How to Obtain Behavioral and Ecological Data from Free-Ranging, Researcher-Habituated... Bears Author(s): Lynn L. Rogers and Gregory W. Wilker

How to Obtain Behavioral and Ecological Data from Free-Ranging, Researcher-Habituated... Bears Author(s): Lynn L. Rogers and Gregory W. Wilker

How to Obtain Behavioral and Ecological Data from Free-Ranging, Researcher-Habituated Black
Bears
Author(s): Lynn L. Rogers and Gregory W. Wilker
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. 321-327
Published by: International Association of Bear Research and Management
Stable URL: http://www.jstor.org/stable/3872935
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HOWTO OBTAINBEHAVIORAL
AND ECOLOGICAL
DATAFROMFREEBLACKBEARS
RANGING,RESEARCHER-HABITUATED
LYNN L. ROGERS, U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station, Kawishiwi Field Laboratory, SR 1,Box 7200, Ely, MN 55731
GREGORY W. WILKER,U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station, Kawishiwi Field Laboratory, SR 1, Box 7200, Ely, MN
55731
Abstract: A study was conducted in northeastern Minnesota from 1986-1989 to determine the feasibility of habituating black bears (Ursus americanus) to observers for
behavioral and ecological research. Of 18 males and 8 females that repeatedly visited an artificial feeding site in the presence of humans, 3 2-year-old females were radiocollared for further habituation away from the site. The 3 females were repeatedly located, fed, and accompanied at various locations in their territories. After 50-100
hours of this additional contact, each bear accepted human presence and mostly ignored observers that followed 1-10 m behind. The bears were no longer fed in their
territories except for the feeding of scat markers for digestion studies. The bears were observed for 24- or 48-hour periods approximately weekly as they matured,
reproduced, and raised cubs. While being followed, they foraged, napped, slept through nights, showed REM and non-REM sleep, mated, played, nursed their cubs,
captured young animals, maintained territories, marked bear trees, prepared dens, and began hibernation. They relied on natural foods and showed activity and movement
patterns similar to daily and annual patterns of 103 non-habituated bears that were radio-tracked previously in approximately the same area.
A field computer with an internal clock was programmed to aid in the recording of activities, habitat use, food consumption, and weather. A personal computer was
programmed to sort and tabulate the data and calculate I) time spent in each activity, 2) time spent in each cover type, 3) number of bites taken of each food in each cover
type, and 4) time spent in each activity and cover type in each weather condition. The computer calculated these time-activity budgets for single 24-hour observation
periods or for any combination of observation periods specified. Problems of excessive hunting loss, habitual nuisance behavior, or appreciable observer injury did not
occur. Study results were directly useful to forest managers for identification of opportunity areas for habitat preservation or improvement. Results provided new insights
into black bear diet, bioenergetics, foraging strategies, activity patterns, sociobiology, communication, and bear-human interactions. Drawbacks were few study animals
and limited study area. Comparative studies are needed in new locations, involving additional age and sex classes, additional physiological data, and additional behavior
regimes such as might be exhibited by translocated bears, nuisance bears, or bears whose ranges have been altered by fire, development, insect defoliation, or extensive
timber management.
Int. Conf. Bear Res. and Manage. 8:321-327
Ecological studiesof elusive, wide-rangingmammals
are often hamperedby the inability to observe study
animals closely for significant periods. Consequently,
researchershave studied wide-rangingspecies in large
enclosures (McMahan 1964, Dzieciolowski 1967, LeResche and Davis 1973, Stringham1974, Ozoga et al.
