Document Sample
                   IN        NATIONAL
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.
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,
                  U.S. FishandWildlife
                                     Service,Billings,                                  campground entrances, parking lots, and park rest-
 Montana59101.                                                                          rooms; (3) articles regardingbears and people in each

Table 1. Propertydamages and personal injuriesattributable black bears, Yosemite NationalPark,1966-76.

                                            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

                                                                                               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



o      16
                                                /                                                             I'
CQ       8
                                                                                                              jPD's =-155.8               + 2.40(year)
                                                                                                                   r = 0.89

        0                     I
                              I           I
                                          I         I      I          a
                                                                      I       a
                                                                              I        A

                          1966        6             8
                                                                                        I        I        I         I             I
                                                                   70       71        72       73        74        75         76
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.

   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.
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

      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%)
      1975                                                            1 (6)                         15(94)                                      16 (2%)
      1976                                                            1(10)                          9(90)                                      10 (2%)
  1974                                                              26(46)          11(20)          19(34)                                      56 (9%)
  1975                                                              19(46)                          22(54)                                      41 (4%)
   1976                                                             11(39)                          17(61)                                      28 (4%)
   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%)
   1974                                                                                                                                         36 (6%)
   1975                                                                                                                                         71 (7%)
   1976                                                                                                                                         94(14%)

 Percent given as percent of total incidents.
bPercentof damaged items given in parentheses.
                                                                                                 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

  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
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
 1975                      196,565               2,654                 13.5                   96                                     2
                                                                                                                 5,762                                  2
 1976                      269,924               1,186                  7.0                  160                                     9
                                                                                                                 4,471                                  3


Table 5. Summary of black bear captures/relocations            and return rates to developed areas for 1-, 2-, and 3-year intervals, 1974-76.

                   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
                  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-
   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
                                                                                     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-

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
                                                                 Serv. Prog. Rep., Contract 8000-6-0036.
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.
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

Shared By: