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. Such entrapment can be fatal. If polar bears or native hunters do not find and kill the whales, they are likely to starve or suffocate. However, sometimes a shift in the wind direction or an early break-up allows the whales to escape.