Population Management of Bears in North America
Author(s): Sterling D. Miller
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. 357-373
Published by: International Association of Bear Research and Management
Stable URL: http://www.jstor.org/stable/3872940
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POPULATION
OF BEARSINNORTHAMERICA1
MANAGEMENT
STERLING D. MILLER, Alaska Department of Fish and Game, 333 Raspberry Rd., Anchorage, AK 99518-1599
Abstr-act: Population management for black bears (Utrsus amer-icanus), brown-grizzly bears (U. arctos) and polar bears (U. maritimus) in North America is reviewed.
In differentareasbearpopulationsare managedto achieve goals of populationcontrol,conservation,or sustainedyield. Most NorthAmericanbearsare managedfor
sustainedyields andthis topic is emphasized.The consequenceof errorin populationmanagementis highas bearsreproduceslowly andreducedpopulationswill require
many years to recover. Simulationresultswhere reproductiverates were generous,naturalmortalityrates were low, and harvestswere 75% of maximumsustainable
ratesindicatedthatpopulationsreducedby half will require>40 yearsto recoverfor brown(grizzly) bearsand >17 yearsfor blackbears. Underoptimalconditionsfor
reproduction,naturalmortality,andwithmalestwice as vulnerableas females,maximalsustainablehuntingmortalitywas estimatedas 5.7%of totalpopulationforgrizzly
bearsand 14.2%for black bears. In recentdecades,all 3 species have obtainedthe statusof game animalsin mostjurisdictionsand managementfor controlobjectives
is increasinglyuncommon. Managementfor conservationrequiresprimaryemphasison habitatprotectionand on minimizingmortalitiesfrom any source. Managers
of huntedbearpopulationsuse informationfromhunters,fromsex andage compositionof killed bears,fromresearchprograms,and fromcomputersimulationstudies.
Non-criticaluses of datafrom any of these sourcesmay lead to managementerror. Dataon age-at-harvestis especially proneto misinterpretation.Techniquesused to
limit harvestsby managersof hunted bear populationsare reviewed. The primaryconstraintsfacing bear populationmanagementderive from inadequatehabitat
protection,political pressures.technologicallimitationsof available populationmanagementtechniques.and inadequatefinancial supportfor management.
Int.Conf.BearRes.andManage.8:357-373
Populationmanagementefforts designed to enhance
or stabilizebearnumbersare recentin the United States
and Canada. In the last centuryand early portionof the
present century, black and grizzly bears were widely
regardedas impediments to desired development and
humansafety. Bountiesfor killing bearswere offeredin
manyjurisdictions. This attitude,combinedwith habitat
destruction,ledto theeliminationof grizzlybearsthroughout most of the United States except Alaska and the
reductionof black bears especially in the southernand
southeasternUnited States (Cowan 1972, Jonkel 1987).
By the mid-19th century, polar bear populationswere
also greatly reduced by markethunting for their hides
(Anon. 1965, Stirling 1986).
Attitudestowardsbears began to change in the 20th
century. Instead of being classified as "predators"or
"vermin"that could be killed indiscriminately,bears
were classified as fur animalssubjectto regulatedcommercialharvests. By the 1920's, bearswere elevated to
the status of "game"animals in most areas (Table 1).
Typically,limitationson sale of hides, meator otherbear
productscame along with game animalstatusas well as
significantlimitationson huntingopportunities(seasons,
bag limits, techniques,etc.). In some areasfurtherlimitations resulted when bear populations were greatly
depleted. At this point populationswere classified as
"threatened",the status of the grizzly in the lower 48
states,or "endangered",such as the blackbearsin Texas
since 1987 (Wallace 1987). There is nothinginevitable
abouta downwardtrendin bearnumbersto a threatened
or endangeredstatus. For black bears,at least, popula'Invitedpaper.
tionscurrentlyarestablein muchof the UnitedStatesand
Canada. Also, in some regions, with formerlydepleted
populationsof all 3 species, bears have recoveredto a
secure status.
The techniquesused in modem bearmanagementare
the subjectof this paper. These techniquesareappliedto
3 general goals for population managementlisted by
Caughley(1977:168): control(treatmentof a population
that is too dense to stabilize or reduce its density),
conservation(treatmentof a small or declining population in such a way as to raise its density), and sustained
yield (exploitationto takefroma populationa long-term
sustained yield of surplus animals without causing a
populationdecline). Although all 3 of these goals are
discussed,primaryemphasisin this paperis on sustained
yield management.
This paperwas preparedin responseto an invitation
from F. Bunnell to prepare a plenary paper for this
conference. Numerouspersonsverykindlyrespondedto
my requestfor managementplansandotherinformation
that describedhow bears are managedin theirjurisdictions including: S. Amstrup(AK), R. Archibald(BC), J.
Beecham (ID), L. Berchielli (NY), J. Brown (MT), J.
Collins (NC), A. Dood (MT). K. Elowe (MA), D.
Garshelis(MN), J. Gunson(AB), R. Johnson(WA). D.
Koch (CA), G. Kolenosky (ON). O. Oedekoven(WY),
A. LeCount(AZ). D. Martin(VA), R. Masters(OK), C.
McLaughlin(MA). E. Orff (NH), J. Pederson(UT), A.
Polenz(OR).J. Rieffenberger(WV).S. Schliebe(AK),L.
Schaaf(KY). C. Servheen(MT). B. Smith(YK), J. Stuht
(MI). D. Taylor (AK). M. Taylor (NWT). C. Winkler
(TX), andJ. Wooding(FL). K. Schneider.C. Schwartz,
S. Stringham.and 3 anonymousreferees offered many
valuable suggestions on an earlier draft of this manu-
358
BEARS-THEIR
BIOLOGY AND MANAGEMENT
Table 1. Year in which bears were declared to be game animals In different portions of North America. Dates refer to black bears except where Indicated by "G" for
grizzly bear or "P" for polar bear.
Location
Alaska
New York
Pennsylvania
BritishColumbia
Montana
Montana
Oregon
Texas
Michigan
Quebec
YukonTerritory
Alberta
Arkansas
Arizona
South Carolina
Arizona
Wisconsin
Maine
Washington
Alaska
Vermont
Colorado
Manitoba
Idaho
California
Alaska
NorthwestTerritories
Maryland
Yukon
Oklahoma
Massachusetts
Newfoundland
Ontario
New Brunswick
Newfoundland
Saskatchewan
Nova Scotia
Utah
West Virginia
Quebec
Ontario
Manitoba
Newfoundland
Minnesota
New Hampshire
Year classified
as game animal
1902(G)a
1903
1905a
19093
1923
1923(G)
1925, 1970"
1925
1925
1926C
1928a
1929(G)
1927d
1927a
1927
1929(G)
1930
1931e
1933, 1969f
1939
1941
1941
1942
1943
1948g
1948(P)a
1949(P)
1949
1950(P)h
1951
1953"
1961
1961'
1961
1962
1963
1966
1967
1969
1969(P)h
1970(p)h
1970(P)h
1971(P)
1971
1983j
Source
57th Cong. Sess. I Chap. 1037
Clark(1978)
Alt and Lindsey (1980)
Anon. 1980
Dood et al. (1986)
Dood et al. (1986)
Anon. (1987a)
Winkler(1975)
Harger(1980)
Caron(1980)
MacHutchonand Smith (1988)
Nagy and Gunson(1988)
Conley (1977)
LeCount(1977)
Stokes (1977)
Brown (1985:154)
Kohn (1982)
McLaughlin(1986)
Poelkerand Hartwell(1973)
Code Fed. Reg. Title 50(91.1)
Wiley (1978)
Beck (1979)
Shoesmith(1977)
Beecham (1986)
Anon. (1987b)
Anon. (1965:51)
Urquhartand Schweinsburg(1984)
Taylor (1984)
Stirlingand Calvert(1985)
Vohs(1977)
Cardoza(1978)
Russell and Forsey (1978)
Clarke(1961)
Cartwright(1978)
Mahoney(1984)
R. Seguin (Sask. Parks,Recreationand Culture,
Meadow Lake, pers. commun.)
