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The conservation of mammals in Victoria's roadsides

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Abstract and Figures

There’s nothing quite like a scenic drive along a tree-lined highway. Majestic eucalypts stand sentry like a guard of honour. As passengers gazing out the car window, we might not think of these narrow, highway-side reserves as prime habitat for wildlife. Yet in many landscapes across Victoria, ‘roadside reserves’ are all that remains of the pre-European woodland vegetation. This poses the question: If the only habitat left occurs along roadsides, what does this mean for wildlife? I discussed this issue at the Mammals of Victoria seminar hosted by the Field Naturalists Club of Victoria in March 2015, with particular reference to woodland mammals. © 2016, Field Naturalists Club of Victoria. All rights reserved.
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This%is%a%pre-published%version.%For%the%final%manuscript,%please%see The Victorian 1!
Naturalist 133(3) 2016, 7984%2!
The$conservation$of$mammals$in$Victoria’s$roadsides$3!
!4!
Kylie!Soanes!5!
ksoanes@unimelb.edu.au!6!
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[Main!text]!8!
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There's!nothing!quite!like!a!scenic!drive!along!a!tree-lined!highway.!Majestic!eucalypts!10!
stand!sentry!like!a!guard!of!honour.!As!passengers!gazing!out!the!car!window,!we!might!not!11!
think!of!these!narrow,!highway-side!reserves!as!prime!habitat!for!wildlife.!Yet!in!many!12!
landscapes!across!Victoria,!‘roadside!reserves’!are!all!that!remains!of!the!pre-European!13!
woodland!vegetation.!This!begs!the!question:!If!the!only!habitat!left!occurs!along!roadsides,!14!
what!does!this!mean!for!wildlife?!I!discussed!this!issue!at!the!!"##"$%&'(&)*+,'-*"!seminar!15!
hosted!by!the!Field!Naturalist!Club!of!Victoria!in!March!2015,!with!particular!reference!to!16!
woodland!mammals.!!17!
!18!
Victoria’s$roadside$woodlands$19!
To!put!it!into!perspective,!in!Victoria!we!have!156,000!km!of!road!travelled!by!more!20!
than!4!million!registered!vehicles!(AustRoads!2003;!Australian!Bureau!of!Statistics).!The!21!
resulting!satellite!imagery!is!striking!(Figure!1).!Most!of!Victoria’s!land!is!within!1!km!of!the!22!
nearest!road,!meaning!that!in!the!vast!majority!of!landscapes,!wildlife!are!living!in!roadside!23!
vegetation!or!road-affected!habitats.!In!fact,!in!many!areas!roadside!vegetation!may!be!the!only!24!
suitable!habitat!that!is!left.!For!example,!within!highly-modified!landscapes!(e.g.!agricultural!or!25!
semi-urban!landscapes),!mature!Eucalyptus!woodland!is!almost!entirely!restricted!to!linear!26!
strips!along!roadsides,!paddock!edges!and!waterways!(Figure!2).!Species!that!depend!on!27!
woodland!habitats!are,!therefore,!largely!restricted!to!living!near!roads!(Suckling!1984;!Bennett!28!
1988;!Gilbert!1998;!van!der!Ree!and!Bennett!2003).!Roadsides!can!represent!high-quality!29!
habitat!for!woodland!mammals!because!they!often!host!a!high!density!of!large,!old,!hollow-30!
bearing!trees!–!a!critical!resource!for!woodland!fauna,!including!threatened!species!such!as!the!31!
Brush-tailed!Phascogale!./%"+'0"$1&,"2'","("&and!Squirrel!Glider!.1,"3-3%&4'-('$+14%*%5!32!
Furthermore,!just!as!the!road!network!provides!connectivity!for!people,!the!network!of!33!
roadside!habitats!provides!connectivity!for!woodland!wildlife,!allowing!them!to!move!through!34!
otherwise!fragmented!landscapes!(e.g.!Suckling!1984;!Bennett!1990;!Downes!1,&"$5!1997).!The!35!
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ability!to!manage!the!negative!impacts!of!roads!on!wildlife!is,!therefore,!a!critical!component!of!36!
conservation!efforts!for!many!threatened!species.!37!
The$danger$zone$38!
Living!in!roadsides!presents!several!challenges!to!wildlife,!and!thus!to!the!managers!39!
wishing!to!conserve!them.!There!are!many!ecological!impacts!that!can!make!roadside!habitats!40!
unsuitable!for!some!species!(Forman&1,&"$5!2003;!Donaldson!and!Bennett!2004;!van!der!Ree&1,&41!
"$5!2015).!For!example,!edge!effects,!dust,!noise!and!light!pollution!can!displace!the!more!42!
sensitive!species!(e.g.!Eigenbrod&1,&"$5!2009;!Parris!and!Schneider!2009).!However,!here!I!focus!43!
on!two!main!impacts!of!roads!on!species!that!live!within!roadside!habitats:!the!mortality!(road!44!
kill)!and!barrier!effects.!!45!
