Lessons from long-term predator control: a case study with the red fox

Lessons from long-term predator control a case studywith the red fox

Roger KirkwoodAC Duncan R SutherlandAD Stuart MurphyB and Peter DannA

AResearch Department Phillip Island Nature Parks PO Box 97 Cowes Vic 3922 AustraliaBEnvironment Department Phillip Island Nature Parks PO Box 97 Cowes Vic 3922 AustraliaCPresent address IMARES Wageningen University Research PO Box 167 1790 AD Den Berg TexelThe Netherlands

DCorresponding author Email dsutherlandpenguinsorgau

AbstractContext Predator-control aims to reduce an impact on prey species but efficacy of long-term control is rarely assessed

and the reductions achieved are rarely quantifiedAims We evaluated the changing efficacy of a 58-year-long campaign against red foxes (Vulpes vulpes) on Phillip

Island a 100-km2 inhabited island connected to the Australian mainland via a bridge The campaign aimed to eliminatethe impact of foxes on ground-nesting birds particularly little penguins (Eudyptula minor)

Methods We monitored the success rate of each fox-control technique employed the level of effort invested ifavailable demographics of killed foxes the numbers of penguins killed by foxes and penguin population size

Key results The campaign began as a bounty system that ran for 30 years and was ineffective It transitioned into acoordinated although localised control program from 1980 to 2005 that invested considerable effort but relied onsubjective assessments of success Early during the control period baiting was abandoned for less effective methods thatwere thought to pose fewer risks weremore enjoyable and produced carcasses a tangible result Control was aided by a highlevel of public awareness by restricted fox immigration and by a clear achievable andmeasurable target namely to preventlittle penguin predation by foxes Carcasses did prove valuable for research revealing the genetic structure and shifts in foxdemographics The failure of the program was evident after scientific evaluation of fox population size and ongoing foximpacts In 2006 the campaign evolved into an eradication attempt adopting regular island-wide baiting and since thenhas achieved effective knock-down of foxes and negligible predation on penguins

Conclusions Effective predator control was achieved only after employing a dedicated team and implementing broad-scale baiting Abandoning widespread baiting potentially delayed effective control for 25 years Furthermore bothpredator and prey populations should be monitored concurrently because the relationship between predator abundanceand impact on prey species is not necessarily density dependent

Implications Critical to adopting the best management strategy is evaluating the efficacy of different methodsindependently of personal and public biases and having personnel dedicated solely to the task

Additional keywords eradication Vulpes vulpes wildlife management

Received 18 November 2013 accepted 23 July 2014 published online 26 August 2014

Introduction

Red foxes (Vulpes vulpes) were first introduced from Europeto Australia in 1845 (Abbott 2011) established in the 1870s(Rolls 1969 Abbott 2011) and since the 1880s they have beensubjected to continuing control attempts (Saunders et al 1995)They have contributed to population declines and extinctions ofnative fauna (Dickman 1996 Kinnear et al 2002) and severelyaffected livestock industries (Rowley 1970) The cost of foxesto industry and the environment in 2004 was estimated at AU$227million (McLeod 2004) In Australia red fox control hasbeen attempted by poison baiting hunting (using spotlights ordogs) cage and leg-hold trapping and implementation of

bounty systems that require lsquoproof-of-killrsquo (Saunders andMcLeod 2007) Few control programs empirically monitor theeffect of control at the population level or assess the impact onprey populations Several short-term studies have correlatedreductions in fox sign with immediate increases in preyabundance (Banks et al 1998 Harding et al 2001) althoughstudies that experimentally tested the efficacy of fox control onlivestockproduction found that it hadminimal effect (Mann1968Kinnear et al 1988Greentree et al 2000)Case studies that detaileffort and effect (for example Lokemoen and Woodward 1993Priddel and Wheeler 1997 Kinnear et al 1998) can inform andguide predator-control attempts elsewhere

CSIRO PUBLISHING

Wildlife Research 2014 41 222ndash232httpdxdoiorg101071WR13196

Journal compilation CSIRO 2014 wwwpublishcsiroaujournalswr

Attempts at fox control are hindered by their high breedingproductivity and flexible behaviours (Harris 1979 Lloyd 1980Harris 1981 Cavallini 1996) Foxes readily travel tensof kilometres in a night (Voigt and Macdonald 1984Goszczynski 1989 Adkins and Stott 1998) and can migratefurther to establish in unoccupied territories (Trewhella et al1988) Where fox immigration is restricted control actions tendto have a more lasting effect (Lokemoen and Woodward1993 Ebbert and Byrd 2002 Kinnear et al 2002) Generallyonly sustained and intense control efforts supress fox populations(Heydon et al 2000 Harding et al 2001)

Phillip Island on theVictorian coast in south-easternAustralia(Fig 1) has had resident red foxes since 1907 (Gabriel 1919Glidden 1968) Attempts to control the fox populationcommenced in ~1918 (Gabriel 1919) primarily to protectground-nesting seabirds namely little penguins (Eudyptulaminor) and short-tailed shearwaters (Ardenna tenuirostris)(Norman 1971 Dann 1992) Foxes on Phillip Island aregenetically distinct from those on the adjacent mainland ofAustralia (Lade et al 1996) with an estimated level ofmigration to the island of one fox every 3 years based ongenetic analysis of 480 foxes caught on the island between1994 and 2008 (Berry and Kirkwood 2010) The main accesspoint for migrant foxes is likely to be a 600-m bridge that hasconnected the island to the mainland since 1945

The present paper documents red fox management on PhillipIsland as a case study compares the efficacy of control techniquesand discusses factors that can improve success of pest animal-control campaigns Documenting the evolution of control effortprovides an insight into human aspects of predator-controlcampaigns the ecology of a fox population during intensiveharvesting (also see Berry and Kirkwood 2010) and the efficacyof control as indicated by indices of fox abundance (see also

Rout et al 2014) and reduced impacts on principal beneficiariesincluding the little penguin

Materials and methodsStudy site

Phillip Island comprises 100 km2 of low-lying (max altitude110m) sand and clay soils has a wet-temperate climate (Glidden1968) The island has a resident human population of ~9400(Australian Bureau of Statistics 2013) which is augmented bymore than 50 000 temporary residents during holiday periods(van Polanen Petel et al 2004) Approximately 20 of theisland is urbanised another 20 natural or re-plantedbushland and the remainder cleared for livestock grazingLittle penguins once nested in colonies at 10 sites around theisland During the mid-1900s the penguins at nine sites wereeliminated attributed largely to fox predation but also byroaming dogs and urban developments (Dann 1992) Theremaining colony was the largest of the 10 colonies (Harrisand Bode 1981) it was semi-isolated on SummerlandPeninsula at the western end of the island and it supported atourism venture which meant predator control received somesupport The eastern edge of this colony attracts up to 500 000tourists annually with visitors viewing the lsquoparadersquo of penguinsacross Summerland Beach every night of the year (Dann 1992)

Fox-control periods

Bounty period (before 1984)In 1918 the Phillip Island Shire Council decided to sponsor

two residents to hunt foxes on the island (Gabriel 1919) then in1954 the Council introduced a bounty system for island-caughtfoxes which ran for 30 years

145deg00 E

38deg3

0 S

38deg3

0 S

145deg30 E

20 km

145deg00 E

120deg

ndash20deg

ndash40deg

ndash20deg

ndash40deg

140deg

120deg 140deg

145deg30 E

Fig 1 Location of Phillip Island off the coast of Victoria Australia

Lessons from long-term fox control Wildlife Research 223

Control period (1980ndash2006)A fox-control team was established in the early 1980s after it

was illustrated that foxes could eliminate the penguins if foxeswere not better controlled Gradually data recording improvedwith the inclusion of dates locations and methods that yieldedfoxes as well as indices of effort In the early 2000s the long-running control team dwindled through changes in staff andmanagement priorities

