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Sexual Segregation and Female Grizzly Bear Avoidance of Males
Author(s): Robert B. Wielgus and Fred L. Bunnell
Source:
The Journal of Wildlife Management,
Vol. 58, No. 3 (Jul., 1994), pp. 405-413
Published by: Wiley on behalf of the Wildlife Society
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J. Wildl. Manage. 58(3):1994 MARTEN
ACCESS
POINT
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* Sherburne
and Bissonette 405
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world-1991. W. W. Norton and Co., New York,
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R. M. 1983. Winter habitat use and re-
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TAYLOR,
S. L. 1993. Thermodynamics
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ZIELINSKI,
W. J. 1981. Food habits,
activity
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and ectoparasites
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, W. D. SPENCER,
AND R. H. BARRETT. 1983.
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Received 24 May 1993.
Accepted 8 December 1993.
Associate Editor: Vaughan.
SEXUAL
SEGREGATION AND FEMALE GRIZZLY
BEAR
AVOIDANCE
OF MALES
ROBERT
B. WIELGUS,'
Department
of Fish and Wildlife
Resources, University
of Idaho, Moscow, ID
83843
FRED L. BUNNELL,
Centre
for Applied
Conservation
Biology, Faculty
of Forestry,
University
of British
Columbia, Vancouver,
BC V6T 1Z4, Canada
Abstract: We examined seasonal
use of habitat for 14 male and 5 female grizzly bears (Ursus arctos) in
southwestern
Alberta,
1981-84, to test 2 competing hypotheses
regarding
segregation
of the sexes. The male
avoidance hypothesis predicts increasing differences in use of habitat with increasing male use of female-
occupied areas because of female avoidance of males. The no avoidance hypothesis predicts decreasing
differences
in use of habitat with increasing
male use of female-occupied
areas
because
of increasing
similarity
of available habitat. Differences in use of habitat were greatest during late summer, when many males
concentrated
in the female-occupied area, and they were less during other seasons when few males were in
the female-occupied area. Three of 4 habitat variables differed (P < 0.10) between the sexes during late
summer, whereas 2, 1, and 2 variables differed during spring, early summer, and autumn, respectively.
Grizzly bear females segregated from males and data support the hypothesis that females avoid males. If
females avoid males and male-occupied
habitats,
reproduction
could decline because
of nutritional
deprivation
and survival could decline because of their increased use of human-occupied
areas.
J. WILDL.
MANAGE.
58(3):405-413
Key words: Alberta, grizzly bear, habitat, sexual segregation, Ursus arctos.
Grizzly bears have disappeared from most of
their historic range, largely by incremental pop-
ulation and habitat losses at the contracting edg-
es of the species' range (Servheen 1990). In Al-
berta, there were an estimated 780 grizzly bears
in 1990, and numbers were declining (Servheen
1990). Nagy and Gunson (1990) estimated 62
grizzly bears in southwestern Alberta, the edge
of the species' range. In this study, we radio-
monitored 19 of 38 bears in a declining popu-
lation of Kananaskis Park and Bow Crow Forest,
southwestern Alberta (Wielgus and Bunnell
1994). We must understand use of habitat and
I Present address: Centre
for Applied
Conservation
Biology, Faculty of Forestry, University of British
Columbia, 193-2357 Main Mall,
Vancouver,
BC V6T
1Z4, Canada.
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406 GRIZZLY HABITAT
* Wielgus and Bunnell J. Wildl. Manage. 58(3):1994
population dynamics in small peripheral pop-
ulations to prevent further range contractions
and eventual extinction of the grizzly bear. The
sparse nature or small size of these populations,
however, makes large samples impossible and
impedes understanding of contracting popula-
tions.
Most studies of grizzly bear use of habitat
have not examined seasonal differences between
the sexes. The sexes often are not identified
(Hamer and Herrero 1987a,b; Phillips 1987), are
analyzed together (Blanchard 1983, Zager et al.
1983), or only one sex is studied (Hamilton and
Bunnell 1987). Some researchers have examined
family and single bear use of habitat (Atwell et
al. 1980, Darling 1987) but did not discriminate
between habitats used by females and those used
by males. Only a few studies examined sex-
specific seasonal use of habitat. Berns et al. (1980)
found little difference between male and female
use of habitat. Russell et al. (1979) found that
females in Jasper National Park, Alberta, tended
to use higher elevations more than did males,
especially during spring. Nagy et al. (1983a)
reported elevation differences in use of habitat
between males and females in the Arctic Moun-
tains but reported no sexual segregation in the
Tuktoyaktuk Peninsula (Nagy et al. 1983b).
