Alternative methods for monitoring polar bears in the North American arctic

Abstract

Because polar bears (Ursus maritimus) are dependent on sea ice, climate change poses a significant threat to their long-term existence. The forecasted impacts of sea ice loss are circumpolar, but to date, effects have been documented in only a few, well-studied populations. Data demonstrating the impacts of climate change are less conclusive or simply lacking elsewhere. In general, current inventory regimes do not enable monitoring with enough regularity to meet the information needs of decision-makers. This reality, combined with pressures from northern communities to reform invasive research techniques (i.e., capture and marking), provided the backdrop for my dissertation. My objective was to implement and evaluate novel, efficient and broadly applicable methods for monitoring polar bears. I first conducted comprehensive aerial (helicopter) surveys of the Foxe Basin population in Nunavut, Canada during the summer, ice-free season. This work demonstrated the utility of the method for estimating the abundance of polar bear populations on land and provided a model for applications in other seasonally ice-free populations. I applied this framework to a neighboring population (Western Hudson Bay) and compared the result to an estimate obtained from physical mark-recapture. This comparison suggested negative bias in the mark-recapture estimate due to spatially limited sampling and resultant capture heterogeneity. Next, I assessed the potential for employing aerial surveys on sea ice in springtime. Although results suggest that detection can be estimated with adequate precision, logistical constraints may hinder the ability to obtain a representative density estimate during springtime. Monitoring programs based on aerial surveys can be designed with sufficient power (>0.8) to detect declines of 40% and 50% over 15- and 30-year periods, with costs comparable to mark-recapture. Costs may be significantly diminished and safety concerns alleviated, however, if bears could be monitored with satellite imagery. I evaluated this technique in a low topography, ice-free setting. Results indicate that bears were reliably identified on imagery, and an estimate of abundance was highly consistent with an independent aerial survey.