Post by grrraaahhh on Jul 14, 2013 20:08:16 GMT -9
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Text & Material Extract
Overall population size and distribution of grizzly bears in Canada are not known to have changed since 1991. The total extent of occurrence may approximate 3,469,000 km² as reported by Banci (1991) and McLellan and Banci (1999), although the current area of occupancy is probably closer to 2,574,000 km².
Humans kill a reported mean of 504 grizzly bears in Canada each year (Table 12). About 84% of these mortalities are by legal hunters (including First Nations). Defence of Life or Property (DLP) kills account for another 13%. Based on the estimates of total Canadian population size (Table 6), known man-caused mortality accounts for an average of about 2.0 to 2.4% of the grizzly bear population each year. This mortality rate is not distributed evenly across the jurisdictions.
Population Size and Trend—Summary
The total grizzly bear population in Canada is estimated to be a minimum of 27,421, with a range of 26,916+ to 29,150+. Of these, 6,890+ to 17,199+ are of reproductive age. Grizzly bears currently occupy several discontinuous areas and therefore comprise several subpopulations. Eight population isolates have been identified along the southern fringe of grizzly bear distribution in BC, with a total population of < 250 bears (T. Hamilton and B. McLellan, pers. commun.). For 6 of these units, population estimates are < 30 bears each. For each of the remaining 2 units, estimates are 60-70 bears. The remainder of the Canadian grizzly population occupies some 2,574,000 km² that is essentially continuous. Grizzly bears have been extirpated from the prairie ecozone.
Canadian grizzly populations have been greatly reduced from historic levels, but have remained essentially consistent since 1990. Even the small and isolated populations in southern BC are believed to be stable.
Population status and growing threats. The status of brown bears in Canada was reviewed by Macey (1979) and more recently by Banci (1991). Macey concluded that brown bears were not endangered or threatened but were extremely vulnerable. Because Canada is a large and diverse country and brown bears are distributed over approximately 3,470,000 km² (2.4 times the size of the state of Alaska) Banci (1991) decided that an analysis of their status required dividing the country into 14 “brown bear zones” based on similar climate, land forms, and human activities. The status of brown bears in the zones is closely linked to the number and distribution of people. In inhospitable areas of the north or in the rugged mountains, there are limited human settlements and brown bears are relatively numerous for the habitat, while brown bears are relatively rare where people have settled. Estimating bear numbers is notoriously difficult.
Without an intensive marking program, only estimations based on largely subjective information and extrapolation from research areas are available (Table 5.3). Banci (1991) estimated that about 25,000 brown bears live in Canada and this number has unlikely changed significantly in the past few years. In two of the brown bear zones, the Non-Mountainous Boreal Plains and the Glaciated Prairies, brown bear have been extirpated. In the Hot Dry Plateaus, brown bears are rare and considered threatened. The status of brown bears in the remaining zones are often debated; some people suggest that they are vulnerable while others believe they are doing fine.
Arctic Coastal Plains: An estimated 2,860 brown bears occur in this zone. Although there have been some sightings on Banks and Victoria Island, these bears are mostly limited to the mainland. This zone is sparsely populated by people and there is little road access. Impacts on bears occur near settlements and petroleum exploration and development have had a significant impact in localized areas. Over most of the area, brown bears are likely near carrying capacity. Taiga Shield: The status of brown bears in this region is poorly known but an estimate of 790 was provided by Banci (1991). The bear habitat is thought to be relatively poor on the Taiga Shield. There are no known recent records of brown bears from northern Manitoba or Saskatchewan. This zone has few human residents and bear kills are rare.
Taiga Plains: The bear habitat in this zone is also inferior and, although density estimates are poor, a total population of 1,520 bears has been estimated. This zone has few residents and access remains poor.
Subarctic Mountains: There are an estimated 2,540 brown bears in the Subarctic Mountains and this population has been hunted since 1965. The productivity of the population is low and hunting regulations are consequently strict. Access is limited in the zone and there are few human settlements.
