Cryptic Behavior of Black Bears (Ursus americanus) in Rocky

Cryptic Behavior of Black Bears (Ursus americanus) in Rocky Mountain National Park,
Colorado
Author(s): Henry E. McCutchen
Source: Bears: Their Biology and Management, Vol. 8, A Selection of Papers from the Eighth
International Conference on Bear Research and Management, Victoria, British Columbia,
Canada, February 1989 (1990), pp. 65-72
Published by: International Association of Bear Research and Management
Stable URL: http://www.jstor.org/stable/3872903
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CRYPTIC
BEHAVIOR
OF BLACKBEARS(URSUSAMERICANUS)
INROCKY
MOUNTAIN
NATIONAL
PARK,COLORADO
HENRY E. MCCUTCHEN, Research Biologist, National Park Service, Rocky Mountain National Park, Estes Park, Colorado 80517
Abstract: Black bear (Ursus americanus) in many U.S. and Canadian national parks become habituated to humans. They are often bold, frequent human use areas and
are generally a nuisance. At Rocky Mountain National Park, Colorado, the antithesis of this behavior has been observed in the black bear population. A 4-year study
using radio-telemetry and observation indicates that although many bears have home ranges in high human use areas, they are secretive and avoid humans and developed
areas. The behaviorof 2 of the park'sradio-collaredbears is documentedand discussed.
Int. Conf. Bear Res. and Manage. 8:65-72
Most U.S. and Canadiannationalparkswith populations of Americanblack bears(Ursus americanus)have
reportedproblemswiththis species. In partbecausethey
are protectedin parks,bearshave become habituatedto
humans,humanactivity, and development. They have
tended to depend on humanfoods and refuse, and they
have causedhumaninjuryandpropertydamagebecause
of these unwantedhabits. Black bearsin most parksare
highly visible and arecommonlyobservedby the public
along roads, trails, and in campgrounds. Many parks
have historicallyexperiencedhigh numbersof bearincidents anddepredations(Barnes 1967, Bray 1967, Marsh
1972,Peltonet al. 1976,ZardusandParsons1980,Harms
1979 and 1980, Singer and Bratton1980, Graber1981,
Keay and VanWagtendonk1983, Herrero1985).
Because of beardepredationsandhumaninjury,most
nationalparkshave developedprograms,costly in funding and manpower, to mitigate or reduce black bear
problems(Marsh 1972, Pelton 1972, Pelton et al. 1976,
Harms1979 and 1980, Zardusand Parsons1980, Singer
and Bratton 1980, Keay and VanWagtendonk1983).
These include: educationalprogramsto teach parkvisitors and employees properbehaviorand food handling
techniquesin regardto bears;establishmentandvigorous
enforcement of rules and regulations relating to food
handlinganddisposalandfeeding bears,andcaptureand
transplantor removalof problembearsfromthe population. Expensive schemes to handle humanrefuse have
been devised, such as installationof many bear-proof
food containersandgarbagecans;closing openpitdumps;
scheduling daily garbage pickups, and hauling refuse
long distances out of the parks. These measures have
significantlyreducedthe numbersof bear incidentsand
bear-related human injuries over the past 15 years.
However,manyparksstill have manybearincidentsand
depredations.
The blackbearsituationat Rocky MountainNational
Park,Coloradocontrastswiththatof theotherparks.The
parkhas a small black bearpopulationand althoughthe
area is predominatelyforested and receives 2.5 million
visitorsduringmostyears,depredationsorincidentshave
been few to non-existent. Therehas seldom been a need
to destroyor transplanta bear. Further,black bears are
rarelyobservedby parkvisitorsor employees. The park
has never had to implementa majorbear management
programor install bear-proofgarbage cans because of
bears.
In 1984 a researchprogramwas initiatedon the black
bearsin the parkto determinetheirpopulationdynamics,
status, and behavior. The bears here were generally
found to be shy and secretive. Theirbehavioris similar
to that of Europeanbrown bears (Ursus arctos) (Roth
1976 and 1977, Roben 1980, HuberandRoth 1986, Elgmork 1976 and 1987) ratherthan that of black bears in
North American national parks (Marsh 1972, Pelton
1972,Peltonet al. 1976,ZardusandParsons1980,Harms
1980, Graber1981, Herrero1985, Hastingset al. 1986).
This paperdescribesand documentsthe behaviorof the
bears at Rocky MountainNationalPark.
