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Science and Research Technical Report TR-13
Estimating the abundance of American
black bears (Ursus americanus) on the
Bruce Peninsula, Ontario
Science and Research Technical Report TR-13
Estimating the abundance of American black bear (Ursus americanus) on the Bruce Peninsula, Ontario
M.E. Obbard1, E.J. Howe1, C.J. Kyle2, J. Haselmayer3, J. Scheifley4
1 Wildlife Research and Monitoring Section, Science and Research Branch, Ontario Ministry of Natural Resources and Forestry
2 Natural Resources DNA Profiling and Forensics Centre, Trent University
3 Fathom Five and Bruce Peninsula National Park, Parks Canada Agency
4 Midhurst District, Ontario Ministry of Natural Resources and Forestry
2016
Science and Research Branch
Ministry of Natural Resources and Forestry
© 2016, Queen’s Printer for Ontario
Copies of this publication are available from and questions about content can be
directed to: [email protected].
Cette publication hautement spécialisée, Estimating the abundance of American black
bears (Ursus americanus) on the Bruce Peninsula, Ontario n’est disponible qu’en
anglais conformément au Règlement 671/92, selon lequel il n’est pas obligatoire de la
traduire en vertu de la Loi sur les services en français. Pour obtenir des renseignements
en français, veuillez communiquer avec le ministère des Richesses naturelles et des
Forêts au [email protected].
Cover photo: Shoreline of the Brue Peninsula, courtesy of Ontario Tourism Marketing
Partnership Corporation's (OTMPC) Image Ontario
Cite this report as: Obbard, Martyn E., Eric J. Howe, Chris J. Kyle, John Haselmayer,
Jody Scheifley. 2016. Estimating the abundance of American black bears (Ursus
americanus) on the Bruce Peninsula. Ontario Ministry of Natural Resources and
Forestry, Science and Research Branch, Peterborough, ON. Science and Research
Technical Report TR-13. 25p.
Some of the information in this document may not be compatible with assistive
technologies. If you need any of the information in an alternate format, please contact
Science and Research Technical Report TR-13 Page | ii
Abstract
We estimated the population size of black bears on the entire Bruce Peninsula north of
Highway 21 and on the smaller area contained by Bruce Peninsula National Park and
interspersed lands by sampling bears noninvasively at 90 barbed wire hair corrals on 5
occasions in May and June of 2012. We extracted DNA from hair samples captured on
the barbed wire corrals, and identified individuals based on microsatellite genotyping at
14 loci combined with a gender test. We assumed that the height of the barbed wire
strand excluded cubs and yearlings from possibility of capture. Therefore, we estimated
density and population size of bears aged >1 year from the resulting individual
encounter histories using spatially explicit capture–recapture models. We calculated the
expected age and sex distribution of the population based on demographic data for
black bears elsewhere in Ontario so that an appropriate number of cubs and yearlings
could be included in the estimates of total population size.
We obtained 368 hair samples, of which 265 included >3 roots and were processed. Of
these, 184 were profiled to a sufficient number of loci to identify individuals. Seventy-
one unique individuals (30 females and 41 males) were detected a total of 117 times
(excluding duplicate detections of the same individual on the same trap and occasion).
We estimated that 316 black bears (SE 46.6, 95% confidence interval 225–408)
inhabited the entire Bruce Peninsula, and that 97 of these (SE 15.6, 95% confidence
interval 67–128) occupied Bruce Peninsula National Park and the interspersed lands.
Science and Research Technical Report TR-13 Page | iii
Résumé
Nous avons estimé, au cours des mois de mai et juin 2012, la population d’ours noirs
sur la totalité de la péninsule Bruce au nord de la Route 21 et dans la petite zone du
parc national du Canada de la Péninsule-Bruce et des terres disséminées en
échantillonnant les ours de façon non invasive, grâce à 90 stations de collecte de poils
à l’aide d’un fil barbelé. Nous avons extrait l’ADN des poils ainsi obtenus et avons
identifié les individus grâce au génotypage sur 14 loci microsatellites, combiné à un test
déterminant le sexe. Nous avons présumé que la hauteur du barbelé excluait les
oursons et les ours d’un an. Nous avons par conséquent estimé la densité et la taille de
la population des ours âgés >1 an à partir des témoignages de rencontres individuelles
à l’aide de modèles de capture-recapture spatialement explicites. Nous avons calculé la
répartition vraisemblable de l’âge et du sexe de la population d’après les données
démographiques pour les ours noirs ailleurs en Ontario, de sorte que le nombre
approximatif d’oursons et d’ours âgés d'un an puissent être inclus à l’estimation de la
population totale.
