8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep http://slidepdf.com/reader/full/slope-use-by-cattle-feral-horses-deer-and-bighorn-sheep 1/8 David Ganskopp, tlnted StatesDepartrnent i Agricu ure-Agricuura ResearchService EasternOregon AgriculluralResearchCentea StarFt. 1 4.51 Hwy.205, Burns,Otegot\97720 an o Martin Vavra, Oregon Slate Universily, EasternOregon AgriculluralResearchCenter Sfar Rt.1 4 51 Hwy. 2 0 5 , B u r n s ,A r e g o n9 7 7 2 0 SlopeUseby Cattle,FeralHorses,Deer,and BighornSheep' Abstract Parfernsofslope urilizarionby cattl€ Bosspp.), eral horses tqaus calallrr), Rocky Mountain nule deer Odocoileus emionus hemionus),and California bighorn sheep Oaiscanadensis aLifuntdnd) were monitored ro compare heir distributions ro rhe topographiccompositionsof iheir respectivehabitals. The hypothesis hal each species tilized slope ciasses n proportion ro rhe ropographiccornpositions f thei. respective abitats {as rejected P < 0.01).Bighorn sheep aciivilies {€re nol impair€d by slopesof up to 80%. Cattle,horses, and deer demonstrated negativ€ cur linear responses o increasing slopewirh initial sire avoidanceexhibired on 20, 30, and 40% slopes, €spectively. Vhere large expanses f level topography were available, cardeandhorsesmade ess use ofsteep slopes han th€ir counterparts nhabiting more rugged €rrain. Th€sedaia demonslrat€ that cattl€, horses,and d€er should not b€ €xpect€d o nake randon us€ of fotrge r€sources n rugged terrain. lntroduction An awareness f the distribution nd movement patterns of large herbivores is particularly valuable to managers chargedwith allocating resourcesr assessing he mpacts f utilization by large herbivores. The arrangementof food, water, nd shelter, nd heir concuirent nterac- tions ryith topographic features obviouslyin- fluences he distribution of animals and their simultaneous se of an area's esources. lope gradientmay also be a major determinant of her- bivore distribution n rugged errain. With the exception of cattle (Bos spp.), few data are available escribing he upper imits of slopeuse by largeherbivores. Cattle favor the relatively level ground associateddth drainages,asins,nd idgetops (Glendening 944,Blood 1961,Demarchi1965, Julander and Jeffery 1964, Mueggler 1965, Phillips1965,Cook 1966,Mackie 9?0, Patton 1971,Gillen1982,Barrett1982).n general at - rle limit their use of hillsides when gradesap- proach30% (Blood1961,Patton1971,Cillen rThe EastemoregonAgricullural Res€arch enter, ncludins the Squaw Buue and Union Stations, sjoinlly operatedby oregon Agricultural Experin€nt Sradon and U.S. Depart- ment of Agrirultur". {griculruralRpscar.hServi.e. 'lThis researchwasa cooperatireeffortjointly funded by the Bureau oi Land Managenent, conlract number YA-s12-CT8-137,and tbe Easrern oregon Agricultural Research enter.Technical paper nunber 7793.Oreson Agricultural Experinent Station. 74 NorthwestScience, ol. 61, No.2, l9B7 1982, Yan Vuren 1982).Upslope presence of palatableforage (Gonzalez1964, Cook 1966, Bryant l9B2),salt(ChamplineandTalbot 1926, Skovlin1965), r water Skovlin1965), owever, may encourage dditionalutilization of hillsides. Feral horses Egaascoballas)havean affin- ity for ridgetops or elevated errain (Pellegrini 1971, Welsh l9?5, Miller 1980, Keiper and Berger 1982); owever, o one has attempted o quantify heir use of hillsides. eJlegriniI971) notedhorses voided teep ills,and that they rapidly traveledoverunavoidableough terrain. Most workers eportmule d.eetOdocoiLeus hemionushemionus) hov little response o topographic ariation Demarchi 965,Mackie 1970, Barrett 19B2).Someobservers eport, however,hat slope ndirecdyaffectsdistribution of deer hrough ts impacton snorv ccumulation and persistenceWilkins195?,Loveless 967, Gilbenet al.1970,Dusek1975) r microclimate and vegetation atternsJulander1966,Loveless 1967,Mackie 9?0). Although bighorn sheep (Oois canadensis) habitat is synonymous with rugged cliffs and highly dissectederain (McCann1953,Harris 1956,Russo1956, McCullough nd Schneegas 1966, odd 9?2,Jones 9B0), ewworkers ave addressed heir use of rugged topography. Demarchi1965)eported positive orrelation between he frequencyof sightings of bighorn and ncreasing egree f slope, utprovided o
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Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep
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8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep
In this project we monitored the frequencyof use of slopes y cattle, er al horses,RockyMountain mule deer, and Californiabighornsheep Ooiscanadensis aliforniana) iorr' Apil
1979 through March 1981. Our goal was toestablish hresholds f slopeuse or horses, eer,andbighornsheep, nd o supplementhe nfor-mation available or cattle. We first tested hehypothesis hat each herbivoreutil ized slopeclassesn proportion o their availabil ity.Whenthishypothesis as ejected,we urther examinedthe data o deteminewhichslopes ere avoredor avoided.
