The eastern part of the sea is a major habitat of beluga whales with an estimated population of 39,000. This population is stable and might even be increasing; it is not affected by the offshore oil exploration in the area. Belugas spend summer in the coastal area and Mackenzie River delta, which are free of ice then, and in winter migrate long distances to the polynyas of the deep sea. Genetic analyses have confirmed that belugas of the Beaufort Sea are clearly distinct from those of other Canadian and Alaskan waters, despite they often share a common wintering habitat.