Subarctic Mountains and Plains: The density of brown bears in this zone appears higher than the more northern and eastern areas. A total of 5,680 bears are estimated to live here. There are three major highways crossing this area and there are a few communities with more than 2,000 people. Poor garbage management has resulted in bear deaths and many translocations. Mining and petroleum are the major industries in this zone. Hunting mortality associated with big game guiding is the major source of bear mortality.
Cold Boreal Plains: Agricultural development has eliminated brown bears from a portion of this zone, however, an estimated 970 bears remain. Natural gas development is the major industry although the amount of forestry, in particular pulp production, is rapidly increasing. Access developed by the various industries is becoming a significant problem for brown bears. Human settlements are rare; however, there are three communities with over 4,000 people.
Cold Moist Mountains: This zone is relatively good bear habitat and has an estimated population size of 2,940 brown bears. Forestry, mining, and big game hunting are the major industries. Human settlements are rare and small in this zone and although access is currently limited, it is rapidly increasing in certain locations. Temperate Wet Mountains: Some of the most productive brown bear habitat in the country occurs here. Vancouver, the largest city in western Canada, is located in the southern tip of this zone and the influence of such a large settlement has greatly affected brown bear numbers in this corner of the country. The southern coast supports about 90 brown bears which is only 5% of its estimated capability. There are few settlements in the north coast and access is generally difficult. Range fragmentation is a concern in the southern portion. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. Although timber harvest and trophy hunting are very extensive in the north coast, an estimated 3,210 brown bears inhabit the area.
Cool Moist Plateaus: Cattle ranching is extensive in portions of this zone and intolerance of large carnivores has significantly impacted brown bear numbers. Due to the generally flat topography, timber harvest is highly mechanistic and extensive. There are several large and many small communities in this zone and road access is extensive. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. The estimated number of bears in this zone is 1,100.
Cool Moist Mountains: This zone has some very productive bear habitat but there is also much rock and ice. A variety of human activities and in particular forestry, hydroelectric developments, and hunting have had a significant impact on bears in this area. Range fragmentation is a concern along transportation corridors. There are several towns of between 5–20,000 people and access is extensive. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. Banff, Jasper, Glacier, and Mt. Revelstoke NPs are in this zone and although some very productive habitat occurs in these parks, as a whole, they are relatively poor for bears and support only about 250 of the estimated 2,540 brown bears in this zone.
Hot Dry Plateaus: For brown bears, this is a relatively unproductive zone and, when combined with extensive areas of human settlement, agriculture, forestry, mining, recreation, and extensive access, only about 140 brown bears remain. Most of these bears occur along the border of the Wet Temperate and Cool Moist Mountains. Range fragmentation is a serious concern. Cool Dry Mountains: This zone has some very productive brown bear habitat but poor habitat is also common. Human activities are varied and brown bears have been impacted by agriculture, forestry, mining, hunting, and recreation. There are numerous small communities, and several with more than 5,000 people. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. Access is widespread. Range fragmentation is a serious concern. There are an estimated 930 brown bears in this zone.
The total grizzly bear population on provincial lands in Alberta was estimated to be 841 in 2000 (Kansas 2002). In addition, about 175-185 bears are estimated to occur in Waterton Lakes, Banff, and Jasper National Parks for a province-wide total estimate of 1,016-1026 bears.
Alberta is the only jurisdiction to report an increase in grizzly bear population over the period covered by this status report update. The estimated absolute increase on provincial lands of 46.3% equates to an average annual increase of 3.9%. National Park totals remained essentially stable during this period. The 1990 estimate for Banff National Park of 75 bears (Nagy and Gunson 1990) is within the current estimated range of 60-80 bears (Gibeau et al. 1996; Herrero et al. 2001).
About 154,000 – 200,000 km² of provincial lands in Alberta are considered to be potential grizzly bear habitat (Nagy and Gunson 1990; Alberta Environmental Protection 1997). Although this is substantially reduced from historical levels (grizzlies formerly occupied virtually the entire province: 661,000 km²), this range reduction occurred primarily in the 1800s and early 1900s. Range contraction since 1990 has not been documented, although it may have occurred at local levels. Recolonization of historic ranges is suspected in some areas, especially the agricultural fringe along the eastern and northeastern boundaries of current distribution (H.D. Carr, pers. comm.).