Mattson et al. (1987) and MacLellan and Shack-
leton (1988) found that females used habitats
nearer to roads more than did males. These find-
ings indicate that sexual segregation may occur
in some populations but not in others.
When sexual segregation has been observed
in grizzly bears, it usually has been interpreted
as female avoidance of aggressive or cannibal-
istic males (Russell et al. 1979, Nagy et al. 1983a,
Mattson et al. 1987, McLellan and Shackleton
1988), but that inference has not been tested.
This male-avoidance hypothesis predicts that
sexual differences in use of habitat should in-
crease with increasing male use of female-oc-
cupied areas; that is, females should shift their
activity away from males when males move into
their areas.
An alternative, no-avoidance hypothesis is that
differences in use of habitat result from seasonal
differences in habitat availability or diet. For
example, males may have different habitats
available to them because of their larger home
ranges (LeFranc et al. 1987). In this case, dif-
ferences in use of habitat should decrease with
increasing male use of female-occupied areas
because of increasing similarity of available
habitat. Differences in use of habitat also may
result from females with offspring having re-
duced mobility and hence reduced access to
various habitats. In this case, differences should
be greatest early in the year when cubs are most
sedentary. Finally, differences in use of habitat
may result from sexual differences in dietary
preference. In this case, differences should de-
crease as similarity in diet increases.
We use data collected during a study of griz-
zly bear use of habitat, movements, and food
habits (Wielgus 1986) to determine if sexual
segregation occurred and to evaluate conse-
quences predicted by the male-avoidance and
no-avoidance hypotheses of such segregation.
The biological and behavioral reasons for fe-
male avoidance of males were addressed else-
where (Wielgus 1993, Wielgus and Bunnell
1994).
This is publication R-10 of the Centre for
Applied Conservation Biology at the University
of British Columbia. Financial support was pro-
vided by the Alberta Fish and Wildlife Division,
Alberta Recreation, Parks and Wildlife Foun-
dation, Boreal Institute for Northern Studies,
Carthy Foundation, Home Oil Ltd., Natural
Sciences and Engineering Research Council of
Canada, and the World Wildlife Fund (Cana-
da). R. B. Wielgus collected data under the su-
pervision of J. M. Peek. B. O. Pelchat initiated
the study and encouraged Wielgus' participa-
tion. C. Mamo and T. Manning were responsible
for trapping and collaring bears. Field and tech-
nical assistance was provided by J. Bicknell, R.
Foreman, and L. Meszaros. H. D. Carr provided
logistical support. The late O. Pall conducted
many telemetry flights prior to Wielgus' partic-
ipation; we lost him during one of his flights and
remember him fondly. The manuscript bene-
fitted from comments of F. W. Hovey, D. Je-
linski, W. E. Klenner, and B. N. McLellan.
STUDY
AREA
The study area covered 6,286 km2 in Kana-
naskis Provincial Park and Bow Crow Forest,
southwestern Alberta (50-510N, 115-1160W).
Elevation ranged from 1,300 to 2,700 m in
mountainous terrain. Climate was continental
with long, cold winters and short, cool summers.
Vegetation was in the subalpine fir-Engelmann
spruce (Abies lasiocarpa-Picea engelmanni)
forest region (Rowe 1972). Forests comprised
lodgepole pine (Pinus contorta), Engelmann
spruce, and subalpine fir. Details of the study
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J. Wildl. Manage. 58(3):1994 GRIZZLY HABITAT
* Wielgus and Bunnell 407
area are given in Wielgus (1986) and Wielgus
and Bunnell (1994).
Sport hunting of grizzly bears was closed in
the study area from 1970 to 1981 but was re-
opened from 1982 to 1987. The study popula-
tion showed high mortality of older adult males
and a corresponding high immigration of youn-
ger males after 1981 (Wielgus and Bunnell 1994).
The small population appeared to be declining
from 1981 to 1984 (Wielgus and Bunnell 1994)
and was designated as vulnerable by the Com-
mittee on the Status of Endangered Wildlife in
Canada.
METHODS
Trapping
We trapped grizzly bears from 1980 to 1984
using Aldrich leg snares and immobilized them
with ketamine HCI and xylazine HCI in a 1:1
ratio at a dosage of 6.5-10.0 mg/kg body mass.
