Red Fox Spatial Characteristics in Relation to Waterfowl Predation Author(s): Alan B. Sargeant Reviewed work(s): Source: The Journal of Wildlife Management, Vol. 36, No. 2 (Apr., 1972), pp. 225-236 Published by: Allen Press Stable URL: http://www.jstor.org/stable/3799055 . Accessed: 06/02/2012 09:22 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected] Allen Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management. http://www.jstor.org TO IN RELATION REDFOX SPATIALCHARACTERISTICS PREDATION WATERFOWL NorthernPrairieWildlife ResearchCenter, JamestownRNorthDakota ALANB. SARGEANT, red foxes (Vulpes vulpes) on the CedarCreekareain Minnesotawerespatially Abstract: Radio-equipped contiguousterritories.Terdistributed,with individualfamiliesoccupyingwell defined,nonoverlapping, ritoryboundariesoftenconformedto naturalphysicalboundariesand appearedto be maintainedthrough some nonaggressivebehaviormechanism.Individualfoxes traveledextensivelythroughoutthe family 1 to 3 squaremiles in size, territoryeach night. Fox territoriesappearedto rangefrom approximately dependentlargelyon populationdensity. Red foxesused a sequenceof dens to reartheirpups,and the amountandlocationof foodremainsat individualdenschangedas the pupsmatured.The denningseason periodsof 4 to 5 weekseach. Remains confined-use,and dispersed-use was dividedinto pre-emergence, of adultwaterfowlwere collectedat rearingdens on six townshipsin threeecologicallydifferentregions of easternNorth Dakota. Remainsof 172 adult dabblingducksand 16 adultAmericancoots (Fulica americana) were found at 35 dens. No remainsfromdivingduckswere found. The numberof adult ducksper den averaged1.6, 5.9, and 10.2 for pairedtownshipsin regionswith relativelylow, moderate andhigh duckpopulations,respectively.Eighty-fourpercentof the duckswerefemales. The speciesand sex compositionof ducksfound at dens duringearly and late samplingperiodsreflectedthe nesting chronologyof prairiedabblingducks. Occupiedrearingdenswerefocalpointsof red fox travel,and the influenceon predation.Thirty-fiveof 38 densfoundon the locationsof densmay havehad considerable six townshipstudyareaswere on pasturedor idle lands. The distributionof rearingdens on the Sand nationalwildliferefugessuggestedthat,on theseareas,fox denswereconcentrated Lakeand Arrowwood becauseof the topographyandland-usepractices. specificcharactermuch studiesthatdemonstrate Redfoxesareabundantthroughout to theirinterin in relation areas of red foxes production istics of the prairiewaterfowl the UnitedStatesand Canada.They prey actions with waterfowl populationsare on waterfowland theireggs, but few data presented.A more detailedand compreareavailablethatdocumentthe use of these hensivereporton the CedarCreekstudy is beingpreparedfor publication. foodsourcesby red foxes. The purposesof thispaperareto discuss of red foxes STUDYAREAS certainspatialcharacteristics thatrelateto theirpopulationdensitiesand The CedarCreekstudyareaconsistedof predator-preyinteractions,and to portray 16 square miles centeringon the Cedar and discuss red fox utilizationof adult CreekNaturalHistoryAreain Anokaand waterfowlduringthe nestingseason. Data Isanticounties,Minnesota.This area conincludedin thispapercameprimarilyfrom tains a mixture of deciduouswoodlots, ( 1) literatureon the subject,(2 ) a studyon cultivatedand idle fields, and open and the ecologyandbehaviorof radio-equipped woodedswamps.Severallakesandmarshes, red foxeson the CedarCreekNaturalHis- a permanentstream,and numeroussmall toryAreain east-centralMinnesota,(3) a farmsandwell-traveled roadsare scattered studyof red fox utilizationof adultwater- throughoutthe area. The heterogeneous fowl on six townshipsin eastern North makeupof thisstudyareaprovideda varied on locations environment Dakota,and (4) observations fortheresidentfoxpopulation. of red fox dens on Sand Lake National Sixtownshipstudyareaswereselectedin WildlifeRefuge,SouthDakota,andArrow- three ecologicallydifferentprairieregions wood National Wildlife Refuge, North of easternNorthDakota (Fig. 1). These Dakota. Only certain aspects of these sites were not intendedto representbroad 22S 226 Journal of Wildlife Management, Vol. 36, No. 2, April 1972 Fig. 1. Locationof six townshipstudyareas in NorthDakota. geographicareas. Two of the townships werein BarnesCountyon the DriftPrairie, two in StutsmanCountyon the Coteaudu Missouri,and two in KidderCounty,predominatelyan OutwashPlain area of the Coteaudu Missouri(Bradleyet al. 1963, Huxeland Petri1965, Kelly1966). The BarnesCountytownshipswere intensivelyfarmedfor smallgrainproduction and had relativelylittle pasture or idle lands. Agricultureon the Stutsmanand Kiddercountytownshipswas an interspersion of small grain farmingand livestock grazing.Becauseof heavysnowfallduring the