Nous avons obtenu 368 échantillons de poils, dont 265 comprenaient >3 racines et ont
été analysés. De ceux-ci, 184 ont permis d’identifier les individus grâce à un nombre
suffisamment élevé de loci. Soixante-et-onze individus distincts (30 femmes et
41 mâles) ont été repérés sur un total de 117 fois (exclusion faite des détections
doubles du même individu à la même station et la même fois). Nous avons estimé que
316 ours noirs (écart-type 46,6, intervalle de confiance de 95 %, écart 225–408)
habitaient la totalité de la péninsule Bruce et que de ceux-ci, 97 ours (écart-type 15,6,
intervalle de confiance de 95 %, écart 67–128) occupaient le parc national du Canada
de la Péninsule-Bruce et les terres disséminées.
Science and Research Technical Report TR-13 Page | iv
Contents
Abstract ........................................................................................................................ii
Résumé ....................................................................................................................... iii
Introduction .................................................................................................................. 1
Methods ....................................................................................................................... 2
Data analysis ............................................................................................................... 4
Results ......................................................................................................................... 8
Discussion ................................................................................................................. 13
Acknowledgements .................................................................................................... 15
Literature cited ........................................................................................................... 16
Science and Research Technical Report TR-13 1
Introduction
The population of American black bears (Ursus americanus) occupying the Bruce
Peninsula, Ontario, Canada is apparently geographically isolated. It represents a
conservation concern due to its small size (Howe et al. 2007), limited habitat (Obbard et
al. 2010a), and low genetic diversity (Mills 2005, Pelletier et al. 2011, 2012). In a
previous study, the population’s estimated risk of extirpation was highly dependent on
the current population size (Howe et al. 2007). Based on capture-recapture surveys
conducted in 2004 and 2009 in Bruce Peninsula National Park (BPNP), and in 2007 and
2009 south of BPNP on the Bruce Peninsula, the bear population was estimated to be
approximately 240 animals (95% CI, 114 – 336; MNRF unpublished data). However,
this estimate was considered to be unreliable due to the length of time between the
2004 and 2009 sampling efforts in BPNP, and low genotyping success from samples
collected in BPNP in 2009. In addition, some occupied bear habitat was not sampled in
those years, so it was necessary to extrapolate density estimates from the sampled
areas over unsampled areas to obtain an estimate of total population size. Accordingly,
in 2012 the Ontario Ministry of Natural Resources and Forestry (MNRF), Parks Canada
Agency, and Saugeen Ojibway Nation (Chippewas of Nawash First Nation and
Chippewas of Saugeen First Nation) collaborated to obtain an improved estimate of the
black bear population on the Bruce Peninsula by conducting a spatially comprehensive
survey.
Science and Research Technical Report TR-13 2
Methods
Field sampling and DNA analysis
From May 23–June 28, 2012, we sampled black bears by collecting hair samples for
DNA analysis at barbed wire corrals (Woods et al. 1999). We assumed that the height
of the barbed wire strand (~50 cm above ground) would exclude cubs and yearlings
from the sample (Woods et al. 1999). We spaced 90 corrals throughout the peninsula in
an attempt to expose all bears to the possibility of capture (Figure 1). For logistical
reasons we were unable to place traps in the Township of Georgian Bluffs on the east
side of the peninsula between Wiarton and Owen Sound. We baited corrals with 3
partially opened tins of sardines in oil suspended from a board nailed 2.5 m high on a
tree. We firmly attached barbed wire strands to surrounding trees such that the wire was
> 2 m from the baited tree at any point along the wire to ensure bears could not reach
the bait without entering the corral. On approaching the bait, bears would either crawl
under or step over the wire strand, leaving a hair sample attached to a barb (Figure 2).
We baited sites first on May 23 and collected samples and rebaited corrals one week
later, ensuring any extra hairs were removed from barbs. We repeated this for a total of
5 sampling occasions. We air-dried hair samples in paper envelopes and stored them at
room temperature until DNA extraction was performed.
We did not attempt to extract DNA from hair samples with less than 3 roots. Individuals
were identified from their microsatellite genotypes at up to 14 polymorphic loci (Paetkau
and Strobeck 1994, Paetkau et al. 1995, Taberlet et al. 1997, Kitahara et al. 2000), and
sex was determined from amplification of a region of the amelogenin gene (Ennis and
Gallagher 1994). Individual microsatellite genotyping, gender determination, and
estimation of genotyping error (2.18%) were performed following the conditions
described in Pelletier et al. (2011, 2012). For additional details on methods for DNA
extraction, amplification, and profiling see Obbard et al. (2010b) and Pelletier et al.