We weighed, eartagged, and aged bears by ex-
tracting a premolar (Stoneburg and Jonkel 1966).
We then fitted them with activity-sensing radio
collars. We trapped and radiocollared bears in
the 254-km2 Highwood trapping zone, which
covered a 50-year-old burn in the mountains
(1,800 m elevation) and was dominated by soap-
berry (Shepherdia canadensis) shrubfields. Sur-
rounding areas were unburned and appeared to
have comparatively little berry production
(Wielgus 1986, 1993).
Seasonal
Habitat Use
We monitored radioed bears (14 M, 5 F) from
fixed-wing aircraft once every 1-2 weeks during
the nondenning period (15 Apr-1 Dec), 1981-
84. We estimated bear locations from the air-
craft (Whitehouse and Steven 1977) and marked
them on 1:50,000 topographic maps. We esti-
mated radiolocation accuracy by noting signal
strength when bears were sighted, then used
signal strength for determining nonvisual lo-
cations. We visually confirmed 81 of 451 loca-
tions (18%). We only used locations judged to
be accurate within 1 ha and within 1 habitat
type (451 of 526 locations, 86%) in habitat anal-
yses. The ratio of radiolocation error (1 ha) to
mean forest stand size for a representative map-
sheet (28.4 ha, SE = 7.8 ha, n = 335) was low,
indicating little potential for error (White and
Garrot 1986). Only 5% of forest stands had areas
< 1 ha. A self-developing photograph was taken
and marked to indicate bear location within the
vegetational mosaic. We later transferred lo-
cations from topographic maps and photos to
corresponding forest habitat maps.
Habitat variables for each location were forest
type and age, elevation, aspect, and slope. We
assumed those variables to be related to grizzly
bear food and cover requirements (McCrory and
Herrero 1981, 1983a,b; Zager et al. 1983; Hol-
croft and Herrero 1984), and they were already
mapped and used for forest management. Hab-
itat variables and criteria for designating them
were determined in advance by the Alberta For-
est Service. Prior to analysis, we reduced the
number of forest types to facilitate statistical
testing by combining similar classes into broader
types on the basis of type and openness of veg-
etation. Our forest types were alpine (grassy
meadows, alpine tundra, barren soil, rock),
shrubfield (avalanche chutes, burns, clear-cuts,
brushfields), pine-dominated forests (Pinus spp.),
and spruce-dominated forests (Picea spp.). We
recorded elevation, aspect, and slope from to-
pographic maps.
We defined seasons by changes in plant phe-
nology and corresponding shift in food habits
as determined by seat analyses (Wielgus 1986).
We identified 4 seasons: spring (15 Apr-11 Jul,
pre-berry season), early summer (12 Jul-15 Aug,
onset of berry season), late summer (16 Aug-17
Sep, peak of berry season), and autumn (18 Sep-
1 Dec, end of berry season).
Data
Analysis
We tested for sexual differences in seasonal
use of habitat by comparing seasonal counts of
male and female locations using the Chi-square
test of homogeneity (Daniel 1978, Wilkinson et
al. 1992). We pooled radiolocations of bears into
male and female sex classes and across years
(1981-84) into seasons, in a modified type-2 de-
sign (Thomas and Taylor 1990). Pooling of data
allowed adequate sample sizes for tests of sea-
sonal habitat segregation (Roscoe and Byars
1971), assuming no effect of years.
We ensured that our pooled sex-seasonal da-
tasets were not biased toward individual bears
or reproductive classes by balancing our radio-
telemetry effort across individuals and classes.
Data were not biased toward particular indi-
viduals because each bear contributed an ap-
proximately equal number of locations (Wielgus
1986). Pooled data were representative of in-
dividual bears and years because annual use of
habitat did not vary among individual bears or
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408 GRIZZLY
HABITAT
* Wielgus and Bunnell J. Wildl. Manage.
58(3):1994
Table 1. Percent use and Chi-square
tests (5 df) for homogeneity
of forest age types used seasonally
by male and female
grizzly
bears in Kananaskis
Park and Bow Crow Forest,
Alberta,
1981-84.