STUDY AREA
Rocky MountainNationalPark,locatedin northcentralColorado,is 106,700ha in size. The park,established
in 1915,lies alongtheContinentalDivide. Situatedabout
65 km northwestof Denver, a majormetropolitanarea,
theparkpreservesone of themostruggedandspectacular
reachesof the ColoradoFrontRange. The elevationsare
high, rangingfrom 2,329 m to 4,345 m. There are over
100 mountainpeaks exceeding an elevation of 3,000 m.
Most of the area is mountainouswith steep cliffs and
rugged U-shapedvalleys formedby glaciers duringthe
Pleistocene epoch. The climate is continental with a
mean annual temperatureof 6 C and a mean annual
precipitationof 41 cm at the lower elevations. Mean
annualtemperaturesdecreaseandprecipitationincreases
withanincreasein elevation(Stevens 1980). Thehighest
precipitationoccurs in the spring in the form of heavy,
66
BEARS-THEIR
BIOLOGY AND MANAGEMENT
wet snow. In the summer,afternoonthunderstormsalso
bringprecipitation.
Abouttwo-thirdsof the parkis forested. At the lower
elevations,from2,300 m to 2,700 m, is a mosaicof forests
and grasslandswith meadows and ripariantypes along
the floodplains and river bottoms. The forests contain
standsof ponderosapine (Pinusponderosa),Douglas-fir
(Pseudotsugamenziesii), aspen (Populus tremuloides),
and lodgepole pine (Pinus contorta). On the more open
slopes thereare standsof big sage (Artemisiatridentata)
andbitterbrush(Purshiatridentata)as well as grassland
containing mountainmuhly (Muhlenbergiamontana),
needle-and-thread(Stipa comata) and sedges (Carex
spp.). Wetmeadowscontaintimothy(Phleumpratense),
tuftedhairgrass(Deschampsiacaespitosa)andKentucky
bluegrass(Poa pratensis). Along the riversarestandsof
willow (Salix spp.), narrowleaf cottonwood (Populus
angustifolia)and birch(Betula glandulosa).
At mid-elevations, from 2,700 m to 3,500 m, are
subalpineassociationswith standsof Engelmannspruce
(Picea engelmannii)andsubalpinefir (Abieslasiocarpa)
with an understoryof whortleberry(Vaccinium spp.).
Lodgepolepine is presenton areasof shallow soil andin
old burs. Limberpine (Pinusflexilis) and aspen stands
are also presentin some sites.
The upperelevations, above 3,500 m, containalpine
tundra. Tundrais fairly extensive in the parkcovering
aboutone-thirdof the area. Vegetationconsists of tufted
hairgrass,sedges, Mt.Washingtondryad(Dryasoctopetala), cliff sedge (Carex scopulorum), Parry primrose
(Primulaparryi), kobresia(Kobresiamyosuroides)and
golden avens (Geumrossii).
The area had a long history of land use before its
establishmentas a nationalpark. Settlersbeganto arrive
in the 1860's. Many areas in the park were farmed,
mined, logged, and burned. Large rancheswere established and there was heavy grazing by domestic livestock. Because of its scenic beauty, the area was also
recognizedfor its recreationalopportunities,whichled to
the earlydevelopmentof duderanchesandresorts. In the
earlydays the areawas notedfor its good hunting. Large
ungulates, including elk (Cervus elaphus), mule deer
(Odocoileushemionus)and bighornsheep (Ovis canadensis) wereextremelyabundant(Stevens 1980). Wolves
(Canis lupus), grizzly bears (Ursus arctos), and black
bears were present, but not as common as ungulates
(Armstrong1975). Loss of habitat,local hunting,and
markethuntersfrom Denver reducedthe ungulateherds
so that by the turn of the century the elk had been
extirpated(Sprague 1925, Stevens 1980). The bighorn
populationspersisted but declined drasticallypossibly
from scabies and loss of winter range in the 1930's
(Wrightet al. 1932). The wolf becameextinctin theearly
1900's and the grizzly by the late 1920's (Wrightet al.
1932, Armstrong1975). The black bear survivedthese
humanimpactsbut in low numbers(Wrightet al. 1932).
In 1915, after 15 years of effort by conservationists,the
areawas establishedas a nationalpark.
Since then, a majoreffort in managingthe parkhas
been aimed at restoringthe area to naturalconditions
frompast land uses. Farms,ranches,homes, andresorts
within the park boundary were purchasedand razed.
