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Yarra Bend Park Flying-fox Campsite: Review of the scientific Research A Victorian Government Project
Yarra Bend Park Flying-fox Campsite:
Review of the Scientific Research
Prepared for the Department of Sustainability and Environment by:
Rodney van der Ree, Caroline Wilson and Vural Yazgin
Australian Research Centre for Urban Ecology,
Royal Botanic Gardens Melbourne
(Note that this document is based upon a scientific paper with
complete references. For easier reading, citations have been
removed and a list of sources is provided at the end of the
document.)
Published by the Victorian Government Department of
Sustainability and Environment Melbourne, November 2009
Also published on www.dse.vic.gov.au/flyingfoxes
© State of Victoria, Department of Sustainability
and Environment 2009
This publication is copyright. No part may be reproduced by any
process except in accordance with the provisions of the Copyright
Act 1968.
Printed by Stream Solutions
Printed on 100% recycled paper
Vivien Jones Wildlife Photography, Cover Image
and pages 2, 4, 5, 6, 9, 11, 13, 14, 17, 18 & 21
Other Images are from photographs supplied by staff
from ARCUE and DSE
ISBN 978-1-74242-142-1 (print)
ISBN 978-1-74242-143-8 (online)
For more information or to obtain copies of this plan contact the
DSE Customer Service Centre 136 186
Disclaimer This publication may be of assistance to you but the
State of Victoria and its employees do not guarantee that the
publication is without flaw of any kind or is wholly appropriate for
your particular purposes and therefore disclaims all liability for any
error, loss or other consequence which may arise from you relying
on any information in this publication.
The views expressed in this document are not necessarily those
of the Department of Sustainability and Environment.
B | Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research
Assessment approach (methods)
Contents
Executive Summary 3
Background and purpose of the review 4
Introduction 5
Data collection and results 6
Research and monitoring themes 6
Camp and population dynamics 8
Number and distribution of Grey-headed Flying-foxes 8
Accuracy and reliability of counts 9
Reproductive output 10
Male to female sex ratios 11
Rate of mortality within the Yarra Bend Camp 11
Rate of mortality as a result of heat events 12
Roost and camp conditions 14
On-site tree assessments 14
Photo analysis 15
Artificial roosts 16
Climatic conditions within selected camps 16
Future management activities 18
Future research 19
Acknowledgements 20
List of sources 20
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 1
About this review
This Review is part of a set of three review
papers addressing the effectiveness of the
2005 Yarra Bend Park Flying-fox Campsite
Management Plan. The other two are:
• Yarra Bend Park Flying-fox Campsite:
Review of the Management Plan
• Yarra Bend Park Flying-fox Campsite:
Review of the Revegetation Plan
These three Reviews have been prepared
for consultation purposes and to inform
the development of a new Yarra Bend Park
Flying-fox Campsite Management Plan.
2 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research
Assessment
Executive Summary
approach (methods)
Since 2004, the Australian Camp and population dynamics Roost and camp conditions
Research Centre for Urban The number of flying-foxes within the Dieback and defoliation of canopy
Ecology (ARCUE) has been camp varies seasonally and annually. trees used by roosting flying-foxes is
The peak in summer/autumn is a common occurrence at flying-fox
undertaking a research and approximately 20,000–27,000 for static campsites. Monitoring the health of
monitoring program of the counts, and up to 30,000–35,000 roost trees is important for managing
Grey-headed Flying-fox (GHFF) for fly-out counts. The minimum the campsite at Yarra Bend Park. It will
population size is typically around assist in identifying which sections of
colony at the Yarra Bend 10,000 flying-foxes, but has been as the campsite may need to be restored.
Campsite. low as approximately 5000 flying-foxes
To determine the rate of roost tree
in mid-2007 and mid-2009.
The GHFF were relocated to Yarra Bend defoliation at Yarra Bend, on-site tree
Park from the culturally and historically Estimating reproductive output is an assessments have been carried out
significant Royal Botanic Gardens important element in understanding every 4–5 months since October 2006.
Melbourne where they were causing the demographic status of GHFF
The results of the research suggest
serious damage to vegetation. populations. The reproductive output
that flying-foxes are having an impact
results suggest that the Yarra Bend
In 2005, the Department of on roost trees, causing over 50%
colony has a consistent annual birth
Sustainability and Environment (DSE) defoliation for some trees within
rate, with approximately 85% of
developed a Flying-fox Campsite sections of the campsite. In particular
females each year giving birth and
Management Plan for Yarra Bend there is a lower percentage of leaf
carrying young.