1982,andothers),on leashes(Wallmo 1964,Watts1964,
Healy 1967, Neff 1974, Bauer 1977, Crawford 1982,
Lautenschlagerand Crawford 1983, Thill and Martin
1989, and others), or by temporarilyreleasing tame
animals (Buechner 1950). Otherresearchershave observedwild, free-ranginganimalsthatwerehabituatedto
vehicles (Schaller 1972, Bertram1973, Douglas-Hamilton 1973) or people (Graf 1955; Brown 1961; Goodall
1965;Geist 1971; Sade et al. 1976;Fossey and Harcourt
1977;Chepko-SadeandSade 1979;Rogers 1981, 1987a;
Rogerset al. 1987; Mech 1988). Eachstudymethodhas
its advantages,dependingupon the researchquestions.
During1985-1989,we developedmethodsfor habituatingfree-rangingblackbearsto observersandfor using
computersto recordandanalyzedetailedbehavioraland
ecological data rapidly. Areas of study includedblack
bear habitat use, diet, bioenergetics, activity patterns,
sociobiology, behavior, communicationmethods, and
bear-humaninteractions. The objective was a better
understandingof blackbearenvironmentalrequirements
and behaviorto aid decision-makingby forest managers
andcampgroundmanagersandto increasepublicunderstandingof black bears. This paperdiscusses methods,
benefits, and shortcomingsof the study.
We thankC. Cowden,P. Miles, V. O'Connor,S. Paul,
and S. Scott for help in developing techniquesand collecting data; Kawishiwi Ranger District personnel for
relaying 2-way radio transmissions;SuperiorNational
Forestchief biologistE. Lindquistandpilots C. Palumbi,
D. Bowman, and S. Durst for help in radio-tracking
particularlywide-rangingbears;C. Robbins,G. Pritchard,
andD. Hewittfor help withdigestivestudies,residentsof
the study area for their interest and support;and R.
Archibald,L. Darling, K. Elowe, B. Peyton, and two
anonymous reviewers for thoughtful reviews of the
manuscript.
STUDY AREA
The study was conducted in the SuperiorNational
Forestin northeasternMinnesota(47049'N, 91 45' W).
The primarystudyareawas the contiguousterritoriesof
3 principal study animals and was 6 km in diameter.
Longermovementsduringlate summer,fall, and estrus
increasedthe overall studyareato approximately24 km
by 34 km. The primarystudyareacontaineda networkof
logging roads,a paved 2-lane highway, a 32-unitcampground, 24 summerhomes, and the researchfacilities.
The homes and researchfacilities were all located on
KawishiwiRiverandBirchLake,a waterway150-650m
wide thatformedthe westernedge of the study area.
The study area was almost entirely forested and had
gently rolling terrain with occasional rock outcrops.
Mixed coniferous-deciduousforest predominated(Rogers 1987b). Standsrangedin age fromnewly clearcutto
322
BEARS-THEIR BIOLOGYAND MANAGEMENT
virginstands>100-years-old.Wetlandsincludedstreams
and beaverimpoundments,scatteredbogs and marshes,
anda 2.5-halake,each typicallyborderedby alder(Alnus
rugosa) swamps.
Bear foods available in season between May and
Septemberincluded wild fruit, beaked hazelnuts (Coryluscornuta),digestiblevegetation,andHymenopteran
insects (Rogers 1987b). Wild fruit was available from,
July to early September,if crops were successful, and
included wild strawberry(Fragaria spp.), dwarf red
raspberry(Rubuspubescens),serviceberry(Amelanchier
spp.), lowbush blueberry (Vaccinium angustifolium),
sourtop bilberry (V. myrtilloides),pin cherry (Prunus
pensylvanica),choke cherry(P. virginiana),wild sarsaparilla(Aralia nudicaulis),red raspberry(R. strigosus),
red-osierdogwood (Cornusstolonifera),roundleafdogwood (C. rugosa), highbush cranberry (Viburnum
trilobum), and mountain-ash(Sorbus spp.). The only
hardmastwas beakedhazelnuts,which were availablein
AugustandearlySeptemberin occasionalyears. Acorns
(Quercus spp.) and other fall mast species were essentially nonexistent. Bears entered dens in October and
emergedin April. Snow was presentfromlateOctoberor
Novemberto April.
