Group characteristics and spatial organization of the Eastern Beaufort Sea beluga whale (Delphinapterus leucas) population using aerial photographs

Abstract

While it is known that beluga whales ( Delphinapterus leucas (Pallas, 1776)) are social animals, sociality within populations remains complex and poorly understood. Using aerial photographs taken in mid-July and early August 2019, we examined group characteristics and spatial organization of the Eastern Beaufort Sea beluga population in two distinct summering areas: (1) the continental shelf and offshore region of the southeast Beaufort Sea and (2) the inshore of the Mackenzie Estuary. Observations revealed that the mean group size was similar in both environments. A piecewise regression analysis showed that belugas were found to be most frequently within 24.6 m of another beluga in the offshore and within 22.0 m in the inshore. The mean interindividual distance of groups composed of subadults and (or) adults was greater than that of groups including younger whales in both environments. Also, the swimming direction of individuals in a group differed less in the offshore than in the inshore. We suggest that habitat shapes the types of activity conducted and that spatial cohesion within groups persists across environmental conditions but changes with age composition. By identifying elements of social structure and important areas for Eastern Beaufort Sea belugas, our results highlight the value of habitat conservation.