ESTIMATION OF POPULATION DENSITY, AGE-GENDER STRUCTURE AND SEASONAL MORTALITY LEVEL OF PACIFIC WALRUSES ODOBENUS ROSMARUS DIVERGENS ON THE ROOKERY “CAPE VANCAREM” IN 2018

The research was based on our observations at the Pacific walrus rookery on Cape Vankarem (the Arctic coast of the Chukchi Sea) from August 6 to October 15, 2018. The number of the animals on the shore and in the water wеre estimated daily from images taken by a DJI Phantom 4 Pro Plus quadrocopter, and with the use of binoculars and panoramic images as well. Coastal mortality of the animals and age and gender composition of the group was also recorded and evaluated. In 2018 the animals had been arriving to the rookery a week later (August 6) than in 2017, but due to warm weather, the rookery functioned approximately 10 days longer (until October 26). The rookery worked during 90 days in 2018. In 2018, same as in 2017, the number of newborn pups in the period of mass migration of females with calves was 7.4%, what is rather high. The maximum number of walruses on the rookery (23 072 individuals, including the animals in the water), was observed on the 9th of October, what is about 10 thousand less than in the same time during the mass migration in 2017. In 2018 the number of dead animals at the rookery was approximately 350. The major part (72.6%) consisted of yearlings, including 64.7% of males and 35.3% of females. The part of adult animals (older than 6 years) was 21.1%, including 64.0% of females and 34.0% of males. The part of calves from 1 to 3 years was 5.7%. In 2018, similar to 2017, there were cases of miscarriage (13) observed on the rookery.

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