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There is a significant difference
in size between the males and the females (known as sexual
dimorphism), this male can be recognised by the bump on his head,
but most easily by the fact that he is so much larger than the
females, all the large Sea Lions you will see will be males.
The size difference is due to the
breeding behaviour, whereby males compete with each other for access
to females at breeding time and don't have any further part in
bringing up the pups. A "Harem" system operates, with the largest
and dominant bull being referred to as "beachmaster". He will defend
an area of a beach from all other males and will be the only one who
mates with them, there may be just a few females in the harem or up
to 30 or more. Such breeding behaviour leads to the largest males
becoming the most dominant and fathering all the pups. An individual
male may not be able to mate for several years after becoming
sexually mature while he builds up size and strength, he may only be
able to have a single season where he is big and strong enough to be
beachmaster, but it may be enough to ensure that he successfully
fathers enough pups to survive and carry his genes on. |
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