Science and Research Technical Report TR-13 3
(2011, 2012). Genotypes identified from a single sample were only considered to
represent a unique individual if they were genotyped to at least 11 loci.
Figure 1. Map of the Bruce Peninsula, Ontario, Canada. Red triangles show locations
of barbed wire hair corrals used in 2012. Landcover types are from the Southern
Ontario Land Resource Information System (Ministry of Natural Resources, 2008). The
integration mesh used in spatially explicit capture-recapture analyses appears as grey
dots; points within BPNP and interspersed lands are shown in darker grey. Heavy black
lines show boundaries used to define spatial covariates of bear density. ML = Miller
Lake; LH = Lion’s Head; WI = Wiarton.
Science and Research Technical Report TR-13 4
Figure 2. Photograph of a black bear inside a barbed wire hair corral. When a bear
enters the corral to access the bait, a DNA sample may be obtained from hairs snagged
on the barbed wire (Photo: John Connor, MNRF)
Data analysis
We estimated population size using spatially explicit capture-recapture (SECR) models
(Efford 2004, Efford et al. 2009, Efford and Fewster 2013). The models assumed that:
(1) bears did not enter or leave the study area during sampling (demographic closure);
(2) individuals were accurately identified; (3) detections of different individuals were
independent events; and (4) individuals occupied approximately circular home ranges,
the central locations of which were fixed during sampling (Efford 2004). In the SECR
framework, probability of detection is modeled as a decreasing function of the distance
between traps and the unobserved central locations of individual home ranges or
Science and Research Technical Report TR-13 5
“activity centres” (Efford 2004). The simplest detection function has two parameters: the
magnitude (g0) and spatial scale (σ) of a half-normal spatial detection probability
function; g0 may be thought of as the probability of detection of an individual animal
where a trap is placed at the individual’s activity centre (i.e., at distance zero), and σ
and the shape of the detection probability function describe how detection probability
declines with increasing distance between home range centre locations and traps
(Efford 2004). Animal density, g0, and σ may be described as functions of covariates
(Efford et al. 2009).
We defined a set of candidate SECR models with different combinations of the following
covariates of the parameters of the detection probability function and of bear density.
For g0, we considered general and trap-specific responses to initial detection (hereafter
denoted b and bk, respectively), individual heterogeneity (h), sex, and interactions
between behavioural responses and sex. For σ we considered unique values on all
sampling occasions (t), a linear trend over occasions (T), h, and sex. For bear density
we considered sex and six covariates for spatial variation. Spatial covariates were: (1) a
linear relationship with UTM Northings (hereafter denoted " N
"); (2) a 2-level factor
allowing for different densities north and south of UTM Northing 4996500 just north of
Miller Lake, ("ML"; Figure 1); (3) a 2-level factor allowing for differences north and south
of a line just south of Lion's Head ("LH"; Figure 1); (4) a 2-level factor allowing for
differences on either side of a line separating largely forested habitat north of the town
of Wiarton from largely agricultural habitat to the south and east ("WI"; Figure 1); (5) a
3-level factor employing the ML and WI boundaries; and (6) a 4-level factor employing
the ML, LH, and WI boundaries.
We initially defined the region of integration as the area within a 20-km buffer around
traps and set the number of mesh points in the x- and y-directions to 80 and 120,
respectively. We then removed mesh points that fell in open water, offshore islands,
Science and Research Technical Report TR-13 6
cleared land, and developed areas using spatial data defining the outline of the Ontario
mainland and land cover data for southern Ontario (MNR 2008; Figure 1).
We fit SECR models by maximizing the full likelihood for proximity detectors (Efford et
al. 2009). We used the half-normal form of the detection probability function. Individual
heterogeneity was modeled using two-point finite mixture distributions (Pledger 2000).
To reduce the total number of models to be fitted, we did not consider all possible
subsets of the above covariates. We initially fit models with constant g0 and σ and each
covariate of spatial variation in density. We then emphasized models where density was
held constant or was a function of N
and fit models with various combinations of
covariates for g0 and σ to identify the best supported detection model. Finally, we
crossed the top detection model with all models of spatial variation in density. We used
Akaike’s Information Criterion for small sample sizes (AICc; Hurvitch and Tsai 1989) to
evaluate support for different candidate models, and compared density estimates from
high-ranking models.