The!most!obvious,!and!distressing,!impact!is!roadkill.!Common!mammal!victims!on!46!
Australian!roads!include!kangaroos,!wallabies,!wombats,!echidna,!koalas,!bandicoots!and!47!
possums!(e.g.!Coulson!1982,!1997;!Dique&1,&"$5!2003;!Taylor!and!Goldingay!2004;!Russell&1,&"$5!48!
2009;!Bond!and!Jones!2014).!McCall!1,&"$5&(2010)!showed!that!the!survival!rate!of!Squirrel!49!
Gliders!living!adjacent!to!the!Hume!Freeway!was!approximately!60%!lower!than!populations!50!
living!more!than!5!km!away.!Roadkill!has!also!been!implicated!in!the!population!decline!of!the!51!
Swamp!Wallaby!6"$$"7*"&7*+'$'-!in!Royal!National!Park,!NSW!(Ramp!and!Ben-Ami!2006),!and!52!
the!Eastern!Quoll!8"%93-3%&:*:1--*43%,!and!Tasmanian!Devil!;"-+'2/*$3%&/"--*%**!after!a!road!53!
upgrade!in!Tasmania!(Jones!2000).!!54!
Roads!also!create!barriers!to!movement,!restricting!access!to!resources!and!reducing!55!
dispersal!and!gene!flow!(Shepard&1,&"$5!2008;!Holderegger!and!Di!Giulio!2010).!Arboreal!56!
mammals!are!particularly!vulnerable!to!the!barrier!effect!of!roads,!with!larger!roads!such!as!the!57!
Hume!Freeway!and!Goulburn!Valley!Highway!proven!to!restrict!the!movement!of!Common!58!
Brushtail!Possums!(Gulle!2006)!and!Squirrel!Gliders!(van!der!Ree!2006;!van!der!Ree&1,&"$5!59!
2010).!Studies!from!Queensland!show!that!even!narrow!roads!can!be!barriers!for!smaller!60!
mammal!species!(e.g.!Burnett!1992;!Goosem!2001).!!Ultimately!a!road!can!be!a!tipping!point!in!61!
already!vulnerable!populations,!where!the!loss!of!even!a!few!individuals!through!roadkill,!or!the!62!
creation!of!barriers!that!restrict!gene!flow!and!access!to!patchy!resources!can!lead!to!rapid!63!
population!declines!(Bennett!1991;!Forman!1,&"$5!2003;!Coffin!2007).!!64!
Managing$the$risks$to$wildlife$65!
Given!the!extent!of!land!already!affected!by!roads,!we!need!methods!that!effectively!66!
mitigate!their!negative!effects!on!wildlife.!Wildlife!fencing!can!reduce!rates!of!roadkill!by!67!
keeping!animals!off!the!road.!However!fences!can!make!the!'barrier!effect'!of!roads!worse!by!68!
further!restricting!animal!movements,!and!are!detrimental!when!species!persistence!depends!69!
on!movement!among!multiple!patches!of!habitat!(Jaeger!and!Fahrig!2004).!Wildlife!crossing!70!
structures!can!allow!safe!passage!across!roads!to!improve!habitat!connectivity,!and,!when!used!71!
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in!conjunction!with!fencing,!they!can!simultaneously!reduce!roadkill.!There!are!many!different!72!
types!of!crossing!structures,!but!they!generally!fall!into!two!categories:!those!that!allow!animals!73!
to!move!over!the!road!(e.g.!rope!bridges,!land!bridges,!overpasses),!and!those!that!allow!animals!74!
to!move!under!the!road!(e.g.!culverts,!tunnels,!creek-crossings).!While!crossing!structures!are!75!
more!common!in!Europe!and!North!America!(van!der!Ree&1,&"$5!2007,!van!der!Ree!1,&"$5!2008),!76!
road!agencies!in!Australia!are!increasingly!including!crossing!structures!in!road!projects!(e.g.!77!
Taylor!and!Goldingay!2003;!Bond!and!Jones!2008;!Goldingay&1,&"$5!2013).!In!Victoria,!wildlife!78!
crossing!structures!have!predominantly!been!constructed!on!major!roads!such!as!the!Hume!79!
Freeway,!Calder!Freeway,!Princes!Highway!and!Peninsula!Link!(Abson!and!Lawrence!2003;!van!80!
der!Ree!1,&"$5!2008;!Soanes&1,&"$5!2013;!Soanes&1,&"$5!2015).!!81!
One!of!the!most!famous!structures!in!Victoria!is!the!aptly-named!'Tunnel!of!Love',!at!the!82!
Mount!Hotham!Ski!Resort.!A!long-term!population!study!of!the!critically!endangered!Mountain!83!