Disturbedareaswere revegetatedor allowed to revegetate naturally. Criticalungulate winter range was purchasedandrestored.Elk andbighornsheepwerereintroduced and have shown impressive increases (Stevens
1980, Stevens and Hanson 1986).
The presence of the park now dominates the local
economy. Tourism has become the major business.
Tourismanddevelopment,particularlyalong the eastern
boundary,has increasedto the point thatit threatensthe
integrityof the park. The gatewaytown of Estes Parkto
the east has expanded to the park boundary. Dude
ranches,condominiums,conferencecenters,andprivate
homes areincreasingin numberseveryyear. Fortunately
the areas adjacent to the north, west, and south park
boundaries are primarily public lands where human
developmentanduse is controlled.Huntingforbearsand
otherwildlife species occurs outside the parkboundary.
Regionally, urbanizationis occurring at a rapid pace
along the FrontRangelowlandsnorthof Denverandeast
of the park.
Rocky Mountainis one of the most heavily used U.S.
nationalparkswith 2.6 million visits in 1987,down from
3 million in 1978 (Rocky MountainNationalParkFact
Sheet, Oct. 1988). The parkreceives morevisitationthan
Yellowstone, yet is only one-eighth the size. Day use
predominates;however, there are over 300,000 camper
nights annually at the 5 campgrounds(Statementfor
Management, 1982, Rocky Mountain National Park).
Use is highly seasonal with the bulk occurringduring
June, July, and August. Over 75% of the visitor use is
concentratedon the east side of the ContinentalDivide in
the park(MasterPlan, 1976, Rocky MountainNational
Park). There are 250 backcountrycamp sites with an
annualuse of about35,000 usernights,downfroma peak
of 62,000 in 1977 (Statementfor Management,1982,
Rocky MountainNational Park). Day hikeruse is also
high,estimatedatabout600,000 peryearon the300 miles
of parktrails(Statementfor Management,1982, Rocky
IN ROCKYMOUNTAIN
NATIONALPARK * McCutchen
BLACKBEAR BEHAVIOR
MountainNational Park). Commercialhorse rides are
estimatedat 40,000 to 50,000 per year originatingfrom
2 liveries in the parkand 24 outside. Automobiletraffic
is heavyon thepark's100mile$of roadsduringpeakdays
of visitoruse. TrailRidgeRoad,whichtraversesfromthe
east side to the west side of the park,can receive more
than 1,000 cars per hour use during peak periods
(McCutchenunpubl.data). To alleviate trafficcongestion to Bear Lake, anotherfavored area, a shuttle bus
system is in operationduringthe summer.
Blackbearsarepresentin theparkbuthaveneverbeen
considered common (Armstrong 1975). Currentresearchindicatesthatthe populationin the parkis 30 to 35
bearswith about 1 bearper 30 km2(McCutchenunpubl.
data).Thebearpopulationin theparkis viewed as a "high
elevation"subpopulationcontiguouswith a largerpopulation of "low elevation" bears surroundingthe park.
Becausethebearsaresecretive,theyareseldomobserved
by the manyvisitorsusing the roadsandtrails. Bearscat
and feeding sign is seldom seen in or near visitor use
areas. Althoughbears have access to garbagecans and
dumpsters(whicharenotbear-proofed),as well as campgrounds, picnic grounds, and backcountrycampsites,
there is seldom an incident of a bear raiding them
(McCutchenunpubl.data).
A review of the historic records suggests that bear
incidentsaresomewhatperiodicin the park(McCutchen
unpubl.data). Bear incidentswere low in the late 1950's
and early 1960's. During the 1960's there were 2 high
years, 1963 and 1967, with 45 and 27 incidents,respectively. From 1959 to 1967 there were about 2 control
actionsperyear with bears(14 transplantedand2 killed)
in the park. From 1968 to 1983 therewere only 17 bear
incidents for a rate of 1 per year. Three bears were
capturedandtransplantedin controlactions. The reasons
for the 2 years of high incident rates in the 1960's as
comparedto the 1970's and early 1980's is not known.