Eradication period (from 2006)The program was resurrected in 2006 with a switch in

objective from control to eradication Two designated fox-control officers were employed and the primary technique thatwas relied on switched from day hunts assisted by dogs to island-wide poison baiting

Killing techniques

Foxes on Phillip Island were killed using three principaltechniques First poison baits consisting of sodiummonofluoroacetate (1080) injected into blocks of deep-fried oxliver or commercial Foxoffreg baits (Animal Control TechnologiesMelbourne Victoria Australia) were buried in two formatsPrior to 2000 during the fox-control period targeted areaswere saturation baited at ~50-m intervals Thereafter duringthe eradication period baits were broadly distributed at morethan 500-m intervals (as in Saunders et al 1995) Secondfoxes were captured with wire snares (up until the early 2000sduring the control period) aswell asVictor lsquoSoft-CatchrsquoNo3 leg-hold traps (Meek et al 1995) then shot throughout the controland eradication periods Occasionally carcasses of seabirds orlambs were dragged through zones of leg-hold traps as luresThird foxes were shot during the day by using dogs to drivethe foxes into the open during the control period as well as atnight with the aid of spot-lights during both the control anderadication periods Secondary techniques that were lessfrequently employed and mostly during the control periodwere poisoning with M44-ejectors that administered 1080 amethod that prevents bait caching (Marks et al 1999 vanPolanen Petel et al 2004) and den control by fumigation withcarbon-monoxide(Den-co-fumeregAnimalControlTechnologies)Several dens were excavated to record their contents includingall dens after 2006 Foxes were also killed occasionally by localfarmers in daylight and accidentally by road traffic

Biological data

All methods except baiting and most instances of den fumigationproduced a carcass from which biological data could becollected Prior to 1994 sex and stomach contents of foxcarcasses were recorded Thereafter body mass and lengthwere measured teeth were collected for age determination andtissue samples (ear trims) were taken for genetic analysisPrevious publications have detailed diet (Kirkwood et al2000 2005) and population genetics (Lade et al 1996 Berryand Kirkwood 2010) We estimated age from annual cementumlayers in the canine and pre-molar teeth (Grue and Jensen 1973Harris 1978 Coman 1988) Lower jaws were removed andboiled to loosen the teeth which were extracted by dentalpliers Teeth were sectioned stained and any growth rings

evident in their cementum were counted under a lightmicroscope (Johnston and Watt 1980) The birth date of allfoxes was assumed to be the first of October whichapproximated the midpoint of a 6-week period when mostcubs were born on Phillip Island (based on measurements offetuses and cubs and observations of denning behaviour)

Indices of foxes killed

Methods that produced carcasses provided an accurate measureof foxes killed by those techniques however baiting and denfumigation were estimated from other evidence Estimates ofthe number of foxes killed during poison baiting on Phillip Islandin the control period (1980ndash2006) were inferred from fox signbefore and after the baiting and the number of baits taken Theaccuracy of this technique cannot be quantified and probablyvaried with the experience of staff During the eradicationperiod (after 2006) it was assumed that ~25 baits taken froman area by a fox represented one fox killed A bait take by foxeswas identified from spoor at sand-pads where baits were buriedSand-pads were checked at least every third day The rate wasadopted on the basis of published ranges of 16ndash30 and 17ndash28(Trewhella et al 1991 Thompson and Fleming 1994) but werecognise that the relationship between fox abundance and baittake may be weak (see Marks et al 2009) The rate accounts formultiple takes by a single fox regurgitation caching withoutreturning to consume the bait and takes by other animals allbeing factors that mean that one bait taken does not equate withone fox killed (Trewhella et al 1991 Thompson and Fleming1994 van Polanen Petel et al 2001)

In den fumigation the number of foxes killed in dens thatwere unexcavated was estimated at the time on the basis of foxprints evident before and after the fumigation Unfortunatelyrecords were not kept of which counts came from recoveredcarcasses in excavated dens and which were estimates forunexcavated dens However it is probable that the number offoxes killed by den fumigation were overestimated

Indices of fox abundance

Data on fox ages revealed a minimum number of foxes known tobe alive (KTBA) on the island each year (pups and adults) Thiswas the sum of those killed in the year plus those killed inlater years andold enough tobe alive in theprecedingyearsThesedata are a minimum because they do not include the proportionof the population that avoided being killed Foxes that died fromconsuming baits were of unknown age so to minimise theirinfluence on population-size estimates we assumed that theywere less than 1-year old But undoubtedly some baited foxeswere older which further attests to the numbers being bareminima Relative indices of fox activity through time included(1) counts of individual foxes per hour spent tracking (recognisedby pad size route and behaviour quantified to the best of thetrackerrsquos ability) (2) foxes sighted per hour of spot-lighting andof dog-hunting and (3) public sightings of foxes

Indices of fox impact

On Phillip Island from the 1980s onwards we monitored relativeabundance and impact of foxes with two measures of numbersof penguins killed by foxes The first method of recording

224 Wildlife Research R Kirkwood et al

penguins killed by foxes involved searches of the penguincolony on the Summerland Peninsula (Fig 1) These searchescommenced in 198081 and consistently comprised at leasttwo person-hours every day of the year Prior to 198687 andafter 200203 searches focussed on the colony area behindSummerland Beach between 198788 and 200203 they werealso performed over most beaches on the SummerlandPeninsula The second method of monitoring fox-killedpenguins involved individually marked penguins As part of along-term monitoring program that commenced in 1968 (Dann1992) penguins in the Summerland Beach area were fitted withindividually numbered metal flipper-bands until 2000 Thenumber found killed by foxes each year could be comparedwith the number of banded birds known to have been alive inthe area on the basis of numbers of bands applied each year andpublished survival estimates of this population of penguins(Sidhu et al 2007) This provided a measure of the risk of apenguin being killed by a fox thatwas independent offluctuationsin penguin population size penguin activity on land and searcheffort

Analysis

Data collected from 198081 to 201112 were analysed perfinancial year (JulyndashJune) Data on foxes killed over time wereinvestigated by regression analyses with statistical significancetaken to be Plt 005 Comparisons of fox age and sex ratiosover time on Phillip Island were examined using Chi-squaredtests (c2)

Results

Foxes killed

During the bounty period between 1954 and 1983 an average of18 sets of fox ears (range 1ndash71) were submitted each year to

receive the local fox bounty (Fig 2) It could never be proventhat a fox actually came from the island and several anecdotalaccounts suggest that some did not The control period from 1980to 2006 saw the take of foxes increase into the late-1990s whenmore than 70 foxes were taken in each of four consecutive yearsInitial take of foxes during this period came from the western endof Phillip Island where the penguin breeding colony is locatedAfter 198687 harvesting spread across the island and the meandistance from the Penguin Parade that a fox was taken steadilyincreased with time from 1980 to 2012 (r2 = 058 F115 = 333Plt 0001) From the late-1990s fox kills declined to 30 foxes in200304 (Fig 2) Each year during the control period there wasa dip in the number killed during AugustndashSeptember despitesustained effort through all months coinciding with whenbreeding foxes were denning Then in the eradication periodfrom 2006 estimates of fox take peaked again in 20078 at 80foxes per year but by 201112 the estimated number killeddeclined to 19