Between 1981 and 1999, the numbers of males, females, and total bears in the Alberta grizzly harvest have declined (Table 7), most likely due to changes in management practices. Hunting regulations became increasingly restrictive over that period, including the implementation of limited-entry permits, closure of fall seasons, and prohibition of non-resident hunting. Annual numbers of bears killed by other man-caused means did not change, but the total of all recorded man-caused mortalities declined.
Grizzly bear distribution in southern Alberta consists of a strip along the Continental Divide, in places narrowing to 30 km. This is contiguous with grizzly habitat on the BC side of the Divide, but even so remains constricted. The risk of population fracture along this strip, combined with relatively high mortality and control-removals of grizzlies from the southwestern corner of the province as a result of livestock depredation (Gunson 1995; H.D. Carr, pers. commun.), dictate a particular need for cautious management in this area. A Population Viability Analysis (PVA) was conducted for the Central Rockies Ecosystem in Alberta and BC (Herrero et al. 2000). The model was based on assumptions for many input parameters, which were derived from science and which represented the best professional judgement of many of North America’s grizzly bear experts, but the reliability of the model’s predictions remains highly sensitive to even minor changes or errors in those assumptions. The model predicted that the grizzly bear population in that region is not presently secure. Increasing human population in the region was assumed (based on region-specific empirical data) to result in increased adult female grizzly mortality and/or decreased population fecundity. When projected increases in the human population were incorporated, the model predicted a rapid decline of the grizzly population. The model further predicted that goals of maintaining or increasing the population are unlikely to be met without strong mitigation efforts leading to a decrease in annual mortality. Consequently, even as the human population increases in the region, it will be essential to reduce human impacts on bears (Herrero et al. 2000).
The Yukon Territory-wide estimate in 2000 is 6,000 – 7,000 grizzly bears. The estimate of 6,300 reported by Banci (1991) is consistent with the current estimate and reflects changes in reporting precision rather than population size (J. Hechtel, pers. commun.). With local exceptions, the grizzly population in Yukon is considered to have remained stable since 1991.
Nearly all of the Yukon’s land mass (483,000 km²) is occupied by grizzly bears. No reduction in bear distribution has been documented in the Territory.
From the 1980s to the 1990s, the Yukon harvest of males, females, and all grizzly bears declined slightly. Other man-caused mortalities remained constant, but the total man-caused mortalities declined.
Direct comparisons of grizzly bear population estimates and evaluation of trends in the Northwest Territories are complicated by changes in jurisdictional boundaries. Nunavut was declared as a distinct territory on 1 April 1999, including a substantial land mass and a grizzly bear population. The bear population in Nunavut is considered later.
Additional land-claim agreements include the establishment of the Inuvialuit Settlement Region, the Gwich’in Settlement Area, and the Sahtu Settlement Area. The Government of the Northwest Territories continues to manage wildlife within these settlement areas, but does so co-operatively with a variety of agencies and land-claim organizations.
The total grizzly bear population for the Northwest Territories is estimated at about 5,100 (Gau and Veitch 1999; Table 6), within an area of about 641,000 km². After accounting for the removal of the bear population to what is now Nunavut, an increase is suggested since 1991. However, no data exist in support of either an increase or a decrease during that period. Official estimates of the grizzly bear population size had not been made previously. It is the opinion of regional wildlife managers that grizzly populations within the Northwest Territories have been essentially stable since 1991 (D. Cluff, J. Nagy, and A. Veitch, pers. commun.). There is no evidence of a change in distribution of the grizzly bear in the Northwest Territories since historic times (Schwartz et al. in press).
