Forecasting cattle depredation risk by recolonizing gray wolves

1 May 2018

Hanley, Zoe; Cooley, Hilary; Maletzke, Benjamin; Wielgus, Robert

Minimizing wolf-livestock conflicts requires identifying conditions placing livestock at risk and focusing adaptive management at a local scale. Gray wolves (Canis lupus) began recolonizing Washington in 2008. We used generalized linear mixed models to investigate characteristics of wolf pack territories in Idaho and Montana from 1991 – 2008 (n = 137) and predict cattle (Bos taurus) depredation risk for current and probable wolf-occupied areas in Washington. Cattle depredation risk increased with cattle abundance and if the pack depredated cattle the previous year. When models were applied to wolf pack territories in Washington from 2008 – 2016 (n = 43), 3 of 7 (43%) depredating pack territory/years were predicted at ≥61% depredation risk. During the summer grazing season (May 1 – October 31) when most cattle depredations (97%; n = 34) occurred in Washington, cattle east of the Cascade Mountains were often on grazing allotments whereas cattle west of the Cascade Mountains were located on small, private farms. Thus, relative cattle abundance per grazing allotment and county likely represented cattle depredation risk east and west of the Cascade Mountains, respectively. County-wide and allotment cattle abundance forecasted 10.3% and 1.4% of probable wolf-occupied areas at ≥61% cattle depredation risk, respectively. These risk models and maps provide locations for federal and state wildlife managers to focus depredation prevention measures and a template for future analyses as wolves continue to recolonize Washington.

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