Fox abundance

The minimum number of foxes known to be alive (KTBA)climbed between 199495 and 19992000 despite intensiveefforts to remove foxes At least 100 individuals remainedincluding at least 139 in 199697 (Fig 3) In contrast theperception within the fox team in 199697 was that fewer than20 foxes remained Knowing theminimumnumber of foxes aliveand the number killed in a year also enabled estimates ofmaximum harvest rates These represent maximum ratesbecause they do not include foxes that evaded detection anddied of other causes or potentially emigrated from the islandInyears between199394 and200304 (n = 11) at best 63 2were harvested (Fig 3) From 2005 harvest rates were notmeaningful because the implementation of broad-scale baiting

Time (financial year)

Num

ber

of fo

xes

kille

d

01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

20

40

60

80

100

Bounty

Dog battue

Baiting

Spot-light

Leg-hold trap

Den fume

M44 ejector

Other

Roadkill

BountyControl

Eradication

Fig 2 Foxes recorded as killed on Phillip Island between 1954 and 2012 during the lsquobountyrsquo lsquocontrolrsquoand lsquoeradicationrsquo periods byfinancial year and techniqueBounty claimswere of foxes shot during eitherdog battues or spot-lighting


in 200506 meant that older foxes killed by baiting could not beback-dated to being alive in the preceding years

Relative fox abundance

The relative indices of fox abundance on Phillip Island allindicated that the population declined in the late-2000s Thenumber of individual foxes recognised per hour of trackingfluctuated for 18 years from 198081 to 200405 between 020and 075 (mean = 047 003) rose to 065ndash100 for the next4 years (mean = 082 006) then dropped to between 017 and020 (mean = 019 001) during 200910 to 201112 The highrate between 200405 and 200910 possibly related to theswitching of emphasis from hunting and trapping to baitingthe former techniques required more in-depth knowledge of afoxrsquos routine to be successful so individual foxeswere tracked forextended periods

Reported sightings by members of the public remained at87 007 per year for 11 years to 199798 and then rose sharplyto a peak of 57 in 200001 The peak coincided with a researchproject using M44-ejectors to kill foxes which engaged farmersthe public and the local media (van Polanen Petel et al 2004)Thereafter reports generally declined to 11 in 201112 (r2 = 049F111 = 978 P = 0011)

Most of hunts involved a full day of hunting Between 198788 and 199394 most day hunting with dogs was conducted atthe Penguin Parade end of the island and the number of foxessighted per day of hunting declined from 18 to 045 (r2 = 090F15 = 461 P = 0001 Fig 4) Day hunting subsequently spreadisland-wide with one member being employed throughthe week to locate sites with fox activity for the team to huntwhich they did on a near-weekly basis The rate of fox sightingsper day of hunts increased and peaked at 20 in 199899coinciding with the maximum level of expertise in the huntteam both personnel and dogs After 199899 rates of foxsightings per day declined steadily to zero in 200910(r2 = 049 F110 = 150 P = 0011) The frequency of hunts

with dogs also declined for a range of reasons principallydiminishing returns

Night hunting with spotlights was conducted predominantlyover the Summerland Peninsula during the 4 years to 199293Annual rates of foxes seen per spot-lighting night (usually 2 hin duration but up to 6 h) averaged 053 008 Thereafter thetechnique was applied across the entire island Rates of foxsightings promptly rose and remained above 10 in all but 4 ofthe next 17 years to 200708 then declined to zero by 201112(Fig 4)

Between 198788 and 201112 the success rate (percentageof foxes seen that were killed by shooting) during night-timespot-lighting declined (r2 = 024 F123 = 743 P = 001) anapparent decline during day hunts was not statisticallysignificant (r2 = 014 F120 = 333 P = 008 Fig 5) After200607 however few foxes were seen during day hunts twowere killed in 200708 one killed in 200809 and none was seenthereafter Between 198788 and 200607 the decline in successrates of dog hunts was statistically significant (r2 = 043F118 = 141 P = 0001)

Fox impact

Between 1980 and 2011 little penguins were most vulnerableto surplus killing by foxes during March to June (Fig 6) Thisperiod may correspond with the time when cubs disperse(Coman et al 1991) There was no clear trend toward areduction in penguin kills during daytime searches until200809 from when just two penguins were killed by foxesin a 3-year period (Fig 7) Using just the data from bandedpenguins a high kill rate is evident between 1976 and 1983when the deaths constituted 14ndash85 of banded penguinseach year (36 09 data for 7 years) (Fig 8) Only intwo other years did the level exceed 10 of the bandedpenguins

Technique biases and population structure

Although a greater proportion of foxes harvested and sexedwere males (433 compared with 397 females) the ratio of


40

50

60

70

80

Per

cent

age

harv

este

d

Fox

es K

TB

A

01994 1996 1998 2000 2002 2004 2006

20

40

60

80

100

120

140

Fig 3 Change over time in the minimum number of foxes known to bealive (KTBA) on Phillip Island (black circles) and maximum potentialpercentage of the population harvest (grey bars) The minimum number offoxes KTBA equalled the number of foxes killed in the year plus those killedin later years and old enough to be alive in earlier years The maximumpotential harvest ratewas the number of foxes killed in the year as a percentageof the number known to be alive in that year These data indicated thatdespite the intensive control program many foxes remained and harvestingwasbarely achieving theminimum60required to affect apopulationdecline(dashed line)


Fox

es s

een

per

hunt

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

05

10

15

20

25Day Night

Fig 4 Numbers of foxes seen per hunt during day shoots (aided bydogs) and night shoots (aided by spot-lights) on Phillip Island Variabilitybefore the decline after 2006 probably reflected changes in fox numberseffort and expertise The sustained decline from 2006 probably depicts adecline in fox numbers and potentially increasing anthropophobia ofremaining foxes


males to females (13 12) did not differ significantly from parity(c2 = 157 P = 021) Of the foxes harvested and aged 69werejuveniles (461 compared with 210 adults) The proportion offemale foxes recovered increased over time (r2 = 019F126 = 609 P= 002)

Discussion

Failed paradigms in fox management

The early attempts of fox control on Phillip Island reflect ahistory of failures in fox-control methods more generallyfound in Australia The early reliance on a lsquobounty systemrsquoand then reliance on a lsquosporting-shooterrsquo approach reflected atendency in many programs to focus only on control withoutalso monitoring control efficacy Bounty systems and sporting-shooter approaches have been used frequently in Australia yethave failed to effectively control fox populations (Coman 1988Saunders et al 2010) During the bounty period on PhillipIsland and early in the control period there was no clearscientific basis to or use of monitoring data The ad hocnature of both bounty and sporting-shooter approaches meantthat they failed to appreciably reduce fox numbers on the islandor their impacts on prey

There is little information on fox population size or trendson Phillip Island before 1980 Estimates of fox density fromsimilar environments in central Victoria (Coman et al 1991)which are consistent with other estimates for rural and urbanisedareas (Thompson and Fleming 1994 Marks and Bloomfield1999 Heydon et al 2000 Webbon et al 2004) equate to~300ndash390 foxes on 100 km2 Phillip Island

The control program was initiated in 1980 following thesubstantial peak in penguin kills that year (Fig 8) Theprogram was structured with a focus on protecting penguinsand some attempt was made to estimate fox abundance

The vulnerability of penguins to fox predation and theeconomic value of penguin tourism meant that fox controlreceived the support and focus it ultimately needed to beeffective However the control program relied on subjectiveinterpretations of efficacy which led to the incorrectconclusion that foxes were under control and that harvestingfoxes was useful At the beginning of the control period in 1980broad-scale baiting was the first technique applied It wasapplied only briefly though with no monitoring to determineits impact Even so it may have had a resounding impact on the