Pygmy!Possum!<3--"#9%&2"-:3%=!revealed!that!the!Great!Alpine!Road!bisected!important!84!
habitat!patches!(Mansergh!and!Scotts!1989).!This!barrier!disrupted!the!social!organisation!of!85!
the!local!population,!restricting!dispersal!in!males!and!reducing!over-winter!survival!in!females.!86!
Two!tunnels!(0.9!x!1.2!m!cross!section)!were!constructed!in!1985!through!the!rock!scree!under!87!
the!road!in!1985!to!restore!connectivity.!Ongoing!research!showed!that!Mountain!Pygmy!88!
Possums!used!the!tunnels,!and!that!dispersal!and!over-winter!survival!rates!recovered!89!
(Mansergh!and!Scotts!1989).!This!information!was!later!used!in!a!population!viability!analysis,!90!
which!suggested!that!while!the!crossing!structure!improved!the!viability!of!the!Mountain!Pygmy!91!
Possum,!the!negative!effect!of!the!road!may!have!been!only!partially!mitigated!(van!der!Ree&1,&92!
"$5!2009).!!93!
Larger!underpasses!can!cater!for!a!wide!variety!of!species.!When!the!Black!Forest!94!
section!of!the!Calder!Freeway!was!upgraded!in!1997,!VicRoads!included!a!large!wildlife!95!
underpass!to!provide!connectivity!between!forest!patches!that!were!bisected!by!the!road.!The!96!
open-span!bridge!was!built!as!an!extended!creek!crossing,!long!enough!to!allow!both!the!creek!97!
and!the!surrounding!riparian!vegetation!to!pass!under!the!road.!The!structure!was!monitored!98!
five!years!after!it!was!built,!and!researchers!detected!several!mammal!species!using!the!99!
underpass!including!microbats,!koalas,!wombats,!echidna,!possums,!gliders!and!macropods!100!
(Abson!and!Lawrence!2003).!A!recent!review!showed!that!these!open-span!bridges!are!an!101!
effective!way!to!maintain!connectivity!across!roads!for!multiple!species!(Lesbarreres!and!Fahrig!102!
2012).!!103!
Aerial!crossing!structures,!rope!bridges!and!glider!poles,!were!used!to!reduce!the!impact!104!
of!the!Hume!Freeway!in!north-east!Victoria!on!arboreal!mammals.!A!before-after!research!105!
project!was!established!to!test!their!effectiveness,!focusing!on!the!ability!to!restore!movement!106!
and!gene!flow!in!Squirrel!Glider!populations.!Initial!studies!set!out!to!measure!the!effect!of!the!107!
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four-lane!divided!highway!on!Squirrel!Gliders!before!crossing!structures!were!installed.!108!
Researchers!found!that!where!the!gap!across!the!freeway!was!wider!than!50!m,!Squirrel!Gliders!109!
were!largely!unable!to!cross;!however,!where!tall!trees!had!been!left!in!the!roadsides!and!centre!110!
medians!(referred!to!as!‘vegetated!medians’),!the!animals!could!cross!freely!(van!der!Ree!1,&"$5&111!
2010).!Rope!bridges!and!glider!poles!were!then!retrofitted!to!the!freeway!in!July!2007!at!five!112!
sites!where!the!barrier!effect!occurred!(Figure!3).!Motion-triggered!cameras!detected!five!113!
species!of!arboreal!mammal!using!the!structures!to!cross!the!freeway,!including!the!Squirrel!114!
Glider,!Sugar!Glider,!Brush-tailed!Phascogale,!Common!Brushtail!Possum!and!Common!Ringtail!115!
Possum!(Soanes&1,&"$5!2013;!Soanes&1,&"$5!2015).!Further!radiotracking!and!genetic!research!was!116!
conducted!after!the!crossing!structures!were!installed,!and!revealed!that!rope!bridges,!glider!117!
poles!and!vegetated!medians!all!facilitated!movement!and!gene!flow!across!the!Hume!Freeway!118!
and!that!this!would!not!have!occurred!had!crossing!structures!not!been!present!(Soanes!2014).!119!
There!are!other!methods!to!reduce!the!effects!of!roads!on!wildlife,!such!as!those!120!
designed!to!alter!driver!behaviour!(e.g.!warning!signs),!or!repel!animals!from!the!road!(e.g.!121!
reflectors!or!ultrasonic!warnings).!Unfortunately!the!research!to-date!shows!that!these!are!122!
largely!unsuccessful!(Bender!2003;!Ramp!and!Croft!2006;!Bond!and!Jones!2014).!Methods!that!123!
force!drivers!to!slow!down!(e.g.!reduced!speed!limits,!pinch!points!and!rumble!strips)!have!been!124!
shown!to!be!effective!at!reducing!roadkill!in!'hot!spots'!(Jones!2000),!but!can!be!difficult!(and!125!
unpopular)!to!implement!over!large!areas.!A!potentially!promising!method!is!an!automatic-126!
warning!system,!designed!with!flashing!lights!that!warn!drivers!only!when!an!animal!is!127!
approaching!the!road!(Huijser!and!McGowan!2003;!Bond!and!Jones!2014).!128!
