Arctic Marine Mammals

Abstract

This chapter explores the Arctic marine mammals, specifically bears, pinnipeds, cetaceans, and fresh water seals. The Arctic seas are those in which unmixed polar water from the upper layers of the Arctic Ocean appears in the upper 200–300 m. A large portion of this zone is ice covered throughout the year. Most species of the so-called Arctic marine mammals are associated with the seasonal ice during the breeding period. They cope with the annual expansion and contraction of the ice cover in a variety of different species-specific ways. Clearly, there are many kinds of ice-dominated habitats formed in response to factors such as regional climate, weather, latitude, currents, tides, winds, land masses, proximity of open seas, and others. There are great differences in how marine mammals exploit ice-dominated environments. Polar bears (Ursus maritimus) are the most recent arrivals in the high-latitude northern seas, having evolved directly from brown bears (U. arctos). They utilize relatively stable ice as a sort of terra infirma on which to roam, hunt, den, and rest. Like their contemporary terrestrial cousins, they are generally not faced with the problem of ice being a major barrier through which they must surface to breathe. Cetaceans are at the other extreme. They live their entire lives in the water and have limited (though differing) abilities to make breathing holes through ice and are therefore constrained to exist where natural openings or thin ice are present. Pinnipeds spend most of their time in the water, but they must haul out to bear their young. Most of them also haul out on ice to suckle their young, to molt, and to rest.