THE DISTRIBUTION AND ABUNDANCE OF LEADBEATER’S POSSUM
GYMNOBELIDEUS LEADBEATERI IN LOWLAND SWAMP FOREST AT
YELLINGBO NATURE CONSERVATION RESERVE
DAN K.P. HARLEY, MARIANNE A. WORLEY AND TERENCE K. HARLEY
Harley DKP, Worley MA and Harley TK, 2005. The distribution and abundance of
Leadbeater’s possum Gymnobelideus leadbeateri in lowland swamp forest at Yellingbo Nature
Conservation Reserve. Australian Mammalogy 27: 7-15.
In 1986, a small, outlying population of Leadbeater’s possum (Gymnobelideus leadbeateri)
was discovered inhabiting lowland swamp forest at Yellingbo Nature Conservation Reserve. It
is the only known extant lowland population, and occurs in habitat dramatically different to
that throughout the possum’s core range in the montane ash forests of the Victorian Central
Highlands. As part of an investigation into the species’ ecology in lowland swamp forest,
surveys were undertaken to establish the possum’s distribution and abundance at Yellingbo.
The population is estimated to contain 80 - 100 individuals, distributed along a narrow, 6 km
length of riparian forest. Most of the suitable foraging habitat is presently occupied, and
densities are similar to those previously reported for the species in montane ash forest. The
possums are breeding year round, with significant recruitment of young into the population,
and data obtained between 1995-2004 suggest that the population size is currently stable. A
highly targeted revegetation program focused on the floodplain has the potential to improve up
to 85 ha of degraded swamp forest, and in so doing would more than double the area of suitable
habitat for G. leadbeateri in the reserve.
Key words: Leadbeater’s possum, Gymnobelideus leadbeateri, distribution, swamp forest,
Yellingbo Nature Conservation Reserve.
DKP Harley, School of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria
3800, Australia. Current address: Department for Environment and Heritage, PO Box 1046,
Mt Gambier, South Australia 5290, Australia. Email: [email protected]. MA Worley,
School of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800,
Australia. TK Harley, 750 Mt Macedon Rd, Mt Macedon, Victoria 3441, Australia. Manuscript
received 1 May 2003; accepted 4 April 2004.
LEADBEATER’S
possum
(Gymnobelideus
leadbeateri) is a small (110 – 160 g), nocturnal,
arboreal marsupial that is restricted in distribution
entirely to Victoria, where it is one of the state faunal
emblems. During the first part of last century it was
not sighted for over 50 years and was presumed to be
extinct (Spencer 1921; Calaby 1960). In 1961, the
species was rediscovered in montane ash forest near
Marysville, in the Victorian Central Highlands
(Wilkinson 1961). During the next three decades,
considerable survey work was undertaken to
establish the species’ distribution in this habitat type
(e.g., Smith et al. 1985; Lindenmayer et al. 1989).
Extensive research also investigated the species’
ecology and habitat requirements (e.g., Smith 1984a;
Smith and Lindenmayer 1988; Lindenmayer et al.
1991a).
The possum is currently listed as ‘Endangered’
under the Victorian Flora and Fauna Guarantee Act
1988 and the Commonwealth Environment
Protection and Biodiversity Conservation Act 1999,
due to its restricted distribution (~ 60 x 80 km area)
and a scarcity of mature trees with hollows (that the
possum requires for denning) (Smith and
Lindenmayer 1988; Lindenmayer et al. 1991a). Past
fires and current logging regimes have both
contributed to this latter threat (Lindenmayer et al.
1990; Lindenmayer 1992). While population
estimates vary, it is generally thought that around
4000 individuals occur in the wild (Lindenmayer
1996). However, over the next 65 years it is
predicted that the carrying capacity of montane ash
forest in the Victorian Central Highlands will decline
by 90% due to a shortage of tree hollows
(Lindenmayer et al. 1990, 1997; Smith and
Lindenmayer 1992). It is anticipated that this will
result in a massive decline in the possum’s
abundance by 2020, followed by a population
bottleneck lasting until 2075.
8
AUSTRALIAN MAMMALOGY
In recent years there have been several reports of
G. leadbeateri from habitats outside its core range in
the montane ash forests of the Victorian Central
Highlands (Harley 2004a). These include the
discovery in 1986 of a small, outlying population in
lowland swamp forest at Yellingbo Nature
Conservation Reserve (Smales 1994). As part of a
study examining the ecology of G. leadbeateri in
lowland swamp forest, surveys were undertaken to
establish the species’ distribution and abundance at
Yellingbo. This paper reports the findings of these
field surveys and discusses the conservation of the
possum at this site.
METHODS
Study site
Yellingbo Nature Conservation Reserve is located
approximately 50 km east of Melbourne (37° 51’ S,
145° 29’ E) in the eastern foothills of the Dandenong
Ranges (Fig. 1). The reserve (640 ha) comprises
three linear sections of remnant riparian vegetation
stretching along four watercourses, the Woori
Yallock, Sheepstation, Macclesfield and Cockatoo
Creeks. It has a particularly high perimeter (> 50 km)
to area (640 ha) ratio. The nearest populations of G.
leadbeateri occur approximately 17 km to the east
and north-east in montane ash forest at Mt Beenak
and Ben Cairn (Owen 1963; Loyn and McNabb
1982; Lindenmayer et al. 1989).
Three main forest types occur in the reserve.
Open forest dominated by messmate (Eucalyptus
obliqua), green scentbark (Eucalyptus fulgens) and
narrow-leaved peppermint (Eucalyptus radiata)
occurs on the drier, well-drained slopes near the
periphery of the reserve. The riparian forest, around
which the reserve is focused, is dominated by two
distinct vegetation associations: (i) manna gum
(Eucalyptus viminalis) forest with an understorey of
blackwoods (Acacia melanoxylon), and (ii) mountain
swamp gums (Eucalyptus camphora) with, in places,
a dense middlestorey of woolly tea-tree
(Leptospermum lanigerum), manuka (Leptospermum
scoparium),
prickly
tea-tree
(Leptospermum
continentale),
swamp
paperbark
(Melaleuca
ericifolia) or scented paperbark (Melaleuca
squarrosa). The latter, referred to hereafter as
‘swamp forest’, occurs in the wetter parts of the
reserve along the Cockatoo and Macclesfield Creeks,
parts of which are permanently inundated. All three
sections of the reserve are surrounded by extensively
cleared farmland. The area receives approximately
1100 mm of rainfall annually.
Survey techniques
In order to establish the distribution of G. leadbeateri
at Yellingbo, two survey techniques were employed,
‘stagwatching’
and
nest
box
monitoring.
‘Stagwatching’ (sensu Smith et al. 1989) involves
direct counts of arboreal mammals emerging from
tree hollows at dusk. Observers position themselves
near the base of hollow-bearing trees prior to dusk
and sit quietly for an hour, recording all animals that
emerge. To distinguish among species, observers rely
on natural light, using the animals’ silhouettes and
behaviour. Approximately 170 stagwatches were
undertaken at scattered locations throughout the
reserve. Other animals active at the stagwatching
sites were also noted. Spotlighting and call imitation
were used in an ad hoc way in conjunction with this
technique.
Fig. 1. Location of Yellingbo Nature Conservation Reserve (+) in relation to the core distribution of G. leadbeateri in the
Victorian Central Highlands. Historic records from lowland habitats in south-west Gippsland are also depicted (V).
HARLEY ET AL.: A LOWLAND GYMNOBELIDEUS POPULATION
9
The nest box surveys involved the initial
installation of 57 boxes throughout the reserve in
July 1995. This number was later increased to 86 as
the survey area was extended. A further 64 boxes
were deliberately positioned within occupied
territories, bringing the total number of boxes to 150.
Aspects of the nest box work (e.g., box dimensions
and placement) are described in detail in Harley
(2004b). Nest boxes were installed at a height of 4 m
on eucalypts and were inspected using an extension
ladder. Most had a south-easterly aspect to reduce
exposure to the afternoon sun. They had hinged lids
or side panels, enabling box contents to be examined.
All boxes had a small entrance hole of approximately
50 mm diameter, which prevented access by larger
species of arboreal mammal. To facilitate the
movement of possums, particular effort was taken to
select sites that had considerable inter-connecting
vegetation in the middlestorey and/or canopy,
including to the tree the box was installed upon.
distance of 165 ± 44 m (range 100 – 230 m, n = 14)
between the den sites of adjacent colonies. A similar
pattern was observed for the species in montane ash
forest by Smith (1984a). It should also be noted that
a single G. leadbeateri was detected on the Woori
Yallock Creek in April 2001 (Harley 2002). It is
likely that this individual dispersed more than 1 km
from the Cockatoo Creek across habitat that is
unsuitable for the species.
Most boxes were positioned in the swamp forest
along the Cockatoo and Macclesfield Creeks. Ten
boxes were installed in drier forest on the adjacent
slopes to examine the extent to which the species’
distribution extends into this forest type. Smaller
numbers of nest boxes were also installed along the
Sheepstation (2) and Woori Yallock (5) Creeks. The
nest boxes were monitored every 6 - 8 weeks from
September 1995 to November 1998 (24 occasions).
Additional inspections were conducted in March and
November 1999, April 2001, April 2002, May 2003
and February 2004.
The best foraging habitats at Yellingbo (i.e.,
supporting the largest possum colonies) were
dominated by young stands of forest (i.e., 20 - 40
years old) supporting high stem density. Areas
supporting mature swamp forest were more open in
structure, and consequently less suitable for G.
leadbeateri. Dense stands of Melaleuca spp. and
Leptospermum spp. were particularly valuable in that
they provided well-connected pathways for
movement through the forest (pers. obs.). The lower
trunks of these middlestorey species were incised and
the sap harvested as a food source (Harley, unpubl.
data).
RESULTS
Between 1995 and 2004, twenty-nine G. leadbeateri
colonies were located at Yellingbo. For this purpose,
a ‘colony’ is defined as the individuals that denned
together daily. Typically, colonies were made up of a
single breeding pair with one or more generations of
their young. Mean colony size was 3.6 individuals
(Harley, unpubl. data). Twelve colonies were
detected during stagwatching surveys and 17 via the
nest boxes. A small number of these colonies have
now disbanded, so that at any time the reserve is
likely to support 25 - 30 colonies, containing
collectively 80 - 100 individuals.
The survey results indicate that G. leadbeateri is
confined to a single section of Yellingbo Nature
Conservation Reserve, encompassing lengths of the
Cockatoo and Macclesfield Creeks. The possum’s
distribution extends over a narrow corridor of swamp
forest, 6 km long and rarely exceeding 100 m in
width. Approximately two thirds of the population
occurs in a 3.5 km length of riparian forest (∼30 ha).
Within this area colonies were evenly distributed
through the intact swamp forest, with a mean
All of the colonies that were located were
distributed within the reserve and associated with
lowland swamp forest. While the floristic species
composition varied little at occupied sites (i.e., a
canopy of E. camphora with Melaleuca spp. or
Leptospermum spp. in the middlestorey), the relative
abundance of each varied markedly. For instance,
some territories were dominated by E. camphora,
while others were predominantly tall, dense stands of
Melaleuca spp. or Leptospermum spp. with only
occasional, emergent E. camphora.
One hundred and thirteen (75%) of the 150 boxes
showed signs of use by G. leadbeateri (i.e., animals
or nesting material were present). The number of
possums present in the boxes reached a maximum in
May 2003, with 95 individuals from 21 colonies
present. Colonies occupied the nest boxes year
round, and each group made use of multiple boxes
positioned within their territories. The occupancy
patterns are described in detail by Harley (2004b).