Park to “provide a clear framework cover in areas that the flying-foxes
for managing Melbourne’s flying-fox The number of males is also recorded occupy year-round.
colony at Yarra Bend Park and creating in order to give an estimate of
A potential measure to reduce the
a sustainable campsite”. female to male sex ratio during the
impact of roosting flying-foxes on
breeding season. Studies on sex ratio
ARCUE has conducted a review of the the vegetation is to provide artificial
variations help to understand the social
Flying-fox scientific research as part roosting structures. However, data on
organisation and dispersal behaviour of
of the overall review of the Campsite the roosting characteristics of flying-
GHFF. At Yarra Bend Park the average is
Management Plan. foxes at Yarra Bend Park suggest
0.83 males to each female during the
that if 20% of GHFF colony (5000
This is a summary of the research breeding season.
flying-foxes) required roosts this would
report prepared by ARCUE. It provides a Since January 2006 there have been equate to approximately 3.1 km of
snapshot of the results of the research searches for dead flying-foxes within roosting space, which makes this
conducted and makes conclusions and the Yarra Bend camp at fortnightly to option logistically impractical at Yarra
recommendations about potential future monthly intervals and also following Bend Park.
management activities. heat events. Flying-foxes are particularly
Climatic conditions play an important
This research work has been conducted sensitive to the effects of extreme
role in the dynamics of flying-fox
in two broad research themes: temperatures, as they roost among
camps. To explore the importance
the exposed branches of canopy trees.
• Camp and population dynamics and of microclimate of the camp sites,
The extreme heat events in January
loggers were installed to record
• Roost and camp conditions. and February 2009 caused a significant
temperature and humidity at 15
number of flying-foxes to die.
minute intervals. There is now more
than three years of data from
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 3
Background
Executive Background and
Summary continued purpose of the review
Yarra Bend, Geelong, Royal Botanic In March 2003 the flying-foxes were
Gardens Melbourne (RBGM), and dispersed from the Royal Botanic
four camps in East Gippsland. Gardens Melbourne (RBGM) as part
The data is still being analysed, of a strategic relocation program.
however, it is likely that an A small proportion of the colony
increase in understorey/mid-storey moved to Eastern Park in Geelong,
vegetation at Yarra Bend, plus and the remainder of the colony
efforts to restore the tree canopy, settled at Yarra Bend Park.
will be effective at reducing
A Flying-fox Campsite Management
temperature and increasing
Plan for Yarra Bend Park was prepared
humidity. The combination of
in 2005 to “provide a clear framework
temperature and humidity which
for managing Melbourne’s flying-fox
may reduce or prevent heat-related
colony at Yarra Bend Park and creating
mortality is not known at this stage.
a sustainable campsite”.
Based on the scientific research
Now, in 2009, the Campsite
data, the following management
Management Plan is in the process of
activities are proposed:
being renewed. To feed into the renewal
• Continue planting indigenous process, three reviews have been
grasses and understorey plants. prepared. These are:
• Plant more trees for future 1. Review of the Campsite
roosting opportunities, amongst Management Plan
existing roost trees as well as in
2. Review of the Revegetation Plan
sparse areas further up the Yarra
River. 3. Review of the Scientific
Research (this report).
• More shrubs and small trees
(particularly Silver Wattle) could The Review of the Campsite
be planted, especially in areas Management Plan looks specifically at
with little mid-storey on the the goals and actions outlined in the
golf course side of the Yarra 2005 Flying-fox Campsite Management
River to provide more roosting Plan and assesses the effectiveness
opportunities/shelter during of the actions. The Review of the
future heat events. Revegetation Plan assesses the works
that were implemented to improve
Ongoing research is important for vegetation quality and habitat at
understanding population dynamics the site.
and roosting requirements of GHFF
at Yarra Bend Park. This review has been carried out to
provide objective information about
Potential additional research which the scientific research associated with
may assist in managing this GHFF delivery of the plan. The results will be
camp has also been identified in considered in the development of the
this review. next Management Plan.
4 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research
Introduction
The Grey-headed Flying-fox This 450 km expansion of the GHFF proportion of the total GHFF population
(Pteropus poliocephalus) range may have been due to a (the national population of GHFF was
combination of local climate change estimated at 674,000 in 2005) it is
(GHFF) is endemic to south- (the city is now warmer, with less clear that urban areas are becoming
eastern coastal Australia, from frost and higher humidity; as well as increasingly important for GHFF. There
Maryborough, Queensland, increased diversity, abundance, and are flying-fox camps (GHFF, Black
availability of food resources). Smaller Flying-fox, Little Red Flying-fox) within
though New South Wales to camps also occur in Geelong and or in close proximity to urban centres in
southwest Victoria. East Gippsland (Bairnsdale, Dowells eastern and northern Australia (such as
Creek, Karbethong and Swans Track). Melbourne, Sydney, Brisbane, Darwin
Grey-headed flying foxes are nationally GHFF will form camps, usually near and other smaller towns in eastern
threatened and listed as endangered water, often in dense stands of native Australia). It is thought that GHFF have
in Victoria. This is due to population vegetation. During summer these moved further into urban areas as a
declines resulting from threatening camps may consist of several thousand result of the large-scale clearing and
processes such as habitat destruction, individuals, however over winter adults fragmentation of the species natural
roost disturbance, and culling. The will disperse up to 1000 km away, habitat, and the availability of food
species is highly mobile and genetic though some will remain in winter sources and suitable climatic conditions
exchange occurs across the entire camps when food is plentiful. in these areas. Urban areas offer a more
geographic range of the species. At night, GHFF forage for nectar, reliable food source (120 plant species,
For this reason the entire Australian pollen and fruit; sometimes travelling native to Queensland and NSW, which
population is considered to be one up to 50 km from their camp to feed. are favoured by GHFF have been planted
single interbreeding population. in Melbourne’s parks and streets),
To avoid further damage to the
GHFF have been an occasional visitor provide protection from shooting,
culturally significant Royal Botanic
to the Melbourne area since 1884, and street lighting may provide easier
Gardens Melbourne, GHFF were
although it wasn’t until 1986 that a navigation. However, the modified
relocated to Yarra Bend Park, Kew
permanent camp was established at environment of urban areas limits
in 2003. Since 2004, the Australian
the Royal Botanic Gardens Melbourne the available choices of roosting sites
Research Centre for Urban Ecology
(RBGM). for flying-foxes. Thus the appropriate
(ARCUE) has been undertaking a
management of existing campsites
This newly-formed Melbourne camp research and monitoring program at
(including the provision of new roosting
was located 450 km west from the the Yarra Bend campsite.