Spring Early summer Late summer Autumn
15 Apr-11 Jul 12 Jul-15 Aug 16 Aug-17 Sep 18 Sep-1 Dec
Forest type
(age in yr) M F M F M F M F
Alpine 17 29 15 12 16 21 10 25
Shrubfield 5 14 10 19 10 23 3 14
Pine (5-50) 22 27 36 42 51 41 18 39
Pine (>50) 31 14 21 15 12 7 33 4
Spruce
(5-50) 5 2 4 6 0 4 4 0
Spruce (>50) 20 14 14 6 11 4 32 18
n locations 64 63 51 53 61 43 67 49
n bears 11 5 14 5 14 5 12 5
x2 10.87 4.37 8.65 28.81
P 0.05 0.49 0.12 <0.01
years, except between subadult and adult fe-
males (Wielgus 1993). We assumed data to be
independent because all bears traveled alone
and radiolocations were obtained at weekly or
biweekly intervals (Swihart and Slade 1985).
Analyses of annual, not seasonal, use of habitat
by individual bears by year were treated else-
where (Wielgus 1993).
We used log-linear models (Feinberg 1980,
Wilkinson et al. 1992) to test if male locations
for a given season were obtained during some
years and female locations for the same season
were obtained during other years. Any such
findings would constitute a sex by season by year
interaction and would invalidate our test of fe-
male seasonal avoidance of males. This analysis
comprised 2 sexes, 4 years, and 4 seasons, for a
total of 32 cells. Sample sizes and expected val-
ues were adequate (<20% of cells with expected
values <5) for testing (Wilkinson et al. 1992).
We tested hypotheses of sexual segregation
by determining seasonal numbers of individual
male bears and percentage of male locations
within the female 97.5% multi-annual, com-
posite range of 868 km2 (Ackerman et al. 1990).
The female composite range was centered on
the Highwood trapping zone. Most bears using
that zone were believed to be captured and col-
lared (Wielgus and Bunnell 1994). If differences
(P < 0.10) between the sexes occurred for use
of habitat variables during late summer, when
many males concentrated in the female-occu-
pied area, we interpreted that as support for the
male-avoidance hypothesis. If differences were
not significant (P > 0.10), or if differences were
less during the late summer, we interpreted that
as support for the no-avoidance hypothesis.
RESULTS
Structure of Pooled Data
Mean number of locations/bear/season was
10.4 (SE = 0.8, n = 20) for females and 4.7 (SE
= 0.4, n = 51) for males (Table 1). Male bears
had fewer locations than did females because
they suffered higher mortality (Wielgus and
Bunnell 1994). Data were not biased toward
particular age classes. Single adults (>5.5 yr, n
= 4) contributed 35%, adults with offspring (n
= 4) 42%, and subadults (2.5-5.5 yr, n = 2) 23%
to the female radiolocation data. Adults (>5.5
yr, n = 7) contributed 46% and subadults (2.5-
5.5 yr, n 9) 54% to male location data.
Sample size or number of locations per cell
in the log-linear model varied with sex, year,
season, and 2 of their interactions. The most
parsimonious log-linear model that fit our data
was sex + season + year + sex by year + season
by year (x2 = 13.23, 12 df, P = 0.35). The sex
main effect reflected differences between the
sexes (M had 54% of locations, F had 46%). The
year main effect reflected differences among
years. Most data were obtained from 1982 to
1984 (6%
of locations were in 1981, 29% in 1982,
48% in 1983, and 17% in 1984). One female was
monitored in 1981, 4 in 1982, 5 in 1983, and 5
in 1984. There were 3 males in 1981, 6 in 1982,
10 in 1983, and 5 in 1984. The season main
effect was included to account for the seasonal
term of a significant year by season interaction.
Percents of locations among seasons were similar
(28% in spring, 23% in early summer, 23% in
late summer, and 26% in autumn). The sex by
year interaction reflected occurrence of pro-
portionately more male locations in 1981 and
more female locations in 1984. Percents of total
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J. Wildl. Manage.
58(3):1994 GRIZZLY
HABITAT
* Wielgus and Bunnell 409
SPRINGEARLY SUMMER
? ??
.\ ?
? ..
r? ?
20 KM
LATE SUMMER AUTUMN
.?
t?.
...
!?
,~
I II I
%? ?
+ t I ? ??
???
?I ? ??
?I~~ ??
\?
??
Fig. 1. Seasonal (spring
= 15 Apr-11
Jul,
early
summer
= 12 Jul-15 Aug,
late summer
= 16 Aug-17 Sep, autumn
= 18 Sep-
1 Dec)
distribution
of male
grizzly
bear radiolocations
(dots) in relation
to 97.5% multi-annual
composite
home range
of female
grizzly
bears (polygon)
in Kananaskis Park
and Bow Crow
Forest,
Alberta,
1981-84.
female locations distributed across years were
3, 27, 43, and 27% for 1981-84, respectively.
Percents of total male locations distributed across
years were 9, 30, 53, and 8% for 1981-84, re-
spectively. The year by season interaction re-
flected scarcity of locations in spring and early
summer 1981 and autumn 1984, because mon-
itoring began in 1981 and ended in 1984.
Adding more interactions (e.g., sex by season
or sex by season by year) to the model did not
improve fit of the data (x2 = 1.1, 3 df, P > 0.10).
Therefore, seasonal data were not biased by the
uneven distribution of the sexes' locations among
years.
Seasonal
Segregation
Data on use of habitat (Tables 1-4) were pre-
sented as percentages rather than counts to fa-
cilitate comparisons (Hellgren et al. 1991, Wil-
kinson et al. 1992). During spring, overlap
between males and females was low (Fig. 1).
We observed 8 male bears and 20 of 64 male
locations (31%) in the female composite range.
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410 GRIZZLY
HABITAT
* Wielgus and Bunnell J. Wildl. Manage. 58(3):1994
Table
2. Percent use and
Chi-square
tests (4 df)
for
homogeneity
of elevation zones used seasonally by male and female
grizzly
bears in Kananaskis
Park
and Bow Crow
Forest,
Alberta,
1981-84. Sample
sizes are as in Table
1.
Spring Early summer Late summer Autumn
15 Apr-11 Jul 12 Jul-15 Aug 16 Aug-17 Sep 18 Sep-1 Dec
Elevation (m) M F M F M F M F
<1,680 22 5 13 10 7 0 28 2
1,680-1,830 25 22 22 25 36 16 18 22
1,831-1,980 22 33 41 36 32 45 32 27
1,981-2,130 22 21 17 14 20 25 15 25
>2,130 9 19 7 15 5 14 7 24
x 10.68 2.89 10.01 18.85
P 0.03 0.57 0.04 <0.01
Use of habitat differed between the sexes for
forest age (Table 1) and elevation (Table 2).
In early summer, males began to converge on
the female range (Fig. 1). We observed 9 males
and 34 of 51 male locations (67%) in the female
composite range. Use of aspect differed (Table
3) between the sexes.
During the late summer berry season, geo-
graphical overlap between sexes was most pro-
nounced (Fig. 1), when we observed 11 male
bears and 55 of 61 male locations (90%) in the
female range. Sexual differences for use of hab-
itat variables were greatest during late summer
despite concentration of males and females in
the same area. Three of 4 habitat variables dif-
fered: elevation, aspect, and slope. Location of
females shifted to higher elevations (Table 2),
different aspects (Table 3), and steeper slopes
(Table 4) when males moved into the female
area.
During autumn, overlap between the sexes
declined as males moved out of the female range
(Fig. 1). We observed 8 males and 20 of 67 male
locations (30%) in the female range. Use of 2
variables differed: forest age (Table 1) and el-
evation (Table 2).
DISCUSSION
Our results show differences between seasonal
male and female use of habitat, so we reject the
hypothesis that male and female bears used the
same habitats. We are confident in our test re-
sults despite small sample size, because small
sample sizes decrease statistical power, making
rejection of null hypotheses more difficult (All-
dredge and Ratti 1986). Although large samples
are desirable they cannot always be obtained,
especially when studying small populations
(Wielgus and Bunnell 1994).
Sexual differences in grizzly bear use of hab-
itat were greatest during the late summer berry
season when the most spatial overlap between
the sexes occurred. Sexual difference in diet was
unlikely to account for habitat segregation in
late summer because of hyperphagia (Nelson et
al. 1983) by both sexes on soapberries (McCrory
Table 3. Percent
use and Chi-square
tests of homogeneity
(8 df)
for
aspects used seasonally by male
and
female
grizzly
bears
in Kananaskis Park
and Bow Crow
Forest, Alberta,
1981-84. Sample
sizes are as in Table
1.
