A. Grant MacHutchon,Department
of Bologcal Sciences,
SimonFraserUniverstV,
Burnaby,B.C. CanadaVsA 156
Spring and SummerFood Habitsof Black Bearsin the
Pelly RiverValley,Yukon
Abstract
Food habits of black besrc (U.sus anericdnus) tron rhe Pelly River Valley, Yukon, were exanined ro d€ternine the seasonal
inportance of yarious foods for bears inhabiting a north€rn environment.Food habns llere dererminedby analysisof59 scats
and one stomach Herbaceousmalerial and berries accouni€dfor 95 percent of the scat volume during sp.ing and sunne..
Ho.s€tail (tqltseru m spp.), bearberry (Arctostaphylusuu urci), soapheftr gheperd.ia conadens;s),and graminoids were the
nost important foods.Overwinteredberries were ealen early in spring until h€rbaceousvegerationbecan€ ayailable.New b€r
ries w€.e important fron nid to late-sunn€r. Insec!s,particularly ants, were frequent in 6carsfron May to August, bur vere
only two p€.cent of the total diet volume. Seasonalfood habit informarion is imporrant becauseit reflectsseasonallrends in
b l a c k b e a r h a b i r a tu s e .F o o d h a b i t p r e f e r e n c eosf b e a 1 6i n n o r t h e r ne n v i r o n m e n rasr e g e n e r a l l ys i n i l a r t o t h o s ei n s o u r h e r n
areas;howeverthe restricted availability of differeni foods limits diversiry in northe.n or€rs.
Introduetion
north alongthe RossRiverand southalongthe
Lapie River. The town of RossRiver is located
on the Canol Highway at the confluenceof the
Ross and Pelly Rivers.
Foodhabit studiesprovideinformationaboutthe
relative importance of different foods to an
animal's diet. For blar"kbears lUrsus ameri.
The study area lies within rhe Pelly River
cozzs),this information is important to unders t a n dt h e i r l i f e h i s t o r ya n d h e l p i n v e s r i g a t o r s Ecoregion(Oswaldand Senyk1977).It hasrnean
annual temperaturesranging from -4oC to
assessthe seasonalimportanceof different habi7'C, with mean Ja[uary temperaturesof
tats,Habitat usehasbeenshownto vary with the
27"C to -35oC and meanJuly temperatures
availability, distribution and abundanceof preof l3"C to l5oC. Valleybottomshavemeananferred foods (Hatler 1967, Jonkel and Cowan
nual precipitation of between250 and 300 mm.
l97l) and changesin the seasonaluse of plant
and animalfoodsby black bearsis common(PenThe Pelly River Valley is dominatedby white
ner el al 1980).There is little infornation on rhe
spnrce(Piceaglauca)forest on dry siresand black
food habitsof northern black bears(Hader 1972).
spruce(Piceamariano)forest on wetter sites.In
Information on the ecology of northern black
white spruce forest, shaded sites are sparsely
bears is important for their effective managevegetated with mosses,horsetails (Equisetum
ment,particularlyunder the increasingencroachspp.), and, rose (Roso acicularis). Where the
rnent of human development.
canopyis open,willows(Salir spp.)are prevalent
Food habit information wasobtainedin 1984
and thereis a greaterabundance
of herbaceous
for black bearsinhabiting the Pelly River Valley
v e g e l a t i o nI n. b l a c ks p r u c ef o r e s t h e r ei s m o s s
near RossRiver,Yukon. My objectiveswereto
groundcoverwith densewillowsand encaceous
determinethe seasonalimportanceof various
shrubswherethe canopyis open.Steepsouthfacfoods in the diet of black bears inhabiting a
ing slopes rise severalhundred feet above the
northernenvironmentand to comparethe diet
Pelly River and are dominated by sagewort
of nonhern black bearswith thosein other areas.
(Artemesia spp.) grassland. Aspen (Populus
tremuloides)occurs in gullies that drain these
StudyA.ea
hillsides.Aspenforestalsooccursin burnedover
s i t e st h a l a r e n o m m o ni n t h p s o u l h e r np o r t i o n
The study area is locatedalong the Pelly
'
of the study area.
