Wyoming Game and Fish has released a story claiming for the first time that they have data showing wolves are hurting elk cow:calf ratio.
Story in the Jackson Hole News and Guide.
Here is a link to the WY Game and Fish web site where you can find a link about the study. Unfortunately, it is a Word file, rather than an HTML or pdf file.
At any rate, the claim is that cow:calf ratios are down in 4 of the 8 elk herd areas occupied by wolves. There are 21 herd areas in total in Wyoming.
Update: OK the correct link the the report has been forwarded. Read it at: http://gf.state.wy.us/downloads/pdf/FinalElkCCRatios3-23-07.pdf.
There has been a general negative trend in cow/calf ratios throughout Wyoming since 1980, both in areas without wolves and with wolves. Of the eight herd units where wolves are present, 4 showed statistically significant changes in the slope of the regression line since wolves were reintroduced. In order of magnitude of change, most changed was the slope for the Cody herd (most change downward), then Gooseberry, Clarks Fork, and Green River. The four herds that did not show statistically significant changes in slope, post wolf, were Jackson, Fall Creek, Wiggins Fork and Piney herd (just southwest of Green River).
Three of the four herds with statistically significant changes are east and/or southeast of Yellowstone Park (one is south–Green River).
Clark’s Fork, and Jackson are the 2 herds that have had wolves for the longest period. In terms of numbers of wolves, the study did not have the data to calculate firm correlations (due to changes in packs size and location). However, it is clear to me that the area east of the Park has had a substantial and an increasing number of wolf packs, more so than other parts of Wyoming.
The study did not rule out competing hypothesis for the decline in cow/calf ratios, but I think the study lends support to the hypothesis that wolves are responsible for some of the decrease in elk recruitment.
I have to wonder why the Jackson herd did not show a statistically significant downward change in regression slope because it has had wolves packs for a long time, and the packs have been large.
There might be important other factors east of Yellowstone Park that affect cow/calf ratios of which I am not aware. If anyone is aware, please comment. Since the Dept. study performed analysis of variance, I wonder if there were any significant interaction terms?