Beluga whales are born grey, and are white when mature. They grow to a maximum size of 5 metres, and 1,360 kilograms. Unlike other cetaceans the Beluga Whale has no dorsal fin, having a dorsal ridge instead, which is believed to make it easier to navigate under the ice-pack.
The most southerly range of the whales is the estuary of the St. Lawrence River. In more northern waters they are able to breathe by finding polynas -- stretches of open water that tear open in the ice-pack due to stresses as the pack travels.