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
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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-
*g@@
:
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,
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1963. Geology and groundwater resources
Wildl.Mgmt.24(4 ):432-434.
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northernplains red fox. Ecol. Monographs
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W. W.> D. W. WARNER,
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in
R. L. 1967. Fox-preyrelationships
DRIESLIEN,
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DakotaStateUniv. 89pp.
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IllinoisUniv.Monograph
P. L. 1937. Foodhabitsof Iowared
ERRINGTON,
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1. DoubledayCompany,Gardencity7 New
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K. L., ANDJ. R. TESTER. 1967. EvaluaHEEZEN,
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SHELDON,
by triangulationwii
tion of radio-tracking
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specialreferenceto deermovements.J. Wildl.
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L. K. 19SS. Prairieducks: a study of
HUXEL,C. J., JR.,ANDL. R. PETRI. 1965. Geol- SC)WLS,
theirbehavior,ecologyandmanagement.The
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Pennsylvania.
StackpoleCompany,EIarrisburg,
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Geol.SurveyBull.41. 58pp.
STORM,G. L. 1965. Movementsand activities
T. E. 1966. Geologyand ground7ater
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