Galápagos Sea Lion - Behavior and Male Competition

Behavior and Male Competition

Galápagos sea lions are especially vulnerable to human activity. Their inquisitive and social nature makes them more likely to approach areas inhabited by humans, and thus come into contact with human waste, fishing nets, and hooks. They occupy many different shoreline types, from steep, rocky cliff sides to low-lying sandy beaches. To avoid overheating during the day, sea lions will take refuge from the sun under vegetation, rocks, and cliffs.

Not only are sea lions social, they are also quite vocal. Adult males often bark in long, loud and distinctive repeated sequences. Females and juveniles do not produce this repetitive bark, but both sexes and the younger pups will growl. From birth, a mother sea lion recognizes her pup’s distinct bark and can pinpoint it from a crowd of 30 or more barking sea lions.

On land, sea lions form colonies at their hauling-out areas. Adult males, bulls, are the head of the colony, growing up to 7 ft (2;m) long and weighing up to 800lb. As males grow larger, they fight to win dominance of a harem of between five and 25 cows, and the surrounding territory. Swimming from border to border of his colony, the dominant bull jealously defends his coastline against all other adult males. While patrolling his area, he frequently rears his head out of the water and barks, as an indication of his territorial ownership.

The average dominant bull holds his territory for only a few months, until he is challenged by another male. On land, these fights start by two bulls stretching out their necks and barking in attempt to test each other’s bravery. If this is not enough to scare the opponent off, they begin pushing each other and biting around the neck area. If males were not equipped with thick, muscular necks, their vital organs would be easily damaged during these fights. Blood is often drawn, however, and many male sea lions have battle scars due to these territorial competitions. Losers are dramatically chased far from their territory by the new dominant bull with much splashing.

Because there is only one male in each harem, there is always a surplus of “bachelor” male sea lions. They usually congregate fairly peaceably on less favorable areas of the coastline in “bachelor colonies”. One of the most commonly known is atop the cliffs of the South Plaza Island of the Galápagos chain. Because the dominant male of the harem cannot feed while defending his colony, he eventually becomes too tired and weak, and is overpowered by a well-nourished, fresh bull.

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