The agency attributed the increasing numbers primarily to Idaho's growing wolf population. The number in Montana is up from 2004 but below 2003, and it is down in Wyoming, where illness and competition for food and territory in Yellowstone National Park seem to have hit the population hard.

Overall, the population is doing well and has grown since December, when an estimated 835 wolves roamed the region, Ed Bangs, U.S. Fish and Wildlife's wolf recovery coordinator in Helena, Mont., said Tuesday.

''But people who think wolves are just going to keep going, that's not true,'' Bangs said.

According to the mid-year estimates, used by wildlife officials to gauge where monitoring efforts need to be focused, there were 912 wolves in the three-state region - 166 in Montana, 221 in Wyoming and 525 in Idaho, which Bangs said offers by far the most and best wolf habitat in the region.

At the end of 2004, there were an estimated 153 wolves in Montana, 260 in Wyoming and 422 in Idaho, according to Fish and Wildlife.