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Bear Anatomy
Bear Anatomy
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Bear Anatomy
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Just as I expected, Agriotherium's bite force is approximately 14.4 times its own weight, but even with this chart, I still have trouble believing that a polar bear has a lower bite than a brown bear at parity.
Consider that these bears might not be trying their fullest potential, as with many other bite force charts. 
@Polar , I believe these studies don't actually have any live specimen bite down. Its all from 3D modeling of a skull, which is taking skull element measures to estimate bite force. Here's the study.
http://www.nbcnews.com/id/40422298/ns/technology_and_science-science/t/polar-bear-skulls-cant-take-stress-biting/#.WDSVx9UrLC0
"Question: What kind of bear is best?" Jim once asked Dwight on the television show "The Office." Answer: The brown bear, at least in comparison to the polar bear, according to research published this month in the journal PLoS One. Polar bear (Ursus maritimus) skulls may put them at a disadvantage when competing with their close relative, the brown bear (Ursus arctos), concluded a team of researchers led by Graham Slater of UCLA. The researchers created computer simulations of polar and brown bear skulls to estimate their bite strength and the stresses put on the skull by biting. They found that polar bears skulls were less capable of withstanding the strain from chewing hard foods. Polar bears are the only completely carnivorous bears. Their skulls have adapted to a diet of mostly seal meat and blubber. This diet of soft food resulted in a weaker skull. They also lost the grinding molars that brown bears use to chew up plant matter. These changes make polar bears less capable of surviving in a rapidly warming arctic, according to the study. Brown bears eat everything from caribou to berries. Their skulls are built to withstand greater stress from chewing tougher food like grasses. Since 1996, grizzly bears, a subspecies of brown bear, have been observed moving further north, encroaching on the polar bear's habitat. Arctic sea ice is also disappearing, reducing the territory of the polar bear's seal prey. With increased competition and less food, the polar bear has become the poster child for extinction threats caused by climate change. Polar bears evolved rapidly from brown bears within the last million years. They may disappear even more quickly.
From days gone by in the stress-filled wild animal face-off debates of old; the topic of bite force was way over-played. The shape and size of the skull and jaws play a major part, along with muscle attachment, teeth, and diet of the animals involved. But, bite force plays only a minor role in any wild animal confrontation. I remember reading something about "rapid evolution" ( concerning the polar bear ), but I did not really grasp an understanding of what I was reading.
Also, after reading the actual study ( thanks to Tigerluver ), the Asian bear in the study is surprisingly an Asiatic black bear. My mistake. I am surprised at the Asian black bear's low number.
Great Bear Almanac by Gary Brown.
Bipedal Standing and Walking. Bears are plantigrade and capable of standing upright on their hind legs. They stand unaided to observe or increase sight distance, to fight, and to reach to feed, prey, or mark. Some species of bears are capable of walking bipedally, though this is not a normal means of locomotion. They do not attack in this position, though they may raise their upper body to better reach and grasp their prey or enemy. The American black bear, grizzly, polar, sloth, and sun bears walk bipedally, but only steps. The giant panda and the spectacled bears do not walk bipedally. The Asiatic black bear walks bipedally extremely well. "Asiatic black bears are very bipedal," according to Terry Domico in 'Bears of the World,' "and have been known to walk upright for over a quarter of a mile... on their hind legs," Circus, menagerie, and other performing bears walk bipedally, being trained to perform stunts and walk distances in this manner. *The fact that neither the giant panda nor the Andes bear can walk bipedally brings me to suspect that neither could the short-faced bears.
The Grizzly Bear - The Narrative of a Hunter-Naturalist by William H. Wright - published in 1909.
This book is dedicated with the respect, admiration, and affection of the author to the noblest wild animal of North America, the grizzly bear. These little animals hibernate, as do the grizzlies, but they turn in earlier; and in a region where they are found the bears take great delight in unearthing them, and sometimes will dig out carloads of earth and rocks to secure a small feast of the little fellows. This is the last food the grizzly obtains before he goes into his long winter sleep. The claws of the grizzly are well adapted for this peculiar sort of work; yet, long and strong as they are, so much of it does he have to do that, by the time he is ready to go into winter quarters, they are worn down to the quick, and not much, if any, longer than those of the black bear. After his long winter's sleep, however, when he emerges from his den in the spring, he is once more armed with strong curved claws, from four to six inches long. In those parts of the country where he does not have to hustle so hard for roots and ground squirrels - for instance, in some parts of Wyoming, central Idaho, and Montana - the grizzly does not wear his claws down so close. Yet he seems, on the whole, to attain a larger growth where he has to work most.