Patton(1978)
Burruss(1979)
Rieffenbergerand Alien (1978)
Stirlingand Calvert(1985)
Stirlingand Calvert(1985)
Stirlingand Calvert(1985)
Stirlingand Calvert(1985)
Hugie et al. (1978)
Orff (1987)
a Date of first bag limit or season restriction.
b Firstdeclared
game in 1928, replaced,then redeclaredin 1970.
c Vallee
(1977) gives 1970 as date game statuswas assigned in Quebec.
d Date of total season closure.
e Hermesand Hugie (1977) note black bearswere bountieduntil 1957 and game statuswas being recommendedin 1977.
f Date of first season,
game animal statusrepealedin 1951 in some areas,reinstitutedin 1969.
g Burton(1977) gives 1957 as date game statuswas assigned in California.
h Date of
legal basis for currentmanagement.
i Polarbears in Ontariohave been treated,for managementpurposes,as a furbearersince 1971 (G. Kolenosky,Ont. Ministryof Nat.
Resour., Maple, pers. commun.).
J $20 bountyremovedfrom bears in 1955, first season in 1961.
* Miller
BEAR POPULATION
MANAGEMENT
script. The workwas fundedby FederalAid in Wildlife
RestorationProjectW-22-6, Job 4.18R and the Alaska
Departmentof Fish and Game.
CONSEQUENCEOF ERROR
For all 3 managementobjectives the consequenceof
errorin managingbearpopulationsis high. Bear populationsthatareinadvertentlyreducedto lower levels than
desired will require many years to recover. This is
becauseall 3 species of NorthAmericanbearshave long
lifespans(>20 years),low reproductiverates(an average
of 2 cubs producedby adult females every 2-6 years),
delayedreproductivematurity(firstbreedingat3-7 years),
high survivorship of adults, variable survivorship of
young, which is frequentlydependenton environmental
conditions(Rogers 1983), andtypicallylittle fluctuation
in numberof adultsfromyearto year(Jonkel1987, Kolenosky and Strathern1987, Kolenosky 1987).
The periodrequiredfor recoveryof reducedpopulations of black and grizzly bears was simulatedusing a
simple deterministicmodel (MillerandMiller 1988) in a
scenario involving overharvestsby hunters. In these
simulations,maximallyproductivepopulationsof black
and grizzly bears that were stabilized by hunting were
suddenly overharvestedby doubling the exploitation
rate. When the populationdeclined to half its original
size, huntingwas restrictedandthe time requiredfor the
populationto recoverto its initial size was noted. When
no huntingoccurredduringtherecoveryperiod,theblack
bear population recovered in 6 years compared to 10
years for grizzly bears(Table 2). When huntingduring
the recovery period occurredat 75% of the maximum
sustainablehuntingrate,it took almost3 times longerfor
blackbearsto recoverand4 timeslongerforgrizzlybears
(Table 2). These results are minimal values as the
reproductiveand naturalmortalityratesused were set at
themostoptimisticvaluesthathavebeenreported(Miller
1989).
Table 2. Simulation results for estimating period required to recover from
overhunting that caused a 50% reduction in maximally productive grizzly bear
and black bear populations. During recovery period population was subject to
hunting rates of 0, 50, and 75% of the initial rates at which populations were
stable.
Grizzlybear
Years requiredto recoverfrom
reductionwhen huntingis held
at following fractionsof initial
huntingrate:
(No hunting)
50%
75%
10
19
40
Blackbear
6
9
17
359
MANAGEMENT
FORCONTROLOF BEAR
NUMBERS
Until the currentcentury,reductionof bear numbers
was the most common objective for bear population
management.In some partsof NorthAmerica,bearsare
still sufficientlyabundantor troublesometo humansthat
managementeffortsinvolvereducingbeardensities(e.g.,
PoelkerandHartwell
1973,Jorgensenetal.1978,Ambrose
andSanders1978, PoelkerandParsons1980, Will 1980,
Miller 1990a, Gasaway in press). Such areas have
becomeincreasinglyrareandgeographicallyrestrictedin
recentdecades. They will likely become even rarer.
However,wherehumanandbearpopulationscoexist,
managerswill have to deal with some problems. These
problems can result in bear mortalities that are large
enoughto be significantfrom a populationmanagement
standpoint.ForYellowstonegrizzlies,controlkillingsof
only a few additionalfemales may mean the difference
between continued population decline and recovery
(KnightandEberhardt1984,1985). Insuchcases,human
populations,not bearpopulations,mustmakethe needed
accommodationsfor coexistence.
Many states and provincescompile dataon the number of human-bearconflicts reported. It is sometimes
implied that an increasein the numberof nuisancebear
complaintsreflects an increasein bear numbers. More
often, however,increasedcomplaintsreflecta changein
humanuse of bear habitat. Increasedhuman-bearconflicts more commonly correspondto a decline in bear
populations,not an increase.
Research in Alaska and other northernregions has
demonstrated
thatpredationfrombearsandwolves (Canis
lupus) can inhibit recovery of depleted moose (Alces
alces) and caribou (Rangifer tarandus) populations
(Ballardet al. 1980, Franzmannet al. 1980, Gasawayet
al. 1983, Ballardand Larsen 1987, Ballardand Miller
1987, Boertjeet al. 1988). These findingshave resulted
in pressurefrom sportsmenand subsistence huntersto
reducenumbersof predatorsto permitfastergrowthand
higherharvestsof preypopulations. In responseto such
pressures,grizzly bearseasons have been liberalizedand
harvests have increased in many portions of interior
Alaska (Miller 1989). These changes representa geographicallywidespreadshift from conservativegrizzly
bear managementstrategiesto more aggressive ones in
which the likelihoodof managementerrorin these areas
is increased. In at least 2 areas,increasedharvestshave
resultedin declinesin grizzlybearpopulations(Reynolds
and Hechtel 1988, Miller 1990a). Elsewhere,resultsare
inconclusive (Gasaway 1988) or no field studies designed to evaluate trendsin bear numbersare ongoing.
360
BEARS-THEIR
BIOLOGY AND MANAGEMENT
Responsiblemanagementof bearpopulationsundercircumstances such as these is especially challenging because the techniquesavailable to documentchanges in
bearpopulationsareimprecise. This makesit difficultto
establish realistic criteriaby which to judge when bear
populationreductiongoals have been met. Also, there
sometimes is inadequaterecognition that management
prescriptionsfor predatorreductionprogramsthat involve bears(e.g., Gasawayin press)need to be different
than for predatorslike wolves that have much higher
reproductiverates.
MANAGEMENTFOR CONSERVATION
Conservationis the generalobjectivefor grizzly bear
managementeffortsin the lower 48 states,for blackbear
managementin southernandsoutheasternstates,andfor
managementof all species in nationalparks. In some
large Alaskan parks where grizzly bears are abundant,
population managementis less importantthan people
managementandhabitatprotection.Most nationalparks
in the U.S. and Canadaare not so fortunateand require
active bear managementto assure perpetuationof bear
populations(Knight and Eberhardt1987, Knight et al.
1988, Horejsi 1989).