METHODS
Habituating Black Bears To Observers
To habituatebearsto humanpresence,researchersestablisheda beef fatfeeding site, whichwas visitedrepeatedly
by 18 males and8 females.Within4 bearvisits, eachbear
becameaccustomedto the presenceof a recliningperson
within30 m. Within8 visits, mostreadilytookfood from,
or within5 m of, an immobileor slowly moving person.
Personality,wariness,and time requiredfor habituation
variedwithindividuals.Veryfew becameaccustomedto
being touched.All became accustomedto talking. Two
adults, a male and a female, remaineddefensive after2
and 10 weeks of occasional encounters and were not
studied closely. Three other females (401, Patch, and
Terri), all 2-years-old, were more receptive and were
capturedand radio-collaredfor furtherstudy away from
the feeding site.
These 3 females were initially timid when they were
approachedin new areas.Theyretreated,usuallyunseen,
for up to 2 hoursbeforecirclingdownwindandstopping
40-80 m away to smell the person and the beef fat he
carriedandto listen to his voice. After<30 minutes,the
bears approached,often demonstratingtheir uneasiness
by lunging, blowing, and slapping vegetation before
calming down and resumingtheir familiarfeeding rou-
tines. Over the next 50-100 hoursof contact,each bear
became accustomedto being approached,fed, and accompaniedin the forest. Supplementalfeeding was then
stopped.The bearscontinuedto approachobserversfor
food butreadilylearnedthatopen,emptyhandsmeantno
food. After a food-check, the bears typically resumed
foraging and ignored observers. However, if food was
hiddenin pocketsorbackpacks,thebearsoftencontinued
theirattentionorreturnedrepeatedlyto observers.Therefore,no food was broughtduringdatacollectingsessions.
Observersfollowed <10 m behindforagingbears. At
greaterdistances,the bears sometimes lost trackof observers and became wary of their rustlings. Bears also
sometimesbecame wary when observersapproachedto
within a few meters, although this wariness waned as
bears became more habituated. An intent look from a
bearindicatedits concernoveranobserver'sproximityor
actions. Bears sometimesgave "threat"displays (lunging, slappingvegetation,blowing) whenobserversgot in
theirway in unusuallyfood-richareas. Most startledor
defensive reactions (jumping away, whirling around,
startingup trees) were due to sudden,seemingly aggressive acts by observers(sneezing, tripping,falling, accidentallyhittingthe bear)or by the suddenappearanceof
anextraobserverin densebrushor on an overheadledge.
Therefore,data collecting sessions were conductedby
lone observers.
"Threat"displayswere actuallyexpressionsof fearor
uneasiness ratherthan threats. No bear attacked,and
bearsretreatedif an observeracted aggressively. Bears
were calmed by giving them more room and by talking.
Although difficult to describe, it became easy to read
bears'expressionsandanticipatetheirmovements.Thus,
observersavoided causing "threat"or defensive behaviors. Withtime (100-150 hours),mutualtrustdeveloped,
"threats"all but disappeared,and the fully habituated
bearsforaged,slept,andappearedto be comfortablewith
a single observer1-5 m behindor occasionallycloser to
see certainfoods. Sensitive, experiencedobserverssaw
<1 "threat"per 100hoursof observation,withmost of the
threatsoccurringin dusk or darknesswhen it was more
difficult to anticipatebears' movements.
Observersuseddimflashlightsto aidobservationsand
computerentries at night. The bears typically slept or
nursedfrom 1-2 hoursaftersundownto 0.5 hoursbefore
sunrise. Observersspent nights in sleeping bags 1-8 m
from the sleeping bears.
To begin a new year of observations, researchers
reinforcedthepreviousyear'shabituationby restingnear
dens and day beds before extensive movement began.
