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BLACKBEAR MANAGEMENT YOSEMITE
IN NATIONAL
PARK
DALE R. HARMS, Wildlife Biologist, National Park Service, Yosemite National Park, California 95389'
Abstract: Conflicts between parkvisitorsand the Americanblack bear(Ursus americanus)in Yosemite National Parkpose seriousmanagement
problemsfor the NationalParkService and often resultin extremeinconvenienceand monetarylosses to parkvisitors. Food-reward associations
with humanshave resulted in the loss of the black bear's instinctive fear of people and in the developmentof highly sophisticatedpatternsof
depredation.A managementprogramconsisting of 5 basic elements was implementedin the springof 1975 to meet bearmanagement objectives
of the National Park Service. The effects of managementon bears and parkvisitors were evaluatedby monitoringthe patternsof damage that
bears displayedbefore and duringthe program.Analyses of data accruedfrom propertydamage, personalinjuries, and controlof problembears
were also made. The results of these analyses are discussed and their implications applied to managementpractices and research needs.
Comparisonsof data accruedbefore and throughthe first 2 years of the programappearto supportthe hypothesisthat the programis achieving
its stated objectives.
The naturalbehavior, foraging habits, distribution, Through food-reward association, bears have
and numbersof black bears in Yosemite National Park learned the relationship between vehicles and food
have been significantly altered by habituation to stored in them. In the last 3 years, 1,493 vehicles were
human-suppliedfood sources. During the past 6 de- damaged or broken into by bears seeking food - 65
cades of food-reward associations with people, bears percent of the 2,293 recorded bear incidents. Bears
have evolved deeply ingrained, sophisticatedpatterns have also learnedthe associationbetween backpacksor
of depredation. foodsacks suspendedfrom trees and the ropes holding
The Yosemite Human-Bear Management Program them up. Today, the average backpackerfinds it in-
was implemented in 1975 to meet bear management creasingly more difficult to suspend food supplies in a
objectives of the National Park Service with minimum mannerthat prohibitsbears from reachingthem. In the
adverse impact on the black bear populationand envi- past 2 years, it is estimated that 3,840 bear incidents
ronment. This paper summarizes the management occurred in the backcountry. The level of sophistica-
problem and managementactivities, describes evalua- tion shown by bears in their patterns of depredation
tion procedures, presents preliminary results, and appears to be increasing as their instinctive fear of
brings together data that may be used for future pro- people decreases.
gram analysis. After review of available information, the Superin-
The conflict between bears and people and the ef- tendentof Yosemite National Parkdirectedthat a pro-
fects of people upon bears are seen nowhere more gram be implementedto (1) restore and maintain the
dramaticallythan in Yosemite National Park. Exten- natural distribution, abundance, and behavior of the
sive development, high levels of visitor use, and pat- endemic black bear population; (2) provide for the
terns of visitor use are key factors contributingto the safety of park visitors and their property;and (3) pro-
conflict. Visitation has exceeded 2.25 million people vide opportunitiesfor visitors to observe, understand,
since 1968 and 2.7 million in 1976 (Table 1). Levels of and appreciatethe black bear in its naturalhabitat.
use
backcountry tripledin less than 10 years. Recorded
visitor-nightsof use increased from 77,654 in 1967 to METHODS
169,924 in 1976. In 1976, 64,606 people spent nights
Methods employed included (1) public information
in the backcountry.
and education, (2) removal of all artificial food
Extensive development including campgrounds,
sources, (3) enforcementof regulationsregardingpro-
hotels, restaurants, stores, swimming pools, tennis
per food storage and the feeding of wild animals, (4)
courts, golf courses, a ski area, and 5 backcountry
control of problem animals, and (5) research and
High Sierra Camps concentrateshuman use in avail-
able bear habitat, increasing the potential for encoun- monitoring.
