The females tend to live longer than the males - up to 35 years old, as against 25 years for the male. The Common Seal is the smaller of the two species, and is sometimes known as the Harbour Seal. Adult males weigh up to 115kg and females 80kg. As with the Grey, the female will tend to live longer - 25 years compared to 20 years for the male. Both species can dive for over 20 minutes when required., but seldom dive for more than a few minutes at a time.
Most seals spend a considerable part of their day on land, usually fast asleep.
However, they do not need to come ashore and can survive and sleep in the sea for as long as necessary. They sleep upright with just their heads out of the water and this is called 'bottling'. The timing of births is also a major difference between the two species. The pups at birth weigh approx. I I kg and are ready to swim once the tide comes in and covers the sand bank.