This presence was especially importantwith newborn
BLACKBEARS* Rogers and Wilker
STUDYINGRESEARCHER-HABITUATED
litters because cubs developed wariness of strangersin
late MarchandearlyAprilaroundthe time of emergence
(Rogers 1989). Prolongedhandlingof cubs duringthat
time (the thirdmonthof life) furtherhabituatedthem to
people (Rogers 1989 and unpublisheddata), making
them less likely to distracttheir mothers with distress
calls when observersaccompaniedthem later.
The artificialfeedingsite was essentiallydiscontinued
in 1988 and 1989. Bearuse of the feeding site hadwaned
by then, and observerswere concentratingon obtaining
datafromhabituatedbearsratherthanon habituatingnew
ones. Only 1 habituatedfemale (Terri)visited the site in
1988 and 1989 because Bear 401 had been thrownfrom
a treeby anotherfemale andkilled on 10 June 1987, and
Patchhad shifted her territory3 km away by the end of
1987 and did not returnin 1988. She was killed by a
hunter16 km away on 5 September1988. Terri'suse of
the site in 1988 and 1989 was limitedto a few visits each
year in late May (after springforbs became unpalatable
but before ant pupaebecame abundant)and in early fall
(afterberriesand hazelnutsdisappeared).On each visit,
she was given a few grams of food to entice her onto a
platformscale, and she was given more food duringthe
fall 1988 huntingseason to diverther from any hunters'
baits and to increase the chance of her producingcubs
(which she did) for study of mother-cubinteractions.
Data Collection Procedures
Field equipment(Table 1) includeda Husky Hunter
field computer (Husky Computers,Inc., Sarasota,FL
34236), which is a small, immersible, shock resistant
computerworn in a harnessthatleaves both handsfree.
The computerwas programmedto acceptentrycodes for
describing activity, food consumption, habitat, and
weather(Rogers et al. 1989a). A clock in the computer
automaticallyrecordeddatesandtimesof entries.Activities recordedincludedwalking, sitting, standing,reclining, running,sleeping, climbing, defecating, urinating,
digging, grooming, scent-marking,nursing,vocalizing,
playing, drinking, bathing, wading, and eating. For
eating, numberof bites of each food was recorded.
Data were recordedcontinuouslyduringobservation
periodsof 24 or48 hours. Twenty-four-hourobservation
periods providednatural,around-the-clocktime frames
for collecting dataon activity,food consumption,habitat
use,andweatherandwererepeatedapproximatelyweekly
to keep pace with changes in phenology. Forty-eighthour observationperiods were used when digestibility
data were collected in additionto the above data. The
longer observationperiod was needed to collect fecal
droppingscontaining foods observed eaten during the
323
Table 1. Equipmentneeded for extended bear observations.
1.
Shock resistant,immersible,field computerwith harnessthat
leaves handsfree. AA batteriesfor change at 24 hours.
2.
I4.
Backpackwith no framestructureto catch on vegetation.
Lightweightreceiver(in ziploc bag to preventraindamage)
and a folding mini-antenna.
Two-way radio.
5.
Small transmitterfor locating the observerin case of injury.
i
6.
Scat marker(if doing digestion studies-see text).
7.
Pocket-sizednotebook.
8.
Habitatforms for describinghabitat.
9.
Two dozen gallon-sized, prelabelled,datedziploc bags for
collecting unknownfoods and (if doing digestion studies)
scats.
3.
10. Two ballpointpens with waterproofink for takingnotes,
filling out habitatforms, and writingcollection times on scat
bags.
11. Compass,laminatedtopographicmap, and laminatedaerial
photo.
12. Two quartsof drinkingwaterin collapsible goatskincontainers. (As the wateris used, more room becomes availablefor
scats).
13. Insect repellent.
14. Light sleeping bag in a compressionsack; waterproofshell for
the sleeping bag (if observingovernight).
15. Dry socks and t-shirtin a ziploc bag (if observingovernight).
16. Flashlightwith fresh batteriesand an extrabulb.
17. Plastic trashbag for keeping the above items dry in backpack
when swimming across streams.