Pro

port

ion

kille

d w

hen

seen

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

02

04

06

08

10

Fig 5 Mean proportion of foxes seen on Phillip Island that were killedduring day shoots aided by dogs (r2 = 014 P= 008) and night shoots aidedby spot-lights (r2 = 024 P= 001)

Time (month)

Pro

port

ion

of p

engu

ins

kille

dby

foxe

s

0Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

005

010

015

020

025

030

035

Fig 6 Mean proportion of little penguins surplus killed by foxes ineach month between 1980 and 2012 on Phillip Island The MarchndashMayperiod coincides with when young foxes leave natal territories

Year

Pen

guin

s ki

lled

by fo

xes

01980 1985 1990 1995 2000 2005 2010

50

100

150

200

250

300

350

Fig 7 Number of penguins killed per financial year on Phillip Island witha 4-year running mean Search effort (and area) initially was low but steadilyincreased through 198081 to 198687 then remained relatively consistentand high

Year

Per

cent

age

of b

ande

d pe

ngui

nski

lled

by fo

xes

01970 1980 1990 2000 2010

1

2

3

4

5

6

7

8

9

Fig 8 The percentage of flipper-banded little penguins on Phillip Islandthat were killed by foxes each year from 1971 to 2012 (data unavailable for1981 and 1984)


resident population This is evidenced in catch-effort data (Routet al 2014) in which the population through the late 1980s andearly 1990s appeared to be increasing despite the control effortand one possibility is that it was recovering from the baiting ofthe early 1980s However there was no monitoring of theimpact at the time and alternative techniques soon took overbecause they (1) resulted in carcasses ndash an apparent sign ofsuccess (2) required individual skill ndash so were more appealingto participants and (3) did not endanger domestic petsAlthough reducing penguin deaths was the primary motivatorof the fox-control program the most efficient and effectivemethod was not persisted with because of social motivatorsand a lack of evidence for relative efficacy

The indices of abundance that were monitored were ofminimal value to understanding fox abundance or controlefficacy Indices included rates of fox sightings during variousforms of hunting and included rates of tracks and scats detectedduring tracking such as has been used elsewhere (Kurki et al1998 Sharp et al 2001 Webbon et al 2004 Field et al 2005)and monitoring is invariably tied to eradication success (Baker2006) On Phillip Island these indices did not reveal anyindication of a declining population during the control periodPublic sightings were clearly more related to efforts at publicengagement than fox abundance so are of little use as an index offox abundance Comparisons of several commonly used indicesof fox abundance with a benchmark method of estimating foxdensity using markndashrecapture modelling from scat DNA alsoindicated that indices were unreliable (Marks et al 2009)Alternative methods to estimate population size or density ofred foxes have been based on foxes removed for example anindexndashremovalndashindex technique (Fleming 1997) or den densityand litter sizes combined with estimates of family groupcomposition (Coman et al 1991 Marks and Bloomfield 1999)

Insights from scientific evaluation

Carcass collection during the control period allowed scientificanalyses of fox population demographics and the first objectiveinsights into population size and control efficacy Foxes couldbe aged from cementum layers in their teeth so we coulddescribe the age structure of the harvested populationFurthermore it could be determined in which years each foxwas alive and hence a minimum number of foxes known to bealive each year Additional foxes would have escaped detectionor capture so were unaccounted for in these estimatesAccordingly in the late-1990s the population on PhillipIsland was at least 139 individuals (the total for 199697) adensity of at least 14 foxes kmndash2 By the early 2000s thepopulation comprised at least 86 individuals or 09 foxes kmndash2

Retrieving fox carcasses also provided DNA samples thathave been used to estimate the number of fox litters producedper year Temporal changes in allele frequencies and gameticlinkages in DNA samples collected from 1994 to 2006 indicated13ndash28 (mean19) litters per year (Berry andKirkwood2010) Thisrepresents family-group densities of 01ndash03 kmndash2 Red foxfamily-group densities recorded elsewhere have been 06 kmndash2

in rural central Victoria (Coman et al 1991) and 05ndash36 kmndash2 inurban Melbourne (Trewhella et al 1988 Marks and Bloomfield1999) Using the mean of 19 litters per year on Phillip Island

and assuming family groups averaged two adults and four orfive cubs (Harris and Smith 1987 Marks and Bloomfield 1999)and all adults were paired a minimum population for the islandbetween 1994 and 2006 would have been 78ndash196 (mean 124)Like the age data these numbers are underestimates data arebased only on foxes killed not all litters on the island wouldhave been sampled and some family groups probably comprisedmore than two adult foxes

Another potential technique to monitor fox population sizesis via molecular scatology which involves extraction of DNAfrom scats to identify individuals (Paxinos et al 1997) then amarkndashrecapture exercise to estimate numbers (Kohn et al 1999Berry et al 2012) This approach has been found to be moreinformative than other monitoring techniques when comparedfor estimating population size (Piggott et al 2008 Marks et al2009) Changes in detection probabilities over time differencesin detectability between demographic groups or behaviouralclasses and changing patterns in spatial activity could beincorporated in models to provide more robust estimatesHowever at very low fox abundances when specimens arehard to come by the approach is unlikely to be informativebecause insufficient data would be available to generateestimates

Fox numbers on Phillip Island from 1987 have also beenestimated on the basis of a Bayesian catch-effort model thatincorporates rates of foxes removed per unit effort as well asdetection probabilities for each of five control methods employedon Phillip Island (trapping baiting day hunting night spotlighthunting and den searches) Results suggested that numberswere greater than 130 foxes between 1987 and 2005 andreached ~200 foxes in 1996 (Rout et al 2014) Throughoutthe control period the fox team would have considered all ofthese numbers implausible believing there were considerablyfewer foxes left on the Island

Linking fox control to fox impacts

Monitoring of little penguins on Phillip Island suggested that theimpact of foxes was being reduced during the 1980ndash2006 fox-control program however it did not eliminate the depredation ofpenguins Little penguins continued to be killed in large numbersbecause even at lowered densities individual foxes couldsurplus kill many birds Consequently the control programwas failing because it was not meeting its primary aim ofpreventing all seabird deaths

The program goals changed from fox control to eradicationonce it was recognised that the number of penguins killed wasnot reduced in a density-dependent relationship with foxesIsland-wide baiting was implemented in 2006 but this newstrategy took several years to achieve a clear and measurablereduction Indices of fox presence (sightings and catch rates)suggested that a greater than 90 reduction in fox activity wasachieved between 2006 and 2011 comparable levels of knock-down have been demonstrated in previous baiting programs toreduce fox populations (Banks et al 1998 Risbey et al 2000Berry et al 2012) Concurrently there was a decline from 125penguins killed by foxes on the Summerland Peninsula in 200708 to five penguins killed in the next 4 years (although 15 werekilled at an establishing colony on the eastern end of Phillip


Island in late June 2011) In addition there has been evidencefor population recovery of little penguins the population onSummerland Peninsula grew from ~12 000 breeding birds in1978 to ~30 000 in 2010 (Harris and Bode 1981 Sutherlandand Dann 2012 2014) Furthermore two new colonies haveestablished elsewhere on the island in the past 5 years (P Dannunpubl data) Each of these changes was likely caused by arange of factors and not by fox control alone but theircorrelation in time is highly suggestive that this fox-controlattempt is contributing significantly to the expansion of thepenguin population The success of broad-scale baiting onPhillip Island after years of applying alternative techniqueslends support to the use of poison baiting as a significantlymore effective means of red fox control

