Often swim into bays and estuaries, and sometimes venture into rivers in northern California. In the water, harbor seals usually occur singly, in mother-pup pairs, or occasionally in small groups. Courtship and mating activities appear to take place in the water. Females usually give birth on land, often at low tide, although the newborn pups are able to swim immediately after birth. No information found regarding existence of aquatic territories.
Females appear to give birth every yr to a single pup.
Total gestation period is 11 mo, with a delay in implantation of 1.5 to 3 mo. Lactation lasts 4-6 wk. As top-level consumers in the kelp forest ecosystem, harbor seals play a role in enhancing diversity of organisms and overall productivity of the kelp forest. Harbour seal - Phoca vitulina and P. largha. Pages 1-27 in S. H. Ridgway and R. J. Harrison, eds.