Opportunities$and$challenges$for$research$and$conservation$in$Victoria$129!
The!importance!of!managing!wildlife!in!linear!habitats!along!roads,!railways!and!other!130!
infrastructure!is!increasingly!being!recognised!in!Australia!and!worldwide!(Gilbert!1998;!131!
Carthew!1,&"$5!2013;!van!der!Ree&1,&"$5!2015).!Mammals!are!not!the!only!species!to!benefit!from!132!
roadside!habitats.!Roadside!vegetation!provides!critical!habitat!for!woodland!birds!(e.g.!133!
Robinson!2006),!reptiles!(e.g.!Brown!1,&"$5!2008;!Jellinek!1,&"$.!2014)!and!insects!(e.g.!Major!1,&134!
"$.!1999).!Victorian!roads!therefore!represent!a!great!opportunity!for!the!conservation!of!native!135!
mammals!and!other!fauna.!!136!
The!conservation!value!of!roadsides!will!depend!on!our!ability!to!manage!potential!137!
conflicts.!The!safety!risk!posed!to!drivers,!risk!of!bushfire!and!spread!of!invasive!species!are!all!138!
serious!issues!that!must!be!considered,!but!ones!that!can!be!controlled!through!appropriate!139!
management,!such!as!barrier!fencing!and!weed!control!(Gilbert!1998).!Roadside!habitats!are!140!
also!vulnerable!to!being!incrementally!chipped!away!as!roads!are!upgraded!to!accommodate!141!
higher!traffic!volumes.!For!example,!during!the!last!50!years,!rural!highways!such!as!the!Hume,!142!
Western!and!Calder!have!been!progressively!widened!to!create!four-lane!freeways.!However,!143!
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road!upgrades!do!not!necessarily!have!to!lead!to!the!loss!of!roadside!vegetation.!!144!
Environmentally-sensitive!road!designs,!such!as!the!creation!of!wide!medians!to!retain!145!
woodland!vegetation!and!alignment!of!road!corridors!to!avoid!remnant!patches,!can!help!146!
minimise!vegetation!loss,!and!are!particularly!important!in!landscapes!that!are!otherwise!147!
devoid!of!natural!vegetation.!Without!formal!protection!and!considered!planning!the!extent!and!148!
quality!of!roadside!habitats!for!wildlife!can!rapidly!decline.!!149!
Wildlife!crossing!structures!are!a!promising!tool!for!managing!the!negative!impacts!of!150!
roads,!not!only!for!woodland!mammals!but!also!for!a!range!of!other!wildlife!(van!der!Ree&1,&"$5!151!
2007;!van!der!Ree&1,&"$5!2015).!However,!a!practical!challenge!to!increasing!the!number!of!152!
wildlife!crossing!structures!in!Victoria!is!that!it!would!require!retrofitting!structures!to!existing!153!
roads,!a!process!that!can!be!difficult,!disruptive!and!costly.!One!option!is!to!take!the!opportunity!154!
to!include!wildlife!crossing!structures!and!other!mitigation!measures!in!future!road!upgrades,!155!
thus!minimising!the!cost!and!disruption.!Another!possibility!is!to!modify!existing!structures!that!156!
were!not!specifically!designed!for!wildlife,!such!as!drainage!culverts!and!pipes.!For!example,!157!
adding!guide!fencing,!small!ledges!and!‘fauna!furniture’!to!culverts!can!encourage!their!use!by!158!
fauna!while!maintaining!water!flows!(e.g.!Brudin!2003;!Foresman!2003).!159!
There!are!clear!opportunities!for!further!road!ecology!research!in!Victoria.!For!instance,!160!
there!are!surprisingly!few!published!studies!of!roadkill!on!Victorian!roads!(although!I!suspect!161!
that!many!useful!datasets!are!hidden!within!the!‘grey!literature’).!Research!that!combines!data!162!
from!roadkill!studies,!insurance!reports!and!wildlife!rescue!groups!would!help!provide!a!better!163!
understanding!of!the!extent!of!the!roadkill!problem!in!Victoria.!For!example,!identifying!164!
hotspots,!the!relative!risk!for!each!species,!and!the!degree!to!which!roadkill!depletes!the!165!
surrounding!population!are!important!gaps!in!the!current!knowledge.!There!is!still!work!to!be!166!
done!to!quantify!the!value!of!roadside!habitats!to!wildlife!populations.!Studies!that!assess!the!167!
ability!of!wildlife!populations!to!persist!in!roadside!habitats!are!needed!to!guide!effective!168!
management!and!mitigation.!Can!a!network!of!roadside!reserves!support!viable!populations!in!169!
the!long-term?!Do!species!use!roadsides!as!permanent!habitats!(home!range),!supplementary!170!
resources!(feeding!on!grasses!etc.),!or!simply!as!movement!corridors?!Finally,!we!need!more!171!
studies!that!test!the!effectiveness!of!mitigation!measures!such!as!wildlife!crossing!structures.!172!