We estimated sex-specific population sizes of bears aged > 1 year on the entire Bruce
Peninsula north of Highway 21, and within Bruce Peninsula National Park and the
interspersed lands (combination of lands of Saugeen Ojibway Nation [Chippewas of
Nawash First Nation and Chippewas of Saugeen First Nation] and private land), as the
volume under the fitted density surface described by the top-ranked model (Efford and
Fewster 2013). In the case of BPNP we limited the spatial extent of the population to the
area north of the former St. Edmund’s Township line by defining an appropriate
integration mesh (Efford and Fewster 2013; Figure 1). We summed sex-specific
estimates to estimate population size of all bears aged > 1 year. We calculated standard
errors (SE) of population estimates for both sexes as the square root of the sum of the
variances around sex-specific estimates, and 95% confidence limits as the point
estimate ± 1.96 SEs. Analyses were performed using R software (R Development Core
Team 2012) using the package "secr" (version 2.4.0, Efford 2012).
Science and Research Technical Report TR-13 7
We used the RISKMAN population model (Taylor et al. 2003) to calculate the expected
population age distribution and hence the expected number of cubs and yearlings. We
parameterized RISKMAN with demographic rates reported by Kolenosky (1990;
reproductive rates), Yodzis and Kolenosky (1986; cub, yearling, and subadult survival
rates), and Obbard and Howe (2008; adult survival rates). We added the expected
number of cubs and yearlings to the estimated populations of bears aged > 1 year to
obtain estimates of total population size on the Bruce Peninsula north of Highway 21
and within BPNP and the interspersed lands.
Science and Research Technical Report TR-13 8
Results
We obtained 368 hair samples, of which 103 consisted of fewer than 3 hairs with roots
and were not processed. Of the 265 samples processed, 184 were profiled to sufficient
loci to identify individuals. We identified 71 unique individuals (30 females and 41
males). Bears of both sexes were detected throughout the study area (Figure 3). Thirty-
one individuals were identified from a single sample, 18 were identified in 2 samples,
and 21 were identified in ≥ 3 samples. Sample size of recaptures was 46 (19 recaptures
of females and 27 recaptures of males).
One female moved > 19 km between traps during the fifth sampling occasion. The other
19 movements by females we detected averaged 2864 m (SE 495, maximum 5874).
Based on home-range information for black bears in similar habitat (Rogers 1987,
Powell et al. 1997, Schenk et al. 1998, Maxie 2009, Obbard et al. 2010a), and previous
hair-trapping studies conducted across Ontario (Obbard et al. 2010b, Howe et al. 2013),
we did not expect females to travel > 10 km between traps. The genotypes associated
with the 19-km movement matched at all 14 loci, and we verified all labels, so we are
confident that this was not a case of genotyping or transcription error. We are unaware
of any bears being translocated by management staff of either Parks Canada or the
Ontario Ministry of Natural Resources and Forestry during our study. Although we did
not expect foraging excursions to occur as early in the season as our sampling period,
the spring of 2012 was characterized by higher temperatures and lower precipitation,
compared to climate normals for 1981–2010 (Table 1), beginning with record highs over
much of the province in mid-March. As a result, bears may have been active earlier than
usual, and the phenological development of plants may have been advanced. Either
dispersal or a foraging excursion would violate the assumptions of the abundance
estimators. Furthermore, because our sample of movements among traps by females
was small, one outlier could affect our abundance estimates. Therefore, we censored
one of the two observations of this female.
Science and Research Technical Report TR-13 9
Table 1. Temperature and precipitation values for March–June 2012 compared to
climate normals (in parentheses) for the period 1981–2010 for Wiarton, ON
(Environment and Climate Change Canada 2015).
Month Mean
Maximum
Temperature
(°C)
Mean
Minimum
Temperature
(°C)
Mean Daily
Temperature
(°C)
Total
Precipitation
(mm)
March 11.2 (2.7 ) 0.2 (-6.4) 5.7 (-1.9) 47.4 (67.4)
April 9.8 (10.3) -0.5 (0.4) 4.7 (5.3) 55.0 (73.1)
May 19.8 (16.5) 7.0 (5.4) 13.4 (11.0) 24.2 (83.5)
June 23.3 (21.5) 12.6 (10.3) 18.0 (15.9) 77.9 (76.4)
Figure 3. Locations where hair samples were obtained for female (left) and male (right)
American black bears on the Bruce Peninsula, Ontario, 2012. Dots indicate trap
locations where hair samples were obtained. Crosses indicate remaining trap locations.