Only one of the 10 nest boxes positioned in the
drier sclerophyll forests upslope of the floodplain
showed signs of use by G. leadbeateri (i.e., nest
material). This box was positioned only 25 m from
the boundary with swamp forest. The observation is
consistent with radio-tracking data that revealed
some individuals to move small distances (< 30 m)
upslope out of the floodplain at night whilst foraging
(Harley, unpubl. data).
Eight other species of arboreal and scansorial
mammal were detected during the stagwatching and
nest box surveys. These were the common ringtail
possum (Pseudocheirus peregrinus), common
10
AUSTRALIAN MAMMALOGY
brushtail possum (Trichosurus vulpecula), sugar
glider (Petaurus breviceps), yellow-bellied glider
(Petaurus australis), feathertail glider (Acrobates
pygmaeus), agile antechinus (Antechinus agilis),
bush rat (Rattus fuscipes) and introduced black rat
(Rattus rattus).
DISCUSSION
Habitat requirements
Situated at 120 m ASL, Yellingbo supports the only
known extant lowland population of G. leadbeateri
and the only confirmed extant population outside the
Victorian Central Highlands. Most records of the
species in montane ash forest are from 400 – 1200 m
ASL (Atlas of Victorian Wildlife, Department of
Sustainability and Environment). The possum has
also been recorded in sub-alpine woodland at Lake
Mountain, Mt Baw Baw and Mt Erica at 1400 –
1500 m ASL (Jelinek et al. 1995; Atlas of Victorian
Wildlife, Department of Conservation and Natural
Resources). Historical lowland records include the
Bass River at 60 m ASL (McCoy 1867) and Koo-weerup swamp at 20 m ASL (Brazenor 1962). Thus, the
species’ distribution encompasses a large altitudinal
range in a relatively small geographic area.
The habitat utilised by G. leadbeateri at
Yellingbo is swamp forest dominated by E.
camphora. Dense thickets of Melaleuca and
Leptospermum spp, typically located along the edge
of the floodplain, provide a source of food, nesting
material and highly connected pathways for
movement (Harley, unpubl. data). While this forest
type is dramatically different to montane ash forest, it
bears considerable similarity to the lowland forest
that once occurred along the Bass River and Koowee-rup swamp, where historical records of the
species were obtained (McCoy 1867; Brazenor
1962). These sites occur approximately 65 and
35 km to the south of Yellingbo, respectively (Fig.
1).
There are several differences in the floristics and
structure of the sites occupied by G. leadbeateri in
lowland swamp forest and montane ash forest. These
include: (i) the dominant species of eucalypt at
Yellingbo is E. camphora, whereas in montane ash
forest it is mountain ash (Eucalyptus regnans), alpine
ash (Eucalyptus delegatensis) or shining gum
(Eucalyptus nitens); (ii) the canopy height at
Yellingbo is 15 - 25 m, whereas in montane ash
forest it may reach 90 m; (iii) the middlestorey is
composed of Melaleuca and Leptospermum spp at
Yellingbo, whereas in montane ash forest wattles
(Acacia spp.) constitute the major middlestorey
vegetation.
Despite these differences, the two habitat types
share several attributes likely to be of significance to
G. leadbeateri. These include: the predominance of
smooth-barked eucalypts (given that one of the
species’ main feeding behaviours involves licking
surface exudates from their trunks), hollow-bearing
trees (that provide den sites) and highly-connected
vegetation in either the middlestorey or canopy (that
facilitates the possums’ mode of locomotion through
the forest). At Yellingbo the species’ distribution
does not extend extensively into forest dominated by
eucalypts with thick, fibrous bark extending to the
upper branches, such as E. obliqua. This is also the
case in the Victorian Central Highlands (Smith 1982;
Lindenmayer et al. 1989).
As has been observed for several other cryptic
mammals, such as the brush-tailed phascogale
(Phascogale tapoatafa) and A. pygmaeus (Soderquist
et al. 1996; Ward 2000), nest boxes were a most
effective method of surveying for G. leadbeateri at
Yellingbo. The high occupancy rate (Harley 2004b)
is likely to be, in part, a consequence of the low
abundance of suitable tree hollows in the reserve.
