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Post by grrraaahhh on Jul 14, 2011 11:03:56 GMT -9
Although the brown bear is an omnivore, some populations are more predatory than others. As the title of the thread reads, this thread examines (in general) the brown bear as a predator. For specific brown bear/prey relations please visit the 'INTERSPECIFIC RELATIONS & PREDATION' section. To be continued.
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Post by grrraaahhh on Jul 16, 2011 7:33:24 GMT -9
Bears as predators....
The size of a carnivore strongly influences the size of the prey it is capable of killing, the maximum size of prey killed being slightly larger than that of the predator. For example, a 100 kilogram (220 pound) bear can handle prey weighing up to roughly 150 kilograms (330 pounds). Polar bears prey primarily on the smallish (60 kilogram/ 130 pound) ringed seal and the larger (up to 360 kilogram/790 pound) bearded seal. In some instances, polar bears can remove up to 44 percent of the ringed seal pups born in a particular area. They are also known to kill walruses (500 kilograms/1,100 pounds) and white whales weighing up to 600 kilograms (1,320 pounds).
Brown bears, while primarily vegetarian, can also prey significantly on hoofed mammals. In some areas, adult males reportedly kill three or four adult moose (450 kilograms/990 pounds) per year, with females killing an average of one. Caribou (150 kilograms/330 pounds), musk ox (250 kilograms/550 pounds), elk (200 kilograms/ 440 pounds), and bison (500 kilograms/ 1,100 pounds) have all been taken. Brown bears also prey on ground squirrels, trout, and salmon, but usually only when they are sufficiently abundant to make hunting them energy-efficient.
ANDREW E. DEROCHER AND IAN STIRLING, Bears: Majestic Creatures of the Wild (1993).
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Post by grrraaahhh on Nov 3, 2011 11:44:20 GMT -9
Bears typically kill using brute force and do not seem to exhibit any stereotyped killing postures or behaviours as seen in canids and felids (R. Boertje, pers. comm.; J. Hechtel, pers. comm.). Polar bears and brown bears have been observed to attack their prey both with bites and crushing forepaw slaps, apparently to whatever region of the prey’s body is accessible (Murie, 1985; Boertje et al., 1988; Case & Stevenson, 1991; M. Ramsay, pers. comm; J. Hechtel, pers. comm.).
Sacco, T. and Van Valkenburgh, B. (2004), Ecomorphological indicators of feeding behaviour in the bears (Carnivora: Ursidae). Journal of Zoology, 263: 41–54.
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Post by grrraaahhh on Jan 9, 2012 17:07:53 GMT -9
Text Extract
The bears hunt for moose mostly in spring (seldom in autumn) when a strong frozen snow-crust has formed. Under such conditions, if a bear find fresh sign of moose, this animal is doomed. The brown bear is quite persistent and will continue to chase the moose many kilometers, tiring the moose as they break through this snow crust with each step. Eventually the bear will exhaust all of the victims’ remaining strength and then kills it with powerful fatal blows of the forefoot upon its backbone. During springs with long periods of snow crust condition, up to 10-15% of the moose stock may become victims of the predators in the Pinega reserve. The intelligent omnivorous The fact that the brown bear is omnivorous and its great “intellect” level are interconnected. Only such an animal is able to diversify its menu with the most accessible and high-calorie forages available at all times. As it is, this big predator is mostly vegetarian.
However, it should never be forgotten that first of all the bear is a predator. If humans begin to tempt it with other human-related food, the bear will agree, with pleasure and rapidly become habituated to humans and more of a danger. It is much better to keep certain distance between the bear and the humans because the predator is the predator always and everywhere.
Source: Alexander Rykov, Pasvik Strict Nature Reserve, Russia; Brown Bear, the omnivorous predator in Barents Watch (2008).
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Post by warsaw on Jan 10, 2012 15:00:41 GMT -9
Bears typically kill using brute force and do not seem to exhibit any stereotyped killing postures or behaviours as seen in canids and felids (R. Boertje, pers. comm.; J. Hechtel, pers. comm.). Polar bears and brown bears have been observed to attack their prey both with bites and crushing forepaw slaps, apparently to whatever region of the prey’s body is accessible (Murie, 1985; Boertje et al., 1988; Case & Stevenson, 1991; M. Ramsay, pers. comm; J. Hechtel, pers. comm.).Sacco, T. and Van Valkenburgh, B. (2004), Ecomorphological indicators of feeding behaviour in the bears (Carnivora: Ursidae). Journal of Zoology, 263: 41–54. Bears predation strategies and killing "techniques" are different. I'll write something about it later.
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Post by marksdorcel on Aug 30, 2012 8:01:09 GMT -9
Generally Bear are not much heuristic he become when he need to eat something or so much hungry. The white bear quite one but the brown one are very sensible and we have to care while going near to him.
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Post by Ursus arctos on Apr 10, 2013 16:55:05 GMT -9
Jacoby ME, Hildebrand GV, Servheen C, Schwartz CC, Arthur SM, Hanley TA, Robbins CT, Michener R. 1999. Trophic Relations of Brown and Black Bears in several Western North American Ecosystems. Journal of Wildlife Management 63: 921-929. EDIT: This forum doesn't seem to like photobucket. Not the first time I got this error message. It isn't info on predation, but info on dietary meat content of brown bears (and a little on black bears) based on isotope analysis. EDIT: I also use photobucket. Try shortening the image file name. I shorted the file name, and it appears to work. I had no idea that could be related to the problems. Also, a relevant quote from the article: The high dietary meat content estimated for historical brown bears in Colorado, New Mex- ico, and Arizona may be due to 1 or both of 2 reasons. First, these values must be viewed in the sociocultural context of the period (before 1930) when most bears were collected. This pe- riod was characterized by the lack of modern veterinary medicine (e.g., antibiotics, vaccines, mineral supplements) and droughts and floods that led to extensive livestock losses (Brown 1985). Although brown bears at this time were universally regarded as major livestock preda- tors and were killed by government hunters who donated skins or skulls to museums, these bears may equally have been consuming live- stock that died of natural causes. Stable isotopes cannot distinguish between carrion and live prey. A confounding factor that may have led to a shift toward livestock depredation was massive overgrazing, which depleted natural food re- sources (e.g., grasses, forbs, rodents) historically used by bears (Brown 1985, Abruzzi 1995).
The second potential reason is a technical problem that complicates the use of stable iso- topes in some ecosystems when a major differ- ence occurs between the signatures of the av- erage plant foods consumed by bears and the herbivore used to generate the baseline. For ex- ample, oak (Quercus spp.) mast was an impor- tant fall food for brown bears in many south- western ecosystems (Brown 1985). The nitro- gen isotope signature of Gambel's oak (Q. gam- belii) acorns (2.5%o) in Colorado and New Mexico would produce a bear signature of 7.0%o (as compared to 4.3%o used as the her- bivore baseline) if consumed as the sole diet (Hilderbrand et al. 1996:Fig. 3), which would dramatically reduce our dietary meat estimates. For example, if one assumed that one-third of the annual nourishment consumed by black bears in the Southwest sample came from acorns, the dietary meat estimate of 39% drops to 20%. The high dietary meat estimate (90%) for the Colorado 'Weisman" brown bear killed in 1979, although there was no suggestion of either livestock depredation or garbage avail- ability in the area where this adult female was killed (Peterson 1995), further suggests the di- etary meat content for southwestern bears was overestimated. This example indicates the need for caution in applying this technique.
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