winterof 1968-69 andrapidspringrunoff, both the Barnesand Stutsmancounty townshipshad an abundanceof waterareas and supportedhigh populationsof nesting waterfowlduringthe springof 1969. The KidderCountytownshipseach containeda largealkalinelakebut relativelyfew freshwaterareas,andwaterfowlpopulationdensitieswererelativelylow. ArrowwoodNationalWildlifeRefuge is locatedin Stutsmanand Fostercountiesin easternNorthDakota.SandLakeNational Wildlife Refuge is in Brown County in northeasternSouth Dakota. Both refuges, comprisedof narrowzonesof land bordering impoundedlakesandmarshesalongthe JamesRiver,are surroundedby cultivated lands. Forthe CedarCreekstudyI amindebted to D. W. Warnerand B. R. Peterson,who were primarilyresponsiblefor the author's participationand provided guidance and supportthroughoutthe study;W. W. Cochran and V. B. Kuechleprovidedthe necessaryelectronicsassistance;D. B. Siniffcontributedmuchhelp in the developmentof methods;J. computerizeddata-processing field assistant; E. Forbeswas the principSal and R. L. Himes capturedthe necessary study animals.This study was generously supportedby the LouisW. and MaudHill FamilyFoundationof St. Paul, Minnesota; the NationalInstitutesof Health,U. S. Public Health ServiceTrainingGrant5T1 AI 188;and the Bureauof SportFisheriesand Wildlife,Divisionof WildlifeServices. I appreciatethe help of RefugeManager L. J. Schoonoverfor assistancein locating red fox rearing dens on the Sand Lake NationalWildlifeRefuge,and the help of RefugeManagerA. D. Kruseand graduate studentG. L. Rohdefor assistanceon the Refuge. Arrowwlood For help in documentingred fox population densitiesand theirutilizationof waterfowl on the six townshipsin NorthDakota, I am gratefulto C. M. Pfeifer,who served as both pilot and observer,and to W. K. Pfeifer, who served as an experienced observeron all aerialflights. R. T. Eberhardtand S. H. Allenassistedin collecting and examiningfood remainsfound at red fox dens, and R. E. Stewartand H. A. on waterfowl Kantrudprovidedinformation compositionand populationdensities in easternNorthDakota. For editorialassistancein preparingthis * Sargeant TO WATERFOWL FOXESIN RELATION paper I am particularlygratefulto P. F. Springerand F. B. Lee. 227 observationson SandLake Refugeduring May 1968and on ArrowwoodRefugeduring May andJune1969. METHODS red RESULTS The movelnentsof 32 radio-equipped foxes were followed on the Cedar Creek FoxSpatialOccupancy studyareafrom1963through1965withthe and the SocialGroup equipment An understanding use of portableradio-tracking of red fox spatialocandthe CedarCreekautomaticradio-track- cupancyrequiresconsideration of the social ing system( Cochranet al. 1965). Mostof structureof the species.Theredfoxfamily, thesefoxeswerecapturedin steeltrapswith whichformsthebasicsocialgroup,typically attachedtranquilizertabs ( Balser 1965) . consistsof an adultmale and female,and The automatictrackingequipmentenabled theirpupsfrojmwhelpingtodispersal. Seton recordingof (1929)referredfrequentlyto the fox family. semicontinuous simultaneous, the locationof most study animals.Data Scott (1943:444446) emphasizedthe imfilmby the track- portanceof the fox familyunit and recogrecordedon photographic manuallyand nizedthe tendencyof individualfamiliesto extracted were ing system placedon punchcardsfor computerproc- occupy relativelyexclusiverangeson the essing.Becauseof the largeamountof data, Moingonaareain Iowa. Ables( 1969) used analysiswas based on a samplingof fox radiotelemetry and documentedthe movemovementsat 10-minuteintervals,when- mentsof two spatiallyseparatedbut adjaever possible. Signallosses due to equip- cent groupsof red foxes on the 1,200-acre mentlimitationsoccurredperiodicallywith Universityof WisconsinArboretum, an area resultantminorgapsin the data,but these of mixedprairie,forest,and marshes,surlosses did not preventme from obtaining roundedin partby a residentialarea. an accuraterecordof fox movements. ) suggestedthatif "posiScott ( 1943:441 Systematicaerialsearchesto locate red tive reaction to a particularplace and foxes and active rearingdens were con- familiaritywaththe environment are maniductedovereachof the six townshipstudy festationsof territorythen territorialism is areasduringApril10-12, May 20-24, and characteristic of theredfox."Territorialism June 1S18, 1969. Individualtownships as used in this paper incorporatesScott's were flown at elevationsof approximately definitionbut also denoEtes exclusiveoccu150to 250 feet duringperiodsof favorable pationof specificareasby discretefamilies. light and weatherconditionson transects resultsfromtheCedarCreek Unpublished spaced 0.25 mile apart. Dense habitats that individualred fox established study werecircledformorecompletechecks.The same pilot and two observersparticipated socialgroups(families) mutuallyoccupied in all flights. Aftereachflight,landowners well-defined,nonoverlapping,contiguous integrityappearedto were contacted,and rearing dens were territories.Territorial somenonaggressive through maintained be visited and partiallyor completelyexcavated. All food remainswere collectedfor behaviormechanism.Boundariesof terrifuture identification. When pups were torieswerenotpatrolled,yet thereappeared capturedtheywereear-taggedandreleased to be an acute awarenessof the presence and a mutual avoidancebetween fanaily backintothe dens. Red fox dens were located by ground membersholdingadjacentterritories. 