Weddell Seal (Leptonychotes wedelli) pup with mother

Weddell seals prefer to live on ice that is broken up somewhat, in this way there are often natural cracks and holes through the ice that they can use to get in and out of the sea. There are also holes and cracks around ice bergs that are trapped in sea-ice and often "tide-cracks" appear near when near land, all of these help. These holes are fine to begin with, but when temperatures are well below freezing, they begin to freeze up - quickly. The seals keep the holes open by rasping them with their teeth. They open their mouths wide and move their heads back and forward in a wide arc attacking the ice that is building up around the sides of the hole. This is a very fast and vigorous process that takes a lot of energy and a toll on the seals teeth. Keeping breathing holes open like this wears away the teeth of Weddell seals and it is this that means that the Weddells only live to about 18 years old, about half the life-span of a crabeater seal for instance.

Weddells can swim great distances across apparently continuous sea-ice by detecting the natural cracks and holes along the way. When covering distance rather than fishing, they only dive to a shallow depth and find the next breathing hole in the gloom under the ice by sonar - they emit a series of high pitched sounds and pick up the difference in sound when the sounds reach a hole.