Bear Size ~

[brotherbear]

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In Hudson Bay, the mean scale weight of 94 males >5 years of age was 489 kg. The largest bear in that group was a 13-year-old, which weighed 654 kg (Kolenosky et al. 1992). The heaviest bear we have weighed in Alaska was 610 kg, and several animals were heavy enough that we could not raise them with our helicopter or weighing tripod. Some animals too heavy to lift have been estimated to weigh 800 kg (DeMaster and Stirling 1981). Females are smaller, with peak weights usually not exceeding 400 kg. Total lengths of males in the Beaufort Sea of Alaska ranged up to 285 cm. Such an animal may reach nearly 4 m when standing on its hind legs and is 1.7 m shoulder height when standing on all four legs. Chest girth for large males is close to 200 cm. Although smaller, females in the Beaufort sea were as long as 247 cm with chest girths up to 175 cm. Only prehistoric polar bears and the giant short-faced bear (Arctodus spp.) of the Pleistocene were of greater stature than today's polar bears (Kurten 1964; Stirling and Derocher 1990).

Manning (1971) suggested there is a cline in size of polar bears across the Arctic. Size increases, he suggested, with distance from east Greenland across the Nearctic to the Chukchi Sea between Alaska and Russia. Manning (1971) also suggested that polar bears from Svalbard may be larger than those from east Greenland. A cline in size across the Palearctic also might occur, but samples from the Russian Arctic are inadequate to confirm it (Manning 1971).

The hypothesized cline was based on measurements made from skulls housed in museums around the world. Unfortunately, the sources of skulls in the various collections were not similar. Of particular note was that many of the skulls originating in the Chukchi Sea may have been donated by trophy hunters. These hunters worked over the ice in teams of aircraft (Tovey and Scott 1957) and were quite effective in killing a great number of the largest polar bears (Amstrup et al. 1986). Another potential problem is that ages of bears in the sample were estimated only by class or life stage. Hence, older bears from one locale might have been compared to younger bears (of the same age class) in another.

Potentially non standardized collection methods prevent any meaningful conclusions about relative sizes of polar bears from different locales. Also, if there is a cline in skull sizes around the world, it appears that body sizes and weights of polar bears do not follow a similar cline. The largest bears for which actual scale weights are known have come from the Hudson and James Bay areas of Canada and from the Beaufort Sea of Alaska, not from the Chukchi Sea. That observation, too, may be subject to some bias, as the most prolonged and intensive polar bear studies have been conducted in Hudson Bay and the Beaufort Sea. Greater numbers of captures in those locations may have increased the probability that very large bears were included in the sample. 
 
Here is the problem. A polar bear was weighed in at 610 kg ( 1,345 pounds ) and another at 654 kg ( 1,442 pounds ). These two huge bear weights are confirmed. Those bears too heavy to be weighed have estimated weights, thus unconfirmed. Again, I am not arguing that a polar bear can outweigh a brown bear.  Reply