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.
Photo; © Paul Ward - Pentax equipment,
100mm lens, 35mm film, K64.
This picture may not be copied or
used in any manner without prior written permission.