While!it!is!evident!that!animals!will!use!these!structures,!the!next!step!is!to!determine!whether!173!
they!improve!the!population!persistence!within!a!landscape!(van!der!Grift!1,&"$5&2013).!Only!174!
through!careful!research!and!management!will!we!be!able!maximise!the!value!of!roadside!175!
habitats!for!wildlife,!and!continue!to!enjoy!our!scenic!woodland!drives.!!176!
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References$180!
$181!
Abson!R!and!Lawrence!RE!(2003)!Monitoring!the!use!of!the!Slaty!Creek!wildlife!underpass,!182!
Calder!Freeway,!Black!Forest,!Macedon,!Victoria,!Australia.!In:!.-'+11>*40%&'(&,/1&?4,1-4",*'4"$&183!
@'4(1-14+1&'4&A+'$'09&"4>&B-"4%2'-,",*'4!(Eds!C!L!Irwin,!D!Nelson,!and!K!P!McDermott)!pp!423-184!
431!(Center!for!Transportation!and!The!Environment,!North!Carolina!State!University,!Raleigh,!185!
NC).!186!
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Australian!Bureau!of!Statistics.!Motor!vehicle!census.!Accessed!23/8/2015!188!
http://wwwabsgovau/ausstats/abs@nsf/mf/93090!!189!
!190!
Austroads!(2003)!C'">&D"+,%&EFFF&GH*,/&EFFI&32>",1J5!Austroads!Incorporated!(Sydney,!191!
Australia)!192!
!193!
Bender!H!(2003)!Deterrence!of!kangaroos!from!agricultural!areas!using!ultrasonic!frequencies:!194!
efficacy!of!a!commercial!device.!6*$>$*(1&;'+*1,9&<3$$1,*4!31,!10371046.!195!
!196!
Bennett!AF!(1990)!Habitat!corridors!and!the!conservation!of!small!mammals!in!a!fragmented!197!
forest!environment.!K"4>%+"21&A+'$'09!4,!109122.!198!
!199!
Bennett!AF!(1988)!Roadside!vegetation:!a!habitat!for!mammals!at!Naringal,!south-200!
western!Victoria.!B/1&)*+,'-*"4&L",3-"$*%,!105,!106113.!201!
!202!
Bennett!AF!(1991)!Roads,!roadsides!and!wildlife!conservation:!a!review.!In!L",3-1&203!
@'4%1-:",*'4&EM&B/1&C'$1&'(&@'--*>'-%!(Saunders,!D.A.!and!Hobbs,!J.H.,!eds),!pp.!99118,!204!
Surrey!Beatty!and!Sons.!205!
!206!
Bond!AR!and!Jones!DN!(2008)!Temporal!trends!in!use!of!fauna-friendly!underpasses!and!207!
overpasses.!6*$>$*(1&C1%1"-+/!35,!103112.!208!
!209!
Bond!AR!and!Jones!DN!(2014)!Roads!and!macropods:!Interactions!and!implications.!N3%,-"$*"4&210!
!"##"$'09!36,!114.!211!
!212!
Brown!GW,!Bennett!AF!and!Potts!JM!(2008)!Regional!faunal!decline!-!reptile!occurrence!in!213!
fragmented!rural!landscapes!of!south-eastern!Australia.!6*$>$*(1&C1%1"-+/!35,!818.!214!
!215!
Brudin!CO!(2003)!Wildlife!use!of!existing!culverts!and!bridges!in!north!central!Pennsylvania.!In:!216!
.-'+11>*40%&'(&,/1&?4,1-4",*'4"$&@'4(1-14+1&'4&A+'$'09&"4>&B-"4%2'-,",*'4!(Eds!C!L!Irwin,!D!217!
Nelson,!and!K!P!McDermott)!pp!344352!(Center!for!Transportation!and!The!Environment,!218!
North!Carolina!State!University,!Raleigh,!NC).!219!
!220!
Burnett!SE!(1992)!Effects!of!a!rainforest!road!on!movements!of!small!mammals:!mechanisms!221!
and!implications.!6*$>$*(1&C1%1"-+/!19,!95104.!222!
!223!
Carthew!SM,!Garrett!LA!and!Ruykys!L!(2013)!Roadside!vegetation!can!provide!valuable!habitat!224!
for!small,!terrestrial!fauna!in!South!Australia.!<*'>*:1-%*,9&"4>&@'4%1-:",*'4!22,!737754.!225!
