The breeding season lasts from mid-December to March, and pups remain on the rookery for another month or so. Juveniles of both sexes and adult female elephant seals come ashore again to molt their hair and skin in late April and early May. Large males and a few juveniles come ashore for their annual molt in mid-summer, while yearling and some juvenile elephant seals are on land in autumn. Northern elephant seals make two migrations per year, and the sexes segregate while at sea. Females generally travel to foraging areas in the central Pacific, while males forage in waters in the Gulf of Alaska and south of the Aleutians.
Elephant seals are capable of diving to depths of nearly a mile.
They apparently forage mainly in waters over and beyond the continental shelf, and feed on a wide variety of prey, including squids, fishes, sharks and rays, lamprey, octopi, crustaceans, and tunicates. Harbor seals in the eastern North Pacific are found along the coastline from Mexico to the Aleutians. The North Pacific harbor seal population is estimated at 320,000 animals and is centered in Alaska. In southern California, harbor seals come ashore in greatest numbers on the Channel Islands, particularly the northern chain. Along the mainland, they occur primarily on secluded rocks and beaches.