228 Journal of Wildlife l&Ianagement,Vol. 36, No. 2, April 1972 ing May FJune 3, 1964. The indicated areasof overlapbetweenfemales32 and35 FEMALE ;g,..^^'1' and females 31 and 35 were eaused by minorchangesin boundaries of homeranges duringthe studyperiod,errorsin locations of foxesdue to limitationsof the telemetry systemand inaceuraciesin recordingdata ( HeezenandTester1967),andthe method used to delineate the boundariesof the homerange.At anyspecifictimetherez was little overlapof the home rangesof these three females. The unoecupiedarea between females31 and 32 was the resultof a seasonalavoidanceof swampyareasalong CedarCreekby female32. ! Females31 and32 whelpedandwereearing for pups,whereasfemale35 was without pups. An adult male residedin each territory.An additionaladultfemale( withFig. 2. Home ranges of three red foxes in east-centralMin- out pups) livedin the territory with female nesota during May 6-June 3, 1964. The lines between fox 32. Thus, three differenttypes of social locations connect consecutivepoints in travel separated by groupsarerepresented in thesedata. no more than a l-hour differencein time. Theinelusionof at leasttwo adultfemales in a soeial group was also observedby Territorialboundarieswere well estab- Ables (1969), who documentedthe att-achlishedandoftenconformedto naturalphys- ment of two female littermatesto the ical boundariessuch as roads,streams,and natalareafor overa year. Sheldon( 1950) lake shores. Wet habitatssuch as marshes suggestedthe possibilityof polygamyin and swampswere avoidedto varyingde- redfoxesandpresentedseveralinstaneesof grees duringthe ice-freeseasonsbut were communaldenningby two littersand one used duringthe winter. All otherhabitats instancewherea barrenfemalewas caught were occupiedby foxes duringall seasons. at an activerearingden. Murie( 1961:152Except for the seasonalavoidanceof wet habitatsnear territoryboundaries,contig- 154) reportedobservingone or moresupuousred fox territoriesencompassed nearly plemental adults at three dens in Alaska. Three supplementaladult females were all landarea. Individual foxes generally traveled seenat one of Murie'sdens,andthe supplethroughoutmuch of the family territory mentaladultat anotherwas a male. of each night. The home rangeof any adult Certainred fox spatialeharaeteristies relevanee to this paper were evident from familymemberduringa 2-weekperiodportrayed the entire family territory.Thus, the findings at Cedar Creek and in the individualhome ranges and family terri- literature.Redfoxeswerehighlyterritorial, toriesweresimilarin theirspatialattributes. and their territorieswere oeeupiedby all Theterritories of threefox familieson the membersof the family. TerritorialboundCedarCreekarea are shownin Fig. 2 by aries often oonformedto naturalphysieal the homerangesof threeadultfemalesdur- boundaries,territoriesoften eneompassed L____. § | * 6 N- *[email protected]@ : FOX LOCATION DEN LOCATION HOME RANGE BOUNDARY -_ ROAD * 1b---- WESTERN 80UNDARY FEMALE35,APRIL.1964 - I MILE - - - * Sargeant TV WATERFOWL FOXESIN RELATION 229 areasavoidedby foxesin theirdailymove- to the west of the westernboundaryof ments, and contiguousred fox territories female35 was part of the territoryof an sometimesoccupiednearlyall landarea. adjacentfamilypriorto late April1964. On adultmale and April28 a radio-equipped Territory Size and Population Densities six pups from this adjacentfamily were Few detaileddescriptionsof the size of killed. After these deaths,female 35 and redfoxhomerangesarefoundin the litera- her mate rapidlyexpandedtheir territory ture. Seton (1929:47S)suggestedthat in- to includepartof the area previouslyocdividualred foxesoccupiedareasnot more cupiedby this family. This majoradjustthan5 milesin diameterbut did not ordi- mentin the territoryboundariessuggested narily range that far. Murie ( 1936:43) that the motherof the six pupshad either founda pair of red foxes occupying1,200 left the areaorwasdead. acresof the GeorgeReservein Michigan, As previouslydiscussed,the size of the areaoutsidethe Re- home range of individualred foxes was plus an undetermined ) concludedthat on similarto the size of