Science and Research Technical Report TR-13 10
High-ranking models of spatial detection probability included (positive) trap-specific
responses to initial detection and individual heterogeneity affecting g0, and differences
in σ between sexes and among individuals of the same sex (Table 2). Top models also
included differences in sex-specific g0 and effects of initial detection on g0 (Table 2). The
best supported model of variation in bear density was a linear relationship with y-
coordinates, where bear density increased with increasing latitude (Table 2). Neither
differences in σ among sampling occasions nor differences in density between the
sexes were supported (Table 2). We attempted to fit models with each form of variation
in bear density crossed with the best-supported detection model. However,
convergence problems and singularities arose when the top detection model was
crossed with ML, LH, and the four-level covariate for density, so AICc-values and
parameter estimates from these models are not presented. The top two AICc-ranked
models accounted for 97% of the total AICc weight (Table 2) and yielded similar
estimates of the detection function parameters and bear density. Densities of bears
aged > 1 year estimated from the top model were 26.8/100 km2 (SE 6.7) in the
northeast corner of BPNP, 20.0/100 km2 in the vicinity of Miller Lake, 12.6/100 km2 20
km north of Wiarton, and 6.4/ 100 km2 10 km south of Wiarton. Densities estimated from
the 2nd-ranked model were 26.0/100 km2 north of Miller Lake, 12.2/100 km2 between
Miller Lake and Wiarton, and 5.6/100 km2 south of Wiarton. The top AICc-ranked model
had nearly 4 times as much support as the second-ranked model (Table 2), so we used
the top model to estimate population size.
Population size of bears aged > 1 year on the Bruce Peninsula estimated from the fitted
density surface was 202.2 bears (SE 29.8, 95% CI 144–261). Population size of bears
aged > 1 year within Bruce Peninsula National Park and all interspersed lands was 62.1
(SE 10.0, 95% CI 43–82). Thirty-six percent of bears in the expected age/sex
distribution were cubs and yearlings. Therefore, we divided population estimates of
bears aged > 1 year by 0.64 to convert them to population estimates for all bears. This
Science and Research Technical Report TR-13 11
yielded an estimate of 316 bears of all ages (SE 46.6, 95% CI 225–408) on the
peninsula north of Highway 21, and 97 bears of all ages (SE 15.6, 95% CI 67–128)
within BPNP and all interspersed lands.
Table2. AICc model selection criteria among spatially explicit capture-recapture models
of detection probability and density of black bears on the Bruce Peninsula, Ontario,
2012.
Density model Detection model npar logLik AICc ΔAICc wi
UTM N g0(h+bk×sex) σ(h+sex) 11 -458.8 944.0 0.00 0.77
3-level factor g0(h+bk×sex) σ(h+sex) 12 -458.7 946.7 2.72 0.20
UTM N g0(h+bk) σ(h+sex) 9 -465.3 951.5 7.52 0.02
UTM N g0(h×bk) σ(h+sex) 10 -464.0 951.7 7.67 0.02
UTM N g0(h+bk×sex) σ(sex) 10 -466.9 957.5 13.55 0.00
UTM N + sex g0(h+bk×sex) σ(h+sex) 12 -464.3 958.1 14.07 0.00
UTM N g0(bk×sex) σ(h+sex) 10 -472.3 968.3 24.31 0.00
UTM N g0(bk×sex) σ(sex) 8 -478.0 974.3 30.28 0.00
UTM N g0(bk×sex) σ(T+sex) 9 -478.0 976.9 32.90 0.00
UTM N + sex g0(bk×sex) σ(sex) 9 -478.0 976.9 32.91 0.00
UTM N g0(bk+sex) σ(sex) 7 -481.1 978.1 34.07 0.00
UTM N + sex g0(bk×sex) σ(T+sex) 10 -478.0 979.6 35.61 0.00
UTM N g0(bk) σ(sex) 6 -486.6 986.5 42.52 0.00
Constant g0(bk) σ(sex) 5 -491.2 993.3 49.30 0.00
Science and Research Technical Report TR-13 12
Density model Detection model npar logLik AICc ΔAICc wi
Constant g0(bk) σ(T+sex) 6 -491.1 995.5 51.55 0.00
Constant g0(bk) σ(t+sex) 9 -490.4 1001.7 57.67 0.00
Constant g0(b) σ(sex) 5 -511.4 1033.7 89.71 0.00
Constant g0(.) σ(sex) 4 -515.5 1039.5 95.51 0.00
UTM N g0(.) σ(.) 4 -520.1 1048.7 104.73 0.00
LH g0(.) σ(.) 4 -520.7 1050.1 106.11 0.00
3-level factor g0(.) σ(.) 5 -520.9 1052.6 108.63 0.00
WI g0(.) σ(.) 4 -522.2 1053.0 109.03 0.00
BPNP g0(.) σ(.) 4 -522.3 1053.2 109.25 0.00
4-level factor g0(.) σ(.) 6 -520.1 1053.5 109.51 0.00
Constant g0(.) σ(.) 3 -525.3 1057.0 112.97 0.00
Science and Research Technical Report TR-13 13
Discussion
The population estimate we developed relied on several assumptions. In order to meet
the assumptions of demographic closure and static home range centre locations, we
sampled during spring and early summer to ensure that we completed sampling prior to