opportunities) within urban areas is
closest known colony at the time Although Melbourne’s Yarra Bend important for the conservation of GHFF
(located near Mallacoota, Victoria). Campsite represents a relatively modest in Victoria and across Australia.
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 5
Data collection
Background and results
Research and monitoring themes
Since 2004, the Australian
Research Centre for Urban
Ecology (ARCUE) has been
undertaking a research and
monitoring program at the
Yarra Bend campsite.
This research work has two broad
research themes:
• Camp and population dynamics
• Roost and camp conditions
(see Table 1) .
The first theme investigated the camp
and population dynamics at Yarra
Bend and other camps across Victoria,
and the second theme focused on
vegetation and microclimate condition
within camps. This report summarises
the outcomes of selected key themes
to enable a review of the Flying-fox
Campsite Management Plan and
support the consultation process
for the development of the next
Management Plan.
6 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research
Table 1. Broad themes of research and monitoring of
the Grey-headed Flying-fox camp at Yarra Bend Park, Kew
Research Theme 1: Camp and population dynamics
Flying-fox population size 1 The number and distribution of GHFF
at Yarra Bend Park and at other
Victorian camps.
2 The reproductive output at Yarra
Bend Park.
Flying-fox mortality 1 Rate of mortality at Yarra Bend Park.
2 Rate of mortality at Yarra Bend Park
(and other Victorian camps) as a result
of heat events.
Research Theme 2: Roost and camp conditions
Vegetation condition 1 To quantify the extent to which
and tree health GHFF and management actions
(e.g. revegetation works, construction
of wetlands) alter the species
composition and health of the
vegetation at Yarra Bend.
2 To quantify basic parameters of roosting
GHFF (e.g. angle and diameter of
roosting branches) for the design of
artificial roosting structures. This is
a potential measure to reduce the
impact of roosting flying-foxes on the
vegetation.
Effect of camp management To quantify the microclimatic conditions
on microclimatic conditions within GHFF camps (Yarra Bend Park,
Geelong, and East Gippsland camps) to
assist in understanding patterns in camp
occupancy.
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 7
Camp and
population
Background dynamics
Figure
Figure11
Number and distribution of Grey-headed Flying-foxes
Number of GHFF roosting at Yarra Bend Park. One of the most basic requirements The camp at Yarra Bend Park has
Solid squares are static count results, while when managing a population of been permanently occupied since
open diamonds are from fly-out counts. wildlife is to have good knowledge 2003 after being relocated from
of the size of the population and RBGM. The number of flying-foxes
35000 its distribution. There are two main within the camp varies seasonally
approaches to assessing the size of and annually (see Figures 1, 2), and
30000
colonies of flying-foxes: also depending on the counting
method used.
No. of roosting GHFF
25000
1. Static counts (when the number
20000 of roosting flying-foxes is Nevertheless, the seasonal pattern
15000 counted from the ground by a is predictable and similar for both
single observer during the day); types of counts, with peaks in
10000
and number from January to April,
5000 2. Fly-out counts (when a group reducing to the lowest point in
of observers are strategically July and August. The peak in
located around the camp and summer/autumn is approximately
01/04
03/04
05/04
07/04
09/04
11/04
01/05
03/05
05/05
07/05
09/05
11/05
01/06
03/06
05/06
07/06
09/06
11/06
01/07
03/07
05/07
07/07
09/07
11/07
01/08
03/08
05/08
07/08
09/08
11/08
01/09
03/09
05/09
each observer counts the flying- 20,000–27,000 for static counts,
foxes as they leave the roost at and up to 30,000–35,000 for
Date (month/year)
dusk). fly-out counts. The minimum
population size is typically around
Both methods have inherent biases,
10,000 flying-foxes, but reaching as
and it is difficult to determine
low as approximately 5000 flying-
which method is the most accurate.
Figure 2 foxes in mid-2007, and reaching
Thus, to ensure the most reliable
similarly low numbers in mid-2009
Seasonal pattern in number of GHFF results, both static counts (at least
(Figure 2).
roosting at Yarra Bend Park. Data twice per month) and fly-out
presented is the mean number of counts (once per month) have been
individuals recorded each month from conducted at Yarra Bend Park since
static counts (± 1 s.e.). the colony was established in 2003.