18. Rain suit (optional).
first 24 hours. Passage time typically was 4-12 hours.
Foodseatenduringthe first24 hoursof observationwere
identifiablein scats because a colored scat markerwas
fed at the beginning of an observation period and a
different colored marker was fed at 24 hours. Scats
collected between passage of the markerscontainedthe
first 24 hours' consumption. Scat markers included
colored beads, corn, peanuts,pieces of colored balloon,
or combinationsof these items. After it was determined
that passage rate was essentially the same for all these
materials,pieces of coloredballoons were used because
they were most easily obtainedand most easily seen in
scats. Approximately 10-20 balloon pieces, each 12 cm2,were fed in a 50-grampiece of fat.
The 48-hourobservationperiodswere conductedin 4
consecutive 12-hour shifts. The 24-hour observation
periodswere conductedin 2-3 consecutiveshifts of 8-12
hourseach or in 1 24-hourshift. The latterwas possible
becauseobserversrestedwhile the bearsslept at nightor
napped in daytime. Longer shifts were precluded by
324
BEARS-THEIR
BIOLOGY AND MANAGEMENT
hungerand the weight of collected scats.
Observationperiods were begun, and shift-changes
made, only when bears were awake, so sleep-activity
cycles were not disturbed.Activity was detectablefrom
telemetry signals. The incoming observer located the
bearby telemetryandthen waited200-300 m away until
telemetry signals indicatedactivity or the observer alreadywith the bearinformedhim by 2-way radiothatthe
bear was active. The incoming observertalked the last
100-200 m to identify himself.
Habitat Description
A goal in collecting habitatuse datain this studywas
to provide national forest managers with information
useful in habitatmanagementdecisions. Forthatreason,
habitatswereclassifiedin U.S. ForestServiceterms-by
forest type, tree size, and tree density. In addition,Ecological LandType (ELT),silviculturalhistory,andnaturaldisturbances(suchas insectdefoliation,winddamage,
fire, old-growthforests breakingup) were recordedto
determinefactors that influence habitatquality. However, not all of this informationwas immediatelyevident
uponenteringa new foresttype. Consequently,observers recordedonly the time when entering a stand and
recordeddescriptiveparameterswhile moving through
it.
To understandfully why bearsused particularforest
types,it was necessaryto describenotonly the foresttype
in generalbut the microhabitats(or forest components)
thatwere used within thattype. To recordmicrohabitat
use, computercodes were created to denote common
microhabitats(e.g., the differenttypesof forestopenings,
rock crevices, thickets, certain tree species, old dens,
game trails)andwere used to denotemicrohabitatsassociatedwith recordedactivities. Thus,each activityentry
hadanaccompanyingmicrohabitatentryif themicrohabitat differedfrom the generalforesttype. Forexample,if
an importantcomponentof a foresttype was blueberries
growingon patchesof shallow,sunlitsoil atedges of rock
outcrops,computerentrieswould indicate,in code, that
the bear,e.g., ate 234 bites of blueberriesfrom edges of
rockoutcrops.An objectivewas to understandwhy bears
used particularhabitatsat particulartimes (time of day,
time of year, time of life), considering food, water,
security, weather, insects, reproductive status, social
constraints,and recentevents.
Post-observation Handling of Data
After an observationperiod was completed,the data
were uploaded from the field computerto a personal
computer for viewing, correction of entry errors, and
printing. The computer was programmedto sort and
tabulatethe data and create the following time-activity
budgets(Rogerset al. 1989b):
1. Amountof time spentin each activity,
2. Amount of time spent in each vegetative cover
type,
3. Numberof bites takenof each food in each cover
type, and
4. Amount of time spent in each activity in each
weathercondition. (Weatherwas classified by temperaturerange,humidityrange,and sky condition.)