Public information systems and steps taken to in-
ters with bears. Stokes (1970) foundthat repeatedvisits
crease the public's awarenessof the programand com-
of bears to developed areas and garbagedisposal sites
to obtain food representreward-reinforced behavior. pliance with its provisions included (1) distributionof
bear brochuresto both frontcountryand backcountry
users; (2) permanentwarning signs at park entrances,
'Present
address:
U.S. FishandWildlife
Service,Billings, campground entrances, parking lots, and park rest-
Montana59101. rooms; (3) articles regardingbears and people in each
206 BEARS - THEIR BIOLOGY AND MANAGEMENT
Table 1. Propertydamages and personal injuriesattributable black bears, Yosemite NationalPark,1966-76.
to
Damage incidents"
Year Park Decrease/increase Numberof Numberof Control
visitation Number Estimated of incidents from personal visitors actionsb
value ($) previous year (%) injuries per injury
1966 1,817,000 49 1,888 29 63,000 47 (24)
1967 2,201,500 72 2,843 47 11 200,000 48 (17)
1968 2,281,100 49 2,670 -47 6 380,000 16 (4)
1969 2,291,300 86 6,360 76 12 191,000 38 (4)
1970 2,277,200 27 4,730 -69 3 759,000 40 (6)
1971 2,416,400 103 11,835 282 10 242,000 61 (13)
1972 2,266,600 262 28,588 154 3 746,000 81 (17)
1973 2,339,400 246 24,367 -6 16 146,000 43 (9)
1974 2,343,100 613 80,248 149 28 84,000 26 (1)
1975 2,619,000 975 113,197 59 15 175,000 135 (10)
1976 2,753,100 688 66,294 -29 12 229,000 147 (16)
"Not includingpersonal injuries.
b Numbersof bears killed given in parentheses.
summer issue of the park newspaper;(4) increases in To control bear densities in each release area, a
the numbersof rangerpatrolsand interpretive programs minimumintervalof 7 days was allowed between suc-
about bears; and (5) an AM taped radio broadcastre- cessive releases in each area: this 7-day release inter-
ceivable on all roads entering Yosemite Valley in- val was violated only when all other release sites were
forming the public about bears. full.
Open garbage pit dumps were sources of artificial Bears were intentionally destroyed using pentobar-
food until 1969 and 1970 when land dumpswere closed bital sodium and processed as scientific specimens if
and a solid waste collection system was adopted. De- they had been relocated twice, captureda third time,
spite the conversion, bears continued to feed on gar- and their individual trappingrecords showed conclu-
bage providedby the non-bearproof dumpsters.In the sively that they were confirmedrogue animals or were
spring of 1975, all dumpstersin use in the park were responsiblefor personalinjuries. Bears twice relocated
bearproofed. Cables from which park visitors could and captureda thirdtime that were not seriousproblem
suspendtheir food supplies out of reach of bears were animals were relocated a third time.
installedin selected backcountryareasandfrontcountry The Division of Resources Managementmaintained
walk-in campgrounds. a central monitoring system that recorded human in-
Effortsto insuredenial of humanfood sources andto juries, propertydamage incidents, and all bear control
have visitors store food so as not to lure bears into actions on a daily basis. Thus, currentinformationfor
campgroundswere aided by the adoption of Special guiding the overall program and data for evaluation
Regulation S7.16e (3) CFR 36 requiringproperfood studies were available.
storagemethods. The level of enforcementvariedfrom A 2-year researchstudyon the populationecology of
verbal warningsto arrestand/orimpoundment prop-of the black bear in Yosemite National Park was con-
erty. tracted to the University of California, Berkeley, in
One control action was recorded each time a bear 1974 and has since been extended to cover a 4-year
was eithercapturedand transplanted, shippedto a zoo, period ending September 1978.
or destroyed. Efforts to remove bears promptly from The success of the programdepends on the validity
park developments when propertydamage or injuries of the hypothesis that removal of unnaturalfoods will
were occurringwere intensified. Bears were captured, restore a naturalpopulationof bears, therebyreducing
while free-ranging, with Serylan (phencyclidine hy- the need to control (captureand transplantor destroy)
drochloride) administeredby projectile-syringe, with bears to protect humans and their property. Data ac-
baited culvert traps, and with Aldrich snares. Mea- crued from problem bear control, property damage,
surements, weight, sex, and age were recorded, and a personalinjuries, and researchon populationdynamics
blood sample was collected. Bears were tagged with will be used to test the following hypothesis:
metal cattle ear tags with vinyl streamersattached.
