Extended Range of Bobucks 'Trichosurus cunninghami' in South-West Gippsland, Victoria

2010·0.97 MB·English

by  D, Cleeland Hynes

Contributions
Extended range ofbobucks Trichosurus cunninghami
in south-west Gippsland, Victoria
D Hynes1 and M Cleeland2
'POBox285Burwood3125
2RMB6080Cowes3922
Abstract
Automatic camera-traps were used to investigate the distribution ofMountain Brushtail Possum or Bobuck
Trichosuruscunninghamiindiversehabitatsinsouth-westGippsland,Victoria. Bobucksoccurwidelyinlow-
landsouth-west Gippsland, with an apparenttendencyto aggregate nearthe coast. There appeared to be no
associationbetweenbobucks and thepresence orabsence ofAcacia spp. orwith old-growthEucalyptusspp.
Anewdesignationofthecommonnamesfortheshort-earedpossum, Trichosuruscaninus,andthemountain
brushtail possum, Trichosurus cunninghami to northern bobuck and southern bobuck, respectively, is pro-
,
posed. (TheVictorianNaturalist127(1)2010, 15-19)
Keywords: Trichosuruscaninus; Trichosuruscunninghami;mountainbrushtailpossum;short-
eared possum;bobuck; cameratrap
Introduction
The Bobuck Trichosurus cunninghami and the The authors previouslyreported the presence
Short-earedPossum Trichosuruscaninusarere- ofBobucks T. caninus living in atypical coastal
portedtoinhabitforestedcountryalongandto habitatin south-westGippsland, namelyatThe
the southand eastofthe GreatDividing Range Gurdies Reserve (Hynes and Cleeland 2005),
of eastern Australia, from southern Victoria north ofGrantville on Western Port, Victoria,
to south-eastern Queensland (Lindenmayer et and in a creek adjoining the Bass River south
al 2002; Menkhorst and Knight 2001). They ofGrantville (Hynes 2006). In view ofthe lack
m
dwell typically at altitudes greater than 300 ofconsensussurroundingtheproperclassifica-
(Martin 2005). Bobucks aremedium-sized (2.5 tion ofthe northern and southern populations
- 4.5 kg), semi-arboreal, nocturnal marsupials ofshort-eared or mountain brushtail possums,
(Menkhorstand Knight2001). the authors now provisionally revert to the
In 2002, based upon morphometric differ- usage of T. cunninghami to refer to the popu-
ences,itwasproposedthattheMountainBrush- lation found in The Gurdies Reserve and in
tail Possum T. caninus be reclassified into two broader Gippsland andwill speakofthese ani-
distinct species (Lindenmayer et al. 2002). The malssimplyas ‘bobucks’.
northern formwas to retain thebinomial name As a resultofthe 2005-2006 discoveryin The
T.caninusbutwashenceforthtobeknownasthe Gurdies Reserve, the question arose as to how
short-eared possum’. The southern population, widespreadbobucks ofthe Western Port shore
prevalentintheVictorianAlpsandelsewherein really were. Did they exist as isolated popula-
Victoria,suchasatWilsonsPromontoryNation- tion ‘islands’ only near The Gurdies Reserve
alPark,wastoretainitsalreadydesignatedcom- itselforwere theyperhaps to be found far and
monname mountainbrushtailpossum’butwas wideinlowlandGippsland?
givenanewbinomial, T. cunninghami.However, In order to discover more about these ani-
genetic divergence between T. caninus and the mals’distribution,automaticcamera-trapswere
putative T. cunninghamimaynotsupporta case placed at a range oflocations over a 12 month
for the establishment ofa new species. Collins periodbeginningearly2006 and continuing to
(2003) noted that the degree of intra-specific the present. We discovered that bobucks are
variationwithin thecommonbrushtailpossum, widely distributed and apparently numerous
T. vulpecula, would ifinterpreted similarly, jus- in south-west Gippsland. This discovery was
tifythe replacement ofthat one taxon byten. It surprising in view of the previous absence of
seems unlikelythatten newspecies ofcommon reportsofthemintheliteratureandthepaucity
brushtail possum would represent a practical ofanecdotalreportsaboutthem.
improvementinthatanimal’s designation.
Vol 127 (1) 2010 15
.
Contributions
Methods
Between early 2006 and April 2007 automatic
cameratrapsweredeployedat 11 sitesinsouth-
west Gippsland. Specific locations are present-
ed in Fig. 1. Sites were selected in state parks
and on public land where native vegetation
was present. Five cameras were purpose built
forthis survey. Afterinitial deploymentateach
site,cameraswereusuallyretrievedafteroneto
twoweeks. Ifasitewasfruitful (Gurdies) or,al-
ternatively, ifa siteappearedbarren ofbobucks
(Outtrim) after one or two visits, the cameras
might be changed over several times in order
to ascertain with reasonable surety whether
bobuckswerepresentornot. A failureto detect
mightbebecausebobuckswereabsentfromthe
general area, or an apparent absence could be
dueto their failure to appearbefore the instru-
ments. The interval between camera retrievals
or change-overs depended upon opportunities
to travel to Gippsland forthepurpose.
The instruments detect animals by means of Promontory
theheatradiationtheirbodiesemit(Hynesand
Cleeland2005).Apassinganimalisdetectedby Fig. 1. Camera-trap sites in south-west Gippsland.
means ofan infrared sensor, an algorithm pro- Solid red triangles = Bobucks detected; empty red
grammed into an embedded microcontroller triangles=Bobucksnotdetected.
then assesses thevalidityofthe contact, taking
into account factors such as ambient light con- in focus at close range which helps with their
ditions,thetargetsrateofmovementanddura- identification.
tionofthecontact. Ifthealgorithmdecidesthat Thedesigner’sdilemmainthistypeofphotog-
a valid target has been acquired, the controller raphyisto find acamerathat isboth cheapand
activates a digital camera and a useful image is technically suitable, as the outdoors environ-
captured. When the target moves away, the in- ment is unforgiving to electronic instrumenta-
strumentrevertstoa sleepmode inwhichvery tion. A major design criterion for this project
littleelectriccurrentisdrawnfromthesystems was to develop aphotographic system that was
battery. By so conserving the battery’s charge, both robustand inexpensive.
the instrument is able to remain active in the In addition to camera placements at suitable
field forlong periods. Because the instruments locations, local information about Bobucks in
attempta shot’ onlywhen thechances ofause- Gippslandwas soughtbymeans ofprint media
ful picture are good, the proportion ofphotos coverageofthesurvey,directpersonalcommu-
with an actual animal in the frame instead of nication and by means ofthe Survey’s website
empty space are higher than with systems that (http://www.thylacoleo.com/bobuck_under-
fireon firstcontact (Hynes 2007). ground/).
The camera used was a Kodak DC50, one of Results
the earliest commerciallyavailable digitalcam- Bobucks occur widely throughout lowland
eras. A severelimitation ofthesecameras isthe south-west Gippsland. Locations of camera-
fact that they do not have a date-time recorder trap sites and the results obtained along with
matsieoapnanrostfootffhetrheDeimCro5ti0enstiosrpuetcrhtaaittoinoitns.elta.AckAsnpoaartnthyiecprurlalacirtmiiactdaa-l- beraicehfsnitoeteasreapbroeustenttheedisnoiTlasblaend1 vegetation at
vantage of the DC50 is its short focal length: Previoussightings
it can focus on objects as close as 12 cm out Surprisingly little local knowledge ofbobucks
to infinity. This means that small animals stay was revealed after efforts were made to deter-
16 TheVictorian Naturalist
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Vol 127 (1)2010 17