Even in parksandotherprotectedareas,baselinedata
on populationdensityandcompositionmay be critically
importantin evaluatingimpactsof environmentalaccidents or changingpatternsof humanuse of areasoccupied by bears. The absenceof a systematicallyobtained
baselineestimateof beardensityin KatmaiNationalPark
made it difficultto evaluatewhetherthe bearpopulation
had declined as a result of the 1989 oil spill from the
Exxon Valdez. Similarly, in Glacier National Park,the
lackof a systematicallycollectedhistoricalrecordof bear
numbersmade it difficult to isolate humanuse patterns,
which may have caused a reduction in bear numbers
(Hayward1989, Keating 1989).
In parts of North America small bear populations
survive only in small pockets of habitatisolated from
each other. This fragmentationexposes these populations to higher probabilities of extinction because of
chanceeventsandenvironmentalvariation.Managersof
these populationsmustdeterminehow largethese populationsandreservesshouldbe to insurepersistencein the
face of naturalcatastrophes,andrandomenvironmental,
demographic,andgeneticevents (SchafferandSampson
1985). For Yellowstone grizzlies the minimumviable
populationthat gave a 95% probabilityof survivingfor
100 years was estimated at 50-90 bears (Schaffer and
Sampson 1985). Using the same general approachbut
with different data on mortality rates, the estimated
minimumviable populationwas estimatedat 125 bears
(Suchy et al. 1985).
The InteragencyGrizzly Bear Committeeformed in
1983 is an example of the kind of coordinationthat is
essential if remnantpopulationsof grizzly bears are to
survivein thelower48 states(Salwasseretal. 1987). This
committee includes representativesof 5 U.S. agencies
that manage portions of grizzly habitatplus 6 state or
provincialwildlife agencies, and 2 Indiantribes. Working together, these agencies have developed a coordinatedset of objectives and strategiesto directconservationefforts. The InternationalAgreementon the Conservationof PolarBearsandtheirHabitatis anotherexample
of the kind of cooperationneeded to perpetuatehealthy
bearpopulations(Stirling 1986, 1988a).
Techniquesfor estimatingpopulationsize and trend,
discussedbelow, areespeciallyneededin managementof
reducedpopulationsfor conservationobjectives. Unfortunately, some of the techniquesthat provide the most
accuratepopulationestimates may frequentlybe inappropriatefor very small remnantpopulationsof bears
because these techniques are usually imprecise when
appliedto smallpopulations.Inaddition,subjectingsuch
populationsto the additionalstressandmortalityassociated with markingstudiesmay be unwise. In managing
greatlyreducedremnantpopulationsof bears,managers
may find it more productiveto concentrateon habitat
protectionissues ratherthanon effortsto documentbear
numbersor mortalityrateswithmarkingstudiesthatmay
produceonly uncertainresults.
SUSTAINED YIELD
Sustainedyield managementof bearpopulationsis the
managementgoal in most areasof NorthAmericainhabited by bears. Most commonly the yields are taken by
hunters.Perhapsbecausesustainedyield managementis
not usuallyconductedin a crisis atmospherewherebear
populationsare threatenedor where bears are seen as
damagingto humans'economicinterests,sustainedyield
managementhas not received as much attentionas it
deserves. More concern is merited because correct
managementof populationsthat have sustained yield
goals may prevent crisis situations from developing.
Also, populationmanagementtechniquesare especially
importantin managingfor sustainedyields. For these
reasons this topic is given primary emphasis in this
review.
The principlebehindsustainedyield managementis
thatpopulationsproducea surplusof animalsthatcan be
removed or harvestedwithout causing populationdeclines. Under sustainedyield management,harvesting
BEAR POPULATION MANAGEMENT * Miller
takes the place of mortalitiesthat would occur from old
age and othercauses. In very dense populations,reproductiveratesof bearsaresuppressedby density-dependent mechanismsthat act to preventthe populationfrom
overshooting carrying capacity. Because population
growthis suppressedby these mechanisms,populations
at carryingcapacity can supportlittle harvest. If such
dense populations are harvested and bear density declines, reproductiverates should increase and natural
mortalityratesshould decline,whichproducesa surplus
that can be taken annuallywithout causing declines in
bearnumbers.Maximumsustainableyield (MSY) is the
point where populationsize and productivitybalanceto
producethe maximumsize of harvestwithoutcausing a
population decline. At populationslower than MSY,
productivityand sustainableharvest rates remain high
but fewer total bearscan be harvestedwithoutcausing a
populationdecline.
For bear managersthe MSY populationsize is more
useful theoreticallythanpracticallysince the "optimum"
populationsize will be unknown. This is becausereproductive and mortalityratescan varyfrom yearto year in
a density independentfashion based on fluctuationsin
food supply (Jonkel and Cowan 1971; Rogers 1976,
1983, 1987). Managersstrivingfor sustainedyields from
exploited bear populationstry to maintainpopulations
that have good average reproductiverates and small
average naturalmortalityrates in the expectation that
suchpopulationswill be producingharvestablesurpluses
at high levels.
The challengefacing managersmanagingbearpopulationsfor sustainedhigh harvestsis to identifycorrectly
whatharvestlevels aresustainableandwhen sustainable
levels are exceeded. To assist in makingthese determinations the populationmanagermay have information
available from hunters,from the animals that are harvested, from field investigations, and from simulation
studies.
InformationProvided by Hunters
Hunterscan providevaluableinformationto managers of exploited bear populations. Informationfrom
huntersis most useful as a flag that alerts managersto
potential problems or helps to form hypotheses about
populationstatus. These hypothesescan then be evaluated using otherlines of evidence.
NumberKilled.-Perhaps the single most basic and
useful piece of informationthat can be provided by
huntersis thenumberof bearskilled. Increasingnumbers
of bears killed should alert managersthat populations
could be declining. Of course, populationtrend is not
361
necessarily correlated with number killed; increasing
harvestscould occur withoutpopulationdecline as long
as sustainableharvestlevels were not exceeded.
Probablythe best way to use dataon harvestnumber
requires calculation of sustainableharvest rate. With
informationon reproductiveand mortalityratesderived
fromresearch,thisratecanbe estimatedusing simulation
models,discussedbelow. Thecalculatedsustainablerate
can be compared with actual harvest rate obtained by
dividing number killed by estimated population size.
This approachresultedin a recommendationagainstan
increase in polar bear huntingquotas in the Northwest
Territories(Stirlinget al. 1985).
In a few instances,efforts have been made to use kill
numbersto derive populationsize by assuming the kill
representssome percentageof the total population,usually the calculated sustainableharvest rate, and backcalculating from this rate to derive a total population
estimate.This is a reasonableprocedureonly if managers
have independentevidence thatthe populationis stable.
Unreportedsport or nuisance kills and wounding
losses can representsignificantsourcesof mortalitythat
managersshouldconsider. In ruralnorthwesternAlaska,
less than half the grizzly bear sport and subsistence
harvestis reportedas required(W. Ballard,Alas. Dep. of
Fish and Game, Nome, pers. commun.). On the heavily
hunted Kenai Peninsula in Alaska, where reportingis
thoughtto be fairly complete, wounding loss of black
bearswas estimatedto be 13-16%of reportedkill based
on mortalities of radio-markedbears (Schwartz and
Franzmannin prep.). "Controlkills" of nuisance black
bearsaccountedfor 36%of known human-causedmortalities and unreportedcontrol kills were estimated to
equalorexceed reportedones in theYukon(MacHutchon
and Smith 1988). Poachingaccountedfor 9% of deaths
of markedblack bearsin Maine (Hughie 1982). A third
of the knowngrizzly bearmortalitywas illegal harvestin
Alberta(Peek et al. 1987). The mortalityrateof marked
grizzlies in Montana was estimated at 0.47, all from
illegal, unreportedkills (Knickand Kasworm 1989). In
6 studies of markedgrizzly bears, 26% of mortalities
werecausedby illegal harvestscomparedto 42%by legal
hunting(McLellan1990). Managersneed to incorporate
estimates of all significant mortalitysources into their
bearmanagementefforts.
