SUMMARY OF GRIZZLY BEAR BIOLOGY 

 (modified from Mincher, B. J., 2000 and Schwartz et al., 2001) 



Grizzly bears in this area come in many sizes and colors. The most prevalent color has medium 

 to dark brown underfiir, brown legs, hump, and underparts, light to medium grizzling on the head 

 and part of the back, and a light-colored girth band or patch behind the forelegs. Other patterns 

 include (1) an overall gold or silver appearance and brown underparts, with an occasional dark 

 back stripe, (2) no distinct silver tipping giving a general black or brown appearance, or (3) 

 medium to dark brown underfur, rump, legs, and hump, with medium to heavily grizzled 

 forequarters and face. Subadults often appear multicolored with various shadings of red, blond, 

 brown, and great variation in silver tipping. Light-colored "yolks" on the chest and dark stripes 

 on the back are common. These patterns fade as the bear matures into one of the four patterns 

 described in adults. 



The size of male and female grizzly bears will vary substantially with males about 1.2-2.2 times 

 larger than females. Differences in body mass between males and females are influenced by age 

 at sexual maturity, samples from within the population, season of sampling, reproductive status, 

 and differential mortality. 



Body mass is dynamic in brown bears. During late summer and fall, brown bears gain weight 

 rapidly, primarily as fat when they feed intensively prior to denning. Because bears rely solely 

 on their stored energy reserves during hibernation, this predenning weight gain is essential for 

 reproduction and survival. Peak body mass generally occurs in fall just prior to hibernation. 

 Bears metabolize fat and muscle during the denning period. 



Habitat 



Brown bears are extremely adaptable and exploit a wide variety of habitats and foods throughout 

 their range indicating relatively broad environmental limits. Individual bears may exhibit 

 individual preferences and tolerances. Most key grizzly foods in the GYE occur seasonally and 

 somewhat unreliably. However, grizzly adaptability often compensates for the lack of some 

 forage thought to be critical. Such a generalized approach to survival necessitates a solitary and 

 mobile lifestyle. Individual grizzlies forage over vast areas and have large spatial requirements. 

 Because the active season for grizzlies is compressed to 5-7 months, during which bears must 

 gain sufficient weight to supply their energetic needs for the next denning cycle, they tend to 

 concentrate their activity seasonally in the most productive habitats available. 



In general, GYE home ranges are larger than those of other brown bear populations. This larger 

 range possibly indicates low environmental productivity in the GYE and increased foraging 

 requirements to meet their nutritional needs or it may be caused more by the wide distribution of 

 favorite foods at different times of the year. Individual ranges of both sexes overlap, but do not 

 appear to be defended, even for adult males. Subadult bears, especially males, disperse from 

 their natal ranges to establish new home ranges, and these spatial requirements probably limit 

 ultimate population density. 



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