Towards fox eradication

Foxes are nearly eradicated from Phillip Island although theremaining few may be challenging to remove and successdifficult to qualify (Rout et al 2014) If successful PhillipIsland will be the largest island from which red foxes havebeen eradicated (Island Conservation 2012) attesting to thedifficulty of placing all foxes at risk of control in larger andmore diverse landscapes Arctic foxes (Vulpes lagopus) havebeen removed from larger islands but none of these islands ispermanently inhabited by humans and the foxes were selectivelybred for their fur (Ebbert and Byrd 2002) Humans and theirdomestic pets permanently inhabit Phillip Island and are widelydistributed across the landscapeAll control techniques employedwere inhibited by the necessity to avoid antagonising people orputting them at risk For example the potential risk of poisoningpets provided a strong argument against baiting and preventedbroad-scale baiting for much of the control program Specificresearch projects were undertaken on baiting techniques in partto provide management with indications that baiting could besuccessful as well as to trial new techniques such as applicationof cabergoline to terminate pregnancies in vixens (Marks et al1996 McLean et al 2007) and presentation of baits in M44-ejectors to prevent movement or caching of poison baits (vanPolanen Petel et al 2004) Urban fox control might be critical toachieving eradication on Phillip Island as well as for campaignsin other human-inhabited sites and may require alternativetechniques that can be employed in urban landscapes

The semi-isolation of the fox population on Phillip Island(Lade et al 1996 Berry and Kirkwood 2010) has substantiallyaided the control program by impairing reinvasion Althoughreinvasions by foxes have been implicated through geneticanalyses (Berry and Kirkwood 2010) it is at a low rate (threeindividuals in 15 years) and all were males Fox control hasbeen sustained elsewhere in situations where reinvasions canbe mitigated such as on islands (Burbidge andMorris 2004) OnPhillip Island effort expanded steadily during the 1980s and1990s to encompass the entire island more than 2000 person-hours each year (more than 20 person-hours kmndash2) and annualharvesting of at best 60ndash70 of the fox population This highand sustained effort likely suppressed the population asdescribed above and recognised elsewhere (Heydon andReynolds 2000) Restricting fox immigration allows singlecontrol efforts to sustain population reductions for longer than

would be possible if migration was open (Algar and Smith 1998Risbey et al 2000) Instances where immigration cannot becontrolled can result in prompt population recoveries evenwithin a year despite knock-downs of gt70 (Thompson andFleming 1994 Greentree et al 2000 Harding et al 2001)Prolonged success in future red fox-control programs may bedependent on isolating or fragmenting the population throughnatural or artificial barriers

As fox density decreases in response to effective control theeffort required to remove each fox is likely to increase as thosefoxes remaining become anthropophobic Supporting this ideais the declining rate of foxes shot per fox seen during spot-lighting after 2000 Selection for fearfulness or tameness infoxes can be rapid as demonstrated through fox farms (Trut1999) Animals selected for fearfulness can exhibit strongerlearnt aversion (Turro-Vincent et al 1995) and prenatal stressexperienced by fox cubs can alter their behavioural responsesto novel situations (Braastad et al 1998) Hence control effortsduring extended campaigns could select for anthropophobicfoxes potentially reducing detectability of foxes and theefficacy of control To demonstrate reduced detectability andcontrol efficacy over time a monitoring technique is requiredthat is independent of the control technique Decliningdetection rates and efficacy have implications for eradicationcampaigns because it may not be feasible to remove asubpopulation of highly anthropophobic animals that will notsuccumb to available control techniques Coordinated campaignsthat are not prolonged may minimise the development ofanthropophobia and be more likely to succeed

Lessons learned for future fox-control campaigns

Each wildlife-control program is different but can be guided bycommon management principles The following are some keylessons for other pest-control attempts from the long-runningcampaign to control foxes on Phillip Island

Evaluating the efficacy of different methods independentlyof personal and public biases is critical to adopting the bestmanagement strategy In our case study genetic analyseswere invaluable to identifying the degree of isolation andsize of the island fox population Molecular scatology pairedwith markndashrecapture modelling is recommended for futurecontrol campaigns

More than one control method has proved successful in thiscampaign and the use of multiple control methods increasesthe chance of placing all individuals at risk (Courchamp et al2003)

Placing all individuals in a population at risk of control isessential for eradication success In our case study urbanfoxes may not be subjected to effective control and furtherdevelopment is required for effective and safe controltechniques in urban environments

Dedicated individuals or teams whose duties are solelydevoted to the control program are essential In thiscampaign emphasis waned and application of techniquesvaried in intensity when individuals had other dutiesunrelated to fox control

Monitoring both control efficacy and the impacts of controltogether is essential For example in our case study the


relationshipbetween foxabundance and impact onprey specieswas not density dependent

Success rates of each technique can change over time as thetarget species adapts Monitoring techniques that areindependent of the control techniques are essential to detecttemporal changes in detection rates

At very low densities target species may become exceedinglydifficult to detect and this presents a particular challenge fordetermining when eradication has been achieved (Morrisonet al 2007) Thought should be given to methodologies thatcan robustly estimate detection rates of a very low densitypopulation On Phillip Island a decision framework has beendeveloped to optimise when eradication should be declaredonce there are no more signs of foxes (Rout et al 2014) Thisframework is based on the costs of management theestimated costs of declaring too early and the fox-detectionprobabilities from five control techniques

Once eradication is declared programs need to remainvigilant and monitor for reinvasions Preventing reinvasionand bolstering quarantine measures should be a priority foreradication programs before any declaration

Acknowledgements

We acknowledge the commitment of past and present members of the PhillipIsland fox team particularly the late A Cleeland and the tremendoussupport given by local land-holders and Department of ConservationForests and Lands (now Department of Environment and PrimaryIndustry) The contributions of many of the staff and Board members ofPhillip Island Nature Parks as well as the assistance of the PenguinStudy Group particularly the late M Cullen and the late P Reilly areacknowledged Long-time resident the late K Grayden providedvaluable discussions on the history of fox control on the island We alsothank the former Pest Animal Unit at the Keith Turnbull ResearchInstitute particularly C Marks F Gigliotti and F Busana for invaluableadvice over the years Further influential contributions to the researchwere given by M van Polanen Petel N Johnson T Bloomfield andS McPhee Valuable comments from two anonymous referees improvedthe manuscript

References

Abbott I (2011) The importation release establishment spread and earlyimpact on prey animals of the red fox Vulpes vulpes in Victoria andadjoining parts of south-eastern Australia Australian Zoologist 35463ndash533 doi107882AZ2011003

Adkins C A and Stott P (1998) Home ranges movements and habitatassociations of red foxes Vulpes vulpes in suburban Toronto OntarioCanada Journal of Zoology 244 335ndash346 doi101111j1469-79981998tb00038x

Algar D and Smith R (1998) Approaching Eden Landscope 13 28ndash34Australian Bureau of Statistics (2013) lsquo2011 Census QuickStats Phillip

IslandrsquoAvailable at httpwwwcensusdataabsgovaucensus_servicesgetproductcensus2011quickstat205031091 [verified 24 October2013]

Baker S (2006) The eradication of coypus (Myocastor coypus) fromBritain the elements required for a successful campaign InlsquoAssessment and Control of Biological Invasion Risksrsquo (Eds F KoikeM N Clout M Kawamichi M De Poorter and K Iwatsuki)pp 142ndash147 (IUCN Gland Switzerland)

Banks P B Dickman C R and Newsome A E (1998) Ecological costsof feral predator control foxes and rabbits The Journal of WildlifeManagement 62 766ndash772 doi1023073802353

Berry O and Kirkwood R (2010) Measuring recruitment in an invasivespecies to determine eradication potential The Journal of WildlifeManagement 74 1661ndash1670 doi1021932009-482

