Beluga whale distribution, migration, and behavior in a changing Pacific Arctic

Thesis (Ph.D.)--University of Washington, 2016-06

Sea ice is disappearing at unprecedented rates in the Pacific Arctic with potential impacts to ice-associated marine predators that migrate to this seasonally accessible and productive ecosystem. In this dissertation I used satellite telemetry data spanning 1993-2012 collected from two migratory populations of beluga whales (Delphinapterus leucas) in the Pacific Arctic (i.e., Eastern Chukchi Sea and Eastern Beaufort Sea populations) to investigate how loss of sea ice and changes in other environmental factors affect distribution, movement, and behavior. I quantified fidelity to summer areas, sexual segregation, and migration timing as well as variations in diving behavior among regions. These analyses illustrate that population-scale patterns of philopatry, migration, and foraging are mediated by the combined effects of seasonal sea ice and oceanographic fluctuations, prey distribution, and social interactions. I also addressed the question of whether belugas would adjust their distribution, migration, and behavior to shifting sea ice conditions and to what extent matrilineally-learned behavior might supersede environmental forcing through the development of resource selection functions. Results indicate that sea ice is a contributing factor but not sole determinant of beluga habitat preferences. One population (Eastern Chukchi Sea) exhibits delayed fall migration in response to later sea ice freeze-up. Changing environmental conditions also seem to favor deeper, longer dives for this population. There were few overall differences in preferred habitat selection during 1990-2014, and summer distribution appears to be governed by philopatry rather than ice conditions. These results correspond to a conclusion that Eastern Chukchi Sea belugas are responding to a changing Pacific Arctic environment through behavioral plasticity in migration timing and foraging behavior. In contrast, there were few examples where migration timing or sea ice associations of Eastern Beaufort Sea belugas changed between the 1990s and 2000s. Taken as a whole, these results suggest population-specific responses by belugas in the face of fluctuating sea ice conditions. Across the circumpolar Arctic, some beluga populations may be more likely than others to adapt and persist in a changing climate.