StudyAreaThe study was conductedapproxirnately65 kmsouthof Vale, Oregon, n a 375 km'] areaad -ministered y the Bureau f LandManagement.
The area ncluded hreedesignatedastures,froughly62,31, and 219 km'?, nd an adjoining
63 km'?unit o the southwhichcontained por-
tion of the bighornsheep ange.Pasture oun-dariesconsisted f 4-wirestock encing, he eastshoreline f the OwyheeReservoir, nd somenaturalbarriers.Approximately 3% of the studyarea was within 1600 rn of permanentwater
sources.
Topography anged rom well-eroded, ently-rolling hills to mountainous idges,cliff rock, andcanyons, levations anged rom 809 m, poollevel of OwyheeReservoir,o 1687m. Majorp l a n t c o m m u n i t ie s u p o t e d o v e r s t o r i c sdominated y Wyomingbig sagebrushlrtemisia
trid,entata uyomingensis) or low sagebrush(Ar temis ia arbuscu la) . Herbaceous ayerdominants included bluebunch wheatgrass(Agropyron picatum),Sandberg's luegrassPoa
sand,bergi), nd cheatgrassBromus ectorum\.Historic overgrazing y large numbersof
horses up to 2500 in the 1940's), ong-termseasonal seby livestock, nd occasional ildfires
have affected the distribution of plant com-munitieson the area.Bluebunchwheatgrass,large and palatable erennial unchgrass, asmost prevalenton slopes n excess f 2 0%,
Cheatgrassand Sandberg's bluegrass, wospec ies t yp ica l l y character i z ing abusedrangelands, ere dominants n drainages ndlargebasinswhereslopesweregenerallyess han207o,Wyomingbig sagebrush nd ow sagebrushdid not exhibit any systematicpatterrs ofdistribution. etailedmapsand descriptionsf
majorplantcommunities reprovided y Gans-kopp(1984).
Feral horses nd bighorn sheepwereyear-round esidents. he total numberof horsesnthe hree asturesncreasedrom 133 o l68 dur-ing our study.Bighornsheep ccupied smallportion of the largestpastureand the adjoining63 km' area o the south.The herdconsisted fabout 100 animals,
Deerand cattlewereseasonal ccupants fthe area.Approximately 00 o 300 deerwinteredon the area rom 0ctober hroughApril. Cattlegrazed he threepasturesrom April throughOc-
tober on a deferred otationbasisduring bothyearsof study. Their use otaled 1600AUMs in1979and 3900AUMs n 1980.Mean ivestockdensity or the threepastureswas0.75 cows/km'in 1979and l.B cows/km']in 98 0.
Methods
The last two weeksof eachmonth weredevotedto suryeying he study area n an attempt oplotthe locationof as many animalsas possible.
Binocularsand a 20 to 40X spottingscopefacil itatedong-rangeearchingor largeherbi-vores.Movement bout he areawas accomp-lishedwith four-wheel rive vehicles nd by foot.
Incidentalsightingswerealso ecordedand onlyanimals nit iallyunaware f our presence er eutil izedas data sources.We did not knowinglyrecord duplicateobservations f a reco gnizedgroupor individualwithin a 24-hour eriod.
Percents lope o f ob le rva t ion i l es nasmeasured ith a clinometer.f more han oneanimalwas nvolved, he measurement asmadeon an areadeemedepresentativef the group.Eachsightingwas reatedas a singleobserva-tion, regardless f the number of animals n-volved.A coordinate rid, superimposedn al:63360mapof the studyarea,alloved documen-
tation of s ighting ocations.Because orsesand bighorn sheepwereyear-
round esidents f the area, heir data eflectarelatively niform distributionof obsenations
SlopeUse by Cat tle,Feral Horses,Deer,and BighornSheep 75
8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep
that cattle,horses, nd bighorn sheepwereeitherconfinedo, or choseo occupy nlycertainpor-
tions of the studyarea,Sightings f mule deerwerewell dispersed ver he entirestudyarea.Based n these istribution atterns, e definedthe geographic oundaries f eachherbivore'shabitat.Consequently,ur data depictonly he
habitat characteristicsf areas requented yeachspecies.