HunterEffort.-Number of bearskilled is best interpretedalong with informationon level of huntingeffort.
Increases in number of bears killed under conditions
whereeffort is constantmay lead managersto suspectan
increasingbearpopulation.The same increasein harvest
numberwhere effort is also increasingmay suggest an
362
BEARS-THEIR
BIOLOGY AND MANAGEMENT
increasedexploitationrateand a declining bearpopulaAlaska(Miller 1988, 1990a). Kill densityestimateswere
tion. This indicatorwas used in Alberta,wheremanagers used to illustratethatdangersof overkillof a grizzly bear
noted that harvests of grizzly bears increased 100% populationwas higher in the Canadianportion of the
NorthernContinentalDivide Ecosystem where a legal
duringa period when effort increased350% (Nagy and
Gunson 1988). In a heavily huntedareain south-central huntingseasonwas in placethanon theU.S. side (Horejsi
Alaska wheregrizzly beardensitywas reducedby about
1989). Kill density also can be used to establishquantihalf as a consequenceof liberalizedhuntingregulations, fiable managementobjectives in managementplans.
successful huntersreportedspendingmore time before
IntegratedApproaches.-In Minnesota, black bear
was
before
reduced
a
bear
than
the
density
populationmanagersuse a huntersurveyto collect data
shooting
on huntingsuccess andbearskilledperhunter-day.Data
hunter
effort
data
are
(Miller 1990a). Typically,
highly
areadjustedto correctfor annualvariationin food abunvariable and statistical tests seldom reveal significant
danceandareusedto select themostconservativegrowth
differences. This does not, however, invalidatethe caucurvethatfits this trendfroma seriesof model-generated
tious use of sucheffortdatato assistmanagersin forming
curves
of populationgrowth. Managersthen use the
trends.
about
population
hypotheses
selected
curve and some subjective criteriato develop
HunterSuccess.-Hunter successratesareinfluenced
by improved access or huntertechnology, motivation, estimatesof populationsize andto set harvestquotas(D.
and number of bears. This means that effort indices
Garshelis, Minn. Dep. of Nat. Resour., GrandRapids,
should be used with caution. Variabilityin effort unrepers. commun.). This approachappearsto be a worthwhile effort toward integrating information obtained
lated to populationstatus is apparentin Alaska where
fromhunterswiththatfromothersourcesintoa standardnon-residentgrizzly bear hunters are requiredto hunt
ized managementframeworkuseful in makingobjective
with guides andpay high fees. Residenthuntershave no
such restrictionand need only buy a $25 tag. These
managementdecisions.
differences in cost of hunt affects motivation and is
InformationProvided by Harvest Composition
reflectedin success rates. The statewidesuccess ratefor
Detectionof bearpopulationtrendfromthe sex and/or
non-residentsis much higher (52% in 1987) than for
residents (8.4%) (Alaska Dep. of Fish and Game
age structureof harvestedbearsis more often attempted
than
achieved(Caughley1974;Wiley 1980;Gilbertet al.
in
the
Game
file
[ADF&G]unpublished data). However,
where
Kodiak
that
includes
1978; Bunnell and Tait 1980, 1981; Miller and Miller
Island,
ManagementUnit
are
allocated
1988). Proceduresthatareappropriatefor moreproduchighly prized brown bear huntingpermits
by lottery,bothtypes of huntershadhighersuccess rates: tive ungulatepopulations(e.g., Fraser1976,Fryxellet al.
19%for residentsand 74% for non-residents(ADF&G
1988) are difficult to apply to bears because they are a
long-lived and low density species thatcan sustainonly
unpublishedfile data for 1986). In contrast, average
harvestsuccess rate for grizzly bear huntersin Alberta low harvest rates (Harris and Metzgar 1987a). Low
was 3% for residentsand 12%for non-residentsduring harvestratesprovidea smallsampleof harvestedanimals
fromwhich to make inferencesaboutthe populationand
1971-1987 (Nagy andGunson 1988). Even wherehuntAra delay in the time requiredfor harvest to perturbthe
be
can
hunter
success
limited
is
low;
by permits,
ing
kansas black bear permitteeshad 0.4-2.2% success in
population'ssex and age structure.Sex ratioof harvest
differentyears(PharrisandClark1987). This variability is moresensitiveas an indicatorof populationstatusthan
underscoresthe need to look for trendsin success rates
age structure(Harris 1984), perhaps because all the
harvestis distributedbetween only 2 sexes comparedto
within groupsthatare as homogeneousas possible with
20 or moreage classes. It is popularto try to use dataon
respect to residency, transportationtype, motive, and
areahunted.
age composition of harvestbecause hunterscan be reKill density.-The geographiclocationof hunterkills
quired to submit teeth from their kills. These can be
is also important. Harvest number with geographic sectionedandageestimatedby countingcementumannuli
locationpermitsmanagersto estimatekill perunitareaor
(StonebergandJonkel 1966). The age of harvestresults
in tablesof supposedly"hard"data,the utilityof which is
sustainof
effects
kill density. Excluding
immigration,
more
sustainable
be
calculated
either
can
ablekill density
frequentlyassumedthandemonstrated.
(like
Differences in the sex and age composition of bear
harvestnumbers)or estimatedbasedon areaswhereboth
populationssubjectedto differentlevels of huntinghave
populationtrendandkill densityareknown. Kill density
divided by populationdensity was used to approximate been documented(Jonkel and Cowan 1971; Beecham
1980; Kolenosky 1986; Reynolds and Hechtel 1988;
grizzly bear harvestrate in a heavily huntedportionof
BEAR POPULATION MANAGEMENT * Miller
Miller 1988, 1990a). As yet, these differenceshave not
been clearlyrelatedto differencesin the age composition
of bearsharvestedfrom these populations. Increasesin
numberof black bearfemales harvestedhas been correlated with increasedharvestrate in Ontario(Kolenosky
1986).
The sample of bears shot by hunters will seldom
directlyreflect the populationcomposition. Huntersare
selective and bearshave differentialvulnerabilitybased
on sex, age, or reproductivestatus (Bunnell and Tait
1980). A furtherproblemis thatmost interpretationsof
harvestcomposition data assume a stable age distribution, which is usuallyinappropriate.Relaxationof stable
age distributionassumptionsmay be possible if independentinformationon rate of change in populationis
available(Eberhardt1985, 1988).
Commonly,age dataon sex orage compositionof bear
harvests are used to infer that populations are stable
because mean (or median) age or sex ratio of harvested
animals is constant. Similarly,some managerslook for
decreasingmean(ormedian)age of harvest(especiallyof
males) or increasingproportionsof females in the kill as
indicatorsof overharvest. Such interpretationscan lead
managersinto unwarrantedcomplacencyaboutpopulation status. When birthand deathratesare constant,the
sex and age compositionof the populationwill stabilize
regardlessof populationtrend.This has been recognized
since the 1907 paper by Lotka (Caughley 1977) but
remains a source of confusion. When birth and death
ratesarenot constantor vulnerabilityby sex or age class
is changing, harvest composition may change in response. This change,however,is not necessarilyrelated
to a change in populationstatus.
Managersshould be cautious in setting planningobjectives based on age or sex ratio in harvest statistics.
Benchmarkssuch as "no fewer than 60% males in the
total harvest"may be inadequateto preventoverexploitation. The sex ratio of harvest at sustainableharvest
levels is not a constant. Instead,this value is a function
of a numberof factorsincludingthe relativevulnerability
of each sex to human-causedmortality, sex and agespecific naturalmortalityrates,proportionof total mortalitythatis representedby harvest,andsex ratioatage of
firstvulnerabilityto hunters.Failureto meetanobjective
of at least 60%males could, for example,be "remedied"
by addingan early springseason when males have high
vulnerability(O'Pezio et al. 1983, Miller 1990/, Van
Daele et al. 1990) rather than by decreasing kill of
females. It is preferableto set exploitationguidelines in
termsof thetotaladultfemaleharvestas hasbeendonefor
polarbears(Tayloret al. 1987b).
363
A promisingapproachto interpretationof sex andage
compositionof blackbearharvestdatawas suggestedby
Fraseret al. (1982). This approachexploits the higher
harvest vulnerability of males compared to females
(Bunnell and Tait 1980), which results in a progressive
decline in theproportionof males in olderage classes. At
some age, the highervulnerabilityof males will be offset
by the largernumberof survivingfemalesandtheharvest
at that age and older will favor females. In lightly
exploitedpopulationsthe age at which females predominatein the harvestwill be olderthanin heavily exploited
populations.A regressionof percentmales in harveston
age class will have a steeper negative slope in heavily
huntedpopulations(Fraseret al. 1982).
Simulationstudies have indicatedthat for bears this
model is sensitive to a number of likely violations of
underlying assumptions (Harris and Metzgar 1987a).
Even if it lacks robustness,however, this approachmay
be useful as a tool to examineconflicting interpretations
of availabledata. Ina portionof south-centralAlaska,the
Fraseret al. (1982) approachwas successfully used to
documentthatcurrentgrizzly bearexploitationrate was
higherthanformerly(Miller 1988). Even thoughharvest
ratecould not be directlyestimatedbecauseof violations
of the model's assumptions,this analysis was useful in
discreditingthe hypothesisthatthe bearpopulationwas
unaffectedby increasedharvests. Also, the most likely
bias in the use of the Fraseret al. (1982) approachin
Alaska would have resulted in an underestimationof
harvestrate. This was because vulnerabilityof females
declined in the adult age classes when females were
periodically protected by being accompanied by offspring(it is illegal to shootgrizzlybearsaccompaniedby
cubs or yearlingoffspring). Because the estimatedharvest ratewas an overestimatebutwas still higherthanthe
calculatedsustainablerate,it was usefulin demonstrating
a clear need for reducedharvests.
A morecomplexapproachfor interpretingsex andage
compositionof harvestdatawasdevelopedby Tait(1983).
Using sex and age composition of harvestdata, Tait's
approach uses non-linear optimization procedures to
developmaximumlikelihoodestimatesforhistoricpopulation size, hunting rate, recruitmentrate, and other
parameters. Unfortunately,Tait's model has yet to be
adequatelytested with real harvestdata or evaluatedto
see how robust it is when underlyingassumptionsare
violated. Alaskais currentlymakingan effortto conduct
such tests.
The limitationsof sex andage compositionof harvest
data should not discourage managers from collecting
thesedataandcontinuingto investigatemeaningfulways
364
BEARS-THEIR
BIOLOGY AND MANAGEMENT
of using them. Comparedto field studies as a way of
evaluatingpopulationstatus,harvestdataare much less
expensive to collect. In using these data,managersmust
be awareof the limitations,however,as commonmisinterpretationscould lead managers into misclassifying
declining populationsas stable. With existing technology, it is clear thatthe limitationson use of composition
of bearharvestdataare such thathuntingremnantpopulationsof bearscannotbe justifiedon the basis thatsuch
datawould be helpful in evaluatingpopulationstatus.
documenting potential changes in density caused by
hunting,development,or habitatdeterioration(Schoen
and Beier 1989, Miller and Sellers 1989, Ballardet al.
1990). Such density estimates were made for 9 grizzly
bearand 3 black bearpopulationsin Alaska in a variety
of habitatsandovera rangeof beardensitiesfrom6.7-380
bears/1,000km2(Miller et al. 1987, Barneset al. 1988,
Schoen and Beier 1989, Miller and Sellers 1989, Miller
1990a, Ballardet al. 1990, Schwartzand Franzmannin
prep.). Not all of the problems associated with using
these techniqueshave been resolved. The best methods
for dealing with capturebias, small sample sizes, and
InformationObtained from Research
Research is an importantcomponent of sustained extrapolationof results to larger areas need additional
study. A correctionfactorfor small samplebias in such
yield management for bears. Research is necessary
estimateswas developed by Eberhardt(in press).
becausebearpopulationmanagementhas few generally
Otherapproachesto estimatingbeardensityarebased
acceptedtechniquesthatcan be widely appliedto evaluon movements of radio-markedbears (Rogers 1977,
atepopulationsize ortrend(Harris1986). Researchis not
needed for each exploited population. Frequently,adeHughie 1982, Reynolds et al. 1987, Schwartz and
in prep.).Typically,thesetechniquesinvolve
Franzmann
cautious
extrapolation
quate results can be obtainedby
home
be
it
should
from researchdone elsewhere. However,
rangesof individualbearsovera studyarea
plotting
recognizedthatresponsiblesustainedyield management and calculating the proportionsof each home range
of a bear populationwill be expensive and may require overlappingthestudyarea.Theseproportionsaresummed
field studies to estimate population size, population to derivea populationestimateanddividedby the size of
density,movements,or criticalreproductiveandmortal- the study area to obtain a density estimate. Such estimates are usuallyidentifiedas minimumvalues because
ity rates.
of the possibilitythatnot all bearsin the studyareawere
most
Trend.-Research
and
Size
programs
Population
These estimatesusually do not include a
radio-marked.
Fresize.
of
estimation
address
population
commonly
and may contain subjectiveelements
estimate
variance
varisome
is
estimated
size
using
quently, population
difficult
to replicateby differentobservthem
make
that
the
as
such
ation of capture-mark-recapture
procedures
ers.
Beecham
al.
et
However,
may
providemore accuratedensity
1980,
they
Seber-Jollytechnique(DeMaster
than
estimates
This
et
al.
proceduresused when
capture-recapture
1986, Kolenosky 1986).
1983, Amstrup
the
estimatedpopulation
area
of
the
size
the
addition
in
rate
of
survival
estimate
an
occupiedby
techniquerequires
is
uncertain
of
1982).
(Hughie
to the other standardassumptions capture-recapture
In the small but politically significantpopulationsof
procedures(Seber 1982). Wheresurvivalestimatesare
not available,black bearpopulationestimateshave been
grizzlybearsin GlacierandYellowstoneNationalParks,
obtained using more traditionalLincoln Index procegrizzly bear populationsize and trend were estimated
fromdirectobservationsof bears(Martinka1971, 1974;
dures (Jonkel and Cowan 1971, LeCount 1982, Young
Craigheadet al. 1974;KnightandEberhardt1984, 1985;
andRuff 1982, MillerandBallard1982, Beecham 1983,
Keating1986;McDonaldet al. 1988;Hayward1989). In
Aune and Brannon 1987). Frequentlyit is difficult to
a Montanastudyarea,numberof grizzlies was estimated
convert populationestimates obtainedusing such techby addingmarkedbears known presentwith unmarked
niquesto densityestimatesbecauseof uncertaintyabout
bearsseen (Aune andBrannon1987). Systematicapplisize of the areaoccupied by the estimatedpopulation.
cationof directobservationtechniquesmaybe preferable
InAlaska,intensivecapture-recapture
techniquesusing
for deriving such estimates for critically small popularadio-telemetryto correctfor lack of populationclosure
tions of grizzly bears such as in the Yellowstone area
have been used to derive black and grizzly bear density
(Harris1986). However,these approachesaretoo laborestimatesin small(<2,000 km2)areas(Milleret al. 1987).