Visitation in 1962 was 1.7 million increasing to 2.5
million in 1972, then staying fairly constant (National
ParkService 1976). Thus, visitationand bear incidents
do not seem to be correlated.The reductionof incidents
afterthe 1960's may be relatedto the purchaseandrazing
of a numberof private guest ranches within the park,
whichhadopenpitdumpsusedby bears,andbearcontrol
in theparkatthattime (D. Stevens1989,RockyMountain
NationalPark,pers. commun.). In 1984, aftera 17-year
hiatus, anotherexceptional year occurredwhen a bear
began to raid backcountrycampsites. That year there
were about90 incidents. The offendingbear,a subadult
male, was captured and removed from the area. In
subsequentyears bear incidentswere again low.
67
MATERIALSAND METHODS
Between 1984 and 1988, we captured23 black bears
in the parkwith culverttrapsor with Aldrichfoot snares.
We immobilizedthem with a combinationof Ketamine
and Rompun. They were markedwith numberedaluminum ear tags, weighed, and measured. The first
premolarwas pulled for cementumaging. Seventeenof
the bears were radio-collared(Telonics, Mesa, AZ).
Radio-telemetrywas conductedon foot, by automobile,
by fixed-wingaircraft,andby helicopter.An attemptwas
madeto obtainat least one accuratelocationon each bear
each week. The usualprocedurewas to obtaina general
location on a bear by vehicle then move in on foot to
obtaina more accuratefix througha series of triangulations. It was extremely difficult to approachto within
about 100 m of the bears without disturbingthem and
chasing them away. Because of this, researcherswould
often stay back about400 m or moreto obtainfixes. We
estimatedthatradio-fixesobtainedat 100 m or less were
accurateto about?25 m. Radio-fixes500 m to 1 km were
accurateto about +150 m. Radio-locationswere only
obtaineddiurnallyas nighttimelocations were too difficult to obtainin the ruggedterrain.
Afterthebearresearchbegan,theparkstaffdeveloped
a bearinformationnetwork. All bearsightingsreported
by parkpersonnel(75 permanentand300 seasonals)and
park visitors were channeled into a central dispatch
office, recorded,then passed on to the researchteam.
Becausebearswererare,parkvisitorsoften stoppedatthe
entrancestationsor visitorcentersandreportedtheirbear
sightings. Backcountryrangersreportedbear sightings
or signs. Garbagehandlersreportedbearor otheranimal
raidson garbagecans along theirroute.
Forthis reportthe 2-yearcompositehome rangesand
radio-locationsof 2 female bearsfor the years 1985and
1986areexamined. These arebearsNo. 2 with 47 radiolocations,andNo. 3 with 52 radio-locations.BearNo. 2
was estimatedto be 14-years-oldin 1985. Shehadno cubs
in 1985and lost her cubs in the springof 1986. Bear No.
3 was estimatedto be 4-years-old in 1985. She had no
cubs eitheryear. These bearswere selectedbecausethey
had home ranges in the portion of the park with the
greatesthumanuse.
Duringthese time periods,no otherbearswereknown
to be permanentresidentsin these bears' home ranges;
however, different bears, believed to have been transients, were sighted in the area. Snarelines were set to
determineif other bears were present. None were capturedexcept the known females.
The relocationdatawere lumpedfor 1985and 1986to
increase the sample sizes for statisticalanalyses and to
68
BEARS-THEIR
BIOLOGY AND MANAGEMENT
show the radio-locationsand home ranges on a single
map. The 2 bearswere capturedin the summerof 1985,
so thatyear's datawere only for a partof the summerand
fall. The 1986 radio-locationdataarefor the entireyear.
Theresultant2-yearcompositehomerangesandsizes for
the 2 bears are similar to those obtainedthroughmore
limited radio-trackingin 1987 and 1988 (McCutchen
unpubl.data).
To provide a measurementof each bear's avoidance
behavior in relation to human use, radio-locationdata
wereplottedon a base map. Thedistanceof each location
to the closest set of humanuse featureswas then measuredto the nearest0.1 km. Humanuse featuresI believed
to be of importanceincluded trails, trailheads,paved
roads,dirtroads, humanresidences,picnic areas,major
campgrounds,backcountrycampgrounds,theparkboundary, and miscellaneous developments (ski area, major
pullouts, parkinglots, visitor centers, stables). Home
rangeswere delimitedby the minimumpolygon method
(Mohr1947).
RESULTS AND DISCUSSION
Figure 1 depictsthe 2-yearcompositehome rangesof
bears No. 2 and 3. The home ranges overlappedonly
slightly. Adult females in the park appearedto have
nearlyexclusive homeranges(McCutchenunpubl.data),
andmay be territorial,similarto the blackbearsreported
by Young and Ruff (1982)and Rogers (1987).