Prior to 1 April 1999, the grizzly bear population in Nunavut existed in the Northwest Territories. Currently, no official population estimate for Nunavut exists. Grizzly bears occur within 2 regions: Kitikmeot and Kivalliq (formerly Keewatin). Densities within either region have not been estimated. However, in an attempt to develop a reasonable guess as to the number of bears within Nunavut, I extrapolated from empirical data collected in the closest proximity, in consultation with regional wildlife managers. It must be stressed that this exercise was completed in order to provide a working guess of population size, in recognition of the fact that grizzly bears do exist in Nunavut. It does not indicate a familiarity with the grizzly bear population or its habitat within Nunavut.
Grizzly bear density in the Brock-Hornaday Rivers area, immediately west of the NWT/Kitikmeot boundary, was estimated at 6/1,000 km² (Nagy and Branigan 1998). In the Lac de Gras area (Central Arctic), spanning the North Slave/Kitikmeot boundary, the bear density was estimated at 3.5/1,000 km² (Penner and Associates 1998; P. McLoughlin, pers. commun.). I assumed a typical density of 4/1,000 km² and applied it to an arbitrarily-defined area of 200,000 km² in the northwestern corner of mainland Nunavut. This value is considered a reasonable guess for grizzly bear density across much of the Kitikmeot Region (B. Patterson, pers. commun.). The result was an estimate of 800 bears.
Grizzly bear densities in eastern mainland Nunavut are believed to be much lower, although no estimates exist (M. Campbell, pers. commun.; R. Mulders, pers. commun.). Consequently, I estimated a density of 1 bear/1,000 km² for an area of 200,000 km² extending west from the Hudson Bay coast, south from the Arctic Ocean coast, and north from the Manitoba border. This yielded an estimate of 200 bears, for a Nunavut total of 1,000 bears. Accounting for uncertainty in density and extent of distribution, an estimated population range of 800-2,000 bears is reasonable. Given the crude nature of these estimates, no assessment of population trend is possible. Local managers are aware of no major changes in grizzly populations in the Kitikmeot and Kivalliq regions over the past decade (B. Patterson, M. Campbell, pers. commun.).
Grizzly bears probably occupy most of mainland Nunavut (Figure 3). This distribution has likely not changed in historic times (Schwartz et al. in press).
Because of changes in jurisdictional boundaries, mortalities in Northwest Territories and Nunavut are considered jointly. Hunter kills, DLP kills, and total mortalities fluctuated over the reporting period.
McLellan, Bruce and Banci, Vivian. 1999. Status and management of the brown bear in Canada. Pages 46 --50 in C. Servheen, S. Herrero, and B. Peyton, comps. Bears: Status survey and conservation action Plan. lUCN/SSC Bear and Polar Bear Specialist Groups, lUCN, Gland, Switzerland, and Cambridge, UK.
Ross PI, 2002, Update COSEWIC status report on the grizzly bear Ursus arctos in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, 1-91pp.
Environmental, biological and anthropogenic effects on grizzly bear body size: temporal and spatial considerations
BMC Ecology 2013, 13:31 doi:10.1186/1472-6785-13-31 Scott E Nielsen (email@example.com)
Background Individual body growth is controlled in large part by the spatial and temporal heterogeneity of, and competition for, resources. Grizzly bears (Ursus arctosL.) are an excellent species for studying the effects of resource heterogeneity and maternal effects (i.e. silver spoon) on life history traits such as body size because their habitats are highly variable in space and time. Here, we evaluated influences on body size of grizzly bears in Alberta, Canada by testing six factors that accounted for spatial and temporal heterogeneity in environments during maternal, natal and ‘capture’ (recent) environments. After accounting for intrinsic biological factors (age, sex), we examined how body size, measured in mass, length, and body condition, was influenced by: (a) population density; (b) regional habitat productivity; (c) inter-annual variability in productivity (including silver spoon effects); (d) local habitat quality; (e) human footprint (disturbances); and (f) landscape change. Results We found sex and age explained the most variance in body mass, condition and length (R 2 from 0.48–0.64). Inter-annual variability in climate the year before and of birth (silver spoon effects) had detectable effects on the three-body size metrics (R 2 from 0.04–0.07); both maternal (year before birth) and natal (year of birth) effects of precipitation and temperature were related with body size. Local heterogeneity in habitat quality also explained variance in body mass and condition (R 2 from 0.01–0.08), while annual rate of landscape change explained additional variance in body length (R 2 = 0.03). Human footprint and population density had no observed effect on body size. Conclusions These results illustrated that body size patterns of grizzly bears, while largely affected by basic biological characteristics (age and sex), were also influenced by regional environmental gradients the year before, and of, the individual’s birth thus illustrating silver spoon effects. The magnitude of the silver spoon effects was on par with the influence of contemporary regional habitat productivity, which showed that both temporal and spatial influences explain in part body size patterns in grizzly bears. Because smaller bears were found in colder and less-productive environments, we hypothesize that warming global temperatures may positively affect body mass of interior bears, provided there is sufficient snow-cover during the denning periods.