Most trees have a small trunk diameter and few
contain hollows in the swamp forest where the
possums forage. This is reflected in the manner in
which the species was discovered at Yellingbo
(denning in a canvas bird-hide; Smales 1994), the
observation of two individuals denning in a P.
peregrinus drey (M. Miller, pers. comm.) and the
observation of a colony regularly denning
underground in the roots of a leaning tree (Harley,
unpubl. data). Eight colonies were observed denning
at the periphery of their territories along the swamp
edge, where large trees possessing hollows are more
prevalent (Harley, unpubl. data). Despite this
apparent hollow scarcity, the nest boxes were
colonised very rapidly, suggesting that possums were
resident prior to box installation at most sites
containing suitable foraging habitat. Thus, whilst tree
hollows were not abundant across much of the
reserve, their availability did not appear to be
limiting the size and distribution of the population.
Rather, the availability of suitable foraging habitat
was probably the limiting factor. This also meant that
the addition of nest boxes did not result in an
expansion of the population.
In montane ash forest, extensive research has
found that G. leadbeateri has very specific habitat
requirements (Lindenmayer et al. 1991a). However,
the recently discovered populations in lowland
swamp forest (Smales 1994) and sub-alpine
woodland (Jelinek et al. 1995) suggest that G.
leadbeateri has more ecological flexibility than has
previously been recognised. For instance, Smith
(1984b) identified Acacia gum as a key food source
HARLEY ET AL.: A LOWLAND GYMNOBELIDEUS POPULATION
for the possum in montane ash forest, and
Lindenmayer et al. (1991a) found that the species’
presence at a site was positively correlated with the
basal area of Acacia spp. However, in lowland
swamp forest at Yellingbo the situation is quite
different, as Acacias are absent from areas where the
possums concentrate their foraging activities (Harley,
unpubl. data).
Lowland swamp forest as G. leadbeateri
habitat
Prior to the establishment of Yellingbo Nature
Conservation Reserve (including recent land
acquisitions which have greatly expanded its size),
approximately 12% of the swamp forest along the
Cockatoo Creek was cleared and drained for
agriculture (McMahon and Franklin 1993). However,
the narrow width of the forest dominated by E.
camphora is not entirely the result of habitat
destruction. This forest type is naturally restricted to
the seasonally inundated floodplain, and rapidly
gives way to drier forests dominated by E. obliqua,
E. radiata and E. fulgens on the surrounding slopes.
It is the latter that has been most affected by clearing
adjacent to the reserve.
The swamp forest in the southern third of the
reserve, which supported eight G. leadbeateri
colonies, is only the width of a single colony’s
territory (i.e., ≤ 120 m). In contrast to this situation,
the species was detected in only one of 49 linear
corridors surveyed in montane ash forest, seventeen
of which were assessed as containing suitable habitat
(Lindenmayer et al. 1993). Collectively, the mean
width of these sites was 110 m (range 30 - 264 m)
and is comparable to that at Yellingbo. While the
lowland swamp forest present at Yellingbo naturally
occurs as a corridor in the landscape (i.e., is not the
result of human activities), corridors of montane ash
forest are the result of recent timber harvesting
activities.
Lowland swamp forest, characterised by
eucalypts such as swamp gum (Eucalyptus ovata)
and E. camphora, with dense thickets of paperbark
and tea-tree in the middlestorey, was once
widespread around Healesville and in south-west
Gippsland (McMahon and Franklin 1993). The
historical records of G. leadbeateri from the Bass
River and Koo-wee-rup Swamp confirm that the
possum once occurred through these habitats. These
swamp forests probably consisted of scattered, broad
floodplains, linked by a network of narrow corridors
stretching along the creeks. Thus, it is probable that
G. leadbeateri has always inhabited corridors of
forest in such areas. However, such was the extent of
clearing for crop planting and dairy farming during
the early part of last century, that by the 1920s
11
G. leadbeateri was thought to be extinct in these
forests (Spencer 1921).