Bear No. 2 had a home range (70.8 km2) that was
roughly boundedby Trail Ridge Road to the north,the
main park road to the east, the Bear Lake Road to the
south, and timberlineto the west (Fig. 1). Within her
home rangewere approximately17 km of roads, 59 km
of trails,11backcountrysites, 9 trailheads,2 majorpicnic
grounds,a majorcampground,a majoroverlook,2 major
parkinglots, and 1 smallresidentialarea. Along theroads
were about 10 small pullouts and picnic tables with
attendantgarbagecans.
BearNo. 2 occasionallycrossedthe roadsto the north
and southbut was never known to cross the roadsto the
east. The greaterportionof her home range was in the
backcountry,accessible only by trails. She frequently
usedthe northwesternsectionof herhome rangecontaining ForestCanyon,a nearly impassablerugged area,of
dense spruce/firforest and deadfall containingno trails.
Her home range was away from areas of majorhuman
development,particularlythe areato the east of her. This
areaincludestheTown of EstesParkoutsidethe parkand
an intensivezone of developmentin the parkcontaining
2 majorcampgrounds,a network of major roads, park
severalresidentialareas,anda visitorcenter.
headquarters,
Althoughcampgroundsarean attractantto bearsin many
nationalparks(Martinka1974, Peltonet al. 1976, Harms
1979 and 1980, Graber1981, Herrero1985), bearNo. 2
was never known to visit the campgrounds.
The distanceof bearNo. 2's radio-locationsto visitor
use areas (Fig. 2a) indicates that although she stayed
away from these areas, the average distance was quite
variabledependinguponthe areatype. Muchof herhome
rangewas dissectedby trails;thus,she was locatedcloser
to trails(0.8 km) and trailheads(1.9 km) on the average
thanotherareasof use. Based on locations in her home
range(Fig. 1) she seemed to be electing to be neartrails
in the southernpart,apparentlyfor 2 reasons. First,trails
in this areaarenearcreeksandwet areas,which,frommy
experience, appearto be favored bear habitat. Second,
there is some researchbias here as her signal was more
easily picked up along trails than in "deadspots"away
from trails. Bear No. 2 was seldom located in or near
areasof majordevelopmentwhere humanuse and residence was on a 24-hourbasis or was year-round,e.g., the
majorcampgrounds,andtheparkboundaryarea(Fig. 2a).
Bear No. 3 had a smaller home range of 35.1 km2
(Fig. 1), which was dissected by 2 major roads, Trail
Ridge Roadto the southandFall RiverRoadthroughthe
valley in the center. Both of these roadsreceived heavy
human use in the summer. Bear No. 3's home range
contained24 kmof roads,9 kmof trails,a ski area,a major
overlook, 6 large pullouts, 3 trailheads, and a small
residentialarea. In addition,a majorpicnic groundwas
located almost in the geographic center of her home
range. At the pulloutsandotheruse areaswerenumerous
garbagecans for the visitors' convenience.
Bear No. 3's home range overlappedonly slightly
withbearNo. 2's. BearNo. 3 tendedto utilizetherugged,
steep, mountain slopes north and south of Fall River,
particularlythenorth-facingslope withits denservegetation. Figure2b indicatesthatshe also was radio-located
away fromareasof humanuse. She was locatedcloser to
thepavedroadsthanotherfeaturesbutstill maintainedan
averagedistanceof 1.1 km from them. She maintained
the farthestdistanceaway from the nearestmajorcampground(6.0 km) and the parkboundary(6.5 km) to the
east, on the average(Fig. 2b). She was never known to
visit the picnic groundin the center of her home range
even though it had dumpstersand garbage cans. In
addition to the radio-telemetry,indirect evidence of
avoidancewas determinedfromthe lack of any reported
bear-raidingof the refuse containersin this area during
thattime period.
Figures 2a and 2b provide a rough index of the
BLACK BEAR BEHAVIOR IN ROCKY MOUNTAIN NATIONAL PARK * McCutchen
3414 m ~/L
approx.
timberline ,
C,
3292 m
NORTH
0
1000
2000
1000
4000
3000
5000 metersI
Rocky Mountain
National Park Boundary
paved road
dirt road
bear #2 location
bear #2 home range boundary
bear #3 location
bear #3 home range boundary
areas of high human use
park headquarters
backcountry campsite
trailhead
trail
*o
o
o
H
A
*
campground
picnic area
A
I
major stopping point
ski area
residence
urban development
X
Fig. 1. Two-year composite
s
home ranges of black bears No. 2 and No. 3 (1985-1986) in relation to human use areas, Rocky Mountain National Park, Colorado.