BerryOAlgarDAngus JHamiltonNHilmerS andSutherlandDR(2012) Genetic tagging reveals a significant impact of poison baiting onan invasive species The Journal of Wildlife Management 76 729ndash739doi101002jwmg295

Braastad B O Osadchuk L V Lund G and Bakken M (1998) Effectsof prenatal handling stress on adrenal weight and function andbehaviour in novel situations in blue fox cubs (Alopex lagopus)Applied Animal Behaviour Science 57 157ndash169 doi101016S0168-1591(97)00114-7

Burbidge A A and Morris K D (2004) Introduced mammal eradicationsfor nature conservation on Western Australian islands a review In lsquoTheDomestic Cat the Biology of Its Behaviourrsquo (Eds D C Turner andP G Bateson) pp 64ndash70 (Cambridge University Press CambridgeUK)

Cavallini P (1996) Variation in the social system of the red fox EthologyEcology and Evolution 8 323ndash342 doi1010800892701419969522906

Coman B J (1988) The age structure of a sample of red foxes (Vulpesvulpes L) taken by hunters in Victoria Australian Wildlife Research 15223ndash229 doi101071WR9880223

Coman B J Robinson J and Beaumont C (1991) Home range dispersaland density of red foxes (Vulpes vulpes L) in central Victoria WildlifeResearch 18 215ndash224 doi101071WR9910215

Courchamp F Chapuis J L and Pascal M (2003) Mammal invaderson islands impact control and control impact Biological Reviews ofthe Cambridge Philosophical Society 78 347ndash383 doi101017S1464793102006061

Dann P (1992) Distribution population trends and factors influencingthe population size of little penguins Eudyptula minor on PhillipIsland Victoria Emu 91 263ndash272 doi101071MU9910263

Dickman C R (1996) Impact of exotic generalist predators on the nativefauna of Australia Wildlife Biology 2 185ndash195

Ebbert S E and Byrd G V (2002) Eradications of invasivespecies to restore natural biological diversity on Alaska MaritimeNational Wildlife Refuge In lsquoTurning the Tide the Eradication ofInvasive Species Vol 27rsquo (Eds C R Veitch and M N Clout)pp 102ndash109 (IUCN Species Survival Commission GlandSwitzerland)

Field S A Tyre A J Thorn K H OrsquoConnor P J and Possingham H P(2005) Improving the efficiency of wildlife monitoring by estimatingdetectability a case study of foxes (Vulpes vulpes) on the EyrePeninsula South Australia Wildlife Research 32 253ndash258doi101071WR05010

Fleming P J S (1997) Uptake of baits by red foxes (Vulpes vulpes)implications for rabies contingency planning in Australia WildlifeResearch 24 335ndash346 doi101071WR95016

Gabriel J (1919) On the destruction of mutton-birds and penguins atPhillip Island Victorian Naturalist 35 178ndash180

Glidden J W (1968) lsquoPhillip Island in Picture and Storyrsquo (Wilke and CoLtd Melbourne)

Goszczynski J (1989) Spatial distribution of red foxes Vulpes vulpes inwinter Acta Theriologica 34 361ndash372 doi104098ATarch89-35

Greentree C Saunders G McLeod L and Hone J (2000) Lambpredation and fox control in south-eastern Australia Journal ofApplied Ecology 37 935ndash943 doi101046j1365-2664200000530x

Grue H and Jensen B (1973) Annular structures in canine toothcementum in red foxes (Vulpes vulpes L) of known age DanishReview of Game Biology 8 1ndash12

Harding E K Doak D F and Albertson J D (2001) Evaluating theeffectiveness of predator control the non-native red fox as a case studyConservation Biology 15 1114ndash1122 doi101046j1523-173920010150041114x


Harris S (1978) Age determination in the red fox (Vulpes vulpes) ndash anevaluation of technique efficiency as applied to a sample of suburbanfoxes Journal of Zoology 184 91ndash117 doi101111j1469-79981978tb03268x

Harris S (1979) Age related fertility and productivity on red foxesVulpes vulpes in suburban London Journal of Zoology 187 195ndash199doi101111j1469-79981979tb03943x

Harris S (1981) An estimation of the number of foxes (Vulpes vulpes) inthe city of Bristol and some possible factors affecting their distributionJournal of Applied Ecology 18 455ndash465 doi1023072402406

Harris M P and Bode K G (1981) Populations of little penguinsshort-tailed shearwaters and other seabirds on Phillip Island VictoriaEmu 81 20ndash28 doi101071MU9810020

Harris S and Smith G C (1987) Demography of two urban fox(Vulpes vulpes) populations Journal of Applied Ecology 24 75ndash86doi1023072403788

Heydon M J and Reynolds J C (2000) Demography of rural foxes(Vulpes vulpes) in relation to cull intensity in three contrasting regionsof Britain Journal of Zoology 251 265ndash276 doi101111j1469-79982000tb00609x

Heydon M J Reynolds J C and Short M J (2000) Variation inabundance of foxes (Vulpes vulpes) between three regions of ruralBritain in relation to landscape and other variables Journal ofZoology 251 253ndash264 doi101111j1469-79982000tb00608x

Island Conservation (2012) lsquoDatabase of Island Invasive SpeciesEradicationsrsquo Available at berrhttperadicationsdbfosaucklandacnz[Verified 1142014]

Johnston D H and Watt I (1980) A rapid method for sectioningundecalcified carnivore teeth for aging In lsquoThe Worldwide FurbearerConference Proceedingsrsquo Vol 1 (Eds J A Chapman and D Pursley)pp 407ndash421 (Frostburg MD)

Kinnear J E Onus M L and Bromilow R N (1988) Fox control androck-wallaby population dynamics Australian Wildlife Research 15435ndash450 doi101071WR9880435

Kinnear J E Onus M L and Sumner N R (1998) Fox control and rock-wallaby population dynamics ndash an updateWildlife Research 25 81ndash88doi101071WR96072

Kinnear J E SumnerNR andOnusML (2002) The red fox inAustraliandash an exotic predator turned biocontrol agent Biological Conservation108 335ndash359 doi101016S0006-3207(02)00116-7

Kirkwood R Dann P and Belvedere M (2000) Effects of the seasonalavailability of short tailed shearwaters (Puffinus tenuirostris) on the dietof red foxes (Vulpes vulpes) on Phillip Island Victoria AustralianMammalogy 22 87ndash92

Kirkwood R Dann P and Belvedere M (2005) A comparison of thediets of feral cats (Felis catus) and red foxes (Vulpes vulpes) on PhillipIsland Victoria Australian Mammalogy 27 89ndash93 doi101071AM05089

Kohn M H York E C Kamradt D A Haught G Sauvajot R M andWayne R K (1999) Estimating population size by genotyping faecesProceedings Biological Sciences 266 657ndash663 doi101098rspb19990686

Kurki S Nikula A Helle P and Linden H (1998) Abundances of redfox and pine marten in relation to the composition of boreal forestlandscapes Journal of Animal Ecology 67 874ndash886 doi101046j1365-265619986760874x

Lade J A Murray N D Marks C A and Robinson N A (1996)Microsatellite differentiation between Phillip Island and mainlandAustralian populations of the red fox Vulpes vulpes MolecularEcology 5 81ndash87 doi101111j1365-294X1996tb00293x

Lloyd H G (1980) lsquoThe Red Foxrsquo (B T Batsford Ltd London)Lokemoen J T and Woodward R O (1993) An assessment of predator

barriers and predator control to enhance duck nest success on peninsulasWildlife Society Bulletin 21 275ndash282

