long-term,
indirect implications for the ability of flying-foxes to survive extreme
weather events, by altering roost macroclimate and removing physical
refuge needed at times of extreme heat (Welbergen et al. 2008).
Individual and council-level roost management plans developed by local
governments under the guidance of these policies, commonly utilise these
vegetation management measures (e.g. EcoLogical 2014; Logan City Council
2015; Sunshine Coast Regional Council 2016; Ku-ring-gai Council 2018),
though the long-term implications for flying-foxes of vegetation works
are rarely noted (with the exception of Ku-ring-gai Council 2018). We
recommend that vegetation removal should not be considered low impact by
default. Routine management actions should follow a mosaic pattern
(State of NSW and Department of Planning Industry and Environment 2019),
or target weeding on a weed-by-weed case basis (Ku-ring-gai Council
2018), and seek to maintain refuges in the mid- and lower storeys at all
times. Special care not to disturb bats should be taken in identified
core areas of the roost.
Conclusion
This study takes a thorough, multifaceted approach to better understand
the ecology of flying-fox roost use and structure in Australia. We build
upon broad-scale knowledge of historic roosting occupancy and abundance
patterns, and provide updated baseline information on roosting structure
in urban and peri-urban roosts by providing fine-scale spatial, and
temporal data on roost and tree use. Specifically, we demonstrate high
variation in patterns of occupancy and abundance between roosts sites,
and provide updated demographic information including the spatial and
temporal distributions of males and females within roosts. We also 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.
The outcomes of this research will be of immediate, practical benefit to
management and conservation of flying-fox roosts in Australia, and meets
research needs specifically identified in the draft Recovery Plan for
the Vulnerable grey-headed flying-fox. The level of spatial and temporal
detail provided in our empirical study will be important in designing
management plans that are sensitive to flying-fox habitat needs, and in
identifying and protecting important habitat areas within roosts that
are reflective of current movements and preferences. Most importantly,
we highlight that a one-size-fits-all approach to roost management will
be inappropriate, given the extent of variation between sites even
within a regional area. Fine-scale information on roost tree preferences
will also improve understanding of the potential impacts of existing
conflict management strategies involving vegetation removal, including
buffer creation, and can guide vegetation removal efforts to heed these
habitat requirements. This information is timely, and much needed in
advance of the recently announced Environmental Trust grants program for
flying-fox habitat restoration, and in the face of continued and
increasing urbanisation of flying-foxes in Australia.
Acknowledgements
We would like to thank Beccy
Abbot, Kirk Silas, Devin Jones, Liam Chirio, Rachel Smethurst and Cara
Parsons for their assistance in the field.
Fieldwork for this work was
supported by a Paddy Pallin Research Grant and a ‘Grants in Need’
science grant awarded to TJL, sponsored by the Paddy Pallin Foundation,
The Royal Zoological Society of NSW and The Foundation for National
Parks and Wildlife, and the National Science Foundation (a Coupled
Dynamics of Natural and Human Systems grant DEB1716698 and a DARPA
PREEMPT program Cooperative Agreement #D18AC00031). TJL was supported
by an Endeavour Postgraduate Leadership Award and a Research Training
Program scholarship sponsored by the Australian Government, AJP was
supported by an ARC DECRA fellowship (DE190100710) and a Queensland
Government Accelerate Postdoctoral Research Fellowship, RB was supported
by a Griffith University Honours Allowance and an EFRI Honours Thesis
Write-Up Scholarship, and RKP was supported by USDA National Institute
of Food and Agriculture (Hatch project 1015891). This research was
conducted under a Griffith University Animal Research Authority permit
(DEB-1716698), a Scientific Purposes Permit from the Queensland
Department of Environment and Heritage Protection (WISP17455716), a
permit to Take, Use, Keep or Interfere with Cultural or Natural
Resources (Scientific Purpose) from the Department of National Parks,
Sport and Racing (WITK18590417), a Scientific Licence from the New South
Wales Parks and Wildlife Service (SL101800) and general and products
liability protection permit (GRI 18 GPL), and with permission to
undertake research on council and private land. The content of the
information does not necessarily reflect the position or the policy of
the U.S. government, and no official endorsement should be inferred. We
acknowledge the Danggan Balun, Kabi Kabi, Turrbal, Widjabul Wia-bal,
Yugambeh and Yuggera Ugarapul people, who are the Traditional Custodians
of the land upon which this work was conducted.