CALIFORNIA SEA LION Zalophus californianus Scientific name refers to “crest” on head and California.
PHYSICAL DESCRIPTION California sea lions can reach a size of up to 8 feet long and 850 lbs. Females are significantly smaller, reaching 6.5 ft long and up to 210 lbs. Sea lions have sleek torpedo-like bodies and are powerful, graceful and acrobatic swimmers. Adult males grow a large bump of bone on the top of their heads as they reach sexual maturity. Females do not exhibit this sagital crest, having lower and smaller foreheads. California sea lions have long, dog-like muzzles. They are a light to golden brown color though the coat darkens when wet. As adult males age, their heads become light tan. Adult females are a lighter golden color. Sea lions molt (shed their hair) every year.
California sea lions have large, wing-like foreflippers and use their hind flippers for locomotion on land as well. Unlike true seals they are quite adept at movement onshore. They have no claws on their foreflippers. but use their nails on the back flippers for grooming their coats. They have a short tail. Unlike harbor seals and other "true seals", sea lions have external ear flaps (see photo below).
RANGE AND HABITAT The California sea lion resides along the Pacific Coast mainly in the waters of central Mexico and California where they breed, but in non-breeding season can be found as far north as Vancouver Island, Canada. These highly intelligent and social mammals breed in large colonies on offshore island rookeries such as California’s Channel Islands. Once the breeding season is over, they will often gather at marinas and wharves and may even be seen on navigational buoys, seeking safe environments from their only natural predators, orcas and white sharks or just to rest and warm up. DIET AND HUNTING California sea lions feed on more than 50 species of seafood, mainly squid and fish. In Oregon and Washington State humans have created unnatural situations by building dams and structures where sea lions will congregate, feeding on salmon and steelhead migrating through the fish ladders. As a result, sea lions are unfairly blamed for declining fish populations ~ read more here. Even though they have fearsome canine teeth (used primarily to grab fish), sea lions typically swallow their food whole.
MATING AND BREEDING California sea lions breed around May to June. Males and females reach sexual maturity between 4-5 years of age. Establishing a territory is important to a male’s success in breeding and mating begins approximately three weeks after the females give birth. Postural displays, fighting (often violent) and barking and growling is common during the mating season as males (known as “bulls”) compete for females (“cows”). Males assemble a number of females and young into a group called a “harem” and protect them throughout the breeding season. Mating and birthing takes place in remote rookery locations safe from humans and predators. PUPPING The females have gestation period of 11 months and give birth from June to August. Mothers may give birth to a single pup on land or in water. Pups and moms learn to recognize each other’s distinct vocalizations and smell, playing a vital part in the survival of the pup. Pups nurse for six months to a year even though they can digest food at three months of age. Pups learn to swim and hunt at about two months and play together onshore. They leave their mother after a year.
BEHAVIOR After the breeding season, female California sea lions normally stay in southern waters while the adult males and juveniles generally migrate north to feeding sites for the winter. Males use raucous vocalization (loud barking, grunts and growls) and posturing movement as they battle for dominance and territory, but non-breeding groups are gregarious and haul out together in groups called colonies. Winter haul-outs are generally in more exposed locations. Most sea lions found in man-made environments such as piers, platforms and buoys are males or juveniles. “Rafting” is an unusual behavior in which a number of sea lions will cluster together and rest or sleep, often submerged with only a flipper or nose visible above water. Typically this will occur in areas where there is no suitable haul-out. This behavior is believed by biologists to be a method of thermoregulation (regulating the body temperature). Sea lions can dive up to 600 feet and stay submerged for 40 minutes. The fastest swimmers of all pinnipeds, they can reach speeds of up to 30 mph. Their ears and nostrils close when diving under water.
SENSES A California sea lion’s hearing is acute on both land and underwater and they are quite vocal. Their vocalizations are much more active onshore and are critical in pups and mothers identifying and locating each other’s unique acoustical voice. They have excellent vision both above and under water and it is believed they are able to discern colors. Sea lions have a highly developed sense of smell above water which is used to identify pups. Their whiskers (vibrassae) are used to detect the vibrations of prey. Sea lions are very tactile and enjoy one another’s touch while hauled out.
PREDATORS The only natural predators of the sea lion are killer whales and great white sharks.
HUMAN IMPACT Commercial fishing is a constant threat to sea lions and all marine mammals. Sea lions become entangled in nets and fishing line with barbed hooks, suffering grave injuries often leading to death. Additionally, they are often intentionally killed by fishermen who mistakenly believe they are responsible for dwindling fish stocks caused by overfishing, habitat destruction and pollution. However, more knowledgeable fishermen no longer blame seals and sea lions and appreciate them for being an integral part of a complex ecosystem.
Pollution poses a tremendous risk for all marine mammals. In recent years, cancer is killing an alarming number of California sea lions. Scientists are trying to determine whether the cause is due to pollution, however, some research points to high levels of PCB's present in sea lions with cancerous lesions.