The status of the fur seal population (Arctocephalus gazelle) on the southern border of the distribution area (the Argentine Islands archipelago)

Abstract

The study of the population status of Arctocephalus gazella (Peters, 1875) in waters of the Argentine Islands was carried out in the period from April 2015 to March 2016 in accordance with the objectives of the State Target Scientific and Technical Research Program of Ukraine in Antarctica for 2011–2020. The aim of the article is to study the population dynamics and distribution of the southern fur seal in waters of the Argentine Islands. Due to the lack of data on the specifics of the seal’s dispersal in different periods of the year and the dynamics of the species population at the southern border of the distribution range, the results of the research are relevant and of great importance. In the second half of the 20th century, some publications presented the results of monitoring of pinnipeds at the Argentine Islands and adjacent territories, but the objects of these studies usually were other seal species: Hydrurga leptonyx, Lobodon carcinophagus, Leptonychotes weddelli, and Mirounga leonina. In the early 21st century, monitoring of the fauna of the Argentine Islands was carried out by Ukrainian biologists. However, they focused on Leptonychotes weddelli and less on other species of pinnipeds. The field material was collected in waters of the Argentine Islands, which is located in the Pacific sector of Antarctica. The fur seal population census and distribution studies were conducted according to the generally accepted methods. After breeding season on the subantarctic islands, during the migration southwards, fur seals reach the Argentine Islands, usually in the third decade of January. In the summer of 2016, the first fur seal was recorded within the archipelago on 31 January. During the study period, the largest number of animals within the archipelago was recorded in March–April and it ranged from 300 to 400 individuals. On the islands of the archipelago, the main resting places of seals were identified. The movement of animals northwards starts in May, consequently a decrease in the number of animals in this region is observed at that time. The last individuals are recorded in the first half of August. In 2015, migration began in May and ended in early August. There are several periods that were characterized by intensive migration of the animals: late June, 5–8 July, and 29 July to 6 August. In winter, one individual was last found within the archipelago on 12 August. The migration is launched by the worsening of weather conditions, formation of a continuous ice cover, reduced availability of food, and other factors.