when bears might leave their spring and early summer home ranges on seasonal
feeding forays (Rogers 1987, Schenk et al. 1998, Noyce and Garshelis 2011), and
before subadult males would be likely to disperse (Lee and Vaughan 2003). Despite the
early spring in 2012 (Table 1), we had little evidence of large-scale movements by bears
during the study; therefore, the assumption of static home range centres was met. The
timing and duration of our sampling ensured that no cubs were born and that mortality
was minimal (none was observed or reported) during sampling, so the assumption of
demographic closure was adequately met. Culling of low-quality samples and profiling
all samples to 14 loci plus gender reduced the potential for violations of the assumption
that marks were not lost or misread. Violation of the assumption of circular home
ranges, if it occurred, should affect only the variance of density estimates (Efford 2004).
We cannot verify that the height of the wire strand excluded cubs and yearlings from the
sample. However, Drewry et al. (2012) did not find hair samples where remote cameras
revealed that small bears had passed under a barbed wire strand set at 40 cm above
the ground, which was 10 cm lower than the level of our barbed wire. They concluded
that they had likely detected a few cubs and yearlings, but that their density estimates
primarily reflected subadult and adult density. If we detected more than one member of
a family group traveling together, then the assumption of independence of captures
Science and Research Technical Report TR-13 14
could have been violated. Furthermore, if any bears < 2 years of age were sampled, we
overestimated the total population when we added the expected number of cubs and
yearlings to population estimates for bears aged > 1 year. However, based on
observations and morphological measurements of black bears in Ontario (M.E. Obbard,
unpublished data) a consistent wire height of 50 cm should exclude cubs and yearlings,
and we are confident it did so.
Bears occupying some patches of suitable habitat may not have been exposed to our
trap array and been vulnerable to capture. However, estimating the density surface
across the entire region of integration enabled us to estimate the number of bears
occupying the entire peninsula, including areas where no traps were located (Efford and
Fewster 2013). Bear density under the fitted surface from the selected SECR model
increased with latitude. Therefore, the number of bears in the northeastern (portions of
Cabot Head) and northwestern (vicinity of town of Tobermory) areas of the peninsula
where no traps were placed was estimated assuming maximal density, and the number
of bears south of Wiarton, including in the Township of Georgian Bluffs, was estimated
assuming minimal density. If bears were not at high density in the northernmost portions
of the peninsula, population size on the peninsula and within BPNP and interspersed
lands may have been overestimated, though we expect bias would be slight. By
including all forest and wetland patches in our integration mesh we may have inferred
the presence of bears where they do not actually occur. This could also result in a slight
overestimation of population size. Nevertheless, we derived population estimates for the
Bruce Peninsula north of Highway 21 and for Bruce Peninsula National Park and
interspersed lands that were based on a sufficient number of captures and re-captures
to provide reliable estimates. Our results confirm that the population size of black bears
Science and Research Technical Report TR-13 15
on the Bruce Peninsula is small, and highlight that this should be a consideration in
land-use planning and harvest management.
Acknowledgements
Field sampling was conducted by members of the Ontario Ministry of Natural Resources
and Forestry, Bruce Peninsula National Park, and Saugeen Ojibway Nation. We
especially thank Doran Ritchie (Saugeen Ojibway Nation), Cavan Harpur (BPNP), and
Dustin Veenhof (MNRF) for their assistance with sample collection. Genetic analyses
were performed at the Natural Resources DNA Profiling and Forensics Centre at Trent
University, Peterborough, Ontario. Thanks to Kevin Middel (MNRF) for preparing Figure
1. We are grateful to the many private landowners who permitted us to sample bears on
their land.
Science and Research Technical Report TR-13 16
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