TheinvasionofArgentinabytheEuropeanwildrabbit
Oryctolaguscuniculus
NEVER BONINO* and RAMÓN SORIGUER†
*EstaciónExperimental Bariloche(INTA),C.C.277,8400Bariloche,Argentina,†Estación
BiológicaDoñana(CSIC), Av.MaríaLuisas/n,41013Sevilla,España
ABSTRACT
1. Weprovideanupdated distributionanddispersalrateoftheintroduced Europeanrabbit
OryctolaguscuniculusinArgentina.
2. According toour results thisinvasivespeciesiscurrently colonizingparts ofMendoza andNeuquén Provinces,whereriversareveryimportantinthespreadoftherabbits, espe- ciallyinunfavourableareas. The maximun rate ofdispersal registered inthis study was
9km/year.
3. Some informationwas obtained to indicate that the presence of this exotic species threatens agriculture, livestock,forestry,andnaturalecosystemsofthePatagoniaregion.
Keywords: biological invasions, dispersal, exotic species, invasive species, Oryctolagus cuniculus
INTRODUCTION
Invasivespeciesareaglobalproblem, affectingagriculture, forestry,fisheries,human health and naturalecosystems (Mooney Drake, 1986;Drake etal.,1989;Sandland,Schei& Viken,1999;Macketal.,2000;Pimentel,2002).
The Europeanwildrabbit Oryctolagus cuniculusisone ofthe most widelydistributed invasive species(Flux Fullagar,1992)and provides one of the best examples of the disastrousconsequencesthatcanresultfromtheintroductionofanexoticspecies(Thompson
King,1994;Williamsetal.,1995;Bomford Hart, 2002;Clout,2002).
Aspeciesnativetosouth-western Europe, theEuropeanrabbit hasbeenintroduced into differentregionsoftheworldincludingAsia,Australia, NewZealandandNorthandSouth America(Flux,1994).Onthislastcontinent, rabbits wereintroduced intoseveralregionsof Chile,from whichtheyinvaded thesouth-western part ofArgentina (Howard Amaya,
1975;Zunino, 1989).InArgentina, therabbits arenowpresentinthreeregions(Fig.1).
1. TierradelFuego–Falkland(Malvinas)Islands
AccordingtoJaksicYáñez(1983),thefirstintroductiontoTierradelFuegowasmadein about1880ontoanumberofislandsin theBeagleChannel.Theoriginalstockcamefromthe Falkland(Malvinas)Islands,ontowhichrabbitshadbeenintroduced bytheFrenchpriorto
1765.SomeoftheseChannelislandrabbitsweresetfreeinabout1936ontheChileansideof
TierradelFuego.Inaround1950 morerabbits werereleasedontheArgentiniansideofthis
Correspondence:N.A.Bonino.E-mail:
Fig.1. Current distributionoftheEuropeanwildrabbit inSouthAmerica.Thedarkgreyareamarksthe rangeinChile;thelightgreyareatherangeinArgentina. 1= TierradelFuegoandFalkland(Malvinas) Islands,2= SantaCruzProvince,3= Mendoza andNeuquén Provinces.
island(Arentsen, 1954).Within afewyearstheseintroductionsproved disastrous: rabbits quicklybecameapest,riddlingthegroundwithholesandleavingitbareofgrass.Thesheep ranchers attempted tocontroltherabbits firstbyhunting andtrapping, thenbyintroducing themainland foxPseudalopexgriseus,whichdidnotnaturally occuronTierra delFuego.
Latertheybrought myxomavirusfromBrazil,andthisvirussucceededinbringingrabbitsto verylowpopulationlevels (JaksicYáñez,1983).
2. SantaCruzProvince
In1985rabbits weredetectedatthesouth-western edgeofthisprovince(ClarkeAmaya,
1986).PresumablytheyhadcomefromnearbyPuertoNatales(Chile),whereseveralanimals (apparentlyoriginating from Tierra delFuego) werereleasedin1970(A.Iriarte Walton, personal communication).These rabbits have apparentlynot dispersed widely, as their current distributionisstillrestricted tothesouth-western partofthisprovince.
3. MendozaandNeuquénProvinces
In1945rabbits werefirstreported intheseprovinces. Theyoriginated from animals that crossedthrough lowpassesintheAndean Cordillera fromadjacent parts ofcentral Chile. ThesecentralChileanrabbitsareofSpanishoriginandhadbeenintroduced atthebeginning ofthe19thcentury(Greer,1965;Howard Amaya,1975).Withinthesetwoprovinces,the rabbit iscurrently dispersing and invading newareas (Bonino Gader, 1987;Bonino & Soriguer,2004).