RiverValley(62"00 N, 133o30'W)and is representativeof major river valleysin the southern
Deciduoustreesand shrubson the studyarea
Yukon. The area is traversedby the Robert
flush by the end of May. Arctic lupine (Lupinus
CampbellHighwayrunning eastto westalongrhe
articus) is the first plant to flower in the spring
P e l l y R i v e r .a n d t h e C a n o lH i g h w a yr u n n i n g
followed by other perennials,vetch (Astragalus
116
N o r t h w e sSt c i e n c eV, o l . 6 3 , N o . 3 , 1 9 8 9
t-
spp.),locoweed(Orytropis spp.),and lousewort
(Pedicularis
spp.)-Majorannualssuchashorsetail
appearin earlyto mid-June.Most plant species
have floweredby the end of June. Frost occurs
in mid-Augustwhichinitiatesthe end ofthe growing season.
TABLE
l. Percenr rcdnerce
Gm.) and nean p€rc€nt
volune (rol.) of food ilems in scat samples and
one stomach from the Pelly River Valley, Yukon,
28 May-16 August, 1984.
Spring
28 May'
30 June
(o=l7)
Methods
Scatsfrom blackbearswere collectedbetween
15 May and 20 August, 1984.All scatswere Iabelled with date of collection and remarks on
probableage.Scatswere frozen until analysisin
Augustof l9B4 and 1985.
Scatswerethawedand washedon a No. l8
sieveto removefines.Sievecontentsweremixed
with water and distributed evenlyin an enamel
pan.A randoml0 ml samplewasremovedfrom
the pan,mixed with 30 ml of water,then put into
a squarepetri dish and spieadover a 25 square
grid (i.e.eachsquare= 4%), The percentvolume
of eachitem in the samplewasestimated.Three
to five sampleswere examinedfrom each scat.
0bservationsof feedingbearsaidedin the assessment of seasonalfood habits.
Resultsand Discussion
The percentoccurrenceand averagepercent
volume of identified contentswere determined
from 59 scatsand one stomach(Tablel). Horsetail was the most frequent item in the samples
alrd accountedfor the greatestpercentyolume.
Next in impo ance was bearberry (lrctostaphylosuoa-ursfiftuit followed by soapberry
(Sheperdia canadensis\fruit and graminoids.
Animal matter, particularly ants and mammal
hair, werefrequentlyfound in samples,but compriseda small percentageof the total volume.
To evaluateseasonaltrendsin food habits,
collectiondateswere divided into two periods:
spring,28May-30June and summer,l-30 July
(Table l). Only known aged scats(t l-2 days)
ivere used.
Bearberryfruits werecommonin the spring
diet.In earlyMay, 1984,rnanyblackbearswere
observedfeedingon open south facing slopes
abovethe floor of the Pelly River.They werelikely feeding on overwinteredbearberriesand
grassesbecausevernal growth did not occur on
the slopesuntil IateMay. Graminoidsand overwinteredberriesare commonin the spring diet
of blackbears(McIlroy 1970,Jonkeland Cowan
0cc. Vol.
Summer
Total
I July.
28 May.
30July
16August
(n=31)
(n= 60)
occ. Vol.
occ. Vol.
Equisetunsp.
?0.6 50.4 32.3 28.5 411.339.1
crases
23.5
0.9 22.6
Unidentitied
5.9
0.7
0iher
0.0
0.0
6.5
6.5
0.4 2t.7
2.4 5.0
1.9 3.3
2.3
r.4
1.0
Fruns:
Arctottdphtlot
urd ulti 52.9 27.4 25.8 9.8 33.3 15.9
Sheperd.iacanadensis 0.0
0.0 51.6 39.2 31.? 20.5
I/acciniun iris-idaea
23.5
3.8
Yaceiniunutginosun
17.6
5.8
Yacciniunsp.