With this approachthe area occupied by the estimated intensive to be useful to managers of exploited bear
populations. They also lack varianceestimates, which
populationdoes not have to be estimated. In 1 areathis
of
the
techniquewas used to documentstatisticallysignificant makesit difficultto evaluate significance reported
numbers.
changes in population
declines in bear numbers caused by hunting (Miller
Anotherpromisingapproachtowardsestimatingbear
1990a). Elsewhere,theseestimatesserveas baselinesfor
BEAR POPULATION MANAGEMENT * Miller-
density withoutmarkinganimalswas describedby Dean
(1987). This method employs intensive aerial surveys
anda sightabilitycorrectionfactorto estimatenumberof
animalsmissed duringaerialsearches.
Researchaimed at developing indicatorsof population trend have not yet producedconsistently reliable
procedures. Different techniques have been used to
detect changes in bear numbers (see review in Harris
1986 and discussions in Peltonet al. 1978, Phelps 1979,
LeFranc et al. 1987). There are ongoing efforts to
develop trend indices based on use of bait stations (D.
Garshelis, Minn. Dep. of Nat. Resour., GrandRapids,
pers. commun.), scent stations (Lindzey et al. 1977, J.
Beecham, Id. Dep. of Fish and Game, Boise, pers. commun.), and on trackcounts in Florida(J. Wooding, Fla.
Game and Fresh WaterFish Comm., Wildl. Res. Lab.,
Gainesville, pers. commun.). In some partsof Alaska,
annual aerial counts of bears are conducted at food
concentrationsites such as along salmon streams. Correct interpretationof such datafrom any 1 year requires
manyreplicatecounts (Ericksonand Siniff 1963). Also,
the utilityof counts at food concentrationareasto detect
populationtrendis questionable.Numerousbearswould
likely be observedin such areaslong afterthe numberof
bearsin less preferredhabitatshaddeclinedsignificantly.
Away from food concentrationareas,high directannual
counts from aircraftmay providea useful index of trend
where bear populationsare dense and visibility is high.
Suchcountsin alpinehabitatsareconductedin southeastern Alaska (Schoen and Beier 1989) and on Kodiak
Island(R. Smith,Alas. Dep. of Fish and Game, Kodiak,
pers. commun.).
Vital Rates.-Rates of birth,death, and recruitment
for bearpopulationscan only be establishedby research
programsor by extrapolationfrom research. For longlived species with low reproductiveand adultmortality
rates like bears,estimationof these parametersrequires
manyyearsof studyof > 10radio-markedfemales(Miller
1989). Estimatesof survivorshipratesbased on regular
locations of radio-markedanimals can be calculated
usingproceduresdevelopedby Heisley andFuller(1985)
and Pollock et al. (1989). These procedureshave been
appliedon populationsof grizzly andblackbears(Knick
and Kasworm 1989, Schwartzand Franzmannin prep.).
Otherapproachesusing kill rates of tagged black bears
were describedby LeCount(1982), Kolenosky (1986),
and Miller (1987). For polar bears and grizzly bears,
mortalityrateof adultfemales was shown to be the most
criticalfactor in correctlyestimatingpopulationgrowth
rateor sustainablemortalityrates(KnightandEberhardt
1985, Tayloret al. 1987b).
365
In cases whereresearchobjectivesrequirecaptureor
handlingof bears, the studies themselves will result in
some mortalitiesor other stresses on bear populations.
These stresses may not be significant to healthy bear
populations(Ramsay and Stirling 1987), but they may
make such studies inappropriatefor depleted populations. Whetherconductedon depletedpopulationsornot,
all proposedstudies requiringhandlingof bears should
receive adequatepeer review to assure that poorly designed or implementedprojectsare not authorized.
InformationObtained from Simulation Studies
Informationobtained from hunters,from harvested
bears,andfromfield studiesneeds to be integratedinto a
conceptualframeworkor model where it can be used to
makemanagementdecisions. Managersareincreasingly
findingmathematicalmodels of populationsto be useful
tools for organizing and making decisions from such
information. Computersare useful tools for examining
suchmodelsas theypermitmanagersto quicklymakethe
lengthy and repetitive calculations needed to estimate
parameterslike sustainableharvestlevels.
Deterministic models used to estimate sustainable
harvestlevels have only 1 resultper set of inputs. These
models are relativelysimple to make. Useful deterministic models can be made by persons withoutprogramming talents using conventional spreadsheetsoftware.
Such models may introducesystematicerrorin species,
like bears, with multi-year periods of maternal care
(Tayloret al. 1987c).
Stochastic models, where life history events are assigned probabilitiesinsteadof fixed rates, are useful in
examining the range of possible outcomes per set of
inputs.Softwareusefulin constructingstochasticmodels
for species with any kind of life historyhas been developed by Harriset al. (1986). This software was used to
evaluate sensitivity of harvestdata(Harrisand Metzgar
1987h)andis usefulin predicting,forexample,probability of survivalof small populationsof bears.
Deterministicmodels basedon ANURSUS (Tayloret
al. 1987a) with optional stochastic features have been
developedspecifically for each of the 3 NorthAmerican
bearspecies. ANURSUS attemptsto mimic the dynamics of bearpopulationsand,as a result,requiresa daunting
numberof inputparameters.The 3 species modelsbased
on ANURSUS are currently being linked and documented(M. Taylor,NorthwestTerrit.Dep. of Renewable
Resour.,Yellowknife,pers.commun.). Whenthis is accomplished,ANURSUS can be more widely tested and
used to establish managementobjectives based on sustainableyield.
366
BEARS-THEIR
BIOLOGY AND MANAGEMENT
ANURSUS was used to estimatesustainableharvest
levels for adultfemalepolarbears. Less than 1.6%of the
total populationof all bearscould be harvestedas adult
females (Taylor et al. 1987b). Based on this finding
sustainableharvest number can be approximated(M.
Taylor, NorthwestTerrit.Dep. of Renewable Resour.,
Yellowknife, pers. commun.)as:
H = (N)(0.015/F),
where H is numberof bears that can be harvested,N is
total population number, F is the proportionof adult
females in the harvest,andthe 0.015 constantis derived
from the simulationresultthat<1.6%populationcan be
harvested as adult females (Taylor et al. 1987b). It
follows that if the whole harvestis adult females, then
harvestsof 1.5%of the populationcan be sustained. If a
proportionof the harvest is male then a largerpercent
harvest can be sustained. The maximum sustainable
harvestrate for polar bears was estimatedat 4.5%; this
occurred when 33% of the harvest is female (Stirling
1988b). In the YukonTerritory,ANURSUS was used to
make preliminaryestimates of maximum sustainable
harvestlevels for male (6%)andfemale (2.5%)segments
of regional grizzly bear populations(B. Smith, Yukon
Dep. of Renewable Resour., Fish and Wildl. Branch,
Whitehorse,pers. commun.).
Deterministicmodels were used by Bunnell and Tait
(1980) to estimatesustainablemortalityfrom all causes.