Afundamentalapproachtounderstandingandmanaging invasivespeciesistodetermine theirgeographical distribution.ThecurrentdistributionoftheEuropeanrabbitinMendoza andNeuquén Provincesandtheirdispersalratearereported here.
MATERIALS AND METHODS
ThedistributionoftheEuropeanrabbit inMendoza ProvincewasdescribedbyBonino & Soriguer(2004).InNeuquén Provinceweperformed fieldsamplingonthebasisofthemap ofrabbit distributionin1986(BoninoGader, 1987).Forthepresentsurveys,undertaken betweenNovember2006andApril2008,theruralinhabitantsoftheperimeterofthemapped distributionareawerevisited.Weaskedthemaboutthepresenceorabsenceofrabbitsinthe surroundingarea.Atthesametimewedirectlysurveyedtheland,searchingforsightingsor signsofindividuals suchasfaeces,burrows andskeletons.Alltheinformationwasgeoref- erencedbyusingaGPSunit.Afterward,thisinformationwasenteredintoadigitalizedmap inorder to determine the current geographical distributionand the dispersal rate ofthis invasivespecies.
RESULTS AND DISCUSSION
Intheeastern sectorofthedistributionalarea inNeuquén Province, weobserved thedis- persalofthisspecies mainlyalongthebanksofriversthatflowthrough theregion,generally fromeasttowest(Fig.2).According toBonino Gader (1987)thefront oftheadvance alongtheColoradoRiverhadprogressedtoabout20kmeastofRincóndelosSauces.Inthis study, Rincón Colorado(37°33′45″S,68°23″32″W)wastheeasternmostsitewhererabbits wereobserved alongthemargins ofthisriver(Fig.2).According toinformationfromthe localinhabitants, thisexoticspeciescausesdamage,mainlyinorchards andcropsofalfalfa. AlongthemarginsoftheNeuquén River,rabbits werefound atSauzalBonito (Bonino& Gader, 1987) andalsonearthebridgeatDiquePortezuelo (38°26′22″S,68°57′19″W).Previ- ously,rabbits hadbeenlocatedonthePicúnLeufúRivernearthetownofthesamename (BoninoGader, 1987),butinthisstudyweobservedthattheyhadadvanced uptowhere thisriverflowsintotheLimayRiverandhavebeguntodispersebothupstream anddown- stream of this latter river. Also, rabbits were observed in Ojo de Agua (39°38′20″S,
Fig.2. DispersaloftheEuropeanwildrabbitintheMendoza andNeuquén Provinces,Argentina. Thedark greyareashowsthedistributionin1986;thelightgreyarearepresentsdispersalduringthe1986–2008period.
69°29′19″W) and along themargins oftheChina Muerta stream, another affluent ofthe
LimayRiver(Fig.2).Ineachcasethedispersalratewaslessthan 5km/year.
Inthesouthernpartofthedistributionalarea(Fig.2),thelimitwasattheEstanciaPulmarí
(39°06′41″S,71°06′32″W)accordingtoBoninoGader(1987).However,inthisstudyrabbits
were detected about 175km further south, in the surroundingsof the Meliquina Lake (40°22′39″S,71°18′89″W).Also,atasite(40°21′36″S,70°39′22″W)locatedontheleftmargin oftheCollonCuráRiver,afewkilometersbeforeitsentryintotheLimayRiver,faecesand burrowsofrabbitswereobserved.Theserecordsindicateadispersalratethatvariedbetween
6and9km/year.
Figure2showstheimportance ofriversinthespreadofthisinvasivespecies,especiallyin unfavourableareas. Thewesternpart ofthedistributionalareaconsistsofAndean forests andsubandeangrasslands. Theeastern sectorsupports scrubformation(Monte Botanical Province)inasemi-desertenvironmentwithannual rainfallunder 200mm,wheresoilsare stoneyorgravely(Soriano, 1983).Themostirregular distributionalpatternisfoundinthis aridregionwheretherabbits liveinplacesbordering theriversandsmallstreams, asalso happens inthearidhabitats ofAustralia (MyersParker, 1975a,b;Myersetal.,1994).
As wasnoted by Bonino Soriguer (2004)in Mendoza Province, the rabbit isalso currentlyundergoing aprocessofdispersalinNeuquén Province.Theenvironments already colonized inthe western part ofthisprovince are beingoccupied, withalittlevariation, towards thesouthoftheregionasfarasSantaCruzProvince.Therefore, wepredictthatin thefuturethisexoticspecieswillinvadethewholePatagonianregion.
