Social organization of belugas Delphinapterus leucas summering off the Solovetsky Islands (the White Sea, Russia) based on photo-identification data: Identifying social clusters

Belugas are gregarious and form different types of social groups, which may include both related and unrelated individuals. Apart from mother–calf dyads, there is almost no information about individual associations in beluga groups. Using photo-identification data, we investigated the social organization of belugas summering off the Solovetsky Islands in the White Sea, Russia, based on sightings of 122 individuals in a reproductive gathering off Cape Beluzhy, Solovetsky Island, in July – August 2022. Data analysis was carried out using the program SOCPROG 2.9. We have not found any social clusters with stable individual composition within the gathering. Nevertheless, some pairs of individuals, which usually included a female, had high association indices. In general, association indices in pairs decreased during the study period. These results could be influenced not only by the nature of social relationships among belugas, but also by the individual variance of visiting patterns to the area of the gathering. These factors cannot be differentiated within the framework of the current study. Associations of individuals outside the study area, as well as beyond the study period, remain unknown.