Bears were relocated 13-48 airline km from their Bear control procedures, law enforcement, public
capturesites and releasedat predesignated release sites. information systems, and management actions to
o
BEAR MANAGEMENT IN YOSEMITE * Harms 207
eliminate unnaturalfood sources, applied under the = 0.01, r = 0.89). A 95 percentconfidence intervalis
1975 Human-Bear Management Program, will (1) constructed around the regression line as graphically
restore a more natural black bear population than portrayedby the dashed lines in Fig. 1. The 975 and
exists at present, as evidenced by fewer bears using 688 incidents recordedin 1975 and 1976, respectively
developed areas and by progressivereductionin the (after removal of unnaturalfoods), fall within these
numbersof bears controlledor destroyed;(2) reduce boundaries, indicating that they do not differ signifi-
the number of propertydamage and human injury cantlyfrom the exponentialgrowthtrend. However, in-
incidents from previous levels; and (3) not prevent cidents in 1976 decreased29 percentfrom those of the
the park bear population from stabilizing at the previousyear. We expect furtherdecreasesin incidents
naturalcarryingcapacity of the park. as young bears without human-altered behavior prog-
ressively replace incorrigible animals and the popula-
RESULTS tion readjuststo naturalcarryingcapacity levels.
Patternsof damageand changes in patternsthatbears
display may be useful in determining the effects on
Property Damage Incidents both bears and people of removing unnaturalfoods.
Removal of artificial food sources in the spring of Patternsmonitoredincluded (1) time of incidents, (2)
1975 marked the beginning of a transition period in location, (3) type of propertydamage, and (4) the rela-
which bears are expected to resort primarilyto natural tion of food and food storage to incidents.
foraging for energy requirements.In the first year after The time thatincidentsoccurredin 1974 through1976
artificialfoods were eliminated, incidents increasedto (month; weekend vs. weekday; hour) remained rela-
a high of 975 but decreased to 688 in the second year tively unchanged;70 percentof the damageoccurredin
(Table 1). Plottingpropertydamageincidents(PDs) on June, July, and August; and 18 percent occurred in
a graph showed that the numberof PDs increased ex- September,October,and November. The percentageof
ponentially from 1961 through 1975. The number of incidentsthatoccurredin the daytime(15 percent)andat
PDs fitted to a regression line with a square-root night (74 percent) also remainedthe same, suggesting
transformation the dependentvariableand with time
as thatthe bearproofing programhas not alteredthe bears'
as the independentvariable (Fig. 1) shows that PDs crepuscular activities(timesof occurrencefor 11 percent
increased significantly with time (t = 5.73, df = 9, a of the incidents were unkown).
,/\ '
32 / \ 955
- Confidence
Interval Based
On Syx
28
24
Uc
r-)
20
co
0
o 16
/ I'
o
12
0D
EH
r.o
CQ 8
jPD's =-155.8 + 2.40(year)
r = 0.89
4
0 I
I I
I I I a
I a
I A
1966 6 8
68
I I I I I
70 71 72 73 74 75 76
YEAR
Fig. 1. Property damage incidents fitted to a regression line using a square-root transformation as the dependent variable
and time as the independent variable.
208 BEARS - THEIR BIOLOGY AND MANAGEMENT
The percentage of incidents that occurred in of bear damage to the vehicle (Table 2). Vehicles that
campgroundsdecreasedfrom 71 percentin 1974 to 46 had food in the passenger sections either because they
percent in 1976 but the percentage of incidents in lacked trunksor because people neglected to store food
parkinglots increased 15 percent. This shift suggests to properly sustained 68 percent of the total vehicular
some degree the effectiveness of the new program.The damage incidents in 1976. Vehicles with properly
percentage of incidents in all other locations except stored food representedonly 18 percent of the inci-
backcountryareas remainedthe same. dents. Fourteenpercentof the damagedvehicles had no
Food rewardsassociatedwith people or with objects food in them. Over $54,000 damage to vehicles oc-
that contain food have resulted in deeply ingrained curredin 1976, a decreaseof 43 percentfrom a high of
patternsof depredation.Some forms of bear behavior $96,594 recordedin 1975. An indicationof a favorable
appearto be conditioned responses from past experi- trendis thatthe percentageof incidentsinvolving vehi-
ences that resulted in positive food rewards;examples cles declined from 70 percent in 1974 to 57 percentin
are smashed windows of vehicles that contained no 1976.
