The Interagency Grizzly Bear Committee says the total number of grizzly bears in the Yellowstone ecosystem will never be accurately known because of the difficulty in counting bears in the 9,600 square miles of rugged land.

At the request of the committee, the status of the Yellowstone ecosystem grizzly bear population was reviewed by a special task force of agency and non-agency scientists."The results show that there are at least 45 adult female grizzly bears alive in the ecosystem as of 1985," the committee said in a statement Friday. "This compares to a minimum of 32 adult females known to be alive in 1983. This increase is partially a result of grizzly bear management programs directed by the interagency grizzly bear recovery program."

The report said the rugged territory in the ecosystem, the area in and around Yellowstone National Park in Wyoming, Montana and Idaho, makes accurate counts of bears difficult.

"However, based on 45 adult females, the population review task force was able to estimate that the minimum number of grizzlies alive in the ecosystem in 1985 was between 170-180," the report said.

The task force estimates the population is increasing at a rate of .07 to 1.5 percent a year. This marks the first time the Yellowstone grizzly bear population has been shown to be increasing since 1975, when the grizzly was declared a threatened species in the lower 48 states and protected under the Endangered Species Act.

The committee has been directing intensive management and research since 1983.

The report did not explain why the 1985 figures were the most recent figures used, and members of the committee were not available Friday.