Nonetheless, Zalophus is highly gregarious, the animals packing themselves tightly together even when empty space is available. On the California Channel Islands territorial behavior by adult males occurs from May to August and is especially intense in late June and early July. In contrast to some other otariids, male Zalophus do not establish territories until females, and some pups, are already present on the breeding beaches. Once territories are established, physical combat is reduced, and boundaries are maintained by ritualized displays such as oblique stares, head shaking, and lunging without making contact. Bulls patrol their areas on land and swim back and forth along the water side, barking incessantly.
Some territories are partly or mostly aquatic.
In the Channel Islands they generally are arranged one deep along the beach, have access to the water for cooling, are not separated by topographical features, and are about 10-15 meters wide. In a rocky area, territories were determined to average 130 sq meters in size. Male Zalophus hold their territories an average of only 27 days. Some territories are occupied by a succession of different males in the course of a breeding season, though sometimes the original owner may return to reclaim his space after an interval of feeding at sea. Males that are too young or too weak to win a territory form groups outside of the breeding zone, though occasionally one of these individuals attempts to slip into a territory and remain undetected.