The computercalculatedthese time-activitybudgets
for single 24-hourobservationperiods,for 48-hourperiods, or for any specified combination of observation
periodsso changesin activitythataccompanychangesin
physiology, food distribution,food abundance,weather,
or other factors could be discovered. Observerswrote
narrativesto describeplay, social interactions,vocalizations, predation,and otherunusualobservationsthatdid
not easily fit the computerformat. Routes of bearswere
mapped, including resting locations, intensive feeding
locations,andhourlyprogress.Uncertaintiesaboutroutes
and locationswere resolved by checkingan aerialphoto
of the study area.
Supplemental Studies
In the days following an observationperiod,followwereconductedto determineamountsingested
studies
up
of each food and the nutritionalvalues of those foods.
After seeing hundredsof bites during an observation
period, observers used their knowledge of bite size to
collect 100 bite-sized samplesof each currentbearfood
andweigh themfresh andoven-dried(48 hoursat 48 C).
Foreach food, the weightperbite (freshandoven-dried)
was multipliedby the numberof bites the bearhadeaten
of thatfood in 24 hoursto estimatedaily consumptionof
eachfood. This informationwas also calculatedby cover
typeto determinefeedingefficiency in thedifferentcover
types. The oven-driedsampleswere then sent to Washington State University for determinationsof gross energy (by bomb calorimetry),percent protein (Kjeldahl
method),digestibleprotein(PritchardandRobbins1990),
and digestible energy (Pritchardand Robbins 1990).
Bodyweight changes were determinedby enticing the
bears onto a platformscale whenever they visited the
artificialfeeding site.
Boundariesof territoriesandannualrangeswere estimated from the maps of 24-hour bear movements and
frominterimradiolocations. Territorieswereconsidered
to be areas of exclusive or nearly exclusive use by a
female and her offspring. Annual ranges included all
STUDYINGRESEARCHER-HABITUATED
BLACKBEARS? Rogers and Wilker
areasknownto be traversedin a year,includingthe sallies
made during estrus and the extraterritorialforaging
movementsmadeduringlatesummer.Theavailabilityof
differentcover types withinterritoriesandannualranges
were determinedfrom aerialphotos,U.S. ForestService
and MinnesotaDepartmentof NaturalResources compartmentexam records,privatetimbercompanyinventories, anda U.S. Fish andWildlife ServiceGeographicInformationSystem (GIS) database. Use and availability
werecomparedto determinehabitatpreferencesin different seasons and years.
EVALUATIONOF METHODS
Data Collected
The habituatedbears provided over 2,000 hours of
observationdata,including6 24-hourperiodsin 1987,23
24-hourperiodsin 1988, and20 24-hourperiodsin 1989.
Human Influences on Bear Behavior
Grossbehaviorof the 3 habituatedfemaleswas similar
to thatof 103 bearspreviouslyradio-trackedin northeastern Minnesota (Rogers 1987b) with no differences in
territorysize, nuisancebehavior(see below), food habits,
socialrelationships,dailyactivitypatterns,seasonaltravel
patterns,or denning habits. Habituatedbears further
appearedto behave normally in that they nursed their
cubsperiodicallythroughthedayandnightanddefecated
at fairlyregularintervalsthatvariedseasonallywithfood
type and abundance.Bearspursuedandcapturedyoung
animals, markedsmall trees with urine, markedlarger
trees by rubbing, and investigated the marks of other
bears. Sleeping bears showed apparentlynormalsleep
thatincludedbothREMandnon-REMsleep. REMsleep
is seldom seen in poorlyhabituatedanimals(Allison and
VanTwyver 1970). The bears also prepareddens and
became lethargic in preparationfor hibernationwhile
being accompanied. A prehiberating female cub that
fell asleep with an observer'shandon her femoralartery
outside her den on 12 October1989 showed a pulse rate
of only 22 beats/minute.