Becausecatt le respected he fences and
naturalboundaries f thepastures, e assumedthey occupied hreedistinct habitatson the area.Datawere a l l i ed ypasture i t h heassumpt ionthat an entirepasturewasavailable or therr use.
Horses n the areawereeasily dentif iedbyreferencing ketches f distinguishing haracter-
istics.Meanhome angesize minimum onvexpolygon)was 12 km'with no seasonal hifts n
home rangesoccurring Ganskopp nd Vavra1986). ix distinctherdsof horseswere dentified
du ng the study.Because andsand bachelorscomposing achherd appearedo restrict heir
movementsvoluntarily, we outlined the outer-most oord ina tesf each erdwi lha m in imumconvex olygon Southwood 966), n d assumed
the circumscribedrea onstitutedhe availablehabitatof eachherd.Threesmallherds each up-porting < l5 anir nals) erenot ncluded n thisanalysrs.
Deer were observed hroughout he studyarea.Total numberof deersightedwas146? ,rithI157 animals lassif iedo sexand age.Buck o
doe ratiosaveraged 3.5/100,nd fawn to doeratiosaveraged 1.4/100. ecausendividualdeercould not be dentifiedor linked o a specificunitof land, we assumedhe entire areawasavailablefor their use.
Bighornsheep ccupied relatively estricted
area n themore ugged outhern ortionof the
study area. A minimurn convexpolygon,cir-cumscribing 3 km'z,was used o define heirhabitat.Bighorn ouldbe oundat any ocation
or elevationwithin their range hroughout hedurationof the study,Total numberof bighornsightedwasBll with 691 animals lassif iedo
sex and age.The lamb to ewe atio averaged
54.1/100, nd the ram t o ewe ratio averaged59/100.
Outlinesof the study areaand the varioushabitats were transferred o U.S. CeologicalSurvey opographicmaps,Map scalewas :24000
with 12.19m belween ontour nteivals. sam-pJe of 1545 randomly sele,"led oinls were
descr ibedoder ivehe opograph icompos i t ion
of thehab i ta ts . i s tanceet$ppn d jacenton-
tour l inesbracketing achpoint ras measuredand convertedo horizontal istance. he ver-t ical distancebetveen contour ntervalswasdivided y rhehorizontal istance etween on-
tour inesandmultiplied y 100 oyieldpercent
slope.Data ere compiled or eachherbivore nd
habitat in l0% intervals ranging from 0 to80 + % slope.Chi square nalysis f homogeneity(P < 0.05)wasused o test the null hypothesis(Ho) hat the proportion f useof slope lasseswasequivalent o the occurrenceof the classesin the polygon, asture, r d esignated abitat.If Ho was ejected, imultaneousonfidencen-tervals for differences between percentages(Snedecor nd Cochran196?,Marcumand Lofts-gaarden9B0)werederived o determine hichclasses ereoccupied t signif icantlyP < 0,02)g r e a l e r h a n e r p e c t e d e v e l s a p o . i t i r epreferenceating),wereutil ized oughly n pro-portion o their occurrencea zeropreferencerating),or wereutil izedat less han expectedleve lsa nega l i ve re ferencea l ing) .
When simultaneo us omparisons re con-ductedwithin several ategories,he probability
that all comparisonsave eached correct on-
clusions a function fthe totalnumberof com-parisonsmade nd heprobabilityevelselectedfor each ndividual omparison.he probabilitythat all comparisons ave eacheda correctcon-
clusion= I - N P where:N is the numberofcategoriesndP is theprobabilityevel elected
for the individual comparisons.f the numberofcategoriess lar ge and a conventional ignif i-canceevelof P = 0.05 s employed,he proba-
bility that all comparisonsave eached correct
76 Ganskopp nd Vavra
8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep
conclusion ecomes uite small.This problemmay be ovcrcome o somedegree y usinga more
conservativeignif icanceevel i.e.,P = 0.01).0ne doesnot wish o besoconservative,owever,
that real differences etween ercentages aygo undetected, nd unconventionalrobabil ityle r . l . a reocca. iona l l l ' edasa compromisen
this procedure. ecause omeof our data con-tainedasmanyas ninecategories, probabil ity
levelof P ( 0.02wasselectedor detecting if-ferences between percentages.With ninecategorieshere s a 0.88probability hat all of
our tests ave eached correct onclusion. euet al (1974) nd Marcum and Loftsgaarden1980)
provide a more detailed discussionof thestatistical rocesses.