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Coffin!AW!(2007)!From!roadkill!to!road!ecology:!A!review!of!the!ecological!effects!of!roads.!227!
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B-"4%2'-,",*'4!(Eds!C!L!Irwin,!D!Nelson,!and!K!P!McDermott)!pp!368382!(Center!for!275!
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8!
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!1"%3-1%&3%1>&,'&>1"$&H*,/&,/1&?%%31&'(&U"7*,",&D-"0#14,",*'4&79&!"V'-&K*41"-&?4(-"%,-3+,3-1,!361!
Report!for!Department!of!Environment,!Water,!Heritage!and!the!Arts!(DEWHA).!362!
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population!viability,!A+'$'09&"4>&;'+*1,9!14.$365!
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van!der!Ree!R,!Cesarini!S,!Sunnucks!P,!Moore!JL!and!Taylor!AC!(2010)!Large!gaps!in!canopy!367!
reduce!road!crossing!by!a!gliding!mammal.!A+'$'09&"4>&;'+*1,9!15$[online].!368!
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van!der!Ree!R,!Smith!DJ!and!Grilo!C!(2015)!U"4>7''Q&'(&-'">&A+'$'095&(Wiley!Blackwell:!370!
London).!371!
!372!
!373!
!374!
!375!
!376!
!377!
!378!
!379!
!380!
!381!
!382!
!383!
!384!
!385!
!386!
!387!
!388!
!389!
!390!
!391!
!392!
!393!
!394!
!
10!
List$of$figures$395!
$396!
$397!
Figure$1$Map!of!roadless!areas!in!south-east!Australia!Green!indicates!locations!more!than!1!398!
km!from!the!nearest!road!Source:!Google!Earth!Engine,!Global!Roadless!Area!1km!buffer!399!
Accessed!20th!August,!2015$400!
$401!
$402!
$403!
Figure$2$Fragmented!remnant!habitat!for!squirrel!gliders!in!south-eastern!Australia!mostly!404!
occurs!as!linear!strips!along!roadsides!and!waterways!(Google!Earth!image!date!14/1/2014)!!405!
$406!
$407!
!
11!
$408!
Figure$3$Canopy!bridge!(a,c)!and!glider!pole!(b,d)!installed!along!the!Hume!Freeway!in!409!
northeast!Victoria!From!Soanes!1,&"$5!(2013)$$410!
!411!
... Roads provide foraging areas and reduce predation pressures for some species [6]. Urban development reduces the available habitat and therefore roadside vegetation provides a significant proportion of suitable habitat in modified landscapes [11]. Animals that frequently cross roads to gain access to resources have an increased risk of road mortality. ...
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Background: Roads have major ecological impacts on wildlife. Vehicle collisions most frequently impact large herbivores due to their larger home range compared to smaller animals, and higher population density compared to carnivores. Kangaroos (Macropus spp.) account for a large proportion of reported wildlife vehicle collisions that occur in N S W, Australia. We aimed to evaluate what influenced road mortality of eastern grey kangaroos (Macropus giganteus) in a temperate rural/suburban region. The location of roadkilled kangaroos found on or near two 1 km stretches of road in Richmond NSW was recorded throughout 2014 and 2015. Weather and moon phase data were recorded for the date of each roadkilled kangaroo. Transects were setup on both roads, and multiple road and landscape features, including the width of roadside, fence construction, habitat type, and distance from street lights measured at 50 m intervals. Data were analyzed to explore which landscape features and temporal factors influenced the occurrence of a roadkill hotspot. Results: More kangaroo road mortalities occurred during periods of low temperature and low rainfall, and these factors are likely to affect forage quality. Fewer mortalities occurred when rain was falling. A greater number of mortalities occurred during the waning gibbous phase of the lunar cycle. Significantly more road mortalities occurred a short distance from the end of a section of street lights. Conclusions: The findings suggest that illumination influences the likelihood of kangaroo road mortalities. Large herbivores are particularly sensitive to habitat fragmentation because they need unrestricted access to large continuous habitat. Knowledge of factors that influence where and when kangaroos are most likely to cross roads can be used to inform more targeted management strategies and improve future road design and habitat connectivity to reduce the incidence of wildlife vehicle collisions.