69
70
BEARS
THEIR BIOLOGY AND MANAGEMENT
13
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HUMAN USE FEATURES
Figs. 2aand 2b. Radio-location distances of black bears No. 2 (N= 47) and No. 3 (N= 52) from human use features (1985-1986), Rocky Mountain National Park, Colorado.
toleranceof bothbearsto variousparkrecreationaldevelopments. The various linear transportationcorridors
(trailsandroads)were moretoleratedthanstructuresand
facilities. Bear No. 2 was located closer to trailsthanto
any other type of area probablybecause there were so
many in her home range. Bear No. 3 was located closer
to paved roads. Althoughpaved roadstendedto receive
much greateruse than dirt roads, both bears seemed to
toleratepaved roads slightly betterthan the dirtroads.
The bears tended to keep about 1.5 to 4 km on the
average from trailheads,human residences, and picnic
grounds. They stayed the farthest, over 4 km on the
average, from the major campgrounds. These average
distances(Figs. 2a and2b) illustratea few generaltrends.
Avoidance behavior of the bears is shown by the minimum distance the bears were located from human use
areas (Figs. 2a and 2b). From the minimum distance
statistics, other than the instance of bear No. 3 being
locatedalong a trail,bothbearswerealways locatedaway
from areasof humanuse. I hypothesizethatsimilardata
developed for a bear habituatedto a campgroundor
roadsidewould show a closer mean distanceand a minimum distance of zero as comparedto a non-habituated
bear showing a farther mean distance and minimum
distance greaterthan zero.
Black bears have been known to stay away from
humanuse areas duringthe day and visit them at night
(Ayreset al. 1986) to obtainfood. Therewas no evidence
that bears No. 2 and 3 did this.
Thatthe bearsdid not use visitoruse areasat nightcan
be inferredin several ways: they were not observed at
night along roads and trails nor in the frontcountryor
backcountrycampsitesby the numerousparkvisitors or
by rangerson patrol;bear scat was rarely observed on
trailsby the bearresearchteam or backcountryrangers;
and the numerousgarbage cans placed along the roads
and in picnic groundsand campgroundswere not raided
at night.
The crypticbehaviorof the bearsin the parkcan also
be shown by the small numberof sightingsandincidents
during 1985 and 1986 (Table 1). An incident was
recordedwhen a bear was observed in a visitor use area
foraging for human food or when a garbage can was
raidedby a bear. In 1985 therewere 16 bearsightingsand
1 incidentparkwide. Of these, 7 were sightings in bear
No. 2's home rangeand 1 was a sightingin bearNo. 3's.
Most of these sightings within the home ranges were of
the radio-collaredbears;however, a large, differentbear
was sighted once in bearNo. 2's home range,duringthe
breedingseason. It was most likely a male becausebear
No. 2 had cubs the following season.
In 1986 (Table 1), there were 13 sightings and 4
BLACKBEAR BEHAVIOR
IN ROCKYMOUNTAIN
NATIONALPARK * McCutchen
incidents parkwide. There were 2 sightings and 1 incident in bear No. 2's home range and 2 sightings and no
incidentsin bearNo. 3's. Again throughradio-tracking
follow-up, the sightings were.most likely of the radiocollaredbears. The 1 incident,however, was caused by
a transientbear. Consideringthatthe bulk of the visitor
use in the park is in bear No. 2 and bear No. 3's home
ranges, including the estimated 600,000 hiker-daysof
trailuse, the numberof sightings is small.
The most graphicdemonstrationof the level of avoidance of these females to human use areas occurredin
1985-1986. In the summerof 1985,bearsNo. 2 andNo. 3
werecaptured.BearNo. 2 weighed49 kg andbearNo. 3,
capturedin late summer,weighed 35 kg. In the winterof
1985-1986they were reweighedat the dens. Bear No. 2,
who had 2 cubs, still weighed 49 kg, and bear No. 3
weighed only 25 kg. In the summerof 1986 bearNo. 2
was recapturedand weighed 71 kg. I suspect thatthese
weightlosses duringthe winterof 1985-1986wereattributedto a poorfood year in 1985. BearNo. 2 lost hercubs
and I suspect that she was in such poor condition at a
weight of 49 kg that she could not provide adequate
nutritionfor them. Also for that winter,bearNo. 3 lost
about26%of her summerweight. Neitherof these bears
raidedreadilyavailablegarbagecans along roadsand in
picnic areas or human food in backcountrycampsites
before or after this apparentlydifficult denning period.