food, tree limbs or ropes chewed into to retrieve sus- To determinethe cause of incidents, causative fac-
pendedfood, and false chargesat people. Behaviorthat tors were assigned to each incidentinvestigated(Table
resulted in bear incidents due to conditionedresponses 3). Unstored food and improperly stored food were
and in which no humanerrorprecipitated incidentis
the major causative factors for 48 percent of frontcountry
referredto in this paperas conditionedbear behavior. incidents in 1976. Forty-six percent of the incidents
Smashing vehicle windows and pulling out window were attributed conditionedbear behavior.
to
and door frames to gain entry into vehicles for food
represent a behavior pattern that characterizes the Backcountry Incidents
Yosemite population. Methods of food storage in a Surveys by backcountry rangers checking com-
vehicle are criticalfactorsin determiningthe likelihood pliance with wilderness permits showed the numberof
Table 2. Analysis of bear incidents relating food and food storage to property damage, Yosemite National Park, 1974-76.
Food in Food in
passenger passenger
Food in section; section; Food Food Food
trunkof vehicle vehicle No food storage Food left hung from Total
vehicle with without present unknown present in open tree/cable
trunk trunk
Vehicles
1974 64(15)b 163(37) 93(21) 33 (8) 86(20) 439(70%)
1975 132(20) 205(31) 237(36) 87(13) 661(68%)
1976 70(18) 124(32) 143(36) 56(14) 393(57%)
Towedunits
1974
1975 1 (6) 15(94) 16 (2%)
1976 1(10) 9(90) 10 (2%)
Tents
1974 26(46) 11(20) 19(34) 56 (9%)
1975 19(46) 22(54) 41 (4%)
1976 11(39) 17(61) 28 (4%)
Backpacks
1974 4 (6) 20(27) 49(67) 73(12%)
1975 8 (6) 38(26) 100(68) 146(15%)
1976 18 (9) 28(13) 165(78) 211(31%)
Ice chests
1974 26(100) - 26 (4%)
1975 7(10) 58(88) 1 (2) 66 (7%)
1976 16(27) 41(69) 2 (3) 59 (9%)
Other
1974 36 (6%)
1975 71 (7%)
1976 94(14%)
Percent given as percent of total incidents.
bPercentof damaged items given in parentheses.
IN
BEAR MANAGEMENT YOSEMITE* Harms 209
Table 3. Causative factors for property damage incidents in Yosemite National Park, 1975-76. Table gives the percentage of incidents assigned to each factor.
Feeding/ Food Improper Improper Conditioned
baiting left in food disposal Accidental bear Unknown
(intentional) open storage of garbage encounter behavior
Frontcountry
1975 1 9 35 0 0 54 1
1976 0
O 12 36 1 0 46 5
Backcountry f
1975 0 8 16 0 1 75 0
1976 0 10 8 0 0 74 8
reported incidents to be low and unrepresentativeof seeking food in an area of high visitor use. The bear
actual backcountry bear encounters. The number of was destroyed the next day.
backcountryincidents can be estimated from the per-
centage of partiescontactedthat sufferedincidents and Problem Bear Control
from data on wilderness permit compliance. The level Cooperative efforts between contract researchers
of incidents expressed as incidents per thousand from the University of California, Berkeley, and park
visitor-nights decreased from 13.5 in 1975 to 7.0 in rangers and biologists have served to accentuateboth
1976 (Table 4). research and managementprograms. Since 1974, 202
The reductionin backcountryincidents is attributed individualbearshave been capturedand marked.Inten-
largely to information systems, enforcement of food sified efforts to keep bears out of developed areas in-
storageregulations,and the installationof food suspen- creased the numberof control actions sharply in 1975
sion cables in selected high-problemareas. However, it and 1976 and yielded many data useful in evaluating
is clear from the numberof incidentsand from personal
currently accepted management practices regarding
observationthatthe large majorityof backcountry users control of problembears. Underthe criteriaoutlined in
the
underestimate cleverness and ability of bears to re- the mangementplan, 26 bears were killed in manage-
trieve food suspendedfrom or between trees. Aversive ment actions in 1975 and 1976. The effects of
conditioning of bears may be requiredto reinstill an management-induced mortality on the population will
avoidance of people and minimize backcountrycon- be analyzed when results of currentresearchon popu-
flicts. lation dynamics become available.