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Roads and traffic reduce landscape connectivity and increase rates of mortality for many species of wildlife. Species that glide from tree to tree may be strongly affected by roads and traffic if the size of the gap between trees exceeds their gliding capability. Not only are wide roads likely to reduce crossing rates, but mortality may also be increased if gliders that do cross have poor landing opportunities. The road-crossing behavior of 47 squirrel gliders (Petaurus norfolcensis) was investigated in southeast Australia using radio-tracking. The proportion of gliders crossing one or both roadways of a freeway where trees were present or absent from the center median was compared to that at single-lane country roads (control). The proportion of gliders crossing the road at control sites (77%) was similar to the proportion that crossed one or both roadways at the freeway with trees in the median (67%), whereas only a single male (6%) crossed the freeway where trees were absent from the median. The frequency of crossing for each individual was also similar at control sites and freeway sites with trees in the median. The almost complete lack of crossing at sites where trees were absent from the median was attributed to the wider gap in canopy (50 - 64 m vs. 5 - 13 m at sites with trees in the median). This suggests that traffic volume, up to 5,000 vehicles per day on each roadway, and the other characteristics of the freeway we studied are not in themselves complete deterrents to road crossing by squirrel gliders. This study demonstrates that retaining and facilitating the growth of tall trees in the center median of two-way roads may mitigate the barrier effect of roads on gliders, thus contributing positively to mobility and potentially to connectivity. This information will be essential for the assessment of road impacts on gliding species using population viability models.
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Context: Wildlife crossing structures are installed to mitigate the impacts of roads on animal populations, yet little is known about some aspects of their success. Many studies have monitored the use of structures by wildlife, but studies that also incorporate individual identification methods can offer additional insights into their effectiveness. Aims: We monitored the use of wildlife crossing structures by arboreal marsupials along the Hume Freeway in south-eastern Australia to (1) determine the species using these structures and their frequency of crossing, (2) determine the number and demographic characteristics of individuals crossing, and (3) use the rate of crossing by individuals to infer the types of movement that occurred. Methods: We used motion-triggered cameras to monitor five canopy bridges and 15 glider pole arrays installed at 13 sites along the Hume Freeway. The five canopy bridges were also monitored with passive integrated transponder (PIT)-tag readers to identify the rate of use by individuals. Key results: Five species of arboreal marsupial were detected using canopy bridges and glider poles at 11 sites. Our analysis suggested that increasing the number and the distance between poles in a glider pole array reduced the rate of use by squirrel gliders. The PIT tag and camera footage revealed that the structures were used by adult males, adult females and juveniles, suggesting that all demographic groups are capable of using canopy bridges and glider poles. At two canopy bridges, multiple squirrel gliders and common brushtail possums crossed more than once per night. Conclusions: Given that previous studies have shown that the freeway is a barrier to movement, and that many of the species detected crossing are subject to road mortality, we conclude that canopy bridges and glider poles benefit arboreal marsupials by providing safe access to resources that would otherwise be inaccessible. Implications: Although the factors influencing crossing rate require further study, our analysis suggests that glider pole arrays with fewer poles placed closer together are likely to be more successful for squirrel gliders. The individual identification methods applied here offer insights that are not possible from measuring the rate of use alone and should be adopted in future monitoring studies.
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Roadside habitats are important for a range of taxa including plants, insects, mammals, and birds, particularly in developed countries in which large expanses of native vegetation have been cleared for agriculture or urban development. Although roadside vegetation may provide suitable habitat for many species, resident animals can be exposed to high levels of traffic noise, visual disturbance from passing vehicles, and the risk of collision with cars and trucks. Traffic noise can reduce the distance over which acoustic signals such as song can be detected, an effect known as acoustic interference or masking. Studies from the northern hemisphere show that the singing behavior of birds changes in the presence of traffic noise. We investigated the impact of traffic noise and traffic volume on two species of birds, the Grey Shrike-thrush (Colluricincla harmonica) and the Grey Fantail (Rhipidura fuliginosa), at 58 roadside sites on the Mornington Peninsula, southeastern Australia. The lower singing Grey Shrike-thrush sang at a higher frequency in the presence of traffic noise, with a predicted increase in dominant frequency of 5.8 Hz/dB of traffic noise, and a total effect size of 209 Hz. In contrast, the higher singing Grey Fantail did not appear to change its song in traffic noise. The probability of detecting each species on a visit to a site declined substantially with increasing traffic noise and traffic volume, with several lines of evidence supporting a larger effect of traffic noise. Traffic noise could hamper detection of song by conspecifics, making it more difficult for birds to establish and maintain territories, attract mates and maintain pair bonds, and possibly leading to reduced breeding success in noisy roadside habitats. Closing key roads during the breeding season is a potential, but untested, management strategy to protect threatened bird species from traffic noise and collision with vehicles at the time of year when they are most vulnerable to their impacts. Other management options include reducing the speed and/or volume of traffic on such roads to an acceptably low level. Ours is the first study to investigate the effect of traffic noise on the singing behavior of birds in the southern hemisphere.
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Global road length, number of vehicles and rate of per capita travel are high and predicted to increase significantly over the next few decades.2The ‘road-effect zone’ is a useful conceptual framework to quantify the negative ecological and environmental impacts of roads and traffic.3The effects of roads and traffic on wildlife are numerous, varied and typically deleterious.4The density and configuration of road networks are important considerations in road planning.5The costs to society of wildlife-vehicle collisions can be high.6The strategies of avoidance, minimisation, mitigation and offsetting are increasingly being adopted around the world – but it must be recognised that some impacts are unavoidable and unmitigable.7Road ecology is an applied science which underpins the quantification and mitigation of road impacts.
