Assessment of the impact of polar bears on the grouping of pacific walruses at the Cape Vankarem rookery during the summer-autumn period in 2017–2021

Abstract

The aim of this work is to assess the impact of polar bears (Ursus maritimus Phipps, 1774) on the distribution, abundance, and migration activity of Pacific walrus (Odobenus rosmarus divergens Illiger, 1815) on the coastal rookery Cape Vankarem (Chukotka Autonomous District) during the period from August to October 2017–2021.Also, based on the analysis of data on the number of walruses and bears on the rookery and analysis of photographs, we tried to assess the physical condition of predators, the degree of their attachment to the rookery, i. e. to determine how the age and sex composition of the bear group at the rookery changes during the development of walrus migration activity on the Cape Vankarem rookery. It has been established that: along with anthropogenic influence, polar bears are one of the main factors scaring walruses on the Cape Vankarem coastal rookery; immature bears spend significantly more time at the rookery than adult females with pups or adult males; the physical condition of the majority of bears is good, but the adult males are more frequently below average in fatness; while in the rookery, no food and space competition for food resources was observed between bears.