Discussion Biological factors and body size Measurements of body mass and length of grizzly bears in Alberta were strongly dependent on intrinsic biological factors: age (positive, non-linear relationship) and sex (males > females). Age, sex and offspring dependence were important factors affecting body condition, which is a short-term measure of growth. Adult females, and especially adult females with cubs of the year, were likely to be in poorer condition than male bears. A negative effect of capture history (number of captures) was also observed for body condition measures which is consistent with previous observations . Although population density (density dependence) is known to inversely affect body-size patterns in animals [80-82], no density dependent effects on body size patterns of grizzly bears were observed in our study. Grizzly bear populations in Alberta are likely to be below carrying capacity given locally high rates of human-caused mortality [83,84], and were recently classified by the province as ‘threatened’ given the low observed population densities . This is in contrast to brown bears in Sweden that are considered healthy , but where body sizes of adult female bears are inversely related to population density . Temporal and spatial environmental heterogeneity Environmental heterogeneity is an important mechanism by which animal populations are regulated . Here, we found that regional heterogeneity in habitat productivity was a moderate predictor of body size patterns of grizzly bears in Alberta. The smallest bears by mass and length occurred in the least-productive and coldest environments as measured by alpine habitat use and home ranges occupying both cool average spring temperatures and high average March precipitation (snowfall). In the Canadian Rocky Mountains, all three of these factors are associated with late timing of spring snowmelt and plant emergence, which are known to affect population dynamics of other alpine mammals . Since den emergence in grizzly bears in our area typically occurs in April to early May , the amount and timing of spring snowpack is likely a factor affecting the availability of early season food resources such as roots , and generally might restrict access to early spring food resources. Inter-annual variations in climate during the years’ prior, duringand/or just following birth (maternal, in-uteroand natal environments, respectively) also affected adult body size. Such silver-spoon effects by which animals that are born into ‘rich’ conditions are favoured throughout life are consistent with observations in other mammals including polar bears , Soay sheep , red squirrels  and caribou . Common among these studies is the importance of winter and spring climate during (natal environments) or just prior (maternal or in uteroenvironments) to the year of birth, which we also observed in this study. Winter and spring climate is related to summer drought conditions in the Canadian Rocky Mountains , which suggests that the effect of winter and spring climate may not necessarily be directly associated with denning period, but affects summer environments where water is limiting. We are unsure, however, how late summer precipitation affects cubs-of-the-year. It may be related to late summer food resources, such as fruit production, or affect foodresource abundance in the following year when bears are yearlings. Further, winter precipitation (December-March) anomalies during the natal birth year were positively related to body mass. We interpreted this as snow cover during winter denning providing energetic benefits (e.g. insulation) in the den for cubs of the year. During the year prior to birth, late summer (July-August) temperature anomalies were negatively associated with body mass but positively associated with body length in grizzly bears. This late-summer environment might have directly affected maternal body condition prior to denning and thus subsequent condition of offspring [e.g. 53] or conversely, it may have affected the following years’ food supply during the cub-of-year period, since lag effects in fruit production are caused by weather conditions favourableto flower primordia in the mid-to-late summer period the year prior to fruiting . Although we cannot be certain which factor is more important, the fact that body mass is negatively associated with late- summer temperature anomalies, where as body length is positively associated with latesummer temperature anomalies suggests to us that maternal condition is less likely (as we would expect similar responses in body mass and length if it were solely a maternal effect). Further investigations of mid and late-summer weather on pulsing in food resource abundance the following year are needed, especially in regard to the apparent opposite effects on bear mass and length. One important consideration to our purported