Extended Abstract: Both human-caused mortality and food are recognized to be the primary determin... more Extended Abstract: Both human-caused mortality and food are recognized to be the primary determinants of the distribution and abundance of grizzly bears (Ursus arctos); however, before our study, there was no information on the ecology of grizzly bears in the arctic watershed of central British Columbia (B.C.). From 1998 to 2002, we monitored habitat use and survival of 59 radio-collared grizzly bears (n = 37 females, n = 22 males) in an area surrounding the Parsnip River in central-eastern B.C. The 18,100-km 2 study area encompassed a heavily timber-harvested plateau and an adjacent relatively pristine mountainous region. Thirty of the radio-collared bears were from the plateau (n = 19 females, n = 11 males); 29 (n = 18 females, n = 11 males) were from the mountainous region. We asked whether grizzly bears were less abundant in a heavily human-modified landscape (plateau) than in a relatively pristine landscape (mountains), and if so, why?
We used resource selection functions (RSF) to estimate the relative probability of use for grizzl... more We used resource selection functions (RSF) to estimate the relative probability of use for grizzly bears (Ursus arctos) adjacent to the Parsnip River, British Columbia, Canada, 1998. We collected data from 30 radiocollared bears on a rolling plateau where a large portion of the landscape had been modified by human activities, primarily forestry. We also monitored 24 radiocollared bears in mountain areas largely inaccessible to humans. Bears that lived on the plateau existed at less than one-quarter the density of bears in the mountains. Plateau bears ate more high-quality food items, such as meat and berries, leading us to conclude that food limitation was not responsible for the differences in densities. We hypothesized that plateau bears were limited by human-caused mortality associated with roads constructed for forestry activities. Independent estimates of bear population size from DNA-based mark-recapture techniques allowed us to link populations to habitats using RSF models to scale habitat use patterns to population density. To evaluate whether differences in land-cover type, roads, or mortality risk could account for the disparity in density we used the mountain RSF model to predict habitat use and number of bears on the plateau and vice versa. We predicted increases ranging from 34 bears to 96 bears on the plateau when switching model coefficients, excluding land-cover types; when exchanging land-cover coefficients, the model predicted that the plateau population would be 9 bears lower than was observed. Large reductions in the numbers of mountain bears were predicted by habitat-selection models of bears using the plateau landscape. Although RSF models estimated in mountain and plateau landscapes could not predict bear use and abundance in the other areas, contrasts in models between areas provided a useful tool for examining the effects of human activities on grizzly bears.
The purpose of our study is to show how ecologists' interpretation of habitat selection by grizzl... more The purpose of our study is to show how ecologists' interpretation of habitat selection by grizzly bears (Ursus arctos) is altered by the scale of observation and also how management questions would be best addressed using predetermined scales of analysis. Using resource selection functions (RSF) we examined how variation in the spatial extent of availability affected our interpretation of habitat selection by grizzly bears inhabiting mountain and plateau landscapes. We estimated separate models for females and males using three spatial extents: within the study area, within the home range, and within predetermined movement buffers. We employed two methods for evaluating the effects of scale on our RSF designs. First, we chose a priori six candidate models, estimated at each scale, and ranked them using Akaike Information Criteria. Using this method, results changed among scales for males but not for females. For female bears, models that included the full suite of covariates predicted habitat use best at each scale. For male bears that resided in the mountains, models based on forest successional stages ranked highest at the study-wide and home range extents, whereas models containing covariates based on terrain features ranked highest at the buffer extent. For male bears on the plateau, each scale estimated a different highest-ranked model. Second, we examined differences among model coefficients across the three scales for one candidate model. We found that both the magnitude and direction of coefficients were dependent upon the scale examined; results varied between landscapes, scales, and sexes. Greenness, reflecting lush green vegetation, was a strong predictor of the presence of female bears in both landscapes and males that resided in the mountains. Male bears on the plateau were the only animals to select areas that exposed them to a high risk of mortality by humans. Our results show that grizzly bear habitat selection is scale dependent. Further, the selection of resources can be dependent upon the availability of a particular vegetation type on the landscape. From a management perspective, decisions should be based on a hierarchical process of habitat selection, recognizing that selection patterns vary across scales.