The study team could only ask "Whywould these bears
risk starvationin the den ratherthan forage on readily
available,highenergy,humanfoodsintheirhomeranges"?
The datapresentedabove suggest thatblack bears in
this park exhibit a "model" behavior that many other
parksare strivingfor. Yet, this "model"behaviorexacts
a cost from the bears althoughthey are persistingin an
areaof high humanuse. In the parkthereis a networkof
humanuse travelcorridorsandcentersof highhumanuse
with readily available high proteingarbage. There are
even humanuse areasin whatwe perceiveas qualitybear
habitat(riparianareas,aspen stands),yet the bearsavoid
Table 1. Black bear sightings
National Park, Colorado.
and incidents, 1985 and1986, Rocky Mountain
Sightings
1985
1986
Home ranges
bearNo. 2
bear No. 3
Otherareas
Total
7
1
2
2
Incidents
1985
1986
0
0
1
0
8
9
1
3
16
13
1
4
71
these areas and utilize the intersticeswithin the human
use web.
Researchersof blackbearsandgrizzlies in some parks
have noted 2 types of behaviorin the same population,
dependingupon whetheror not they visited humanuse
areasfor food. For grizzlies in Yellowstone, Mattsonet
al. (1987) labeled these types "wary"and "habituated".
Ayres et al. (1986) separatedthe black bears in Sequoia
NationalParkinto"natural"
and"campgroundbears".At
Rocky MountainNationalParkthe blackbears,withrare
exception, would be classified as "wary"or "natural".
Thereis no evidenceof"habituation"(McArthur1983)at
the presenttime.
Parkswith a historyof artificialfeedingof bears,such
as Yellowstone, Sequoia and Kings Canyon, Yosemite,
and the GreatSmoky Mountains,have persistingproblems with habituatedbears, even with intensive bear
managementprogramsin place overthepast 15years. At
Rocky Mountainbears were never allowed to feed on
humanfoods (Wrightet al. 1932). Fromthe time the park
was establishedin 1915,bearsthatdevelopedthe habitof
feeding on humanfoods were removed from the park.
Martinka(1972) notes that this was the case in Glacier
National Park. Yet, Glacier regularlyhas problems if
food is unsecured. Black bears commonly enter campgrounds,picnic areasandotherdevelopedareas,andoccasionally obtainunsecuredfood.
Elgmork (1976, 1987) suggested that the cryptic
behaviorof brown bears in Norway may have been the
result of historic overhuntingand "gun selection". He
hypothesizedthatthis traitcould be passedon via heredity andlearningto new generations.Perhapsheredityand
learninghaveinfluencedRockyMountainNationalPark's
blackbearsbecausethey were heavilyhuntedpriorto the
park's establishment. Also, the park is so small that
nearlyevery bearmay be exposed to huntingadjacentto
the parkboundaryduringits lifetime, even thoughthey
areprotectedin the park.Two of the bearsradio-collared
in the park(subadultmales) have been killed by hunters
outside the park. An additionalfactormay be the selective pressureof the removal of problembears that has
been maintained on the small population of Rocky
Mountainbearssince the parkwas establishedin 1915.
At thepresenttimethereasonorreasonsforthecryptic
behaviorof the blackbearsat Rocky MountainNational
Parkwill continueto be investigated.Followingthebears
for severalgenerationsmayprovidesome insightintothe
behavior;however,thisphenomenonmayneverbe easily
explained. The behaviormay be the result of genetics,
learning,or a combinationof these. Otherinterrelated
factors might include a history of huntingpriorto park
72
BEARS-THEIR
ANDMANAGEMENT
BIOLOGY
establishment; National Park Service control actions; a
lack of widespread historical artificial feeding; low population densities with an inability to fill available vacant
habitat; low rates of reproduction; loss of habitat; and
poor quality, interspersion, andjuxtaposition of resources.
Whatever the reasons, these bears apparently give up
valuable habitat to the more dominant species, man,
within their own home ranges.
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