Relocation of problem bears resolved immediate
Injuries problems only temporarily. During 1976, 98 different
A reductionin injuries occurredeach year after the bears were relocated within park boundariesa total of
programwas implemented (Table 1). The 12 injuries 131 times. Observation of bears returned and/or re-
recordedin 1976 representdecreases of 57 and 20 per- capturedat the same or another developed area indi-
cent from the 28 and 15 injuriesrecordedin 1974 and cated a 38 percent returnrate (31 percent returnedto
1975, respectively. Two of the injuriesin 1975 and9 of their original capturesites). In 1975, the rate of return
the injuries in 1976 occurred in backcountry areas. to developed areas for 100 bears relocated 125 times
Four of the backcountryinjuriesin 1976 occurredin 1 was 26 percent (21 percent returnedto their original
night and were attributed to a single yearling bear capture sites); in 1974 the rate was 8 percent for 23
Table 4. Levels of visitor use, bear incidents, personal injuries, and control actions in Yosemite's backcountry, 1973-76.
Estimated Incidents
Recorded numberof per thousand Recorded Recorded Personal Control
Year visitor- bear visitor- incidents damage injuries actions
nights incidents nights ($)
1973 141,464
1974 192,180 61 2 0
2,145
1975 196,565 2,654 13.5 96 2
5,762 2
1976 269,924 1,186 7.0 160 9
4,471 3
_
210 BEARS - THEIR BIOLOGY AND MANAGEMENT
Table 5. Summary of black bear captures/relocations and return rates to developed areas for 1-, 2-, and 3-year intervals, 1974-76.
Total
Total number Sex Cumulative Numberof times captured Total
Year numberof of new ratio new numberof
captures animals M:F animals 3 4 individuals
1974 55 42 21:19 42 32(76%) 7(17%) 3 (7%) 0 (0%) 0 (0%) 42
1975 160 93 50:61 135 78(69%) 25(22%) 8 (7%) 2 (2%) 0 (0%) 113
1976 172 67 55:58 202 75(66%) 23(20%) 10 (9%) 4 (4%) 1 (1%) 113
Number of times each Total Recaptures Returnratesa
Year Total individual relocated number
relocations individuals First Second Third 1-year 2-year 3-year
2 3 4 relocated year year year interval interval interval
1974b 25 21 2 0 0 23 2 8 3 8% (0%) 40% 52%
1975b 125 76 23 1 0 100 33 31 - 26%(21%) 51%
1976b 131 71 23 3 1 98 44 - 34%
1976c 49d - 38%(31%)
aNumbers in parenthesesindicate returnrates to original capturesites.
bReturnrates based on recapturedata only.
'Return rates based on recapturesand observations.
dIncludesobservationsof 5 bears returnedbut not captured.
bearsrelocated25 times. Table 5 shows the successive 1974 and/or1975 and may have improvedtheirhoming
increases in the return rate as the time interval after abilities.
relocation increased. The tendency for bears to return When returnrates to developed areas were analyzed
to their original capture sites, the geographical dis- by age-class (Table 6), yearlingsand subadultsshowed
tributionof developed areas in Yosemite, and insuffi- successes of 29 percentand 11 percent,respectively, as
cient land area for relocation all served to negate the compared with 42 percent for adults. Optimistic in-
effectiveness of transplants. terpretationof these data suggests that successful re-
Transplantsuccess in 1975 was shown to be related habilitationof these age-classes may be occurring.It is
to the distancetransferredfrom the capturesite (Harms recognized, however, thatthe stress of the relocationin
1976). The transplantsuccess (85 percent) for bears terms of placing a subdominantanimal in an area in
transferred37-48 km was significantly greater (P < which the naturalcarryingcapacityis alreadyexceeded
0.05) thatthe success (65 percent)for bears transferred may increase the mortalityrates for these age-classes.
