Rates and causes of grizzly bear mortality in the interior mountains of British Columbia, Alberta, Montana, Washington, and Idaho

Trends of grizzly Lear (Ursus arctos) populations are most sensitive to fem ale survival; thus, understanding rates and causes of grizzly Lear mortalit y is critical for their conservation. Survival rates were estimated and cau ses of mortalities investigated for 388 grizzly bears radiocollared for res earch purposes in 13 study areas in the Rocky and Columbia mountains of Alb erta, British Columbia, Montana, Idaho, and Washington between 1975 and 199 7. People killed 77-85% of the 99 grizzly bears known or suspected to have died while they were radiocollared. In jurisdictions that permitted grizzly bear hunting, legal harvest accounted for 39-44% of the mortalities. Other major causes of mortality included control killing for being close to huma n habitation or property self-defense, and malicious killings. The mortalit y rate due to hunting was higher (P = 0.006) for males than females, and su badult males had a higher probability (P = 0.007.) of being killed as probl em animals than did adult males or females. Adult females had a higher (P = 0.009) mortality rate from natural causes than males. Annual survival rate s of subadult males (0.74-0.81) were less than other sex-age classes. Adult male survival rates varied between 0.84 and 0.89 in most areas. Survival o f females appeared highest (0.95-0.96) in 2 areas dominated by multiple-use land and were lower (0.91) in an area dominated by parks, although few bea rs were killed within park boundaries. Without radiotelemetry, management a gencies would have been unaware of about half (46-51%) of the deaths of rad iocollared grizzly bears. The importance of well-managed multiple-use land to grizzly bear conservation should be recognized, and land-use plans for t hese areas should ensure no human settlement and low levels of recreational activity.