Apparently, even black bears can possess shoulder humps like grizzlies:
But I don't think it is so common as those of grizzlies in terms of bears with the feature, but this black bear population features it nonetheless. Also, from my research about this particular subspecies, they tend to have wider jaw gapes and larger skulls than the average black bear of similar weights: "The subspecies found on HG /QCI is generally larger than its mainland counterparts with a huge skull and molars, and is only found as a black colour phase. These physical differences are thought to result from retaining characteristics after a long period of isolation during the last ice-age." HAIDA GWAII BLACK BEAR (URSUS AMERICANUS CARLOTTAE SUBSPECIES) This might be the primary black bear population that has quite different shoulder characteristics from other black bears in general.
I don't know if @GrizzlyClaws can confirm this, but I think black bears (much like pandas) tend to have higher molar bite forces than brown or polar bears due to tense chewing of vegetation. The more omnivorous bears tend to have thicker tooth roots, and black bears may be subject to this rule more than brown bears. Brown bears, on average, are usually more carnivorous and tend to have thinner tooth roots, and so on for polar bears as well.
Bear metatarsals and paws also tend to have quite an impressive weight for their sizes, moreso than those of primates or even humans? Extremely dense extremity bones, perhaps?
Notice that the bear paws easily surpass the human hands in terms of bone density (whiter concentrations equal greater bone):
 (01-16-2017, 06:03 AM)Polar Wrote: I don't know if @GrizzlyClaws can confirm this, but I think black bears (much like pandas) tend to have higher molar bite forces than brown or polar bears due to tense chewing of vegetation. The more omnivorous bears tend to have thicker tooth roots, and black bears may be subject to this rule more than brown bears. Brown bears, on average, are usually more carnivorous and tend to have thinner tooth roots, and so on for polar bears as well. Not sure about the Black bear, since they also belong to the same genus with the Brown bear and Polar bear, and their skull is structurally less robust than that of the Giant Panda. As for the canine teeth, you are absolutely correct, the omnivorous bears do have bigger canine root and smaller canine crown, while it is the opposite for the carnivorous bears.
@GrizzlyClaws, however, black bears are still in the same genus Ursus as the brown and polar bears, and thus have a higher propensity of shoulder humps than other genuses of other bears. Bears maintain shoulder humps unlike other carnivores.
But bears do have an unusually heavier paw area than any other carnivore, for their size.
Bears are not digitigrade animals like cats, so they do have heavier paws for some quite obvious reason.
From the pictures ( post #22 ) perhaps these bears feed often on shell fish such as clams. Perhaps also they dig for other bear-delicacies such as choice roots or burrowing rodents. Since, as is suggested in your post, these bears have been in this same location since the Pleistocene, they may possibly have been developing similar attributes as the grizzly.
http://shaggygod.proboards.com/
Sylvie McKenzie said she was driving along a highway a few kilometres west of Jasper when she noticed two bears running along the road ahead.She said she slowed down to let the bears cross the road, but only the female bear did so. The second bear – a male – simply stopped and stared at her. McKenzie said she then started driving, putting her car between the two bears. Sylvie McKenzie Asked whether she has any advice for drivers caught in the same situation in the future, McKenzie had simple advice: 'Stop, turn around, wait for a few minutes and go back.' (CBC) "The male didn't like it at all, so he decided to take his feet, charge and hit my car with his two front paws," she said. "[He] just came and pounced on my car with full force and full speed." McKenzie said the car rocked violently when the bear hit it, giving her a close-up view of the bear’s face. "I could see his teeth, the drool on his face. I tried to speed up and put my foot on the gas pedal to get away as fast as I could." Later, she found grizzly prints all over the side of her car, along with two big dents and several scratches. It seem that carpal bone have a high resistance to mechanical deformation. Grizzly bear front paws are surprisingly heavy,maybe due to massive carpal bones? This is the most accurate description of the striking ability IMHO: "...The attack of a Bear is usually sudden and rapid, and he either tries to deal his opponent a blow with a forepaw by executing a rapid and violent movement to the side ,or he quickly trots up to his enemy ,suddenly lift himself on his hind-legs in the immediate proximity of his foe whom he tries to knock down with a violent stroke of the front-paw,or else he deals him a sound blow and gives him a quick bite..." |
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