Mothers ran to distress cries of cubs 1-2 m from
observersbut seemed to discountobserversas possible
sourcesof danger. Habituatedbearschasedor fled from
wolves (Canis lupus) or otherbears, and they remained
awareand responsiveto distant,unidentifiedsoundsbut
apparentlyignored the rustlings of nearby observers
because the focus of bears' ears and eyes was usually in
directionsotherthantowardthe observer. The direction
of their muzzles while doing the special breathingthat
accompaniedintense scenting also was usually directed
325
away from observers. Observationsof the ways bears
sensed their environmentgave insight into the kinds of
stimuli thatmost influencedtheir actions.
However, some aspectsof growthandbehaviorwere
influenced by the study. Habituatedbears reproduced
earlier(at 3, 4, and4 yearsof age) thanmost otherbears
of the region (Rogers 1987b) due to supplementalfood
given to them duringhabituationefforts and September
huntingseasons. Bears' foragingwas sometimes interruptedbriefly when observers got in the way. Mating
activity was slightly disruptedby observers in that 4
strangemales that approachedhabituatedfemales were
initially apprehensiveuntil observers stood back 1520 m. The malesthencourted,copulatedwith,andrested
with the females and within 1-2 hours toleratedcloser
(10-15 m) observation. A habituatedadult (Patch)and
severalhabituatedcubs occasionallyinvolved observers
in play, especiallywhenthey awokefromnaps. This was
remediedby steppingback a few meters.
Potential Problems
Problemsof excessive hunting losses, habitualnuisance problems,and appreciableinjuryto observersdid
not occur. No one was bitten. Habituatedmotherswere
as tolerantof observersas were other bears. One bear
occasionally slappedif she was teased with food or was
eye-to-eye with a personon herlevel within0.5 m. Slaps
that were apparentlyfull power created only welts or
scratcheswithno appreciableinjurydueto thedullnessof
adultblackbearclaws. No threatbehaviorswereof types
used beforefights (deep-throated,pulsingvocalizations;
bellowing, open-mouthedthreats;stiff approacheswith
backsarchedandnoses nearlytouchingthe ground). We
recognize that some danger exists in working closely
with largeanimalsandthatsensitivityandgood manners
are requiredto avoid provoking defensive behaviors.
However,the bearsin this studyshowedrestraintandno
propensityto seriously injure.
No habituatedbearbecamea habitualnuisanceat any
of the 24 homes within the study area or at the 32-unit
campground,whichwas less than500 m fromthefeeding
site. In fact, the feeding site diverted bears from the
campgroundand reduced nuisance problems (Rogers,
unpublisheddata). Two bearsbrieflyate dandelionsand
1 bearlicked grease from a disposal areain yardsof the
homes. Nuisancebehaviorappearedto be more a functionof homerangelocationandnaturalfood scarcitythan
familiaritywith people. When fruit, nuts, or ant pupae
wereabundant,habituatedbearssometimesforagedwithin
200 m of homes, the campground,or the feeding site
without checking for food or being seen. Most of the
326
BEARS-THEIR
BIOLOGY AND MANAGEMENT
homeownersdevelopeda protectiveinterestafterseeing
the bearsand being informed(wheneverpossible) about
new findings.
Mortalityof habituatedbearsduringhuntingseason(1
Sep-mid-Oct) did not exceed mortality in the overall
population, possibly due to partial protection by researchers.Habituatedbearswere studiedthrough7 bearyears of hunting seasons with only 1 hunting death,
showing a slightly lower mortality rate than the 16%
hunting mortalityreportedfor other radio-collaredfemalesin Minnesotaduringthe sameperiod(D. Garshelis,
Biologist, MinnesotaDep. Nat. Resour.,pers. commun.
1989).
Of the 3 radio-collaredbears, 1 is still alive, 1 was
killed by a largerfemale and 1 was killed by a hunter
16 km outside the bear's territory. In 1989, observers
accompaniedthe last survivinghabituatedadult during
most daylighthoursof the huntingseason until she and
her cubs enteredprehiberation lethargyin late September.
