Territorial Behavior

California sea lions do not have a stable social organization during the non-breeding seasons. Territorial behavior in sea lions seems to be strongly correlated to their mating behavior. When the breeding season begins, males establish breeding territories with the use of barking, chest-to-chest pushing, grappling, stares, bluff lunges, and biting. Once a male sea lion has established his territory he will defend it with different boundary displays. Males will often open their mouths and shake their heads from side to side to warn other males who may be trying to intrude. Size is a key factor when it comes to winning fights and defending established territory. The bigger the male, the more blubber he can store and the longer he can go without returning to the water for food. The male’s increase their chances of breeding when they have an established territory so the longer they stay on the rocks the better their chances are of reproducing. A male sea lion can only hold his territory for up to 29 days. The sea lions territories only exist when females are present. The females pay no attention to the male’s territories and move freely between them. Sea lions are highly social and usually only become aggressive during their mating season. California sea lions normally peacefully coexist with other marine mammals during the non- breeding seasons. When in the water sea lions often travel in small groups and when on land they often aggregate in protected areas near the shore. 

Young, J., & Gerber, L. (2008). The influence of social composition on reproductive behavior of territorial male California sea lions. Aquatic Mammals, 34(1), 102-108.

http://en.wikipedia.org/wiki/California_sea_lion
http://www.seaotter-sealion.org/stellersealion/factsssl.html