Wolves are not hurting elk numbers in the Jackson area but are reducing cow-calf ratios in herds on the east side of the divide and in the region north of Pinedale, according to a report the state Game and Fish Department issued Monday.

The report finds wolves are affecting cow-calf ratios in four of eight elk herds where they are present, including the Gooseberry, Cody, Clark’s Fork and Upper Green River herds.

The report found that wolves were not significantly affecting ratios in the Jackson, Fall Creek, Piney and Wiggins Fork herds.

In the report, department biologists analyzed statewide elk population data, which the department has collected on an annual basis from 1980 through 2005. There are 35 herd units across the state and 21 of them had sufficient data for statistical analysis.

Wolf reintroduction began in 1995, when the federal government released 14 wolves in Yellowstone National Park. At the end of 2006, there were an estimated 36 packs in Wyoming, including 311 individual wolves.

“We have seen a downward trend [in cow-calf ratios] in many of Wyoming’s elk herds over this 26-year period,” Jay Lawson of the Game and Fish Department’s Wildlife Division said in a news release. “That trend is likely due to long-term drought and other habitat-related factors. But in half of the herds occupied by wolves, we saw a significantly greater rate of decline after wolves were established compared to herds without wolves. We can’t attribute that increased rate of decline to any factor other than wolves.”

Game and Fish biologists have set a minimum ratio of 25 calves per 100 cows in order to maintain hunting opportunities and have said there is “little opportunity for hunting” when the ratio falls below 20 calves per 100 cows.

The four elk herds in Wyoming that have wolves present and are experiencing declines have dropped below 25 calves per 100 cows, and two of those herds have fewer than 20 calves per 100 cows.

All four herds had declining ratios before wolves were present, but the rate of decline increased significantly after wolves came into the area.