The Parsnip River area in British Columbia (BC), Canada, provides important habitat for grizzly b... more The Parsnip River area in British Columbia (BC), Canada, provides important habitat for grizzly bears (Ursus arctos). This area contains 2 adjacent topographic regions: (1) a relatively pristine portion of the Hart Ranges of the Canadian Rocky Mountains, and (2) a plateau on which timber harvests have occurred. Increasing human modification of both landscapes may affect the quality of grizzly
Philosophical Transactions of The Royal Society B Biological Sciences
With the advent of new technologies, animal locations are being collected at ever finer spatio-te... more With the advent of new technologies, animal locations are being collected at ever finer spatio-temporal scales. We review analytical methods for dealing with correlated data in the context of resource selection, including post hoc variance inflation techniques, 'two-stage' approaches based on models fit to each individual, generalized estimating equations and hierarchical mixed-effects models. These methods are applicable to a wide range of correlated data problems, but can be difficult to apply and remain especially challenging for use-availability sampling designs because the correlation structure for combinations of used and available points are not likely to follow common parametric forms. We also review emerging approaches to studying habitat selection that use fine-scale temporal data to arrive at biologically based definitions of available habitat, while naturally accounting for autocorrelation by modelling animal movement between telemetry locations. Sophisticated an...
On human-used landscapes, animal behavior is a trade-off between maximizing fitness and minimizin... more On human-used landscapes, animal behavior is a trade-off between maximizing fitness and minimizing human-derived risk. Understanding risk perception in wildlife can allow mitigation of anthropogenic risk, with benefits to long-term animal fitness. Areas where animals choose to rest should minimize risk from predators, which for large carnivores typically equate to humans. We hypothesize that high human activity leads to selection for habitat security, whereas low activity enables trading security for forage. We investigated selection of resting (bedding) sites by GPS radiocollared adult grizzly bears (n = 10) in a low density population on a multiple-use landscape in Canada. We compared security and foods at resting and random locations while accounting for land use, season, and time of day. On reclaimed mines with low human access, bears selected high horizontal cover far from trails, but did not avoid open (herbaceous) areas, resting primarily at night. In protected areas bears also bedded at night, in areas with berry shrubs and Hedysarum spp., with horizontal cover selected in the summer, during high human access. On public lands with substantial human recreation, bears bedded at day, selected resting sites with high horizontal cover in the summer and habitat edges, with bedding associated with herbaceous foods. These spatial and temporal patterns of selection suggest that bears perceive human-related risk differentially in relation to human activity level, season and time of day, and employ a security-food trade-off strategy. Although grizzly bears are presently not hunted in Alberta, their perceived risks associated with humans influence resting-site selection.
+ movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behav... more + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period.
+ movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behav... more + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period.
Extended Abstract: Both human-caused mortality and food are recognized to be the primary determin... more Extended Abstract: Both human-caused mortality and food are recognized to be the primary determinants of the distribution and abundance of grizzly bears (Ursus arctos); however, before our study, there was no information on the ecology of grizzly bears in the arctic watershed of central British Columbia (B.C.). From 1998 to 2002, we monitored habitat use and survival of 59 radio-collared grizzly bears (n = 37 females, n = 22 males) in an area surrounding the Parsnip River in central-eastern B.C. The 18,100-km 2 study area encompassed a heavily timber-harvested plateau and an adjacent relatively pristine mountainous region. Thirty of the radio-collared bears were from the plateau (n = 19 females, n = 11 males); 29 (n = 18 females, n = 11 males) were from the mountainous region. We asked whether grizzly bears were less abundant in a heavily human-modified landscape (plateau) than in a relatively pristine landscape (mountains), and if so, why?