Benefits of Habitat Studies
Diet and habitatuse data from the habituatedbears
were directlyuseful to local forestmanagersin identifying opportunityareasfor blackbearhabitatpreservation
orimprovement.Ona broaderscale, thenew information
aided developmentof a habitatsuitabilityindex model
forblackbearsof theregion(RogersandAllen 1987)and,
hopefully, will aid in refining the model. Some of the
informationprovided by habituatedbears has proven
difficult to obtain in other ways. For example, a commonly eatensucculent,jewelweed (Impatienscapensis),
has not been identifiedin scats in this or previousstudies
due to its high digestibility. Grassesin springdiets have
not previously been identified as to species or source
covertypesbecausegrasseswithoutseed headscannotbe
identified in scats. In a previous study in this region
(Rogers 1987b),intensivespringuse of blackash (Fraxinus nigra) swamps and alderswamps by bearsfeeding
onbluejointgrass(Calamagrostiscanadensis)wasmissed
because feeding in those cover types is so efficient and
brief that bears were seldom radio-located in them.
Habituatedbears also revealed the importanceof large
refugetrees (e.g., Pinus strobus>50 cm dbh)to mothers
and cubs in spring, confirming an earlier finding by
Elowe (1987). Habituatedbearsprovidedthe firstinformationon amountseaten in the wild and how consumptiondiffersbetweenyearsandwithphenologicalprogression within years.
Research Needs
Majordrawbacksof thisstudywerefew studyanimals
and the limited study area. Comparativestudies using
habituatedbearsin ecologically differentareasacrossthe
continentare needed. Such studies should providenew
insights into bear behavior and habitatneeds and may
explain regional differences in black bear growth and
reproductiondueto possibleregionaldifferencesin feeding efficiency or diet quality.
Anothershortcomingof thepresentstudywas the lack
of intensive study of males. Few males remainedat the
artificialfeeding site long enough for thoroughhabituation. Males born in the study area dispersed despite
abundantfood at the feeding site, and other subadults
moved on aftera few days or weeks. Maturemales that
visited the feeding site duringmating season appeared
more interestedin estrousfemales thanfood and did not
returnlater. Thereis a need to determinedifferencesin
foragingstrategiesof large-bodied,wide-rangingmales
comparedto smallerbodied,territorialfemales. Studies
of bearsthatmightexhibitadditionalor alteredbehavior
regimes such as translocatedbears, nuisancebears, and
bears whose ranges have been extensively changed by
fire, development,insectdefoliation,or extensivetimber
managementarealso needed. Studiesof habituatedbears
with implantedphysiologicaltransmitters(to determine
heartrate,body temperature,etc.) areneededfor a better
understandingof bioenergeticsandthe factorsthatinfluence habitatselection.
Studiesof habituatedbearsdo not eliminatethe need
for extensive studies of large samples of radio-collared
bears to learn age-specific and sex-specific movement
patternsand survival rates. Habituatedbear studies are
best used for habitatuse studiesandto adddetailsto data
patternsobtainedby moreextensivemethods. Nevertheless, in some situations and locations (e.g., the cloud
forests of South America)habituatedbear studies (e.g.,
studiesof spectacledbears[Tremarctosornatus])maybe
more immediately feasible than more extensive and
expensive studies (B. Peyton, Bear Specialist, InternationalUnion for the Conservationof NatureandNatural
Resources [IUCN], pers. commun. 1989).
Habituatedbearstudiesarelaborintensivebutcan be
accomplished at relatively low cost with few radiocollars and minimal flying time. Computerprograms
developedin this studyareavailableto researchersinterested in similarstudies of any species. Researchersare
welcome to visit the study area and accompany the
habituatedbears to become acquaintedwith field techniques and computerprograms.
STUDYINGRESEARCHER-HABITUATED
BLACKBEARS* Rogers and Wilker
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