Factors Influencing the Efficacy of Forward-Looking Infrared in Polar Bear Den Detection

Female polar bears construct maternal dens in snowdrifts in autumn. Forward-looking infrared (FLIR) has been used to locate dens to prevent disruption of denning by human activities, but the results have been mixed. To identify limitations and optimal conditions for locating dens, we took handheld FLIR images of three artificial dens under varied conditions. We tested variables hypothesized to influence detectability with linear models using the zero-inflated negative binomial distribution. Solar radiation, wind speed, and den wall thickness reduced the likelihood of detecting dens. The negative effect of wind speed on detectability increased with increasing distance. To maximize the efficacy of ground-based FLIR, den surveys should be conducted when solar radiation is less than 16 watts per square meter (night) and when wind speed is less than 10 kilometers per hour. Adherence to these guidelines will maximize the protection that FLIR can afford to denning bears.