ConsideringthattheareasoccupiedbytherabbitinNeuquénProvinceareveryimportant fortheprovincialeconomy,thesituation mayworsensince,accordingtoinhabitantsofthe region,therabbit competeswithcattleforfoodandcausesconsiderable damage toalfalfa crops,orchards andconiferous forestplantations.Theestablishment oftherabbit insome protected areas(Lanín andLaguna BlancaNationalParks) anditspotential invasion into others(Nahuel Huapi NationalPark) posesathreat forthewildfauna oftheseareas.The presenceofthisexoticherbivore, withitssemi-fossorial habit and highreproductiverate (MyersCalaby,1977),couldharmsomeofthenativespeciesdirectly,through competition forfood and/or shelter, orindirectly, byfavouring increases inthepopulationsofnative carnivores (Novaro,FunesWalker,2000;Novaro Walker,2005).
InAustraliaandNewZealand,therabbitisconsideredanimportantthreattotheintegrity oftheecosystemsofaridzones(BomfordHart,2002;Clout,2002),andtherearenumerous examplesofthenegativeimpactofthisspeciesonthenativefloraandfauna(DawsonEllis,
1979;Leighetal.,1987,1989;LunneyLeary,1988;BurbidgeMacKenzie, 1989;Auld,
1990;Morton,1990;Mutzeetal.,2008).
The maximum rate of dispersal registered inthis study was9km/year, similar to the
10km/yearreported byBoninoGader (1987).Thevaluescitedforothercountries where therabbit wasintroduced arehighlyvariable:inAustralia,dispersalvariedbetween15km/ yearindenser woodlands oftheeastern and southern regionsand 300km/year along the drainage channels inthe Simpson Desert (Strong, 1983;Myers etal.,1994);and inNew Zealand, rabbits spreadatarateof16km/year(GibbWilliams,1994).
Theavailableliterature ondispersalratesofintroduced mammalsindifferentpartsofthe world,although notabundant,isalsovariable:Sciuruscarolinensisachievedarateof7.7km/ yearinsouth-western England(WilliamsonBrown,1986);Ondatrazibethicushadvariable ratesbetween1and25km/year,dependingontheregion,inEurope(Andowetal.,1990;Van deBosch,HengeveldMetz,1992)andbetween3.9and10.8km/yearinChileandArgen- tina(Jaksicetal.,2002);Sigmodonhispidushadanaveragerateof8.8km/yearintheUSA (Genoway Schlitter, 1967);Castorcanadensisdispersedfrom3.1to6.3km/yearinChile andArgentina (Jaksicetal.,2002);andCervuscanadensisandRupicaprarupicapradispersed from0.6to8.7km/year, respectively,inNewZealand (Caughley,1963).Acloserelativeto theEuropeanrabbit, theEuropeanhareLepuseuropaeus,hasdispersedintoSouthAmerica
from10to44km/year, depending onthespecificregionsinvaded (Cossios, 2004;Bonino, CossiosMenegheti, 2008).
Theroleofhuman intervention intheprocessofrabbit dispersalisnotwellunderstood, although itcouldfavoursuchaprocess.Forexample,itisknownthatsometimesanimalsare liberated (intentionallyor not) from domestic (breeding) colonies and this action could facilitatefurther invasionofthisexoticspecies.Somepopulations ofastillstrictlylocal character that arefoundinseveralArgentineprovinces(Chubut,SanJuanandRíoNegro) resultfromliberation ofrabbits byhumans.
CONCLUSIONS
We document a notable increase in the Europeanwild rabbit distributionarea in the PatagoniaregionofArgentina. Therefore,regularandcarefulmonitoringisnecessaryforthe earlydetectionandmanagementofnewlyestablishedpopulations. Europeanrabbits are potentially asignificant threat to agriculture, livestock, forestry and natural ecosystems. Thus,thecontinued studyofthisinvasivespeciesinArgentina iswarranted.Thedevelop- mentofapredictivemodelofthepotential distributionandtheecologicalimpactsofrabbits wouldbeinvaluable.Atpresentthereisnoinformationregardingtheecologicalimpactofthe Europeanrabbitinnaturalecosystems,andscantinformationonotheraspectsofitsbiology andecology,inArgentina (Bonino, 2006).
ACKNOWLEDGEMENTS
Wethank R.D.SageandB.B.Cookeforconstructive commentsonanearlierdraftandtwo anonymousreviewers who provided helpful suggestions. Fieldwork was funded by the Consejo Nacional deInvestigaciones CientíficasyTécnicas(CONICETPIP 937)and the ProgramadeCooperaciónCientíficaconIberoamérica(AECI).
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Submitted 17March2009;returnedforrevision30March2009;revisionaccepted28May2009
Editor:KH