the territoryof the serve. Scott ( 1943:441 the Moingonaareain Iowa,"anarc drawn family. Thus,thesefindingsand the home on a one-mileradiuswould ordinarilycir- rangedatapreviouslycited suggestedthat of theresidentin- redfox familiestendedto occupyterritories the movements cumscribe 1 to 3 squaremilesin size. dividual,pair or family"of red foxes. The approximately Low red fox populationdensitieswith daily range of Michiganred foxes, determinedby followingtheirtrailsin the snow, numerousuninhabitedareas developedin was calculatedas 14 squaremilesin south- easternNorthDakotaduringthe winterof ern Michigan(Amoldand Schofield1956) 196S69. Springpopulationdensitiesonthe and 2.8 squaremilesin northernMichigan six townshipstudy areasrangedfrom aptwo to seven familieson each ( Schofield 1960) . Storm ( 1965) found proximately homerangesof 910 and 1,040acresfor two township. Howe^rer,these families apadult male red foxes in northernIllinois. pearedto occupydistinctareasdespitethe Ables (1969) foundthe rangeof an adult low populationdensities. Red foxes have malelivingin a typicalWisconsinfarming been abundantin these countiessince the areato be 1)460acres,but the largestrange early 1940'sand were estimatedat 0.8 to of sevenred foxesresidingon the confined 1.4 adultfoxesper squaremile duringthe WisconsinArboretumwas 400 acres. He springof 1944 (North DakotaGanaeand suggestedthatthe richnessof thehabitat,in FishDept. 19495.Theirdeclinein 196969 termsof food abundanceand availability, occuredduringa severewinterwhensnow was a possible explanationfor the small coverwas optimumfor groundand aerial however,mayhave huntingand red fox fur priceswere high, ranges.TheArboretum, representedan islandof habitatin a sub- rangingup to $13.50each for unskilmed thatconfinedthe move- foxes ( S. H. Allen, personalcommunicaurbanenvironment mentsof theresidentfoxes. tion) . Thehomerangesizesforthe CedarCreek The findingsof this and other studies foxesshownin Fig. 2 were2.S,2.3, and3.3 suggestedthat red foxes have an innate squaremiles for foxes 31, 32, and 35, re- minimumand maximumspatial requirespectively.The home rangeof female3S, ment that was manifestedin their territosizewas however,nearlydoubledin size between riality.Withintheselimits,territory mid-Apriland mid-May1964. The area a reflectionof populationdensity,which 230 Journalof WildlifeManagement,Vol. 36, No. 2, April1972 in turnwas dependenton overallenvironmentalconditions.As densitiesof red fox the sizeof territory populationsdiminished, of the remaininganimalsincreased.Only when populationdensitiesfell below the level at which maximumterritorysize ocareasappearin suitcurreddid uninhabited ablehabitat. (dispersed were oftenused simultaneously use). Duringeachof theseperiods,one or more dens might be used by individual litters. The threeperiodsof den use lastedapproximately4 to S weeks each and were by differencesin pup feeding characterized behavior.Pups were nursedduringmuch period)and few food of the pre-emergence Den Ecology remainswere presentat dens. Duringthe period7pups consumedwhole at redfox confined-use Foodremainsthataccumulated rearingdens have been used to determine food items, but the remainswere often andcompleteexcavathe minimalnumbersand ie speciesand locatedunderground, sex compositionof certainprey used by tiorl of the den was necessaryfor their adult foxes in feedingffieirpups. Several retrieval.Most food remainsoccurredola period7 authorshave shownthat food remainsat thesurfaceduringthe dispersed-use densdo not accuratelyrepresentthe diet of butthe remainsof manywaterfowlbrought pup foxesnbecause desirablesmall items to these dens rnayhave been missed,bemay be totallyconsumed(Errington1937 cause they were often almosttotally conScott 1947>NorthDakotaGameand Fish sumedby the pups and the remainsscatDept. 1949?Drieslien1967). The observed teredoverlargeareas. incidenceof downydtleklingsat dens has littlemeaning,becauseducklingsare easily Incidenceand Abundanceof consumed.Generallyhowever,pup foxes Waterfowlat RearingDens leaveat leastsomefeathersof adultwater- Aerialand groundobservations showed fowlbroughtto the dens. that a minimumof 2S red fox families Whelping usually occurs during late inhabitedthe six township study areas. Marchor April in easternNorth Dakota Thetotalnumberof densnotedduringeach andafter ( NorthDakotaGameandFishDept.1949), of the ffireeaerialsurveyperiods? andfor 10-15weeksthe pupsareconfined wardsconfirmedas beingactiveor usedby in or near a sequenceof severalrearing the foxes earlierin the season,were 3) 12> dens. Scott (1943:144446, 1947.438)and and 21, respectively.Two additionaldens ScottandKlimstra( 1955:1>15)foundthat were locatedby groundobservers.Other individuallittersused fromthreeto seven studies previouslycited showed that