25000
No. of roosting GHFF
20000
15000
10000
5000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
8 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific ResearchAccuracy and reliability of counts Figure 3
Because there is an inherent bias The reliability of static counts was The similarity between two ‘blind’ static
with all methods of counting flying- assessed by the regular observer, counts and one regular static count.
foxes, a combination of both fly- who conducted a second and third All three static counts were conducted
out counts and static counts have static count once a month for two on the same day by a single observer,
been used at Yarra Bend Park to years. The second and third counts and the results of the blind count were
give the most reliable data possible at this time were ‘blind’, in that the not revealed to the observer until after all
on the number of flying-foxes observer did not sum up the results counts were completed.
within the camp. Static counts are himself. Rather, the raw data from
conducted twice per month by a the blind counts were forwarded to
single observer and fly-outs once a second researcher who tallied the
Regular Static Count
per month by 10–20 volunteers scores. The results were not shared
Blind Count 1
with a mix of experience. As the with the regular counter until the
identity of the fly-out volunteers is end of the two-year period. The 30000 Blind Count 2
different each month, it is difficult estimates of the number of GHFF
25000
to assess count to count variation. roosting at Yarra Bend Park were
No. of roosting GHFF
However, because a single observer very similar among the regular 20000
does static counts, it was possible static count and the two blind
to assess the reliability of the static static counts (see Figure 3). This 15000
counts. demonstrates that static counts,
10000
conducted by a single, experienced
observer at Yarra Bend, are very 5000
repeatable or consistent.
Aug 06
Oct 06
Dec 06
Feb 07
Arp 07
Jun 07
Aug 07
Oct 07
Dec 07
Feb 08
Arp 08
Date Jun 08
Yarra Bend Park Flying-fox campsite: Review of the Scientific Research | 9Camp and
population
Backgrounddynamics
Figure
Figure41
Reproductive output
Mean proportion of females with young Since 2004, surveys of the Yarra The first births each year are usually
at Yarra Bend Park per month (± 1 s.e.). Bend flying-fox colony have been recorded in early September, and by
Data is from the 04/05, 05/06, 06/07, conducted to determine female late October and early November an
07/08 and 08/09 breeding seasons. reproductive output. Flying-foxes average of approximately 85% of
have a slow life-history, which females are carrying young (Figure 4).
means that they only produce a The average number of females with
1
single pup annually; however they young declines to about 40–50%
have a long reproductive lifespan. by mid-April each year. During the
0.8
Proportion of females
Females generally do not reach full 2008/09 breeding season 28% of
sexual maturity until three years females were carrying young in late
0.6
of age. It is thought that during September and by mid-November
unfavourable conditions (e.g. when there were 91% females with young.
0.4
resources are limited), female flying- By early April, 13% of females were
foxes might maximize their own carrying or were associated with
0.2
fitness by foregoing reproduction, (hanging next to) a juvenile flying-
thus enhancing their chances for fox. The reproductive output results
AUG SEP OCT NOV DEC JAN FEB MAR APR survival and future reproduction. suggest that the Yarra Bend colony
Month
Estimating reproductive output is an has a consistent annual birth rate,
important element in understanding which is similar to findings from
the demographic status of GHFF other studies, which have found
populations. Reproductive output that approximately 80–90% of
counts are carried out every female flying-foxes produce one
10–14 days from late August/early young each year.
September until mid-March/late
April. During these surveys, the sex
and reproductive condition (carrying
or closely associated with a juvenile
flying-fox) of individuals is assessed.
10 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific ResearchRate of mortality within
Male to female sex ratios the Yarra Bend camp Figure 5
3
The number of males is also Since January 2006 there have Mean male: female GHFF sex ratios for
recorded during the reproductive been searches for dead flying-foxes weekly to fortnightly intervals (± 1 s.e.).
output surveys in order to give an within the Yarra Bend camp at Data is from the 04/05, 05/06, 06/07,
estimate of female to male sex ratio approximately fortnightly to monthly 07/08 and 08/09 breeding seasons.
during the breeding season. Studies intervals and also following heat A sex ratio of 1.2 equals 1.2 males
on sex ratio variations help to events. The date of death of each to 1 female.
understand the social organisation flying-fox is estimated based on the
and dispersal behaviour of GHFF. level of decomposition and whether
The average ratio of male to female the dead flying-fox was found soon 1.4
GHFF during the breeding season at after a heat event. Estimating the 1.2
Yarra Bend Park (Oct 2004 – April annual rate of mortality is important 1
2009) is 0.83. That is, there are 0.83 in understanding the demographic
M:F ratio
0.8
males to each female. status of GHFF population. Figure 6 0.6
displays the predicted dates of deaths
The overall bias towards females in 0.4
for flying-foxes found between
the colony varies seasonally, with a 0.2
January 2006 and May 2009; it
greater proportion of males at the
also includes dates when no dead
beginning of the birthing season
22 Aug
1 Sept
25-30 Sept
6-11 Oct
16-20 Oct
27-30 Oct
2-10 Nov
16-20 Nov
28-30 Nov
2-7 Dec
9-15 Dec
19-31 Dec
2-9 Jan
12-20 Jan
23-28 Jan
1-3 Feb
7-14 Feb
19-27 Feb
4-12 Mar
19-23 Mar
1-4 Apr
10-27 Apr
flying-foxes were found to emphasize
(September/October) and after
the large numbers of deaths caused
young are weaned (March/April)
by heat events over the summer
(Figure 5). Date
months. During 2008/09 the
highest number of deaths occurred
between December and February,
this is consistent with previous years. Figure 6
Mortality rates are generally very
The predicted dates of deaths for dead
low between late February
Grey-headed Flying-foxes found during
and November/December.