Whennaturalmortalitiesare subtractedseparately,such
models estimate sustainableharvestlevels. The consequence of errorsimulationdiscussed earlier illustrates
this application. With the generousestimates of reproductive rates and survivorshipfrom naturalmortality
used to estimate populationrecovery period (Table 1),
maximumsustainableharvestswere estimatedat 7.8%
for grizzly bears older than 2.0 and at 15.9%for black
bears>1.0 (Table 3). These were convertedto estimates
of sustainable harvest of the whole population using
typical values for mortalityof cub and yearlinggrizzly
bearsandcubblackbears(BunnellandTait 1985). Under
these conditions and assumptions,maximal sustainable
annualhuntingmortalitywas 5.7%for grizzly bearsand
14.2%forblackbears(Table3). Elsewherethisapproach
was used to estimatethatsustainableharvestsfor Yukon
grizzlies was 2-3% of the population(Sidorowicz and
Gilbert 1981). McCullough (1981, 1986) estimated
higher sustainableharvest levels than other models by
incorporatingdensity-dependenteffects on recruitment.
Thereis both directand indirectevidence for such relationships (Rogers 1983; Kemp 1972; Stringham1980,
1983;YoungandRuff 1982;SchwartzandFranzmannin
prep.). In my view, however, these relationshipsare as
yet too poorly understoodto be safely incorporatedinto
estimatesof sustainableharvestlevels for huntedpopulations.
Estimatesof sustainableharvest rates derived from
models may be comparedwith calculatedharvestrates
derivedfrom kill numbersand populationestimates. In
cases where differentsexes have differentvulnerability
to hunters, population harvest rate can be estimated
directlyfrominformationon the sex andage composition
of the population (Bunnell and Tait 1985) or harvest
(Fraseret al. 1982). Suchcomparisonsshouldbe viewed
skeptically especially when age distributionsare not
stable (Caughley 1974, 1977; Harris1984).
Harvest Controls
Managershave numerousregulatorytools for influencing the number or composition of bears harvested
(Phelps 1979, Harger 1978). The effectiveness of any
particulartool will varyamongareasdependingon hunting conditionsand the type and motives of the hunter.
Seasons and Bag Limits.-Number of bearstakenby
hunterscan usuallybe reducedby shorteningseasonsand
increased by lengthening seasons. However, season
lengthworksto reducekill only to a point;in Pennsylvania, 736 black bearswere taken in a 1979 open hunting
season only 1 day long (Lindzeyet al. 1983). A similar
numberarecurrentlybeing takenwith a 3-dayseason(G.
Alt, Pa. Game Comm., Moscow, pers. commun.). Seasonscanbe heldperiodicallyinsteadof shortened.Onthe
Alaska Peninsulain southwesternAlaska, grizzly bear
huntinghas been allowed only on alternateyears in an
effortto reduceharvestandmaintainopen hunting(Sellers and McNay 1984).
Shorterseasonsmaygive managersjustas manybears
killed by huntersin a shortertime, huntingundermore
crowded conditions. When this occurs, managersmay
choose to limitthe numberof huntersby issuing permits.
Huntingby limitedpermitcan augmentthe qualityof the
Table 3. Estimated sustainable yield from maximally productive populations of
grizzly and black bears (input parameters reported in Miller [1989]).
Annualhuntingratefor initial
stabilizedpopulationof grizzly
bears (>2.0-years-old)and black
bears (>1.0-years-old)
Equivalenthuntingratefor total
population(all ages)
a Total
7.8%
15.9%
5.7a
14.2%b
populationestimatedfrom numberof 2-year-oldsby assumingyearling
and cub mortalityratesof 0.20 and 0.35, respectively,for each sex.
b Total
populationestimatedfrom numberof yearlingsby assumingcub
mortalityratesof 0.22 for each sex.
BEAR POPULATION MANAGEMENT * Miller
hunting experience and, depending on numberissued,
may serve to maintaintrophybearsin the population.
In some parts of Alaska, special permits and
seasons arealso used to minimizedamageby anddanger
fromgrizzly bearsthatenterruralvillages. By providing
for these bears to be taken legally, managers achieve
moreaccuraterecordson kill ratesandallow thepublicto
effect controlactionsthatwould otherwisehave to be accomplishedat public expense.
Seasons can also be adjustedto influence the sex of
bears taken. This is particularlytrue during spring
seasonsbecausemalebearstendto leave densearlierthan
females,move greaterdistances,arenot accompaniedby
cubs, and springhuntersmay be more selective for large
(male) bears (O'Pezio et al. 1983, Schoen et al. 1987,
Miller 1990b, Van Daele et al. 1990). During spring
grizzly bear seasons in Alaska (1984-1988), 74% of
grizzly bears taken (n = 2,563) were male comparedto
55% of bearstakenin fall seasons (n = 2,963) (ADF&G
unpublisheddata). A similar patternwas evident for
black bear where 75% of springbears harvestedduring
1984-1988 were male (n = 4,691 bearskilled) compared
to 64% in fall harvests(n = 2,887). In some areas,polar
bearskilled in seasons open duringthe den entranceand
emergenceperiodare more likely to be females because
dens aretypicallyon land,which may be nearvillages of
nativehunters,andonly pregnantfemales use dens (Stirling 1986,Kolenosky 1987). Inpartsof Canadapregnant
females areprotectedfrom huntingby delayingopening
of huntinguntil 1 December,afterthedenentranceperiod
(Stirlingand Calvert 1985). Black beartrackingstudies
in Mainerevealedthatblackbearsarelikely to be distant
fromtheirbreedingrangesduringearlyfall seasons. The
geographicdistributionof kill at suchtimes wouldnot, as
a result,accuratelydepict the origins of harvestedbears
(Hughie 1982).
A chronology of sex ratio in kill of grizzly bears
harvestedin a portionof southcentralAlaska was given
by Miller(1990b). Therewas littlechangein sex ratioof
kill over time during fall seasons, but there was an
increasein the proportionof females killed as the spring
season progressed. This suggested that the last partof
springseasonsshouldbe eliminatedif hunterkills needto
be reduced. However, 2-4 times as many females are
killed duringeach of the first 2 weeks of Septemberthan
duringany week of the springseasons. Also, the percentage of females in the kill is higherin the early fall thanat
any other time of the year (Miller 1990b). In this area,
morefemales wouldbe protectedfromhuntersif the first
2 weeks of the fall season were closed than could be
accomplishedby closing the whole springseason.
367
Bag limits can also be adjustedto influencethe number of bears taken. In most of Alaska, grizzly bear bag
limits are 1 per 4 years. The multi-yearbag limit serves
to make huntersmore selective as by takinga bearthey
forego the opportunityto takea betterbearin subsequent
years. In Alaska's Game ManagementUnit 13, grizzly
bearbag limits were changedfrom 1 per 4 yearsto 1 per
yearduringfall seasons in 1982-1986 andharvestsaveraged 81 bearsperseason(range59-96). Whenbag limits
were 1 per4 years,fall harvestswere lower averaging60
bears(range40-73) in the 5 yearsbefore the change and
53 (range48-58) bearsper season in the 2 yearsafterthe
change (ADF&G unpublisheddata).
Increasein reportedkill for certainareas may result
from misreportingby hunters. This may occur when
areaswith multiple-yearand annual-yearbag limits are
mixed. Differencesin baglimitsandseasonsgive hunters
incentivesto reportlocationof theirkills incorrectly. In
Alaska,an investigationby Fish andWildlife Protection
Officers resultedin the prosecutionof a guide who had
misreportedthe locationof at least 25 grizzlybearskilled
by himself, his relatives,andhis clients during 1 season.