We used resource selection functions (RSF) to estimate the relative probability of use for grizzl... more We used resource selection functions (RSF) to estimate the relative probability of use for grizzly bears (Ursus arctos) adjacent to the Parsnip River, British Columbia, Canada, 1998. We collected data from 30 radiocollared bears on a rolling plateau where a large portion of the landscape had been modified by human activities, primarily forestry. We also monitored 24 radiocollared bears in mountain areas largely inaccessible to humans. Bears that lived on the plateau existed at less than one-quarter the density of bears in the mountains. Plateau bears ate more high-quality food items, such as meat and berries, leading us to conclude that food limitation was not responsible for the differences in densities. We hypothesized that plateau bears were limited by human-caused mortality associated with roads constructed for forestry activities. Independent estimates of bear population size from DNA-based mark-recapture techniques allowed us to link populations to habitats using RSF models to scale habitat use patterns to population density. To evaluate whether differences in land-cover type, roads, or mortality risk could account for the disparity in density we used the mountain RSF model to predict habitat use and number of bears on the plateau and vice versa. We predicted increases ranging from 34 bears to 96 bears on the plateau when switching model coefficients, excluding land-cover types; when exchanging land-cover coefficients, the model predicted that the plateau population would be 9 bears lower than was observed. Large reductions in the numbers of mountain bears were predicted by habitat-selection models of bears using the plateau landscape. Although RSF models estimated in mountain and plateau landscapes could not predict bear use and abundance in the other areas, contrasts in models between areas provided a useful tool for examining the effects of human activities on grizzly bears.
The purpose of our study is to show how ecologists' interpretation of habitat selection by grizzl... more The purpose of our study is to show how ecologists' interpretation of habitat selection by grizzly bears (Ursus arctos) is altered by the scale of observation and also how management questions would be best addressed using predetermined scales of analysis. Using resource selection functions (RSF) we examined how variation in the spatial extent of availability affected our interpretation of habitat selection by grizzly bears inhabiting mountain and plateau landscapes. We estimated separate models for females and males using three spatial extents: within the study area, within the home range, and within predetermined movement buffers. We employed two methods for evaluating the effects of scale on our RSF designs. First, we chose a priori six candidate models, estimated at each scale, and ranked them using Akaike Information Criteria. Using this method, results changed among scales for males but not for females. For female bears, models that included the full suite of covariates predicted habitat use best at each scale. For male bears that resided in the mountains, models based on forest successional stages ranked highest at the study-wide and home range extents, whereas models containing covariates based on terrain features ranked highest at the buffer extent. For male bears on the plateau, each scale estimated a different highest-ranked model. Second, we examined differences among model coefficients across the three scales for one candidate model. We found that both the magnitude and direction of coefficients were dependent upon the scale examined; results varied between landscapes, scales, and sexes. Greenness, reflecting lush green vegetation, was a strong predictor of the presence of female bears in both landscapes and males that resided in the mountains. Male bears on the plateau were the only animals to select areas that exposed them to a high risk of mortality by humans. Our results show that grizzly bear habitat selection is scale dependent. Further, the selection of resources can be dependent upon the availability of a particular vegetation type on the landscape. From a management perspective, decisions should be based on a hierarchical process of habitat selection, recognizing that selection patterns vary across scales.