mortality surveys (between January 2006
and May 2009) at Yarra Bend Park.
10000
Predicted date of death
Date of survey where
no bats were recorded
Number of dead GHFF
100
1
Dec 05
Mar 06
Jul 06
Oct 06
Jan 07
Apr 07
Aug 07
Nov 07
Feb 08
Jun 08
Sep 08
Dec 08
Mar 09
Jul 09
Predicted date of death
Yarra Bend Park Flying-fox campsite: Review of the Scientific Research | 11Camp and
population
dynamics
Figure
Figure71
Rate of mortality as a result of heat events
The sex and age of flying-foxes collected after Flying-foxes are particularly colonies being formed near urban
major heat events (2006–2009) at different sensitive to the effects of extreme areas. During both heat events at
stages over summer, at Yarra Bend Park. temperatures, as they roost among Yarra Bend Park in 2009, GHFF were
the exposed branches of canopy observed to display behaviours such
2100
trees. During January and February as wing fanning, seeking shade in golf
1950
1800
2009, 4868 flying-foxes died as a course trees (mainly cypress pines)
No. of GHFF deaths
1650
1500
result of two major heat events. and trees further along the Yarra
1350
1200
A four-day heatwave from 27–30 River, and panting. These behaviours
1050
900
January 2009 resulted in 1213 are thought to help maintain body
750 deaths, and on 7 February 2009, temperature and have been recorded
600
450 3539 flying-foxes died as a result of elsewhere during such heat events.
300
150 extreme temperature (a maximum
Throughout the 2009 heat events,
of 46.4oC). Prior to this, the largest
Adult Male
Adult Female
Juvenile
Unknown Adult
Unknown
Adult Male
Adult Female
Juvenile
Unknown Adult
Unknown
Adult Male
Adult Female
Juvenile
Unknown Adult
Unknown
Adult Male
Adult Female
Juvenile
Unknown Adult
Unknown
Adult Male
Adult Female
Juvenile
Unknown Adult
Unknown
information including sex, age (adult
number of heat-related GHFF deaths
or juvenile) and forearm length was
recorded at Yarra Bend Park was 192
collected from a random selection of
(on 10 December 2006, a maximum
dead flying-foxes. This data is useful
temperature of 42.1oC). See Table
for determining which individuals
10 Dec 06 10-11 Jan 08 22-23 Jan 06 27-30 Jan 09 7 Feb 09 2 for the numbers of GHFF that
(juveniles or adults, males or females)
died during these heatwaves. The
Heat Event are more susceptible to extreme
number of GHFF deaths recorded
weather conditions. For both the
at Bairnsdale and Geelong camps
2009 January and February heat
during these two heat events are
events, more adult males were found
presented in Table 3.
dead than adult females and juveniles
The mass mortality of GHFF during at Yarra Bend Park (see Figure 7).
extreme heat events has been This pattern was also evident among
recorded at other campsites in the dead flying-foxes collected at the
eastern Australia; with evidence Bairnsdale and Geelong camps.
for at least 19 other heat-related
It appears that juveniles and adult
mortality events since 1994, resulting
females appear most vulnerable
in over 24,000 GHFF deaths. One
to high temperatures that occur in
example includes the death of 4800
December and early January (females
GHFF after an extreme heat event in
are lactating and young are still
Sydney, NSW (in early January 2006;
been weaned). In contrast, high
max temperature 44.4–45.2oC).
temperatures in February appear to
Before 1994, there is only evidence
cause higher mortality in adult males
of three mass die-offs in eastern
(possibly related to higher levels of
Australia, suggesting that these
testosterone for mating).
events have recently become more
common and could be attributed Research on GHFF mortality rates
to local climate change. However, during heat events is important for
recent die-offs are also more likely understanding the impact of extreme
to be reported, due to increased temperatures on population dynamics.
environmental awareness and more
12 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific ResearchTable 2. No. of
The estimated date of dead GHFF
death for flying-foxes collected Max temperature (% of total
after two major heat events Estimated date of death in 2009 (degrees Celsius) population**)
(27–30 January and 7 Feb 2009),
at Yarra Bend Park. Note - 27th Jan 36.6 200 (1.2%)
temperatures are recorded 28th Jan 43.5 434 (2.6%)
from the data loggers at
Bellbird Yarra Bend Park. 29th Jan 44.7 330 (1.9%)
* The individuals in these categories were 30th Jan 44.4 51 (0.3%)
found days to weeks after the heat
event and the extent of decomposition
January heat wave
prevented us from confidently assigning (27–30th Jan)* 198 (1.2%)
a date of death.
