When one sex is different to the
other, this is known as "sexual dimorphism". Seals
spend much of the year swimming through the seas fishing as they go, while they
may spend time with other seals, they do not form strong bonds with a partner to
rear their young.
When born, the
young are fed only on milk by the mother and soon learn to fish for themselves.
Birthing usually takes place on a beach with many other seals and the female
comes into oestrous (i.e. is ready to mate again) shortly after giving birth.
Because
of this life-style, many seals have evolved a strong sexual dimorphism. The
males arrive on the birthing beaches often before the females and fight to
establish and defend their territories. The most successful male, often known as
the "beachmaster" gets to mate with as many as a hundred females that
are in his territory.
Therefore there is
a great advantage to being big and strong, and if a male is not among the
biggest and strongest, he will not get to mate at all. This has led to a
pronounced sexual dimorphism. (difference in size and/or appearance between the
sexes)
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.