The Parsnip River area in British Columbia (BC), Canada, provides important habitat for grizzly b... more The Parsnip River area in British Columbia (BC), Canada, provides important habitat for grizzly bears (Ursus arctos). This area contains 2 adjacent topographic regions: (1) a relatively pristine portion of the Hart Ranges of the Canadian Rocky Mountains, and (2) a plateau on which timber harvests have occurred. Increasing human modification of both landscapes may affect the quality of grizzly
Philosophical Transactions of The Royal Society B Biological Sciences
With the advent of new technologies, animal locations are being collected at ever finer spatio-te... more With the advent of new technologies, animal locations are being collected at ever finer spatio-temporal scales. We review analytical methods for dealing with correlated data in the context of resource selection, including post hoc variance inflation techniques, 'two-stage' approaches based on models fit to each individual, generalized estimating equations and hierarchical mixed-effects models. These methods are applicable to a wide range of correlated data problems, but can be difficult to apply and remain especially challenging for use-availability sampling designs because the correlation structure for combinations of used and available points are not likely to follow common parametric forms. We also review emerging approaches to studying habitat selection that use fine-scale temporal data to arrive at biologically based definitions of available habitat, while naturally accounting for autocorrelation by modelling animal movement between telemetry locations. Sophisticated an...
On human-used landscapes, animal behavior is a trade-off between maximizing fitness and minimizin... more On human-used landscapes, animal behavior is a trade-off between maximizing fitness and minimizing human-derived risk. Understanding risk perception in wildlife can allow mitigation of anthropogenic risk, with benefits to long-term animal fitness. Areas where animals choose to rest should minimize risk from predators, which for large carnivores typically equate to humans. We hypothesize that high human activity leads to selection for habitat security, whereas low activity enables trading security for forage. We investigated selection of resting (bedding) sites by GPS radiocollared adult grizzly bears (n = 10) in a low density population on a multiple-use landscape in Canada. We compared security and foods at resting and random locations while accounting for land use, season, and time of day. On reclaimed mines with low human access, bears selected high horizontal cover far from trails, but did not avoid open (herbaceous) areas, resting primarily at night. In protected areas bears also bedded at night, in areas with berry shrubs and Hedysarum spp., with horizontal cover selected in the summer, during high human access. On public lands with substantial human recreation, bears bedded at day, selected resting sites with high horizontal cover in the summer and habitat edges, with bedding associated with herbaceous foods. These spatial and temporal patterns of selection suggest that bears perceive human-related risk differentially in relation to human activity level, season and time of day, and employ a security-food trade-off strategy. Although grizzly bears are presently not hunted in Alberta, their perceived risks associated with humans influence resting-site selection.
+ movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behav... more + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period.
+ movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behav... more + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period. Individual behaviour: 1 Julian date; 2 Hunting season fate + Julian date by hunting season fate; 3 Julian date + movement behaviour; 4 Hunting season fate + Julian date by hunting season fate + movement behaviour. 5 Environment: day period + terrain ruggedness + open areas. 6 Humans: land use + distance from gravel roads + week period.
FULL TEXT FREELY AVAILABLE AT www.escholarship.org/uc/item/6837k4gc . . . Both means and year-to-... more FULL TEXT FREELY AVAILABLE AT www.escholarship.org/uc/item/6837k4gc . . . Both means and year-to-year variances of climate variables such as temperature and precipitation are predicted to change. However, the potential impact of changing climatic variability on the fate of populations has been largely unexamined. We analyzed multiyear demographic data for 36 plant and animal species with a broad range of life histories and types of environment to ask how sensitive their long-term stochastic population growth rates are likely to be to changes in the means and standard deviations of vital rates (survival, reproduction, growth) in response to changing climate. We quantified responsiveness using elasticities of the long-term population growth rate predicted by stochastic projection matrix models. Short-lived species (insects and annual plants and algae) are predicted to be more strongly (and negatively) affected by increasing vital rate variability relative to longer-lived species (perennial plants, birds, ungulates). Taxonomic affiliation has little power to explain sensitivity to increasing variability once longevity has been taken into account. Our results highlight the potential vulnerability of short-lived species to an increasingly variable climate, but also suggest that problems associated with short-lived undesirable species (agricultural pests, disease vectors, invasive weedy plants) may be exacerbated in regions where climate variability decreases.
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Papers by Mark S Boyce