7th Feb 46.6 3539 (22.4%)
** Percentages of total population are
based on static counts carried out on Either heat event
the 19/1/2009 and the 1/2/2009 at Yarra (27–30th Jan or 7th Feb)* 116
Bend; colony sizes were 16,920 and
15,770 respectively.
Table 3. Estimated date Max temperature No. of dead GHFF
The estimated date of death for of death in 2009 (degrees Celsius) (% of total population**)
flying-foxes collected after two major
heat events (27 – 30th January and 7 Bairnsdale Geelong Bairnsdale Geelong
Feb 2009), at Bairnsdale and Geelong 27th Jan 29.3 31.6 – –
camps. Note - temperatures are
recorded from the data loggers on 28th Jan 39.6 39.6 – 66 (2.75%)
site. 29th Jan 43.3 46.1 – 136 (5.7%)
* For the Bairnsdale camp, the percentages
of total population are based on a static 30th Jan 43.5 39.5 4 (0.1%) –
count carried out on the 26/1/09; the
7th Feb 46.0 46.3 329 (12.1%) 53 (1.5%)
colony size was 2,720. For Geelong,
percentages are based on fly-out counts
carried out on the 7/1/2009 and the
4/2/2009; colony sizes were 2,400 and
3,500 respectively.
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 13Roost
and camp
conditions
Figure
Figure81
On-site tree assessments
The differences in defoliation (percentage of Dieback and defoliation of canopy The results from this study suggest
foliage lost) for trees in permanent, non- trees used by roosting flying-foxes is that flying-foxes are having an impact
roosting and seasonal roosting areas at Yarra a common occurrence at flying-fox on roost trees, causing over 50%
Bend Park; and the changes in defoliation over campsites. The weight and movement defoliation for some trees within sections
a period of time. of flying foxes, while they are of the campsite permanently occupied
roosting, can strip leaves off trees and by GHFF. The percentage of defoliation
result in broken branches. Monitoring differed among the three different kinds
Permanent Non Roosting Seasonal the health of roost trees is important of roosting areas, with a statistically
to inform appropriate management significant higher rate of defoliation for
60
55
of the campsite by identifying which trees in the permanent roosting area
50 sections of the campsite may need to (see Figure 8).
Defoliation (%)
45 be restored. To determine the rate of
40 Trees that were used as roosts only during
35 roost tree defoliation at Yarra Bend
the summer months will generally get
30 Park, on-site tree assessments have
25 a chance to recover and develop new
20 been carried out every 4–5 months
growth over spring/winter. In contrast,
15 since October 2006.
10 many trees in the permanent roosting
5
A transect line, approximately 2.5 km area are under constant stress, causing
Oct Feb May 08 Aug 08 Dec 08 May 08 long, is located along each side of the death of several large branches in
/Nov 06 / Mar 08
the Yarra River approximately this section of the campsite.
Date
10 m from the river edge. Along this
There were also changes in the rate
transect 199 trees have been selected
of defoliation over the last three years,
for repeated observations; these trees
especially for trees within the permanent
are located within the permanent
roosting area, where the percentage
roosting area, in the outer seasonal
of defoliation appears to be decreasing
roosting areas which are utilised
over time (see Figure 8); these trees may
during summer, and in non-roosting
have developed new growth (or epicormic
areas just outside the flying-fox
growth). Epicormic growth often appears
colony.
on trees after stresses/disturbances such
The condition of the canopy of roost as fire and defoliation, and is
and non-roost trees was determined an indication of tree recovery.
by scoring the extent of defoliation
Other studies have found that colonies of
(percentage of foliage lost) as a
roosting flying-foxes will gradually shift
category from 1 (0–25% of foliage
and occupy different parts of the available
lost) to 4 (75–100 % of foliage lost).
habitat over time, thus allowing recovery
Dead trees were scored as -1.
of the tree canopy. A similar pattern may
This has proved to be an effective be occurring at Yarra Bend Park, although
method which can be repeated by this is yet to be confirmed.
different observers. The percentage
of dead branches and new foliage is
also recorded during these surveys.
14 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific ResearchAssessment approach (methods)
Photo analysis Figure 9
3
A second method is also used to Three representative examples of tree canopies at Yarra Bend Park: (1) is
further quantify the health of roost located in a non-roosting area just outside the flying-fox colony; (2) is used as
trees. This method can also be a seasonal roost during summer; and (3) is permanently occupied by flying-
easily repeated by any observer. foxes. All three photos were taken in May 2009.
Along the 2.5 km transect line
61 permanent plots (marked by
a wooden stake) are set up at
approximately 50 m intervals.
At each of these stakes canopy
photos are taken. Since March
2007, these photos have been
taken every 4–5 months.
Photos are taken in permanent,
seasonal and non-roosting areas.
