WSU predation study flawed
by Cat Urbigkit, Pinedale Online!
October 4, 2017
The Washington Policy Center took a look at the Washington State University paper authored by Robert Wielgus that claimed that killing wolves increases the number of sheep and cattle that wolves depredate the following year.
The Washington Policy Center researchers found:
• The WSU study’s conclusions are based on erroneous statistical arguments, and are not supported by rigorous analysis of the study’s own data.
• Contrary to Wielgus’ conclusions, our re-analysis of his study’s data finds that the strongest explanation of an increase in loss of cattle and sheep was simply an increase in the wolf population.
• A University of Washington review of his data found a similar error in Wielgus’ analysis.
• Wielgus’ study also fails to replicate his hypothesis on an independent data set to ensure his finding is not merely an artifact of this data set.
• Wielgus’ claim that removing wolves increases the number of breeding pairs is also undermined by the data in his study.
• Data in Wielgus’ study actually support the current Washington state strategy of removing wolves where there is conflict with a rancher, consistent with the common-sense conclusion that removing wolves reduces livestock deaths.
The policy center researchers concluded:
"In such a politicized environment, it is important to ensure that science is sound and free of real or perceived political motives. The failure of the Wielgus study to consider, and rule out, the most obvious alternative explanation, is a serious weakness in the credibility of the study.
"The ironic result is that the data demonstrate a stronger case for the common-sense conclusion that more wolves leads to more livestock depredation than the case Wielgus wants to make."
Click on the link below to read the full Washington Policy Center report.