Today, little lowland swamp forest remains in
this general area other than at Yellingbo. The reserve
is recognised to be of national significance and is
listed under the Flora and Fauna Guarantee Act
1988 as a threatened community (McMahon and
Franklin 1993; Turner 2000). The only extensive area
of this forest type apart from that at Yellingbo occurs
approximately 25 km to the south-east, along
sections of Diamond and Black Snake Creeks in
Bunyip State Park (Blackney 1991; Blackney and
Menkhorst 1993; McMahon and Franklin 1993). This
area is midway between Yellingbo and the historical
collection sites of G. leadbeateri in south-west
Gippsland. Nest box surveys for the possum at this
site have failed to detect its presence (Harley, in
press).
In addition to Yellingbo, G. leadbeateri has been
recorded at one other site dominated by E. camphora.
The species has been observed on two occasions at
the Silver Gum Reserve near Buxton (280 m ASL),
approximately 55 km north of Yellingbo (K. Garth,
pers. comm.; pers. obs.). Sections of this small, 17 ha
reserve bear considerable resemblance to Yellingbo.
The possum’s abundance at this site has yet to be
established. The records suggest that some of the
small stands of E. camphora that were identified by
Simmons and Brown (1986) around Healesville,
approximately 20 km north of Yellingbo, should also
be surveyed for G. leadbeateri. Stands of E.
camphora that occur in north-east Victoria at 400 –
1600 m ASL should also investigated. It is unclear at
present whether G. leadbeateri persists in this part of
its range (Harley 2004a), and to date most searches
for the species in that region have focused on
montane ash forest. It is possible, that small,
undetected populations of the possum occur in forest
dominated by E. camphora there.
Management and conservation
The management of G. leadbeateri at Yellingbo has
received little attention since the discovery of the
population. Fortunately, the population is currently
faring well. Data collected between 1995 and 2004
indicate that the size of the population (80-100
individuals) is presently stable (Harley, unpubl.
data). Territory occupancy has also been extremely
stable over this period. Density estimates (~ 1.9
individuals/ha) are similar to those reported for
montane ash forest by Smith (1984a), and the
possums are breeding continuously. During the nine
years of population monitoring, the proportion of
colonies with females either carrying pouch young or
suckling young just out of the pouch never dropped
below 55%, and typically exceeded 70%. However,
given that most suitable foraging habitat (∼50 ha)
12
AUSTRALIAN MAMMALOGY
is currently occupied (Harley, unpubl. data) and the
reserve is surrounded by extensively cleared
farmland, so that the population is isolated, there is
little scope for it to expand. Although, the recent
discovery of a single individual along the Woori
Yallock Creek presents an opportunity to establish
the species in a second section of the reserve, which
may be able to support a further 20 - 30 individuals.
It is unclear whether the Yellingbo population of
G. leadbeateri is genetically distinct from those
occurring in montane ash forest, and molecular
studies are currently underway at Monash University
to investigate this question. We consider it to be
unlikely that the Yellingbo population is genetically
distinct, given that the nearest populations in
montane ash forest are less than 20 km away. The
period of isolation, due to habitat destruction and
fragmentation, is probably in the order of 50 - 100
years. Another management consideration is the
extent to which the Yellingbo population suffers
from a loss of genetic variation, given that the
number of reproductively active individuals at any
time is only approximately 50 individuals (only half
that of the total population size) (Harley, unpubl.
data).
The conservation of G. leadbeateri at Yellingbo
principally requires the effective management of
foraging habitat (as nest boxes currently ensure that
an adequate number of den sites are available).
Eucalypt dieback, a consequence of several factors,
including altered hydrology patterns, affects more
than 40% of the swamp forest along the Cockatoo
Creek (Turner 2000; Kasel 2001), and constitutes the
major threat to the population in the short-term.