The photos are downloaded onto
the computer and a grid of one
hundred points is overlaid on the 1. Non-roost
photo on-screen. The number
of leaves, flying-foxes, sky and
branches (fine and large) at each
grid point is counted. These values
can then be translated into an
index of cover. After repeated
sampling, these photos can be
used to determine the difference
in leaf cover between roosting
and non-roosting areas, and the
change in leaf cover over time.
The latest analysis (including recent
photos taken in May 2009) shows 2. Seasonal
that there is a lower percentage of
leaf cover in permanent roosting
areas, when compared to seasonal
and non-roosting sites (see Figure
9). This result is consistent with
the on-site tree assessment results.
However, there was no significant
change in leaf cover over time.
3. Permanent
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 15Roost
and camp
conditions
Climatic conditions within
Figure 1
Artificial roosts selected camps
One option often identified as a The roosting behaviour of GHFF Climatic conditions play an important
potential measure to reduce the was quantified at Yarra Bend Park role in the dynamics of flying-fox camps.
impact of roosting flying-foxes on and Geelong camps in winter and One of the hypotheses explaining the
the vegetation is to provide artificial spring 2008, summer 2008/09, establishment of the permanent camp
roosting structures. Artificial roosts and autumn 2009. At each site, a in Melbourne has been the warming
are structures that provide roosting randomly located focal flying-fox was of Melbourne. Recent deaths of large
opportunities for flying-foxes. They identified and its roosting behaviour numbers of flying-foxes at Yarra Bend
may be as simple as ropes suspended recorded. The roosting parameters of Park (and other camps in Victoria and
among the trees, or as elaborate as the next closest flying-fox was then Australia) due to excessive heat have also
engineered structures with multiple assessed, until 20 individuals were prompted queries into the importance
arms and cables, similar to a multi- sampled. Next, another initial focal of microclimatic conditions on flying-fox
storey Hills hoist clothesline. flying-fox was randomly selected until survival. Furthermore, most camps of
20 groups, each with 20 individuals, GHFF are located near to a water source,
However, before designing and
had been sampled, to a total of 3200 suggesting that humidity may be an
testing the suitability of certain
observations. important factor influencing the suitability
structures, it is essential to have
of sites as camp locations.
a good understanding of the The research data indicates that if
roosting behaviour of flying-foxes 20% of GHFF colony (5000 flying- To explore the importance of microclimate
within the target camps. The aim of foxes) required roosts this would at the camp sites, loggers were installed
this research component was equate to approximately 3.1 km of to record temperature and humidity at
Figure 2to quantify basic parameters of roosting space. This makes this option 15 minute intervals. There is now more
roosting GHFF, specifically: logistically impractical at Yarra Bend than three years of data from Yarra Bend
Park. In the future, artificial roosts Park, Geelong, Royal Botanic Garden
• type, angle and diameter of
may still have merit in very specific Melbourne (RBGM), and four camps in
roosting branch
circumstances, such as the protection East Gippsland. The temperature and
• height of flying-fox in the tree of certain high-value trees in garden humidity data across all camps for the
and height of surrounding settings. most recent heat events (late January
vegetation and 2009 and 7 Feb 2009) was extracted to
• maximum, minimum and average characterise the conditions on those days
distance to the next closest and compare among camps.
flying-fox.
16 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific ResearchThe maximum temperatures Table 4.
experienced at each of the camps Mean maximum temperature and mean minimum relative humidity at each GHFF camp
varies, with maximums typically in Victoria at two heat events (late January 2009 and 7 February 2009). Data presented
recorded at Yarra Bend Park are the mean from 3 loggers (except Yarra Bend Golf course with 4 loggers) positioned
and minimums recorded in East within the canopy (i.e. at typical roost height for that camp).
Gippsland (see Table 4). Geelong,
RBGM, Bairnsdale and Yarra Bend
Maximum Temperature at each camp
Park reached > 40 degrees in both
late January and February 2009. 27/01/09 28/01/09 29/01/09 30/01/09 6/02/09 7/02/09 8/02/09
Minimum relative humidity recorded
at the camps follows a similar but Dowells Creek 26.8 35.8 37.8 35.6 28.4 40.9 25.6
reversed pattern, with the hottest Geelong 31.6 39.6 46.1 39.5 26.3 46.3 22.4
camps also experiencing the
lowest levels of relative humidity. Yarra Bend
Further analysis of the large data Golf Course 37.3 44.2 45.6 45.8 30.9 47.3 22.4
set may enable us to identify the Bellbird, Yarra
combination of temperature and Bend Park 36.6 43.5 44.7 44.4 30.2 46.6 22.0
humidity at which GHFF begin
to struggle. It is likely that an Karbethong 27.2 35.8 38.4 36.5 24.9 40.9 27.9
increase in understorey/mid-storey Swans Track,
vegetation at Yarra Bend Park, East Gippsland 32.3 37.6 41.8 41.7 25.1 44.6 26.0
plus efforts to restore the tree
canopy, will be effective at reducing Bairnsdale 29.3 39.6 43.3 43.5 24.9 46.0 29.0
temperature and increasing RBGM 34.1 41.1 42.6 42.7 27.2 45.0 21.3
humidity. However at this stage,
the combination of temperature Minimum Relative Humidity at each camp
and humidity which may reduce
or prevent heat-related mortality Dowells Creek
is not known. East Gippsland 59.9 39.5 21.5 24.6 57.1 30.9 59.4
Geelong 41.0 20.5 16.2 27.1 56.7 12.7 46.2
Yarra Bend
Golf Course 13.6 9.9 14.1 12.1 34.5 10.1 52.2
Bellbird, Yarra
Bend Park 13.8 11.1 14.9 12.9 35.3 10.5 52.5
Karbethong 60.2 27.6 23.7 28.5 64.4 30.5 52.7
Swans Track,
East Gippsland 42.5 26.2 16.1 17.1 61.1 14.5 55.9
Bairnsdale 45.1 22.2 16.5 16.5 66.7 12.5 46.0
RBGM 18.2 14.4 18.2 15.9 41.5 12.9 57.5
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 17Future
management
activities
Based on the scientific • During the two major heat events
research data, the following in 2009, many flying-foxes moved
management activities are to a few large cypress pines on the
proposed: golf course that were close to the
riverside campsite, as a result large
• Continue planting indigenous
numbers of GHFF were clustering
grasses and understorey plants,
within these trees causing a high
this may help contribute to the
number to suffocate and overheat.