13-20 km. However, in 1976, no significantdifference Jonkel and Cowan (1971), studyinga black bearpopu-
could be shown between success rates and transferdis- lation in Montana, found that young bears over 1.5
tances (Table 6). This lack of significance may be years of age rapidly disappearedfrom the population.
explained in partby the fact that many bears relocated No difference was observed in return rates between
in 1976 had also been relocated one or more times in females and males relocated in Yosemite.
Table 6. Black bear return rates, by age-class, in relation to relocation distances, Yosemite National Park, 1976.
Number released Numberretured to developed areas
Relocation Return
distance Year- Sub- Year- Sub- rate
(km) Cub ling adult Adult Total Cub ling adult Adult Total
1.0-17.9 2 7 0 7 16 0 2 0 4 6 38%
18.0-33.9 10 9 3 24 46 3 4 1 10 18 39%
34.0-49.9 23 5 6 35 69 11 0 0 14 25 36%
Total 35 21 9 66 131 14 6 1 28 49 38%
Return rate
by age-class 40% 29% 11% 42% 38%
BEAR MANAGEMENT YOSEMITE* Harms
IN 211
Females with cubs showed the strongest homing mated 125 bears in 1920. Until currentresearchshows
instincts. All females with cubs thatwere relocatedand otherwise, this figure representsout best estimateof the
recovered in 1976 returned to their original capture natural carrying capacity of the park. The present
sites at an average rate of 2.75 km/day (Table 7) with population is estimated to be between 220 and 350
an averagerecoverytime of 21 days. The rate of return animals; this estimate is based upon density levels of
for adult males averaged 1.61 km/day with an average 0.13-0.19 bear/km2 of available bear habitat. The
recovery time of 38 days. numberof bears tagged (202) since 1974 indicates the
Table 7. Transplant/recovery distances (airline km) and rates of return to origi-
minimum estimate of 220 to be low.
nal capture sites for 41 black bears by sex and age-class, 1976. As artificial food sources are removed and natural
carryingcapacitiesrestored, the populationis expected
Transplant/recovery Rate of return Elapsed time (days),
distance (km) (km/day) release to return to decrease. Through scat analysis, Graberand White
Age-class
Male Female Male Female Male Female (1976) showed that the use of humanfoods by bears in
Yosemite Valley duringthe springof 1976 (17 percent
Adult by volume, 17 percentby frequency)was substantially
X 29.45 33.69 1.61 2.44 38.18 21.77 reduced from the summerof 1974 (48 percent by vol-
N 11 13 11 13 11 13
SD 10.59 10.56 1.26 2.02 40.99 16.88 ume, 63 percentby frequency). Continuedresearchon
Subadult food habits and populationdynamics should detect re-
X
N 0 0 0 0 0 0
sponses of the populationto the restorationof natural
SD carryingcapacities.
Yearling CONCLUSIONS
X 10.33 1.24 17.00
N 3 0 3 0 3 0 The basic premises of Yosemite's black bear pro-
SD 5.13 0.21 - 6.92
Cub
gramfollow those for grizzly bears in Yellowstone Na-
X 35.86 38.29 2.75 2.75 20.43 21.57 tional Park (Cole 1976). These premises include: (1)
N 7 7 7 7 7 7 The "right" numberof bears is the numberthat occurs
SD 7.84 6.45 1.27 1.40 21.31 20.90
naturally(i.e., without human influences on bear be-
havior, habits, or populationdynamics). (2) Removals
of unnaturalfood and incorrigible animals will allow
young bears without human-altered behavior or habits
Emigrationand dispersionof bears as a result of the to progressively replace incorrigible animals in the
relocation program and/or removal of artificial food population. Once replacementis accomplished, (3) the
sources have been observed. Some bears made sub- control of humaninfluences alone will preventcorrup-
stantialtreks beyond parkboundariesafter being trans- tion of new bears and will thereby supersedecontrol of
planted. The greatest distance traversedfrom the re- bears. Since the program has been in effect only 2
lease site was approximately100 km. One adult male years, statistical analysis of the effects of the program
traversed97 km in 14 days. A female with a cub was is confined to the limitations set by the sample size.