Spring Early summer Late summer Autumn
15 Apr-11 Jul 12 Jul-15 Aug 16 Aug-17 Sep 18 Sep--1 Dec
Aspect M F M F M F M F
Flat 17 11 19 30 18 11 16 8
Northwest 14 10 2 6 1 16 6 12
North 9 3 15 9 10 5 10 10
Northeast 0 10 9 6 15 7 25 16
East 17 22 26 4 13 14 17 23
Southeast 9 6 4 9 7 9 7 4
South 9 12 9 9 5 9 5 2
Southwest 6 10 5 4 13 2 3 10
West 19 16 11 23 18 27 11 15
X2 10.79 16.34 14.95 8.21
P 0.21 0.03 0.06 0.41
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J. Wildl. Manage. 58(3):1994 GRIZZLY HABITAT
* Wielgus and Bunnell 411
Table 4. Percent use and Chi-square
tests of homogeneity
(3 df) for slope categories used seasonally by male and female
grizzly
bears in Kananaskis Park and Bow Crow
Forest, Alberta,
1981-84. Sample
sizes are as in Table
1.
Spring Early summer Late summer Autumn
15 Apr-11 Jul 12 Jul-15 Aug 16 Aug-17 Sep 18 Sep-I Dec
Slope (*) M F M F M F M F
510 56 44 52 55 56 34 48 35
11-20 19 19 24 17 15 30 29 41
21-30 23 27 19 25 28 21 21 22
>30 2 10 5 3 1 15 2 2
X2 4.68 1.14 13.30 2.74
P 0.19 0.76 <0.01 0.43
and Herrero 1983a,b; Wielgus 1986; Hamer and
Herrero 1987a,b). Low cub mobility was un-
likely to account for habitat segregation in late
summer because cubs are mobile relative to ear-
lier seasons. These results lead us to reject the
no-avoidance hypothesis and accept the male-
avoidance hypothesis of habitat segregation.
Males converged on the female composite
range in late summer and concentrated in
burned-over, young (5-50 yr) pine forests at low
to mid-elevations (1,680-2,130 m), on north-
easterly aspects, and on shallow (<:100) slopes.
These sites contained the best soapberry patches
in our study area (McCrory and Herrero 1981,
1983a,b; Hamer and Herrero 1987a,b). Females
also concentrated in young pine forests and
shrubfields during the early summer onset of
berry season, but they shifted to higher, drier,
steeper, and apparently poorer sites (McCrory
and Herrero 1981, 1983a,b; Hamer and Herrero
1987a,b) when males arrived in late summer.
We feel it is unlikely that females would select
for poorer quality berry patches if males had
not arrived.
Females also may have avoided old forests in
spring and autumn because of the likelihood of
encountering male bears there (Table 1). Wiel-
gus (1986) suggested that males may have used
those forests for predation and consumption of
elk (Cervus elaphus) calves during the spring
calving season and elk bulls during the autumn
rut and hunting season.
Hornocker (1962), Egbert and Stokes (1976),
McCullough (1981), and Stringham (1983) hy-
pothesized that female bears and other subdom-
inants avoid adult males because males compete
with, behave aggressively toward, and even kill
subdominants for food. Stringham (1980), Wiel-
gus (1986), and LeCount (1987) hypothesized
that adult females, especially females with off-
spring, avoid non-sire, immigrant males because
those males may kill cubs to induce estrus and
gain a breeding opportunity (Hrdy and Haus-
fater 1984). The only tests of those hypotheses
were conducted by Wielgus (1993), and results
supported the latter hypothesis. Hunting of old-
er adult males resulted in an influx of younger
immigrant males (Wielgus and Bunnell 1994)
and subsequent female avoidance of those males.
MANAGEMENT
IMPLICATIONS
If female grizzly bears use food-poor habitats
to avoid males, identification and protection of
only food-rich habitats (Mace and Bissell 1986,
McCrory et al. 1986) could leave essential hab-
itats for females unidentified and unprotected.
That could result in dangerous conflicts between
humans and female bears if humans venture
unaware into such unidentified female-occu-
pied areas (Herrero 1985). Avoidance of food-
rich, male-occupied habitats by females also
could slow or stop population growth because
of increased female mortality or reduced female
reproduction. For example, Mattson et al. (1987)
suggested that females avoided males by using
habitats close to roads and this led to increased
deaths of female grizzly bears by humans. In
small populations, the loss of even a few females
can cause population declines (Bunnell and Tait
1981, Eberhardt 1990). Wielgus (1993) found
that females avoided food-rich habitats occu-
pied by immigrant males and that female re-
production suffered, contributing to population
decline. We recommend that other researchers
replicate our tests and examine these phenom-
ena to see if results are applicable elsewhere.
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