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Post by brobear on Jan 27, 2023 9:17:10 GMT -5
How brown and black bear body sizes compare across North America www.nps.gov/articles/000/bearbodies.htm When black and brown bears live together, does their body size differ due to competition? This was the main question we explored in a recent study. We compiled datasets of black and brown bear body sizes across North America, including co-occurring populations of both species as well as those where only one species was present (Figure 1). Then we analyzed how males and females differ in size (in both species), how bear sizes vary from north to south latitudes across the continent, and whether bear populations subject to harvest differed in body size compared to those that are protected. As expected, we found that males are bigger than females in both species, but brown bear males tend to be even bigger proportionally to females than black bears. Unexpectedly, black bears, in general, tend to be about the same size regardless of the latitude where they live, while brown bears are larger at mid-latitudes and smaller at the northern and southern extents of their range (Figure 2). We suspect that brown bears are bigger when there are more resources available to them and that the change in brown bear size is likely due to more salmon being available at mid-latitudes. While we did not detect a direct effect of competition between the two species, the fact that the body size of black bears does not change with latitude as it does for brown bears suggests that brown bears outcompete black bears for resources, such as salmon. We also did not see that harvest had an impact on body size at the population level but suspect that our ability to detect the differences across harvested and protected populations was limited due to having few protected populations in our data and not having an indicator of harvest pressure. We hope that clarifying large-scale physiological patterns of bear sizes may assist in understanding past, present, and future changes to realized niches in relation to environmental, ecological, and anthropogenic changes and subsequent resiliency of species and populations.
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Post by brobear on Jan 27, 2023 9:18:46 GMT -5
Body size plasticity in North American black and brown bears Abstract Body size reflects realized physiological niche width at the population level and provides insights into the potential resiliency of a species to natural and anthropogenic perturbations to ecosystems. We analyzed patterns of American black and brown bear body size through a meta‐analysis of data from 18 studies conducted across North America, to evaluate the effects of species, sex, latitude, sympatry, and harvest. We used a bootstrap model selection procedure, which accounted for differences in sample size and population variation between studies, to investigate patterns in body mass. As expected, we found that brown bears were generally larger than black bears and both species were sexually dimorphic (i.e., males were generally larger than females). Black bear body size was not related to latitude, whereas brown bear body size was greatest at intermediate latitudes, possibly due to the presence of salmon. Neither sympatry nor harvest was associated with body size for either species at the geographic scale of our meta‐analyses, but both may warrant consideration at the local scale. Body size, as an index of population health, reflects phenotypic plasticity within species and populations and may serve as a useful indicator of niche utilization. Indeed, understanding large‐scale physiological patterns such as these can assist in understanding past, present, and future changes to realized niches and subsequent resiliency of species and populations. Cameron, M. D., G. V. Hilderbrand, K. Joly, J. H. Schmidt, D. D. Gustine, L. S. Mangipane, B. Mangipane, and M. S. Sorum. 2020. Body size plasticity in North American black and brown bears. Ecosphere 11(8): e03235
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Post by brobear on Jan 27, 2023 9:19:36 GMT -5
A black bear (left) and brown bears (right). Black bear body size did not change across its range, but brown bears tended to be larger in the mid-latitudes of its range (where there is an abundance of salmon) and smaller at the northern and southern edges of its range. Black bear, Judy Joly; brown bears, NPS/Kyle Joly
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Post by brobear on Jan 27, 2023 11:05:47 GMT -5
Know the Difference www.bearsmart.com/about-bears/know-the-difference/#:~:text=Grizzlies%20have%20a%20concave%20or%20%E2%80%9Cdished%E2%80%9D%20facial%20profile%2C,is%20the%20least%20reliable%20characteristic%20for%20identifying%20bears. Despite apparent differences in size and colour, grizzly vs black bear are often difficult to tell apart. Why is this important? Every year, black bear hunters kill several grizzly bears by mistake, which can have dire consequences for local grizzly bear populations. It is also extremely important to know which species is which when you encounter a bear in your community or in the backcountry. Black bears can be black, blue-black, dark brown, brown, cinnamon and even white. Grizzlies, likewise, may range in colour, from black to blond. Although grizzly bears are, on average, significantly larger than black bears, size is not a good indicator of which species is which. Male black bears in Manitoba’s Riding Mountain National Park, for instance, can weigh up to 800 pounds in the fall, and female grizzly bears on Alberta’s Eastern Slopes can weigh as little as 250 pounds in the spring. The best indicators are the size of the shoulders, the profile of the face and the length of the claws. The grizzly bear has a pronounced shoulder hump, which the black bear lacks. Grizzlies have a concave or “dished” facial profile, smaller ears and much larger claws than the black bear. Black bears have a flatter, “Roman-nose” profile, larger ears, no visible shoulder hump and smaller claws.