ll.8
2.6
Enpetun nigrun
5.9
5.9
Fragoia fighiana
0.0
0.0
Uridentified
5.9
1.0
Ants
11.8
OtherInsecls
23.5
8.3 r.1
8.3 1.8
6.7 t.7
15.0 7.6
5.0 r.3
6.7 t.2
0.0 6.5 3.3 28.3 t.7
l . l 45.2 0.6 10.0 0.4
0.0
0.2 1.7 0.1
0.4 16.? 0.3
0.t 1.7 0.1
47.1
0.{ 38.7
4.0 33.3 25
0.0
Hair
5.9
Bone
TOTAL
0.1
0.0
0.4
6.3
2.4
0.0
0.0 3.2
0.0 22.6
0.0 3.2
F€arhers
Forestliuer
3.2
3.2
3.2
t2.9
9.7
0.0
100.0
100.0
100.0
1971,Hatler 1972,Modafferi1982,Srnith1984,
Herrerol9B5).Blackbearsloseenergybetween
d e n e m e r g e n caen d t h e r i p e n i n go f n u t r i t i o u s
fruits (Jonkeland Cowan 1971,Rogers 1976,
Beeman and Pelton l9B0). Bears use overwintered berries in the spring becausethey are
high in carbohydratesand becausesuitableherbaceousvegetationhasnot yet emerged(Hellero
l9B5). In the Pelly River study area,bearberries
were the most commonfruit in scatscollected
in the spring but they were supplemented
by
blueberries,bog cranberries,and occasionally
crowberries.By early June vernal growth had
begun in the valley bottom and the use of open
slopesdeclined;howeversomeblackbearswere
observedon open slopesuntil late-July.The
Food Habits of Black Bears
Il7
continueduse of the slopescoincidedwith the
presenceof bearberryin scatsuntil mid-July.Insects,particularly ants, were the most frequent
animalfood during June and July. Similar trends
are reponed elsewhere(Chatelain 1950, Tisch
1961,Hatler 1972,Nagyand Russell1978).Horsetail increasedin the diet in the springand summer correspondingwith black bear movementto
the valley bottom. Horsetail is common in the
spring diet of black bears elsewhere(Mcllroy
1970,Hatler l9?2, Nagy and Russell1978).
After mid-summer,soapberrieswere a major
food until frost occurred and berries began to
fall off the plants.Crowberryfiuit occurredmore
frequently in the black bear diet as the summer
progressed.Crowberry fruit cornprised48 percentof the volumeof one stomachcollectedon
l3 August and 73 percentof the volumeof a scat
collectedon l6 August.In other north temperate
and borealforest areas,blueberriesare a critical
black bear food in late summer and early fall
(Mcllroy l9?0, Jonkel and Cowan1971,Hatler
l9?2, Rogers1976,Modafferi 1982).In the Pelly
River study area,blueber es were only common
in scatsduring the spring but likely becamemore
prevalentin the diet in August after scat collection ceased.
Blueberiyand crowberryare scarce
in the Pelly River Valley near Ross River, but
are commonin subalpineareasto the north and
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Receiued9 March 19BB
Acceptedfor publication 19 January 1989
ll8
MacHutchon
south. I suspect black bears disperseto these
areas in the late summer when blueberry and
crowberry fruits ripen. Qualirative evaluations
suggest1984was a moderateto poor year for
blueberry and bearberry production.
The resultsof this study cover only one year
of collection,so they do not take into account
year-to-yearfluctuationsin the availabilityof important foods, particularly berries. The results
are expectedto reflect the generaltrend in black
bear food habits, however.Food habits over the
samplingperiod are consistentwith thosefound
in otherstudies.Herbaceous
foodsare usedearly in the summer,fruir is addedas it becomes
availableand animals(usuallyinsects)are used
opportunistically during summer(Haier 1972,
Penner et aL l9B0). Food preferencesof black
bearsin northern habitats are generallysimilar
to thosein southernareas;however,the restricted
availability of different foods limits diversity in
noithein diets.
Acknowledgments
I wish to thank Carol Domesfor assistancewith
scatanalysis.
Alton Harestadcriticallyrevie*ed
earlier drafts of the manuscript.The study was
supportedby the Yukon Departmentof Renewable Resourcesand a Departmentof Indian and
Northern Affairs, Northern Studies Grant.
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