red foxes used from three to seven different differentrearingdens. Physical and behavioralcharacteristicsrearingdens. The townshipfamiliesapof fox pups changedrapidlyduring the pearedto followthis samepatternof rnuldenningseason. The denningseasonwas tiple den use. Thus,the 38 densvisitedon dividedintothreeperiods:( 1 ) fromwhelp- the townshipswere only part of the total ing to emergenceof the pups from the numberof dens used by the 25 families )) (2) knownto occupy these areas. The total burrows(pre-emergence underground when all pup activitywas confinedto the numberof adult waterfowlfound at the ), and townshipdensis presentedin Table1. The immediatedenvicinity(confined-use (3) when pup activitywas more widely three dens located duringthe first aeriaI dispersedin the den areaand severaldens surveyperiodwerenot includedsincethey FOXESIN RELATION TO WATERFOWL * Sargeant 231 Table 1. Numbersof adult waterfowl as determinedfrom remains at red fox rearing dens in eastern North Dakota. DEN SITE NUMBEROF NUMBEROF ACTIVEDENS FAMILIES TOTAL COOTS COOTS PER DEN TOTAL DUCKS DUCKS PER DEN BARNESCOUNTY Township1 Township2 Subtotal 7 4 11 3 3 6 7 2 9 1.0 0.5 0.8 51 14 65 7.3 3.5 5.9 6 2 8 4 2 6 3 1 4 0.5 0.5 0.5 75 7 82 12.5 3.5 10.2 9 7 16 35 6 6 12 24 2 1 3 16 0.2 0.1 0.2 0.5 13 12 25 172 1.4 1.7 1.6 4.9 STUTSMANCOUNTY Township3 Township4 Subtotal KIDDERCOUNTY TownshipS Township6 Subtotal Total or average werevisitedduringthe periodof pre-emer- KidderCountytownshipson the Outwash gence,when few or no food remainswere Plain. StewartandKantrudalsofoundthat foundat dens. dabblingducksrepresented95, 83, and 91 The total number of adult waterfowl percentof the total duckpopulationin the utilizedby all the familiesunderstudyon three regions encompassingthe Barnes, the sixtownshipswasunknown.Thesedata Stutsman,and Kiddercounty townshipsr representedonly a partialcount because respectively. ( 1) the identificationmethods provided The averagenumberof ducksper den minimalcountson thenumberof waterfowl for the Barnesand Stutsmancountytownrepresented in retrievedremains,(2) many ships(Table1) was approximately proporrearing dens used by the families were tionateto the corresponding duckpopuladoubtlessnot foundor werenot completely tion densities. The average number of excavated,(3) food remainsat the dens ducksper den (4.9) for the combineddata representedonlyfood itemsbroughtto the from all six townshipswas similarto predens and did not include food that was vious findingsin 194347, when 5.0 ducks consumed or cached elsewhere by the perdenwereidentifiedat 62 densin eastern adults, and (4 ) the denningseason ter- North Dakota (NorthDakota Game and minatedpriorto the end of the waterfowl FishDept. 1949) . nestingseason. Differencesin redfoxutilizationof waterDatagatheredbetweenMay20 andJune fowl between the Barnes and Stutsman 17, 1969,in a studyby R. E. Stewartand countytownshipswithhighwaterfowldenH. A. Kantrud(personalcommunication ), sitiesandtheKidderCountytownshipswith indicateddabblingduck densitiesof ap- relativelylow waterfowldensitieswerealso proximately 32 and69 pairspersquaremile reflectedin the totalnumberof dens with for largerareas of the Drift Prairieand duckremainsandthe maximumnumberof Coteau du Missouri,which included the ducks at individualdens. Duck remains BarnesCountyand StutsmanCountytown- were found at 18 of 19 dens on the four townshipsduringtheconfinedships,respectively.Applicabledensitydata high-density use and dispersed-use denningperiodsand for waterfowlwere not availablefor the 232 Journal of Wildlife Management, Vol. 36, No. 2, April 1972 at only9 of 16 denson the two low-density species (Errington1937,Scott 1943,1947, townships.Themaximumnumberof ducks ScottandKlimstra1955) andthuswerenot found at a single den on the low-density dependenton waterfowlfor theirsurvival. townshipswas six. Eightdenson the high- Their utilizationof waterfowlwas dependensityareascontainedremainsof 8 to 33 dent not only on the abundanceof vulnerable waterfowlbut on the abundanecof ducks. preyandthe predatorybeSuccessivedensusedby six litterson the othervulnerable havior of individual foxes. In Barnesand high-waterfowl-density townshipsshowed accumulated totalsof 1, 12,18, 19, 24, and Stutsmancounties, waterfowl were un27 ducks for each litter. In no instance, doubtedlythe most abundantlarge, wild however,werevisitsmadeto all of the dens prey species. Meadowluouse ( Microtus used by a litter. Strangelyenough, the pennsylvanicus) populationswere abnorfamilyfor whichonlyone duckwas found mallyhigh in the springof 1969,and they lived adjacentto a large marshwith an were heavilyused by the foxes in all six abundanceof waterfowl. Although the townships.Theymayhavebufferedredfox foxes appearedto use ducksin proportion utilizationof