JACKSON, Wyo.

Ten grizzly bear deaths have been documented in the Yellowstone ecosystem so far this year, a rate comparable to past years.

One other grizzly death is suspected. Of the 11 deaths, humans caused eight.

The count was seven at this time last year and 13 at this point in 2008.

Biologists keep close track of grizzly bear deaths because the Yellowstone population is classified as threatened under the Endangered Species Act.

Researchers consider the deaths of adult female grizzlies to be particularly important for the species. Two adult females have died this year, compared with one at this time last year.

Wildlife Biologist Mark Haroldson, with the Interagency Grizzly Bear Study Team, says the number of female deaths is not a worry so far.

“It’s a pretty normal spring,” Haroldson said this week.

By the end of last year, the count of all types of grizzlies that died reached 31.

Four grizzly deaths this year remain under investigation, according to the team. Three were in Wyoming and one in Montana.

Haroldson declined to comment on the deaths being investigated, consistent with team policy. Killing a grizzly can be illegal and bring criminal charges.

Four male bears — two adults, a yearling and a subadult — were removed from the population or died as a result of management actions.

One injured bear in poor condition died in a trap. One was killed for causing property damage and killing livestock. One was sent to a zoo after raiding a campsite in Yellowstone.

One was killed after fatally mauling a hiker shortly after its capture and release for research outside Cody on Yellowstone’s east border.