Data werealsopooled or eachspecies ndequations redicting he proportion f observa-
tions expected n sites with increasing lo pederived hrough egression nalysisNeterand
Wasserman9?4),F test s or comparison f tworegressionines P ( 0.05)were onduc ted ithallpossib)enterspecif icombinationso examinethe hypothesishat patterns f slopeuse wereidenticalamongany of the four speciesNeter
and Wasserman 974).
Results
Respective eanslopes f sitesutil izedby cat-t le,horses,eer, ndbighornwere .8, 1.2,15.7,and42.5%.Data or cattle,horses, nd deerwere
skewedn favorof relatively entle opography,
50means hou ld e r ieupdwi thsome aut ion .
The hypothesis hat each herbivoreutil ized
classesfslopesn propo.tiono the opographiccompositionsftheir respectiveabitatswas e-jected n all casesP < 0.01).
Two hundred wenty-trvo bservations f cat-t le were ecorded, ith an average roupsizeof
14.6 nimals. hegreatest lope n whichcattlewereobservednvolvedonesightingon a 70%grade.All otherobse.vations ereon slopes fless han 40%. Patterns f slopeuse by cattlegenerally reflected those reported in theliterature Table ). Cattle avored lopesn the0-9% categoryn all pastures nd appearedn-
d i f fe ren t o s lopesn the l0- l9aoca lcgorynpastures
andC.They
avoidedlopes xceeding
20% in all three pastures.
Catt ledemonstratedome ar iation n theirpatterns f useamong he threepastures. his
is bestevidenced y comparing astures an dC which depict the extremesof topographyarailablpo these nimals. opographynpastureB was elativelygentlewith a meanslopeof 19%.
The mean lopeof pastureC was3?%, and cartle in thispastureweremoreoftenobserved nthe steeper lopes. his suggestshat cattle n-
habit ing ugged errain wil l makemore useofsteep lopes han cattleconfined n more evel
topography. onversely,att lehavingaccessolarge expanses f gentle opography re lesslikely o venture pslopehan heircounterpartsoccupyingmore ruggedareas.
Feralhorserwere bserred n 394occarionr,with a meannumber f 4.7animals erobserva-tion. Onegroup of horseswas observed n a100%slopewith all otherobservationsn slopesof 50% or less.Horses enerally emonstratedan affinity for high benchesand gentlyslopingridgetops. Typically they rapidly traversed
rugged or steep opography to gain access o
elevated ut relatively evel errain.
The 0-19%classesn eachherd ecerveoor 0 preferenceatings, ndicating hat slopeswithin this range were avoredor utilized indif-ferentlyby horsesTable ). The 20-29%categorywasavoided y herds and 2 but used oughlyin proportion o its occurrencey herd3. Meanslopes f thehabitats ccupied y herds , 2, and3 were 20, 24, artl 34%, respectively. ikecat-t le, horses nhabiting ugged er rainappearedwill ing to uti l ize steeper slopes han the ircounterparts n more evel opography. orsesin all three herds avoided lopes n excess f30%.
One hundred seventy-t wo bservations fdeerwere ecordedon the area,with the averagegroupnumbering8.5 animals. he steepestradeon whichdeer vere etected as75%. Like cat-tle and horses, deer favored relatively leveltopography Table l). They were most oftenobseNed n slopesn the 0-9% category hichreceived (+ ) preferenceating. Crades etrveenl0 and39% appearedo haveno effecton theirmovements,scategoriesn this range eceived(0) preferenceatings.Categoriesn exces s f40% were uti l ized at signif icantlyP < 0.02)lower frequencies han their availability would
suggest nd received ) preferenceatings.Bighornsheepwereobserved n l2l occa-
sionswith a meangroup size of 6.? animals.Bighorn requented rades pproaching 50%,
SlopeUse by Catde,Feral Horses,Deer,and BighornSheep 77
8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep
TABLE l . Hab i ta t ava i lab i l i ty (%) and use (%) by ca t t le , horses, deer , and b ighorn sheep. Cetegor ies i t h a (+) pre ference
rating lrere utilized at greater than expecled lelels (P < 0.02). Categories having a (0) preferen.e rating sere uti'
lized in proportion to their occurr ence. Categories with a (-) preference r ating were utilized at less than expected
levels (P < 0.02).