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Post by brobear on Jan 27, 2023 11:07:21 GMT -5
Not all black bears are black and not all grizzlies are “grizzled” Despite the names grizzly and black, coat color is the least reliable characteristic for identifying bears. For instance, grizzlies may be pale—almost luminous blond, or reddish blond, light brown, darker brown, or almost black. To add to the confusion, the common name grizzly is derived from the term ”grizzled,” which refers to white-tipped hair. Grizzled hair occurs mainly on the back and shoulders; thus, from a distance, a grizzly bear appears to have darker legs and lighter upper parts. And to complicate matters just a bit more, black bears, despite their name, are not always black. They can also be brown, cinnamon, blond, or a combination of light and dark hair. Kermode/Spirit/Ghost bears, found in Northwestern BC, Canada, can be white. Pictured: various grizzly bear colorations.
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Post by brobear on Jan 27, 2023 11:11:17 GMT -5
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Post by brobear on Jan 27, 2023 11:13:25 GMT -5
Just like hair color, body size is unreliable for identification Just like color, body size is also not a reliable indicator for identifying bears. Most people tend to overestimate the weight and size of bears. A typical adult female grizzly weighs 200-350 pounds and adult males weigh 300-650 pounds. An adult black bear, which can easily weigh 200-300 pounds, may not only weigh the same as a female grizzly but also be about the same height (3–3½ feet at the shoulder). Then too, an adult male black bear will be much heavier and taller than a young grizzly. And just in case it isn’t difficult enough yet, try to imagine yourself distinguishing a juvenile dark-haired grizzly from an adult cinnamon-colored black bear in the dim light of an early morning or the long dusky shadows of an early fall evening. Even under the best of conditions you’ll find it’s nearly impossible to judge the size and weight of a bear in the wild. Other characteristics such as diet, behavior, and habitat use are even less reliable because black bears and grizzly eat similar food, display similar behaviors, and occupy much of the same areas in some provinces and states.
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Post by brobear on Jan 27, 2023 11:14:13 GMT -5
young grizzly bears are tough to ID; this grizzly is much smaller than an adult black bear.
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Post by brobear on Jan 27, 2023 11:15:05 GMT -5
sub-adult (adolescent) grizzly bear who is smaller than most adult black bears.
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Post by brobear on Jan 27, 2023 11:16:38 GMT -5
large black bear who is bigger than many grizzlies, especially females and younger ones.
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Post by brobear on Jan 27, 2023 11:17:27 GMT -5
very heavy black bear larger than many grizzlies.
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Post by brobear on Jan 27, 2023 11:18:44 GMT -5
Shoulder hump Grizzly bears have well-developed shoulder muscles for digging and turning over rocks. These muscles appear as a prominent shoulder hump between the front shoulders, which is visible in profile. Black bears have no shoulder hump. A black bear’s highest point, when it’s on all fours, is the middle of the back or the rear, depending on how the bear is standing.
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Post by brobear on Jan 27, 2023 11:19:12 GMT -5
grizzly bear – shoulder hump = highest point.
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Post by brobear on Jan 27, 2023 11:20:40 GMT -5
grizzly bear – hump not as prominent, but still highest point on body.
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Post by brobear on Jan 27, 2023 11:21:28 GMT -5
black bear – no shoulder hump; wind is blowing up shoulder fur.
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Post by brobear on Jan 27, 2023 11:22:15 GMT -5
black bear – because the bear is standing on a slope the rump doesn’t necessarly look like the highest point, but there is no shoulder hump.
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Post by brobear on Jan 27, 2023 11:23:03 GMT -5
Facial profile
A grizzly typically has a concave or dishshaped profile that extends from between its eyes to the end of its nose. A black bear normally has a fairly straight profile from forehead to nose tip. A grizzly’s muzzle is broader and more prominent; their eyes appear closer together and deeper set. Black bears look more dog-like and have flatter, shorter fur. Grizzlies appear to have longer, fuzzier looking fur, especially on the face.
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Post by brobear on Jan 27, 2023 11:24:11 GMT -5
grizzly bear – prominent snout with blunt tip and deep set eyes.
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Post by brobear on Jan 27, 2023 11:24:46 GMT -5
grizzly bear – dishshaped side profile.
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Post by brobear on Jan 27, 2023 11:25:41 GMT -5
black bear – eyes set further apart, less prominent snout.
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