Optimal barbed wire height for brown bear hair sample collection

Abstract: Hair samples obtained from barbed wire can identify bears from DNA, assess trophic position from stable isotopes, and yield other data. For brown bears (Ursus arctos), a wire height of 50 cm has become standard protocol, but the efficacy of this height has not been evaluated. Here, we briefly review this protocol, and use data from wires across small streams in Alaska to calculate the probability that barbs at a given height obtained samples. We obtained 1,939 hair samples between 2012 and 2019 for an overall daily sampling success rate per barb of 1.55%. Samples were obtained over the range of barb heights (6–97.5 cm), but daily success rate varied from 0.2% at the lowest and highest barbs to 2% from 40 to 70 cm in height. Thus, 50 cm was an effective height and a wider range yielded similar success rates, though wire height may be selective for bears with respect to size and other traits.