waterfowl. to their abundance,no diving duckswere of foundin the food remainsat dens. Diving Speciesand Sex Composition ducksoccurredin all areas,and theirnon- Dabbling Ducks at Rearing Dens use by foxes is ascribedto their almost The speciesandsex composition of adult totallyaquaticnestingand feedinghabits, ducksfoundat the townshipdensaregiven whichmadethemunavailable to foxes. The in Table2. The sex ratiosof duckson the relativelyhigh vulnerabilityof dabbling townshipswere unknown,but Bellroseet ducksis discussedin the followingsection. al. (1961:405408) determinedthat males Americancootsrepresented12,5, and 11 usuallypredominated amongadultsin most percentof the total waterfowlremainsat duck species. It was evident from these dens in the Barnes,Stutsman,and Kidder datathatredfox utilizationof adultwatercountytownships,respectively(Table 1). fowl duringthe nestingseasonwas directed StewartandKantrud(personalcommunica- towardfemale dabblingducks. The fact tion) found that coots represented6, 27, that females made up 84 percent of all and4 percentof the totalwaterfowlin the ducksthat were identifiedas to sex and regionsencompassing thesesametownships, that femalesnever comprisedless than 75 respectively.The abundanceof coots at percentof any singlespecies,clearlyindidens was lowest in the StutsmanCounty catedselectivepredationon females. townships,wheretheir actualnumberand Thephysicalconditionandcauseof death their populationcompositionwere appar- of the waterfowlutilizedby the township entlyhighest(Table 1). Theseresultsap- foxes could not be determined.No nonpearinconsistent with the nonuseof diving predatormortality,however)such as roadducksby foxes,sincecootsalsowerealmost kills was knownto occurin sufficientmagtotallyaquatic.Coots,however,unlikediv- nitudeto accountfor the numberof ducks ing ducks,were frequentlyobservedwalk- found at the rearingdens. Agricultural ing on the shoresof manymarshes,where practices,particularly haying,were known theymayhavebeenvulnerableto predation to inflictlosseson nestinghens,but haying by foxes. was just beginningin mid-Junewhen the Red foxes utilized a variety of prey last den surveyswere being made. Tllere FOSESIN RELATION TO WATERFOWL * Sargeant 233 Table 2. Species and sex compositionof adult ducksat red fox rearing dens in six townshipsin eastern North Dakota. NUMBER OF DUCKS (MAY26JUNE4) Blue-winged teal Pintail Shoveler Mallard Gadwall Green-winged teal (Anas carolinensis) American widgeon (Mareca americana) Total or average NUMBER SPECIES OF DUCKS COMPOSITION (JUNE16(PERCENT) JULY 9) SPECIES NUMBEROF FENIALE COMPOSITION SEX_DETER_ DUCKS (PERCENT) AfINEDDUCKS (PERCENT) 19 28 10 9 3 26 38 13 12 4 27 18 13 9 12 32 21 15 11 14 39 43 11 16 13 85 79 100 87 78 2 3 5 6 4 75 3 74 4 100 1 85 1 100 3 129 100 84 was also little evidence of remainsfrom points of activity. Foremostamongthese waterfowlutilizedby otheranimals. areas were the active rearingdens. The Sowls (1955:83,8S87), comparingthe concentration of movementaroundrearing nesting chronologyof prairie dabbling dens is illustratedin Fig. 2 by the moveducks,showedthat mallards(Anas platy- ment pattemsof foxes 31 and 32 on the rhynchos) and pintails(Anasacuta) were CedarCreekarea. early nesters,blue-wingedteal (Anas disSince occupiedrearingdens were focal cors) and shovelers ( Spatula clypeata) pointsof red fox travel,the probabilityof were mid- to late-seasonnesters, and foxes encountering nestingwaterfowlnear gadwalls(Anasstrepera) were late-season the dens wouldseem greaterthanin most nesters.This trendin nest chronologywas areaswithinthe territory.Thus,two areas reflectedin the relativespeciescomposition of similarhabitat and similarwaterfowl of ducksfoundat the townshipdensduring densitiesin the same fox territoryInight the samplingperiodsof May2FJune4 and experiencedifferentpredationrates, deJune l>July 9 (Table 2). These differ- pendingon their proximityto the rearing ences in species compositionwere mini- den. This factor becameincreasinglyimmized,sincemanyof the densvisiteddur- portantduringthelatestagesof thedenning ing the late samplingperiodundoubtedly seasonwhenpupmovementwasdistributed containedremainsfromearlierperiods. throughoutthe den area. The high incidenceof female dabbling Natalden sitesmaybe locatedanywhere ducksandtheirchangein speciescomposi- withintheredfox territory, but successively tion in accordancewith theirnestingchro- useddenswereoftenin thenatalarea.Red nologysuggestedthatmostof thewaterfowl fox dens frequentlyhad a historyof prefoundat the rearingdensrepresented selec- vious use, and the site selectionappeared tive predationby redfoxeson nestinghens. unrelatedto preyabundance.Thelocations of the 38 active rearingdens on the six [)en Locationin Relation townshipswere35 