As with other bear species and populations, male grizzly home ranges in the GYE are usually 

 larger than female ranges. The Interagency Grizzly Bear Study Team (IGBST) reported mean 

 range sizes from 1975-1987 of 874 km^ for adult males and 281 km^ for adult females. Females 

 with new cubs used slightly less area, and those with yearlings used more. 



As a group, bear species deviate from most other meat-eating members of the Camivora by the 

 volume and variety of vegetative foods in their diets. Comparing the three North American bear 

 species, feeding habits of brown bears fall somewhere between those of the largely herbivorous 

 black bear and the primarily carnivorous polar bears. Brown bears are opportunistic omnivores; 

 few taxa, from insects to vertebrates and fimgi to angiosperms, are overlooked as potential foods. 

 Evolutionarily, brown bears have developed several adaptations for herbivory, including 

 expansion of molar chewing surfaces and longer claws for digging. Nevertheless, they have 

 maintained an unspecialized digestive system capable of digesting protein with efficiency equal 

 to obligate carnivores. 



In the GYE, the pattern of seasonal elevation use is similar to that found for other populations 

 occupying interior western mountains. Grizzlies utilized carrion and rodents prior to spring 

 green-up, and foraged extensively on grasses, sedges and herbs in season, and berries, nuts and 

 fish in the post-growing season. The most widely used foods were grasses and sedges, which 

 constituted more than half of the diet. 



Long-term study of Yellowstone grizzly bear food habits revealed large year-to-year variations 

 in diet as grizzlies exploited foods that were only infrequently available. Examples of specialty 

 foods included ants, pondweed and sweet cicely. The early season diet was dominated by 

 ungulates, both scavenged and as neonate prey, notably elk calves, mid-season by grasses and 

 sedges, and late-season by pine seeds. The annual percentage of energy obtained from the 

 ungulate meat is considerably higher in the GYE than for other interior populations although 

 herbaceous foods remain important because they are more predictable. Grizzly bears at high 

 densities and in some circumstances can impact the ungulate prey base. However, in this area 

 the ungulate prey base is largely impacted by other factors such as winter severity. Also in this 

 area, an estimated 30-50 grizzly bears forage annually on spawning cutthroat trout in tributary 

 streams of Yellowstone Lake, a food source that may be jeopardized by the introduction of non- 

 native lake frout in the lake. Bear density in Yellowstone may be limited by lack of fleshy fruits 

 such as berries, making them more dependent than many other bear populations on unreliable 

 crops such as moths, pines seeds, and meat. 



Yellowstone area grizzlies preferred open grasslands adjacent to cover for most of their feeding 

 activities. While grizzlies depend on fertile grasslands for their predictable supply of forage, 

 seasonally abundant foods were exploited as available. These foods include whitebark pine 

 seeds and carrion. 



Pine seeds are especially important because they are available during the hyperphagic period 

 prior to denning. Many bears feed on pine seed exclusively at that time. Large amounts of cones 

 are obtained by raiding squirrel caches, which the bears exhume. After good production years, 

 seeds that survive the winter are also used the following spring. Whitebark pine seed is so 

 important that there is currently a relationship between the number of bears destroyed in control 



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