Female core areas were larger during the late season relative to the early season. It is during this season 

 the bears fed extensively on the fruit of several shrubs to gain necessary fat reserves for denning. 



Early season core areas tend to be at mid- to high-elevation sites (temperate and sub-alpine zones) where 

 there are a higher density of avalanche chutes, and lower density of high-use roads and total roads. This 

 suggests that during the early season bears are concentrating their use in areas having minimum human 

 disturbance at a time when much of the higher elevation habitat is still covered with snow. 



Adult females are the most important cohort for population trend and overall health, therefore 

 considerations of the needs and sensitivities of adult females should guide management. Habitat 

 management emphasis in the NCDE is placed on protection of female grizzly bears, and it seems logical 

 that idenHfication of female core areas should receive high priority for habitat conservation. Seasonal core 

 areas of individual females overlap extensively, suggesting that contiguous blocks of core habitat meeting 

 the annual needs of females could be identified. 



Home ranges of grizzly bears in northwestern Montana overlap extensively on a yearly and lifetime 

 basis. However, bears typically utilize the same space at different times. Male home ranges overlap 

 several females to increase breeding potential, but males and females consort only during the brief period 

 of courtship and breeding. Adult male bears whose home ranges overlap seldom use the same habitat at 

 the same time to avoid conflict. 



There is movement of grizzly bears across the political border between the U.S. and Canada. Grizzly 

 bears captured south of the international boundary in the Yaak study area of northwest Montana and 

 northern Idaho were monitored crossing into Canada on an annual basis, and bears marked in the U.S. 

 and Canada in the NCDE have also crossed the border in both directions. 



Natality 



For grizzlies in western Montana, breeding occurs between May and July with cubs bom in the den the 

 following winter. The average litter size is two cubs (range 1-4). Reproductive intervals for females 

 average 3 years, and animals that lose young prior to or during the breeding season may come into estrus 

 and breed again that same year. Age when cubs are first produced is generally 5.5 for females (range 4-8 

 years). Offspring remain with the female 2-4 years before weaning. Grizzly bears are promiscuous. 

 Females can mate with multiple males and have a litter with offspring sired by different males. Males 

 can sire litters with multiple females in a breeding season. Male grizzly bears are sexually mature around 

 4.5 years of age but larger, dominant males may preclude young adult males from siring many offspring. 



The limited reproductive capacity of grizzly bears precludes any rapid increase in the population. Grizzly 

 bears have one of the lowest reproductive rates among terrestrial mammals, resulting primarily from the 

 late age of first reproduction, small average litter size, and the long interval between litters. 



Assuming initiation of breeding at 4.5 years, a female grizzly bear would add her first recruitment to the 

 populaHon when she was 5.5 years. The age of second breeding likely would not occur until she is 7.5. 

 Therefore, during the first 10 years of her life, a female grizzly bear is capable of adding only two litters to 

 the total population. If there are litters of two cubs with a 50:50 sex ratio, and a 50% survivorship of 

 young to age 5.5, at best she can replace herself with one breeding age female in the first decade of her 

 life. 



20 