l0-19 70.790.29 30-39 80+
CdttlePaslure A aYailabilitl
Use
Preference ating
Pasture B availability
Use
Preference ating
Pasrure C availability
Us e
Herd area I a'ailability
Us e
Herd area 2 availability
Us e
Herd area 3 availability
Us e
Deer
Availab it y
Use
Preference ating
A ailability
Use
I I
79
23
a2
l6
70
+
l3
30
27
43
t 5
+
t2
l 7
0
t7
20
0
3 t
58
+
30
4 t
0
16
20
0
l8
l8
0
t 0
8
0
t9
3
24
l 3
5
t 1
l9
23
0
l4
l3
0
I
5
0
1 I
l 4
5
l+
l0
4
20
5
t4
t0
0
l3
8
0
t2
0
t6 t 4
l 5
5
14 7
0
20
t8
0
36
1 5
29
12
? 5 3 5
4
4
I
0
t2
5
l 1 9 9 3 7
4 3 2 3
but mostweresitedon slopes f l l0% or less.Themean lope or allpoints ampled ithin hebighorn heep abitatwas44%, while he slopeof the areasactually utilized by the sheepaver-aged, 2-5%.
The hypothesishat bighorn sheep ti l izedslopes in proportions equivalent to thetopographic omposition f their habitat wasmarginally ejectedP ( 0.01). xamination f
thepreferenceatings or each f thenineslope
categories Table 1) revealed the bighorn
deviated significantly(P < 0,02) rom our ex-
pectedpatternof use n only one nstancethe
70-79%categoryl. ecausehis category eceived
a (+) preferenceating,andall othercategorieswere requented t expectedevels,we concluded
thats lopes e lween and80% d id no l mpa i r
lhe movemenlsnd ac t i v i l i es f b ighorn .
78 Ganskopp nd Vavra
8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep
Second-orderquations rovidedbest it ofdata elatingpercentslope independentariable)to percent f observationsf herbivoresn eachcategory dependent ariable).Signif icant e-sponseunctionsP( 0.05)wereobtained or cartle (Y = -6.0X + 0.09X?+ 96.4, = 0.95),horses Y = -1.9X + 0.02X ' + 54.4,12 =
0.96), nddeer(Y - -1.5X + 0.01X2+ 45.9,r' = 0.89) but no significant relationshipwasderived or bighornsheepFigure ). Our attemptto f it a second-orderolynomialo t he bighornsheep ataproducedan r' of 0.22andan F valueof0,9B.This againsuggestshat slopes etween0 and B0%hadno effecton the habitsof bighornsheep.
Our F t ests or all possible nterspecific om-parisonsof two regressionines rejected hehypothesishat patterns f slope sewere den-tical among att le, orses, nd deer P < 0.01).Although ach quation rovedo be unique,wedo not intend to infer thata clear spatialsepara-
l ion e \ i s ted e tweenhp var ious per ies .
Discussion
Slopes etween and l9% received ither +)or (0)preferenceatings n our analysis f all fourherbivores, hesesame lopes upported 4%of our observationsl catt le,79% f thehorses,66% of thedeer, nd257oof the bighorn heep.I t isobvioushatcattle, orses,nddeerexerted
the majorityof their demands n the resourcesoccurringwithin these ounds.Bighornsheep,with their greater tolerance or preference orsteep lopes, eremuch essdependent n theresources f relatively entle errain.
Thesedata clearly l lustr atehat in ruggedte ain cattle,horses, nd deerwill limit their useof steep idehills.Consequently,angemanagersand researchers eed o consider he effects ofvarying opographyon the distribution patternsof these animals.
Due o severalactors, owevcr,aulionmustbe exercised henapplying hese esults o otherareas.Our first concern s that much of our data
were of a seasonal ature.We recognize hat
60
7 a
\nZO ^r .- J v
ft:L ^l 0
t0
o ? nl l
- -
oF ,l,-.
z . vtr l
CLu l l n
CATTLE
HORSES
DEt rR
BLGHORN
1 0
. \\ " - \
2a 60 70 BO-
Figure t. Re)ationshipo{ slope gradient to the p€rcenlofobse aiions of cattle, feral horses,deer, and bighorn sheep.Rawdala are pres€nted or bighorn sbeepbecsusea significant (P<0.05) relationshipcould not be oblained sith linea.or quadrat icmodels.
30 4a 50PERCFNTSLOPE
SlopeUse by Cat tle,Feral Horses,Deer,and BighornSheep 79
8/12/2019 Slope Use by Cattle, Feral Horses, Deer, And Bighorn Sheep