Mann T L J (1968) A comparison of lamb survival in fox proof andunprotected enclosures Proceedings of the Australian Society of AnimalProduction 7 250ndash254

Marks C A and Bloomfield T E (1999) Distribution and densityestimates for urban foxes (Vulpes vulpes) in Melbourne implicationsfor rabies control Wildlife Research 26 763ndash775 doi101071WR98059

MarksCNijkMGigliotti FBusanaF andShortR (1996)Preliminaryfield assessment of a cabergoline baiting campaign for reproductivecontrol of the red fox (Vulpes vulpes) Wildlife Research 23 161ndash168doi101071WR9960161

Marks C A Busana F and Gigliotti F (1999) Assessment of the M-44ejector for thedeliveryof 1080 for red fox (Vulpes vulpes) controlWildlifeResearch 26 109ndash109 doi101071WR98014

Marks C A Gigliotti F McPhee S Piggott M P Taylor A and GlenA S (2009) DNA genotypes reveal red fox (Vulpes vulpes) abundanceresponse to lethal control and limitations of contemporary surveytechniques Wildlife Research 36 647ndash658 doi101071WR08109

McLean S Brandon S and Kirkwood R (2007) Stability of cabergolinein fox baits in laboratory and field conditions Wildlife Research 34239ndash246 doi101071WR06094

McLeod R (2004) lsquoCounting the Cost Impact of Invasive Animals inAustralia 2004rsquo (Cooperative Research Centre for Pest Animal ControlCanberra)

Meek P D Jenkins D J Morris B Ardler A J and Hawksby R J(1995) Use of two humane leg-hold traps for catching pest speciesWildlife Research 22 733ndash739 doi101071WR9950733

Morrison S A Macdonald N Walker K Lozier L and Shaw M R(2007) Facing the dilemma at eradicationrsquos end uncertainty of absenceand the Lazarus effect Frontiers in Ecology and the Environment 5271ndash276 doi1018901540-9295(2007)5[271FTDAEE]20CO2

Norman F I (1971) Predation by the fox (Vulpes vulpes L) on colonies ofthe short-tailed shearwater (Puffinus tenuirostris Temminck) in VictoriaAustralia Journal of Applied Ecology 8 21ndash32 doi1023072402124

Paxinos E McIntosh C Ralls K and Fleischer R (1997) A noninvasivemethod for distinguishing among canid species amplification andenzyme restriction of DNA from dung Molecular Ecology 6483ndash486 doi101046j1365-294X199700206x

PiggottMPWilsonRBanksSCMarksCAGigliotti F andTaylorA C (2008) Evaluating exotic predator control programs using non-invasive genetic tagging Wildlife Research 35 617ndash624 doi101071WR08040

Priddel D and Wheeler R (1997) Efficacy of fox control in reducingthe mortality of released captive-reared malleefowl Leipoa ocellataWildlife Research 24 469ndash482 doi101071WR96094

Risbey D A Calver M Short J Bradley J and Wright I (2000) Theimpact of cats and foxes on the small vertebrate fauna of HeirissonProng Western Australia II A field experiement Wildlife Research27 223ndash235 doi101071WR98092

Rolls E C (1969) lsquoThey All Ran Wildrsquo (Angus and Robertson Sydney)Rout T M Kirkwood R Sutherland D R Murphy S and McCarthy

M A (2014) When to declare successful eradication of an invasivepredator Animal Conservation 17 125ndash132 doi101111acv12065

Rowley I (1970) Lamb predation in Australia incidence predisposingconditions and the identification of wounds Wildlife Research 1579ndash123 doi101071CWR9700079

Saunders G and McLeod L (2007) lsquoImproving Fox ManagementStrategies in Australiarsquo (Bureau of Rural Sciences Canberra)

Saunders G Coman B Kinnear J and Braysher M (1995) lsquoManagingVertebrate Pests Foxesrsquo (Australian Government Publishing ServiceCanberra)

Saunders G R Gentle M N and Dickman C R (2010) The impacts andmanagement of foxes Vulpes vulpes in Australia Mammal Review 40181ndash211 doi101111j1365-2907201000159x


Sharp A Norton M Marks A and Holmes K (2001) An evaluation oftwo indices of red fox (Vulpes vulpes) abundance in an arid environmentWildlife Research 28 419ndash424 doi101071WR00075

Sidhu L A Catchpole E A andDann P (2007)Mark-recapture-recoverymodellingandage-related survival in little penguinsEudyptulaminorTheAuk 124 815ndash827 doi1016420004-8038(2007)124[815MMAASI]20CO2

Sutherland D R and Dann P (2012) Improving accuracy of populationsize estimates for burrow nesting seabirds The Ibis 154 488ndash498doi101111j1474-919X201201234x

Sutherland D R and Dann P (2014) Population trends in a substantialcolony of little penguins three independent measures over three decadesBiodiversity and Conservation 23 241ndash250 doi101007s10531-013-0597-y

Thompson P C and Fleming P J S (1994) Evaluation of the efficacy of1080 poisoning of red foxes using visitation to non-toxic baits as anindex of fox abundance Wildlife Research 21 27ndash40 doi101071WR9940027

Trewhella W J Harris S andMcAllister F E (1988) Dispersal distancehome-range size and population density in the red fox (Vulpes vulpes)a quantitative analysis Journal of Applied Ecology 25 423ndash434doi1023072403834

Trewhella W J Harris S Smith G C and Nadan A K (1991) A fieldtrial evaluating bait uptake by an urban fox (Vulpes vulpes) populationJournal of Applied Ecology 28 454ndash466 doi1023072404561

Trut L N (1999) Early canid domestication the farm-fox experimentAmerican Scientist 87 160ndash169 doi10151119992160

Turro-Vincent I LaunayFMillsADPicardM andFaure JM (1995)Experiential and genetic influences on learnt food aversions inJapanese quail selected for high or low levels of fearfulnessBehavioural Processes 34 23ndash41 doi1010160376-6357(94)00045-I

van Polanen Petel A M Marks C A and Morgan D G (2001) Baitpalatability influences the caching behaviour of the red fox (Vulpesvulpes) Wildlife Research 28 395ndash401 doi101071WR00046

van Polanen Petel A M Kirkwood R Gigliotti F and Marks C (2004)Adaptation and assessment of M-44 ejectors in a fox-control programon Phillip Island VictoriaWildlife Research 31 143ndash147 doi101071WR02057

Voigt D E and Macdonald D W (1984) Variation in the spatial andsocial behaviour of the red fox Vulpes vulpes Acta Zoologica Fennica171 261ndash265

Webbon C Baker P J and Harris S (2004) Faecal density counts formonitoring changes in red fox numbers in rural Britain Journal ofApplied Ecology 41 768ndash779 doi101111j0021-8901200400930x


wwwpublishcsiroaujournalswr

Attempts at fox control are hindered by their high breedingproductivity and flexible behaviours (Harris 1979 Lloyd 1980Harris 1981 Cavallini 1996) Foxes readily travel tensof kilometres in a night (Voigt and Macdonald 1984Goszczynski 1989 Adkins and Stott 1998) and can migratefurther to establish in unoccupied territories (Trewhella et al1988) Where fox immigration is restricted control actions tendto have a more lasting effect (Lokemoen and Woodward1993 Ebbert and Byrd 2002 Kinnear et al 2002) Generallyonly sustained and intense control efforts supress fox populations(Heydon et al 2000 Harding et al 2001)