Given that young stands of forest (e.g., 20 - 40 years)
provide the closed structure favoured by G.
leadbeateri, and as such constitute the best foraging
habitat, the lack of eucalypt regeneration at several
sites is also of concern (Pearce 2000). This is in part
due to invasion of the ground layer by dense swathes
of the common reed (Phragmites australis) and reed
canary-grass (Phalaris arundinacea); a response to
the increased light levels at sites where the forest
canopy has matured and opened out in structure.
A highly targeted revegetation program focused
on the floodplain has the potential to improve up to
85 ha of degraded swamp forest, and in so doing
would more than double the area of suitable habitat
available for both G. leadbeateri and the
‘Endangered’ helmeted honeyeater (Lichenostomus
melanops cassidix). While extensive revegetation
works have been completed in and adjacent to the
reserve over the past 25 years (Smales et al. 1990;
Gadsden and Ashby 1995), the majority of this effort
has been concentrated on the slopes immediately
adjacent to the floodplain. Thus, thus while creating
an important buffer for the reserve, these plantings
do not constitute core breeding habitat for either G.
leadbeateri or the honeyeater. Future efforts should
be directed at the floodplain itself. Emphasis should
be placed on establishing a canopy E. camphora with
a middlestorey of M. squarrosa, M. ericifolia, L.
lanigerum, L. scoparium and L. continentale.
Several predators present in the reserve,
including the powerful owl (Ninox strenua), red fox
(Vulpes vulpes) and cat (Felis catus), appear to be
having little detrimental impact on the population
(Harley, unpubl. data). Interestingly, P. breviceps,
while most abundant in the drier forests adjacent to
the floodplain (e.g., colonising nine of the ten nest
boxes installed in this forest type), were also detected
at a high proportion of the sites (62%) occupied by
G. leadbeateri at Yellingbo, albeit in lower densities.
Given that the two species are extremely similar in
size and resource requirements, there is the potential
for competition to occur between them (Smith 1982).
Gymnobelideus leadbeateri has several of the
attributes that Bennett (1987) suggested enables the
long-nosed potoroo (Potorous tridactylus) to persist
in small fragments of habitat. These include small
body size, restricted home range, stable population
structure, dispersal of both sexes and a continuous
pattern of reproduction. However, small, isolated
populations, such as that at Yellingbo, are
particularly vulnerable to extinction in the long-term
(e.g., from catastrophic events such as fire) (Shaffer
1981; Pettersson 1985; Clark et al. 1990; Thomas
1990; McCarthy et al. 1994; McCarthy 1996).
More than 90% of the known wild population of
G. leadbeateri inhabits montane ash forest in the
Victorian Central Highlands, and consequently
conservation efforts should primarily remain focused
in this forest type. However, the predicted population
decline in montane ash forest (Smith and
Lindenmayer 1992), coupled with the possible
effects of climate change (Bennett et al. 1991;
Lindenmayer et al. 1991b), make it particularly
important to conserve the possum in other forest
types, such as lowland swamp forest and sub-alpine
woodland. In 2001, Parks Victoria initiated an annual
monitoring program that will provide important
ongoing information on the conservation status of the
population at Yellingbo.
ACKNOWLEDGEMENTS
Funding for the nest boxes was provided by the
Holsworth Wildlife Research Fund and Australian
Geographic. In addition, Barry Traill and Malcolm
Macfarlane kindly donated nest boxes to the study.
Parks Victoria provided the funding and field support
for the 2001-2004 nest box monitoring. We are most
grateful to the numerous volunteers that assisted with
HARLEY ET AL.: A LOWLAND GYMNOBELIDEUS POPULATION
stagwatching and inspecting nest boxes. In particular,
the enormous contribution made by Melinda
Collinson is appreciated. Murray Logan assisted with
preparation of the map. Alan Lill, Andrew Smith and
Steve Jackson provided valuable comments on the
manuscript. The study was carried out under
Victorian Department of Natural Resources and
Environment Wildlife Permit numbers RP-95-103,
10000256 and 10001246.
REFERENCES
BENNETT AF, 1987. Conservation of mammals within
a fragmented forest environment: The
contributions of insular biogeography and
autecology. Pp. 41-52 in Nature conservation:
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