observed near Kings Canyon National Park, a distance Personal injuries decreased in both years of the pro-
of 77 km, 13 days after being released. All bears that grambut it is difficult to show that the reductionswere
made long treks in short periods of time continued to significant. However, the hypothesis that the program
travel in the same approximatedirection as their trans- will reduce injuries need not be rejected. The alterna-
plantation, e.g., bears relocated southwardcontinued tive hypothesis that the programwill increase injuries,
moving south (Graberand White 1976). These move- or the null form that it had no effect on injuries, is not
ments are contraryto the typical response in which 31 supportedby the preliminarydata.
percent of the bears relocated in 1976 returnedto the Regression analysis correlatingincidents with time
exact locations of their capture. Perhaps these bears showed a significant positive relationship before the
were completely confused in their "compass orienta-
program's implementation. The equation of the lines
tion" and moved long distances in an attemptto find allows forecasts of the number of incidents in future
their home territoriesor familiar landmarks.
years. The difference between actual values and pre-
dicted values can be tested to determine whether the
Population Levels observedvalues differ significantlyfrom the trendline.
Present population levels greatly exceed past re- Neither the increase in incidents after program im-
ported naturallevels. Grinnell and Storer (1924) esti- plementationnor the decrease that occurredin the sec-
212 BEARS THEIR BIOLOGY AND MANAGEMENT
ond year differedsignificantlyfrom the trendline. Four reward associations with people. Human-alteredbe-
hundredor fewer incidents in 1977 would representa havior has become deeply ingrainedin the majorityof
significant reduction. the bearpopulationas evidenced by the high numberof
Experience in several national parks demonstrates incidents despite intense control efforts. Visitor use
that relocation programs have limited success unless levels and patternsin Yosemite may precludethe pos-
the homing abilities of the bears can be overcome sibility of achieving a wholly naturalblack bear popu-
throughtransplant distancesof 80 km or more. Reloca- lation. That goal however, should not be reduced. In-
tion at great distances is physically impossible at stead, managers should seek to apply new techniques
Yosemite if bears are to be released inside parkbound- andmethodsin additionto following currentlyaccepted
aries. Informationon recovery times and on rates of management practices. Aversive conditioning, area
return for relocated bears in Yosemite suggests that closures, restrictedvisitor use, and use of individual
preventive programs of sanitation, information, law food lockers in both backcountry and frontcountry
enforcement,visitor control, and perhapsaversive con- areas are possible methods yet to be tried. In the final
ditioning should preclude bear control in the priorities analysis, however, the priority that Park Service ad-
of responsive managementtools. ministratorsplace upon achieving naturalness in the
Levels and patternsof visitor use continuously ex- black bear populationwill determinethe level and na-
pose artificialfood sources to bears and provide food- ture of future managementprograms.
LITERATURECITED the blackbearin YosemiteNationalPark.Natl. Park
CX
Serv. Prog. Rep., Contract 8000-6-0036.
31pp.
a
COLE,G. F. 1076. Progress restoring natural
in grizzly GRINNELL,J., AND T. J. STORER. 1924. Animal life in the
bear population YellowstoneNationalpark. Natl.
in Yosemite. Univerityof CaliforniaPress, Berkeley.
ParkServ.Symp.Ser. 1:183-193.
375pp.
HARMS, D. R. 1976. 1975 human-bearmanagement pro- 1971. The black bear
JONKEL,C. J., ANDI. McT. COWAN.
gram, Yosemite National Park. Natl. Park Serv. Prog. 27.
forest.Wildl. Monogr. 57pp.
in the spruce-fir
Rep. lOpp. STOKES, A. W. 1970. An ethologist's views on managing
GRABER, D., AND M. WHITE. 1976. Population ecology of grizzlybears.BioScience
20(21):1154-1157.