Phillip Island on theVictorian coast in south-easternAustralia(Fig 1) has had resident red foxes since 1907 (Gabriel 1919Glidden 1968) Attempts to control the fox populationcommenced in ~1918 (Gabriel 1919) primarily to protectground-nesting seabirds namely little penguins (Eudyptulaminor) and short-tailed shearwaters (Ardenna tenuirostris)(Norman 1971 Dann 1992) Foxes on Phillip Island aregenetically distinct from those on the adjacent mainland ofAustralia (Lade et al 1996) with an estimated level ofmigration to the island of one fox every 3 years based ongenetic analysis of 480 foxes caught on the island between1994 and 2008 (Berry and Kirkwood 2010) The main accesspoint for migrant foxes is likely to be a 600-m bridge that hasconnected the island to the mainland since 1945

The present paper documents red fox management on PhillipIsland as a case study compares the efficacy of control techniquesand discusses factors that can improve success of pest animal-control campaigns Documenting the evolution of control effortprovides an insight into human aspects of predator-controlcampaigns the ecology of a fox population during intensiveharvesting (also see Berry and Kirkwood 2010) and the efficacyof control as indicated by indices of fox abundance (see also

Rout et al 2014) and reduced impacts on principal beneficiariesincluding the little penguin

Materials and methodsStudy site

Phillip Island comprises 100 km2 of low-lying (max altitude110m) sand and clay soils has a wet-temperate climate (Glidden1968) The island has a resident human population of ~9400(Australian Bureau of Statistics 2013) which is augmented bymore than 50 000 temporary residents during holiday periods(van Polanen Petel et al 2004) Approximately 20 of theisland is urbanised another 20 natural or re-plantedbushland and the remainder cleared for livestock grazingLittle penguins once nested in colonies at 10 sites around theisland During the mid-1900s the penguins at nine sites wereeliminated attributed largely to fox predation but also byroaming dogs and urban developments (Dann 1992) Theremaining colony was the largest of the 10 colonies (Harrisand Bode 1981) it was semi-isolated on SummerlandPeninsula at the western end of the island and it supported atourism venture which meant predator control received somesupport The eastern edge of this colony attracts up to 500 000tourists annually with visitors viewing the lsquoparadersquo of penguinsacross Summerland Beach every night of the year (Dann 1992)

Fox-control periods

Bounty period (before 1984)In 1918 the Phillip Island Shire Council decided to sponsor

two residents to hunt foxes on the island (Gabriel 1919) then in1954 the Council introduced a bounty system for island-caughtfoxes which ran for 30 years

145deg00 E

38deg3

0 S

38deg3

0 S

145deg30 E

20 km

145deg00 E

120deg

ndash20deg

ndash40deg

ndash20deg

ndash40deg

140deg

120deg 140deg

145deg30 E

Fig 1 Location of Phillip Island off the coast of Victoria Australia






Killing techniques


Biological data












Analysis


Results

Foxes killed



Fox abundance



Num

ber

of fo

xes

kille

d

01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

20

40

60

80

100

Bounty

Dog battue

Baiting

Spot-light

Leg-hold trap

Den fume

M44 ejector

Other

Roadkill

BountyControl

Eradication











Fox impact





40

50

60

70

80

Per

cent

age

harv

este

d

Fox

es K

TB

A

01994 1996 1998 2000 2002 2004 2006

20

40

60

80

100

120

140



Fox

es s

een

per

hunt

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

05

10

15

20

25Day Night




Discussion







Pro

port

ion

kille

d w

hen

seen

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

02

04

06

08

10


Time (month)

Pro

port

ion

of p

engu

ins

kille

dby

foxe

s


005

010

015

020

025

030

035


Year

Pen

guin

s ki

lled

by fo

xes

01980 1985 1990 1995 2000 2005 2010

50

100

150

200

250

300

350


Year

Per

cent

age

of b

ande

d pe

ngui

nski

lled

by fo

xes

01970 1980 1990 2000 2010

1

2

3

4

5

6

7

8

9


































Acknowledgements


References






















































































Killing techniques


Biological data












Analysis


Results

Foxes killed



Fox abundance



Num

ber

of fo

xes

kille

d

01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

20

40

60

80

100

Bounty

Dog battue

Baiting

Spot-light

Leg-hold trap

Den fume

M44 ejector

Other

Roadkill

BountyControl

Eradication











Fox impact





40

50

60

70

80

Per

cent

age

harv

este

d

Fox

es K

TB

A

01994 1996 1998 2000 2002 2004 2006

20

40

60

80

100

120

140



Fox

es s

een

per

hunt

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

05

10

15

20

25Day Night




Discussion







Pro

port

ion

kille

d w

hen

seen

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

02

04

06

08

10


Time (month)

Pro

port

ion

of p

engu

ins

kille

dby

foxe

s


005

010

015

020

025

030

035


Year

Pen

guin

s ki

lled

by fo

xes

01980 1985 1990 1995 2000 2005 2010

50

100

150

200

250

300

350


Year

Per

cent

age

of b

ande

d pe

ngui

nski

lled

by fo

xes

01970 1980 1990 2000 2010

1

2

3

4

5

6

7

8

9


































Acknowledgements


References



















































































Analysis


Results

Foxes killed



Fox abundance



Num

ber

of fo

xes

kille

d

01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

20

40

60

80

100

Bounty

Dog battue

Baiting

Spot-light

Leg-hold trap

Den fume

M44 ejector

Other

Roadkill

BountyControl

Eradication











Fox impact





40

50

60

70

80

Per

cent

age

harv

este

d

Fox

es K

TB

A

01994 1996 1998 2000 2002 2004 2006

20

40

60

80

100

120

140



Fox

es s

een

per

hunt

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

05

10

15

20

25Day Night




Discussion







Pro

port

ion

kille

d w

hen

seen

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

02

04

06

08

10


Time (month)

Pro

port

ion

of p

engu

ins

kille

dby

foxe

s


005

010

015

020

025

030

035


Year

Pen

guin

s ki

lled

by fo

xes

01980 1985 1990 1995 2000 2005 2010

50

100

150

200

250

300

350


Year

Per

cent

age

of b

ande

d pe

ngui

nski

lled

by fo

xes

01970 1980 1990 2000 2010

1

2

3

4

5

6

7

8

9


































Acknowledgements


References


























































































Fox impact





40

50

60

70

80

Per

cent

age

harv

este

d

Fox

es K

TB

A

01994 1996 1998 2000 2002 2004 2006

20

40

60

80

100

120

140



Fox

es s

een

per

hunt

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

05

10

15

20

25Day Night




Discussion







Pro

port

ion

kille

d w

hen

seen

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

02

04

06

08

10


Time (month)

Pro

port

ion

of p

engu

ins

kille

dby

foxe

s


005

010

015

020

025

030

035


Year

Pen

guin

s ki

lled

by fo

xes

01980 1985 1990 1995 2000 2005 2010

50

100

150

200

250

300

350


Year

Per

cent

age

of b

ande

d pe

ngui

nski

lled

by fo

xes

01970 1980 1990 2000 2010

1

2

3

4

5

6

7

8

9


































Acknowledgements


References



















































































Discussion







Pro

port

ion

kille

d w

hen

seen

0

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

2012

02

04

06

08

10


Time (month)

Pro

port

ion

of p

engu

ins

kille

dby

foxe

s


005

010

015

020

025

030

035


Year

Pen

guin

s ki

lled

by fo

xes

01980 1985 1990 1995 2000 2005 2010

50

100

150

200

250

300

350


Year

Per

cent

age

of b

ande

d pe

ngui

nski

lled

by fo

xes

01970 1980 1990 2000 2010

1

2

3

4

5

6

7

8

9


































Acknowledgements


References

















































































































Acknowledgements


References


















































































Lessons from long-term predator control: a case study with the red fox

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