Sharp initially, these teeth eventually become badly worn, and many are lost by injury or infection. Experiments have shown them to be adept at echolocation, and judging by the variety of sounds they make, they are also highly communicative. Their sociable nature is manifest in the large size of herds, including up to several thousand individuals, that congregate in river mouths during summer. Most belugas migrate, but the distance covered varies greatly among stocks. For example, the Mackenzie Delta stock, estimated to number about 7,000, leaves its wintering grounds in the Bering Sea during late April to mid-June, heading north through Bering Strait and east along the north coast of Alaska.
Some animals travel in leads through the pack ice far offshore.
In contrast, the St. Lawrence belugas are relatively stationary. There is no evidence for a seasonal migration out of the Gulf through either Cabot Strait or the Strait of Belle Isle. Ice cover appears to be the decisive factor in the distribution of most white whale stocks. They quickly penetrate the cracks and leads formed in the rotting ice. Occasionally they miscalculate and are cut off from open water.