Estimation of the population density, age and sexual structure, seasonal mortality level of the pacific walruses on the Vancarem Cape rookery in 2020

Abstract

The work was based on our observations made at the Pacific walrus rookery on Cape Vankarem in 2020 (the Arctic coast of the Chukchi Sea) from August 10 to September 21. In 2020, the rookery began to fill up two weeks later (August 20) than usual, but the rate of filling the rookery, the number of animals in the rookery and the coastal mortality in the current year was much higher compared to the previous periods of observation (since the early 2000s, when animals began to come regularly to this cape in mass numbers). In the current year, the number of newborn pups in the period of mass migration of females with calves was 10,7%, which is rather high. The maximum number of animals in the rookery was on September 9-42,855 walruses (with animals in the water), which is about 20 thousand more than in the same period of mass migration in 2018, and 10 thousand more than in 2019. In 2020, the registered coastal mortality in the rookery was approximately 555 individuals. Since the rookery continued to function after our departure, and some areas occupied by animals had not been surveyed, the total mortality rate might be 700 walruses and higher. Yearling pups (85,7%) constituted a major part of the dead animals: of them the males accounted for 59,7% and females 40,3%. The proportion of adult animals (over 6 years old) among the dead was 6,5%, of which females were 88,8% and males 11,1%. The proportion of young animals from 1 to 3 years old was 6,4%.