health of roost trees.
To avoid dispersal to and clustering
• Plant more trees for future in these nearby cypress trees, more
roosting opportunities, amongst shrubs and small trees (particularly
existing roost trees as well as in Silver Wattle) could be planted,
sparse areas further up the Yarra especially in areas with little mid-
River. This will give flying-foxes storey on the golf course side of the
the opportunity to move into Yarra River. This may provide more
new roost trees, allowing roosting opportunities/shelter
existing trees to recover. during future heat events.
• Continue research on artificial
roosts. Artificial roosts could
be trialled in specific areas as
alternative roosting habitat to
help ameliorate the effects of
defoliation on roost trees, and
avoid the potential death of
these trees.
18 | Yarra Bend Park Flying-fox Campsite: Review of the Scientific ResearchFuture research
Ongoing research is important for Potential additional research: Potential additional research
understanding population dynamics and • Documentation of preferred during heat events:
roosting requirements of GHFF at Yarra roosting trees (collect extra • A better management system needs
Bend Park. Information gained from data during counts) could have to be designed and implemented
this research is essential to inform the future implications for campsite that incorporates collection and
appropriate management of this GHFF management processing of dead flying-foxes,
camp. transport and disposal.
• Using satellite collars, investigate
GHFF movements within their • The location of dead flying-foxes
It is recommended that the
feeding range, to see in more detail across the camp needs to be mapped
following research should where they are feeding (for example more accurately, to allow for
continue: are certain foraging sites favoured comparisons among preferred roost
• Static counts, twice per month. over others). This could also be locations (e.g. locations resulting in
• Fly-out counts, once per month. carried out at Geelong and East more/less deaths).
• Mortality surveys, twice per month. Gippsland camps. • Monitor the effectiveness of spraying
• Reproductive output, 10-14 day • Continue tagging flying-foxes with individual flying-foxes by volunteers
intervals. thumb bands to determine the (monitor disturbance/estimate
proportion of GHFF that return to percentage that survive).
• Camp microclimate surveys. the colony after seasonal dispersal; • Additional information could be
which individuals (sex/age) stay collected from GHFF during such
Potential amendments to current during winter; and which individuals events. Access to large numbers
research are: are susceptible during heat events of recently-dead flying-foxes is a
• Sex ratio surveys could also be (For example, are the heat susceptible valuable opportunity to answer
undertaken outside of the breeding flying-foxes Melbourne permanents ecological and biological questions
season (May–August); the male to or migrants from other camps?). that would otherwise be costly to
female sex ratio for this period • Investigate the role of GHFF as answer. This could include: teeth
is currently unknown. pollinators/seed dispersers in urban extraction to measure cementum
• Tree heath assessments could be areas. GHFF are thought to be layers and accurately determine
carried out less regularly; once or critical to forest ecology, assisting the age of adults; extracting DNA
twice a year should be enough to to regenerate our diminishing (tissue samples) to compare levels of
see a change in defoliation. forests, but is their role as pollinators relatedness among dead individuals
• Humidity loggers could also be placed important in highly fragmented and movement patterns among
low in the vegetation at wetland urban areas? all GHFF camps (genetic samples
areas to assess the impacts of the • In February 2008, 340 Little Red are now routinely collected during
wetlands on camp microclimate. Flying-foxes Pteropus scapulatus trapping events); and take blood
(LRFF) were recorded at Yarra samples to potentially determine
Bend Park (these individuals were hormone levels in dead flying-foxes
likely migrants from a campsite (e.g. testosterone levels in male
near Numurkah). Research on flying-foxes during the later part
the population dynamics of this of summer).
population would be beneficial for
the management of the Numurkah
camp. It would also be valuable to
determine their foraging range using
satellite tracking.
Yarra Bend Park Flying-fox Campsite: Review of the Scientific Research | 19List of
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