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Road reserves provide habitat for wildlife. Roadside vegetation has greatest value as a wildlife habitat when it comprises remnant or regenerated strips of indigenous vegetation. Road, roadside habitats and the aerial space above roads can facilitate the movement of animals along the direction of the road reserve. Road reserves can act as a filter or barrier to the movements of wildlife through the landscape, thus dividing and isolating populations to varying extents. Roads are a source of mortality for wildlife. For some species, particularly those that are large, rare, or are regularly brought into contact with busy roads, road-kills can have a significant effect on conservation status. Road systems are a source of biotic and abiotic effects on the surrounding landscape. -from Author
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Artificial structures designed to promote road-crossing by arboreal mammals are increasingly being installed in Australia but there is a limited understanding of their usefulness. We studied five 50-70-m-long rope-bridges (encompassing three designs) erected across the Pacific Highway, a major freeway in eastern Australia. Native arboreal mammals showed a willingness to explore these structures, being detected by camera traps on four rope-bridges. The vulnerable squirrel glider (Petaurus norfolcensis) crossed on one rope-bridge at least once every 4.5 weeks over a 32-week period. The feathertail glider (Acrobates pygmaeus), common ringtail possum (Pseudocheirus peregrinus) and the common brushtail possum (Trichosurus vulpecula) were detected on one of two rope-bridges that extended under the freeway at creek crossings. The feathertail glider was detected on all three rope-bridge designs. Our results suggest that rope-bridges have the potential to restore habitat connectivity disrupted by roads for some arboreal mammals. Further research is needed to refine the design and placement of rope-bridges as well as to determine whether these structures promote gene flow.
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We demonstrate that the social organization and survival rates of the mountain pygmy-possum (Burramys parvus), a rare Australian marsupial, had been disrupted because its habitat had been fragmented by roads and other developments within a ski resort. We restored habitat continuity by constructing a corridor leading to 2 tunnels beneath a road that bisected the breeding area. The corridor and tunnels were filled with rocks that imitated the natural habitat of scree. These constructions allowed males to disperse from the female breeding areas; such dispersal is an essential element in the species social organization. After construction the population structure and survival rates in the disturbed area changed to those observed in the undisturbed area. Our results indicate that wildlife managers should consider that dispersal of individuals plays an important role in the social structure of wildlife populations and corridors and tunnels are strategies available for management of wildlife populations in habitats fragmented by roads and other man-made stuctures.
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Along a narrow, unsealed road through rainforest in north-eastern Queensland, movements of small mammals were examined to determine whether the road would inhibit road crossings, thereby causing linear barrier effects. Crossings of a 12- or 20-m-wide road clearing by Melomys cervinipes were severely inhibited, crossing inhibition of Rattus sp. was less severe, while crossings by Uromys caudimaculatus were unaffected. This differential effect was attributed to species differences in size, mobility and behaviour. Baiting on only one side of the road increased crossing rates for all species. During the breeding season, crossings of 20-m clearings by Rattus sp. were almost completely inhibited and were significantly fewer than crossings of 12-m clearings. Clearing width had little effect on crossing rate outside the breeding season. Seasonal dispersal of juvenile and breeding animals appeared to explain this discrepancy in clearing-width effects. Rattus sp. were significantly less likely to cross a road where there was no vegetative cover at the entrance to a road culvert than where there was cover at both culvert entrances. Linear barrier effects for small mammals may be mitigated by narrower road-clearing widths, by replanting of grassy road verges resulting in increased cover at culvert entrances and canopy closure above the road, and by providing more faunal underpasses.
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The impact of road mortality on local populations of wildlife has rarely been quantified. In June 1991, the access road into the northern end of the Cradle Mountain – Lake St Clair National Park in Tasmania was widened and sealed. This occurred part-way through an ecological study of the dasyurid carnivore guild, during which populations were being monitored. In 17 months, the resident population of 19 eastern quolls became extinct and the devil population, of 39 individuals, halved. Concurrently, there was a dramatic increase in the number of road-kills. The main causal factor was probably an increase in modal speed of about 20 km h–1 and a greater increase in maximum speed. Measures were implemented to reduce the incidence of vehicle/wildlife collisions. Measures directed at people included physically slowing traffic speed (using ‘slow points’) and increasing driver awareness (signs and pamphlets). Those directed at wildlife included deterring wildlife from crossing the road in the path of approaching vehicles (wildlife reflectors), and encouraging escape off the road (ramps across gutters and banks, and pipes for shelter). The ‘slow points’ were effective in reducing vehicle speeds by 20 km h–1. Wildlife used the ramps and pipes. The eastern quoll population was re-establishing within six months, and after two years, had recovered to 50% of its former level. There was some indication that devil populations were recovering.