onpastureandidlelands to Waterfowl Predation and 3 on cropland.The high use of pasIndividualred fox movementovas dis- turedand idle landsfor denningoccurred tributedthroughout thefamilyterritor,v, but even on the BarnesCountytownshipsthat certainbehavioraland life historyevents werealmostcompletelycultivated. resultedin specific areas becomingfocal Thedistribution of occupiedrearingdens a.S- 234 Z w Journal of Wildlife Management, Vol. 36, No. 2, April 1972 nestingwaterfowlthanwouldhaveoccurred if the dens had been locatedoutsidethe refugeboundaries. SAN3 LAdE - _ 7 ARROWWOOD N^rlow^L WILDLIrf RErUGE S S ONAL Wl6DLIFE 1968 REFUGE DISCUSSION I Red fox-waterfowlinteractionsin the prairiewetlandregionresultfromthe annual influx of migratorywaterfowlinto areasalreadyoccupiedby spatiallydistrib'. uted red fox familygroups. Thus, unlike many predator-preyrelationships,an annual cycle of renewedencountersoccurs betweenfoxesandwaterfowl.Althoughred s? I ) foxes (a terrestrialspecies) and waterfowl ( an aquaticgroup) occupy differentenvironmental niches during much of the Fig. 3. Locationof active red fox rearingdens on Sand Lake National Wildlife Refuge, South Dakota; and Arrowwood nestingseason,dabblingducksutilize terNational Wildlife Refuge,North Dakota. restrialhabitatfor egg-layingand incubation. Duringthis period,nestinghens apon the SandLakeandArrowwood national pearquitevulnerableto predationby foxes wildliferefugesis shownin Fig. 3. These and,as shownin Table1, areusedforfood. datashoweda concentration of redfox dens Redfoxpredationon waterfowlis related in goodwaterfowlnestinghabitatas a result in part to fox populationdensities. The of certainlandfeaturesand land-useprac- territorialcharacteristicsof the red fox tices. The refuge lands were managedas familygroupresultin completeoccupancy wildlife habitatand were subjectto rela- of nearlyall land areasin the prairiewettivelylittlehumandisturbance, whereasthe land regionduringperiodsof moderateto surroundinglands were intensivelyculti- high populationdensitiesand the occurvatedandsubjectedto greaterdisturbance. renceof uninhabitedareasduringperiods The James River flowing throughboth of low densities. However,even during refugesformeda naturalboundaryseparat- periodsof high fox populationdensities, ing the foxes into subpopulations on each individualwaterfowlengagedin egg-laying side of the river.The refugelandsalsohad andincubation maybe exposedto predation an abundanceof well-drainedslopes that by only a singlefamilyof foxes. Areasof providedgood denningsites. These topo- goodhabitatthatconcentrate nestingwatergraphicalfeaturesand land-usepractices fowl may also be utilizedby only the red resultedin an apparentselection of the fox familyoccupyingthat area as part of refugelandsas denningareasanda spacing its territory. of occupieddenswithinthe refugebound- Duringperiodsof low redfox population aries. No systematicsearchesweremadeto densities,predationon individualsites is locate all dens on eitherrefuge,and it is highly variable,dependingupon whether assumedthatsomeweremissed.The loca- the sites are locatedinside or outsideof tion of these dens concentratedfox move- territoriesoccupiedby foxes. Withinterment on the refuge lands and may have ritoriesoccupiedby foxes, predationmay resultedin considerably morepredationon be of similarintensityto that occurring -! . , ,, = _, - I 3_ S =-- = = - -==._- H , &=n _ _ I F- MF-_ l--' a[' _- J < A J < - N- | HAR5 * ACTlVE H 5 . 0t LAKE REARING M1t t5 n SC ALE DEN5 FOXESIN RELATION TO WATERFOWL * Sargeant 235 duringperiodsof moderatefox population low populationdensities.Huntingcharacdensities,whereasoutsidethe territory,no teristicsof individualfoxes and the abunpredation from foxes ordinarilyoccurs danceandavailabilityof otherpreyspecies unlessit is fromtransientor displacedin- possiblyare reflectedin variablepredation dividuals. Thus, as was observedon the rateson nestingwaterfowl.These charactownshipstudy areas,althoughpredation teristicsfavorsurvivalof waterfowlin areas by individualred fox familiesappearssub- occupiedby redfoxes. stantial,the impacton the total township A high priorityobjectiveof mostwaterwaterfowlpopulationswas relativelyminor fowl management programsis to maintain becausemuchof the areawas unoccupied or increasewaterfowlpopulationsfor recby foxes. reationaluse. The loss of adult hen dabRedfoxpredationon waterfowloccursas bling ducks to foxes affects the annual the result of encountersbetween family waterfowlproductionpotentialof an area membersand vulnerablewaterfowl.Red becauseit occursat that time of the year fox movementwithin the territoryserves when waterfowlpopulationsare at their two fundamentalneeds: to maintainthe lowest levels and losses are largely nonterritoryand to simultaneously fulfill the compensatory. Furthermore, redfoxpredanecessitiesof life. Thus,all movementby tionis not restrictedto adultwaterfowlbut foxesmustnot be interpretedas represent- also occurson waterfowleggs and ducking orbeingmotivatedby huntingbehavior. lings. The significanceof these losses in Red foxes travelin and occupyareasnot terms of waterfowlabundanceand the normallyused for hunting,and predation harvestablesurplusis unknownbut may may occurin these areasas a resultof a proveto be substantialin someareas. circumstantialencounterwith vulnerable Red foses have considerableeconomic prey. valuesandsportingqualitiesthatrankthem highas furandgamespecies.Reductionin fox populationdensities as a means to CONCLUSIONS alleviatepredationhasbiological,economic, In consideringthe impactof red foxes on nestingwaterfowl,a carefuldistinction andnaoralimplications.In any attemptsto mustbe madebetweenwaterfowlsurvival reduce populationdensities,consideration must be given to the social and spatial andwaterfowlabundance.Waterfowlhave of the species that under built-inmechanismsthat favorsurvivalin characteristics normal fox populationdensitiesresult in areasof suitablehabitat. Thus, renesting by waterfowlcompensatesin part for egg the rapid inclusionof uninhabitedareas losses;homingand pioneeringare factors into existing territories.Certainlymuch is neededto understand in repopulation of depletedareas;andlarge moreinformation fox-waterfowl relationships before any clutch sizes providean annualpopulation incrementto compensatefor variousmor- measuresare employedto preventred fox predationon waterfowl. talityfactors. Red fox population densities appear regulatedby inherentspeciescharacteristicsLITERATURE CITED andoverallenvironmental conditions.Areas ABLES,E. D. 1969. Home-rangestudiesof red with little or no use are often includedin foxes ( Vulpes vulpes ) . J. Mammal.50( 1): 108-120. fox territories,and uninhabitedareas de- ARNOLD, D. A., ANDH. D. SCHOFIELD. 1956 (1955). velopbetweenterritoriesduringperiodsof Home range and dispersalof Michiganred 236 Journalof Wildlife Management, Vol. 36, No. 2, April 1972 foxes. MichiganAcad. Sci.,,Arts,and Letters MURIE,A. 1936. Followingfox trails. Univ. of MichiganMuseumof Zool. Misc. Publ. 32. Papers41( pt. 2 ) :91-97. 4Spp. D. S. 1965. Tranquilizertabs for capBALSE;R, in Alaska.The Devin1961. A naturalist turing wild carnivores.J. Wildl. Mgmt. 29 AdairCompany,New York.302pp. ( 3 ) :438 442. AND NORTHDAKOTAGAMEAND FISH OEPARTMENT. A. S. HAWKINS, F. C., T. G. SCOTT) BELLROSEX 1949 The red fox in North Dakota. North Dakota Game and Fish Dept. P-R Rept. Project7-R. 31pp. R. D. 1960. A thousandmilesof fox E., L. R. PETRI,AND:0. G. ADOLPHSON.SCHOFIELD, BRADLEY, trails in Michigan'sruffed grouse range. J. 1963. Geology and groundwater resources Wildl.Mgmt.24(4 ):432-434. of KidderCounty, North Dakota. Part III. Groundwaterand chemicalqualityof water. SGOTTT. G. 1943. Somefood coactionsof the northernplains red fox. Ecol. Monographs NorthDakotaGeol. SurveyBull. 36. 38pp. 13(4 ) :427-479. J. R. TESTER, W. W.> D. W. WARNER, COCHRAN) . 1947. Comparativeanalysisof red fox ANDV. B. KUECHLE.196S. Automaticradiofeeding trends on two central Iowa areas. trackingsystemfor monitoringanimalmoveIowaStateColl.Agr.Expt.Sta.ResearchBull. ments. BioScience15(2).98-100. 353:427487. in R. L. 1967. Fox-preyrelationships DRIESLIEN, , ANDW. D. KLIMSTRA.195S. Red foxes eastern South Dakota. M.S. Thesis. South and a decliningprey population. Southern DakotaStateUniv. 89pp. Ser.1. 123pp. IllinoisUniv.Monograph P. L. 1937. Foodhabitsof Iowared ERRINGTON, foxes duringa droughtsummer.Ecology 18 SETONE. T. 1929. L;vesof gameanimals.Vol. 1. DoubledayCompany,Gardencity7 New ( 1) :53-61. York.640pp. K. L., ANDJ. R. TESTER. 1967. EvaluaHEEZEN, W. G. 1950. Denninghabitsandllome SHELDON, by triangulationwii tion of radio-tracking range of red foxes in New York State. J. specialreferenceto deermovements.J. Wildl. Wildl. Mgnlt. 14(1 ) :3342. Mgmt.31( 1) :12W141. L. K. 19SS. Prairieducks: a study of HUXEL,C. J., JR.,ANDL. R. PETRI. 1965. Geol- SC)WLS, theirbehavior,ecologyandmanagement.The ogy and groundwater resourcesof Stutsman Pennsylvania. StackpoleCompany,EIarrisburg, County,NorthDakota. PartIII. Groundwa193pp. ter and its chemicalquality. North Dakota Geol.SurveyBull.41. 58pp. STORM,G. L. 1965. Movementsand activities T. E. 1966. Geologyand ground7ater KE:LLY, of foxes as determinedby radio-tracking.J. resourcesBarnesCounty NorthDakota. Part Wildl.Mgmt.29(1):1 >13. III. Groundwater resources.North Dakota Receivedfor publicationApril30) 1971. Geol. SurveyBull.43. 67pp. J. B. Low. 1961. Sex ratiosand age ratios in NorthAmericanducks. IllinoisNat. Hist. SurveyBull.27( art.6 ):391-474.
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