Bear deaths high Researchers say human-caused grizzly-bear deaths have taken a toll in the Greater Yellowstone Ecosystem this year, despite estimates that the overall population continues to grow. Interagency Grizzly Bear Study Team officials estimate that 39 grizzly bears have died in 2008. Seventeen of those deaths involved hunting incidents, six where the result of natural causes and four had unknown causes. The remainder of the deaths were some form of human-caused death, including management removals of problem bears. Male grizzly bears have already surpassed a 15 percent mortality threshold that, if observed for three consecutive years, would prompt a management review by state agencies. That review could result in grizzlies being placed back under Endangered Species Act protection. If another female grizzly is shot by a hunter, female mortalities would pass a 9 percent threshold that would trigger a similar review after two consecutive years. Those thresholds were last surpassed in 2000. When a person other than a wildlife manager reports a grizzly bear death, researchers count it as three toward the thresholds because roughly two-thirds of citizen-caused grizzly deaths go unreported, said study team leader and U.S. Geological Survey researcher Chuck Schwartz....