hollow trees are also used. The availability of denning habitat is not thought to be limiting for 

 the GYE. 



Security at den sites appears to be an important management consideration, especially if human 

 disturbance occurs near the time of den entry. There has been some concern of the possible 

 effects of snowmobiles on denning bears. A study in northwestern Montana did not observe any 

 overt effects of snowmobiles within 2 km of dens. The greatest potential impact on bears was 

 during spring when females with cubs were still confined to the vicinity of the den, and also after 

 bears had moved to gentler terrain more suitable to use by snow machines. Predictable denning 

 chronology and the behavioral plasticity bears exhibit toward den and den site charactenstics 

 suggest potential human impacts to denning brown bears may be mitigated by careful 

 consideration when implementing strategies for human activity. 



Habitat for Security 



All current grizzly bear habitat in the continental United States is characterized by extensive 

 timber cover, and most day beds are found in timber. This implies that visual security is an 

 important habitat component, possibly as a ftmction of social pressure from other bears or 

 possibly in response to human pressure. 



It has long been speculated that female grizzlies with cubs avoid adult males due to their 

 aggressive and occasionally cannibalistic nature. The idea that males do not cannibalize their 

 own young has not been tested. 



In the GYE, the only indication of sexual segregation through habitat use is in years of poor pine 

 seed production where females were found more often near roads and areas used by humans. 



The IGBC considers the presence of even lightly used roads to cause a loss in useful bear habitat. 

 Roads are incorporated in cumulative effects models (CEM) of habitat quality. Probably the 

 most significant effect of roads in grizzly habitat is that of increased access by humans. Some 

 researchers have concluded that grizzly bears habituate to roads and human presence as required 

 to meet their caloric energy needs. However, this is a disadvantage for hunted populations. 

 Human presence can lead to grizzly bear moralities, whether due to legal hunting, if allowed, to 

 poaching, or to kills by humans for self-defense. 



In summary, grizzly habitat requirements are determined by large spatial needs for omnivorous 

 foraging, winter denning, aggressive behavior and security cover. Large roadless areas are ideal 

 as year round grizzly habitat. However, grizzly bears can and do survive in roaded areas if 

 tolerance for their presence is high. Home ranges must include a number of habitat types. 

 Habitat needs vary for individual bears depending on their age and sex. These requirements may 

 also vary annually with seasonal changes in foraging needs. 



Population Dynamics 



Grizzly bears are long-lived animals that range over large geographic areas. This trait makes it 

 difficult to census and assess population levels. Capture and marking of grizzlies is expensive 



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