silver spoon effect should be discussed: that is, we have no information on our study animals prior to their first capture. This has two important implications: 1) we cannot account for litter size effects, and 2) the centroid data used to determine natal climatic conditions may not be reflective of the actual natal location. In regards to the former, not accounting for litter size should inflate the variance around our estimates. For the centroid data, this would likely only influence dispersing males, as females are philopatric . For males, average dispersal distances in the province are under 50 kilometers , thus still largely reflective of the climate in the centroid of the current home range (differences in climates among bears are mainly regional in effect, not within populations). Further, for this limitation to bias our results, males would consistently have to disperse to poorer environments, again something we deem unlikely. Thus, weargue that the silver spoon pattern is unlikely to be altered by these factorsin such away that the statistical pattern would disappear. Anthropogenic considerations Human footprint did not directly relate to body size patterns of grizzly bears, but human activity indirectly affected body size by influencing habitats. The two most important measures of habitat quality were canopy closure and the age structure of forests. Bears that used habitats associated with higher canopy variability, such as forest/non-forest landscapes in the mountains or expanses of old growth forests with a recent, single-harvestsequence, had lower body masses. Conversely, bears that used forests with highervariability in regenerating forest age had higher body condition. Likewise, body length was positively related to annual landscape change. Taken together, these results suggest that human activities that fragment forests are positively associated with body size measures, although survival of bears in these environments is compromised due to high rates of human-caused mortalities [57,84]. Early successional and highly variable forests are therefore important indicators of improved habitat quality for bears given the relationship to body size patterns reported here, habitat use studies  and measures of food resource abundance [73,74]. We hypothesize that positive associations between body size patterns and variability in regenerating forest age are due in part to local landscape patterns in protein availability. For instance, both ungulate and ant resource use in Alberta are associated with disturbed forests [46,74]. Conclusions While bear body size is largely dictated by age and sex, it still only accounted for little more than 50% of the variation. More consideration of the spatial and temporal patterns of resource availability, including the conditions early in life, is needed to better understand individual performance of animals and population dynamics. For grizzly bears in Alberta, environmental effects on body size are most affected by regional environmental gradients (space) and the environmental conditions animals are born into (time). Local-habitat heterogeneity (particularly young, patchily disturbed forests), and landscape dynamics also had a small influence on body size. It is important to emphasize that while patchily disturbed forests positively affected body size, these areas also have high rates of mortality, which could negate any positive population-level effect. Worldwide, relationships between carnivore body size and climate warming show ambiguous trends ; however, polar bears body sizes have recently declined, which has been attributed primarily to loss in habitat (i.e., sea ice as a platform for hunting; [96,97]). Despite unequivocal global patterns , a 50 year examination regional study showed that carnivore body sizes have generally increased over the past half century . Given the short season associated with high-alpine environments, such as the Rocky Mountains in Alberta, we hypothesize that individuals with a limited growing season and temperature-limited ecosystems, such as interior grizzly bears, might actually benefit from increases in season length associated with climate change. This prediction is largely consistent with observed body size and seasonality patterns in grizzly bears across North America , but is dependent on sufficient snow cover during the denning period. In conclusion, we have demonstrated a complex interplay of biological, spatial and temporal factors on body size that collectively explained between 60 and 84% of the variation seen in Alberta’s grizzly bears. www.biomedcentral.com/content/pdf/1472-6785-13-31.pdf Marc RL Cattet (firstname.lastname@example.org) John Boulanger (email@example.com) Jerome Cranston (firstname.lastname@example.org) Greg J McDermid (email@example.com) Aaron BA Shafer (firstname.lastname@example.org) Gordon B Stenhouse (email@example.com)