Halfof these werewronglyreportedas havingbeentaken
in areaswitha 1peryearbag limit whenthey had,in fact,
been taken in an area with a 1 per 4 year bag. Such
misreportingcan result in serious managementerrorin
circumstanceswheremanagersrely on accuracyin these
statistics.
Another way to affect bear harvests is to time bear
seasons to occur at the same time as hunts for other
species. In some areas harvests will be increased if
hunterscan take bears incidentalto hunts designed primarilyto takeungulates. This approachhas been used in
a number of different areas to influence taking black
bears (Burk 1977) as well as grizzly bearsin Alaska.
Closed Areas.-Areas closed to hunting are also a
potentiallyuseful tool for managers. Closed or lightly
huntedreservoirareascan be sourcesof surplusanimals
that immigrateto open or more accessible areas where
theycanbe hunted(Beecham 1986). To be effective such
areasmust be large.
Methods,Means, and Legal Bear Definitions.-Besides season adjustmentsand limited entry systems,
managers use restrictions on methods and means of
huntingto influenceharvest. These includerestrictions
on weapon type, transportationmethods, use of attractants like bait, and use of dogs. In Michigan,the age of
blackbearstakenby huntersusingdogs was olderthanfor
huntersnot using dogs (Harger1978). However,regulationsthatpermitbaitingor huntingwithdogs couldresult
in adverse populationimpacts if huntersselect for fe-
368
BEARS-THEIR
BIOLOGY AND MANAGEMENT
males, which are more likely to "tree"when chased by
The ability of managers to maintain or increase bear
dogs.
populationnumberssuccessfully is limited by 4 major
One of the most effective ways to maximize sustainconstraints.
able harvest of bears with minimal influence on the
The first constraint is adequate protection of bear
of
the
is
to
direct
habitat.
This topic is treatedelsewhere (McLellanand
reproductivecapability
population
hunterharvestaway from adult females by prohibiting Shackleton1988, McLellan1990, Mattson1990, Schoen
shooting females accompanied by offspring. Where
1990).
female bearsproducenew littersevery 2 or 3 years,adult
The second constrainton bear populationmanagefemales are vulnerableonly 1/2 to 1/3 as frequentlyas
ment is political. Bear populationmanagersare presmales. Experimentsare ongoing in the YukonTerritory sured by many special interestgroups, frequentlywith
to direct the harvests of outfitters away from female
diametricallyopposed objectives. In Alaska, for exgrizzly bearsby giving them incentivesto harvestmales
ample,subsistenceandsporthuntersfrequentlypressure
(Smith 1990). Clearly, it is difficult to differentiate managersto reducepopulationsof bearsandotherpredabetween sexes of bearsbut it will be done more often if
tors. On the other extreme are groups that agitate to
huntershaveincentivesto do so. InOntarioit was shown
reduceor eliminatehunting.One suchgroupmanagedto
that not all females contributeequally to reproduction eliminatethe black bearhuntingseason in Californiain
1989 (D. Koch, Calif. Dep. of Fish and Game, Sacra(Kolenosky 1990). Protectionof maternalblack bear
females, which are producing the bulk of recruits, is
mento, pers. commun.). Wildlife managersmust spend
an increasingamountof theirpersonnelandfinancialreespecially importantwhen this is the case (Kolenosky
sources dealing with the demandsand proposalsof spe1990).
Commercialization and Restrictions by Class of
cial interest groups. These expendituresrepresentreHunter.-Limitations on commercialuse of bearpartsis
sources that are diverted from habitat and population
a useful tool in preventingexcessive harvests. Commer- managementprograms. Some groups,commonly those
cial exploitationof wildlife has the potentialto reduce
opposed to hunting, even target resource management
and eliminate wildlife populationsand species quickly
agencies as the problem. These activities reducepublic
confidence and support for managementefforts. An
(Geist 1988). The Lacy Act of 1900 in the UnitedStates
was a largely successful effort to stop the trendof comimportantchallengefacing wildlife managersis to direct
the activitiesof these groupsinto activitiesthatincrease
mercial overexploitationof many wildlife species and
supportfor soundlybasedmanagement.This is easierto
populations(Trefethen1961). In many areasthe sale of
blackor grizzly bearhides or parts,such as gall bladders, say thanto do. Clearly,however,in the NorthAmerican
is illegal as is the sale of polar bear hides. These
political system, the concernsof such groupscannotbe
restrictionsreduce harvests over what would occur if
ignored without ultimate counter-productive consecommercial sales of bear parts were allowed (Geist
quences. Althoughit maybe frustratingatthetime,it will
be
allowed
of
bear
could
sales
Commercial
help if these special-interestgroups are involved in the
1988).
parts
in some states withoutcreatinglocal managementprobdevelopment of managementplans. This provides a
forum where their concerns can be heardby managers
elsewhere
exacerbate
this
but
lems,
by
problems
may
and managers'concernscan be heardby them.
claim
the
came
to
the
lawbreakers
parts
ability
giving
There appears to be more political will to protect
from somewheresales were legal.
remnant
or
restrict
to
benefit
populationsof bearsthanthereis to reestablish
special
Regulations designed
in
bears
areas where they have been eliminated. Alas
groupsof hunterssuch resident,non-resident,native,
be
used
can
to
thoughgrizzlies have been eliminatedfrom99%of their
sport, trophy, or subsistence hunters
former
limited
to
constrainharvests. As an alternative using
range south of Canada(Servheen 1987 cited by
Jonkel
certain
classes
1987),thereis little interestin reestablishingthem
entrypermits,suchregulationsallow only
in
of huntersto participate.This is the system in effect for
places like California,Colorado,or Arizona (Brown
States
where
1985). In Texas much of the public is opposed to
polar bear in both Canadaand the United
managementactions that would result in a significant
only indigenouspeople have huntingrights.
increasein blackbearpopulationnumbersor distribution
DISCUSSION
(C. Winkler,Tex. Parksand Wildl. Dep., Austin, pers.
has
evolved
Inmostareas,bearpopulationmanagement
commun.). Reintroductionof bears into an area where
based
to
numbers
from efforts to reducebear
they have been eliminatedis a positive action that will
objectives
of
numbers.
on maintenanceor augmentation population
provoke some opposition. In North Americanpolitical
BEAR POPULATION
MANAGEMENT
* Miller
systems,it appearsto be moredifficultto takeactionthan
to do nothing. Thus, it is importantto assure that the
status quo includes bears.
The thirdconstraintis the technologicaltool kit available for use by managers. Many of the tools used by
managersto assess the success or failureof bearmanagementstrategieslackprecision,estimatesof variability,or
producepotentiallybiased results. It is easier to detect
potentialsources of bias and imprecisionin analyses of
bearpopulationsthanit is to develop approacheswithout
these flaws. Unfortunately,the decisions managershave
to make do not disappearjust because the information
availablehas uncertainaccuracyor precision. In making
these decisions, however, managersshould incorporate
the limitationsof the datainto theirmanagementstrategies. Usually this will mean settingmanagementobjectives and guidelines on the conservative side of what
might be estimatedto be optimal. The costs associated
with unintendedpopulationdeclines and the difficulties
of detecting such declines until they are far advanced
mandate a conservative approach to bear population
management.
The fourth major constraintto populationmanagement is financial. Some of the technologicalconstraints
of existing bearpopulationmanagementtechniquescan
be overcomeif adequatefundswereavailable.Wherethe
commitmentto spend the necessary money is lacking,
bearpopulationmanagershave littlechoice butto implement conservativemanagementstrategies.
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