California Sea Lions
The California sea lion is a constant presence at Piedras Blancas. Large numbers of these noisy pinnipeds gather on the wedge-shaped rock off the elephant seal viewing area and on the Outer Islet, the large rock off the point. California sea lions are probably the most familiar pinniped in the world. Easily trained, they are featured in zoos, circuses, and oceanariums. They also have a habit of hauling out on docks, boats, and buoys. Although sea lions are present year-round at Piedras Blancas there are fluctuations in numbers. The ones we see at Piedras Blancas are usually the young of either sex or mature males. Once females begin reproducing they stay near the breeding rookeries, located at the Channel Islands or off Mexico .
Color: California sea lions have solid-color coats that range in color from tawny yellow to dark brown. When wet they look dark, almost black. Most adult males are dark brown to black with light tan areas on the face. Adult females and juveniles are a lighter color. Sea lions shed their fur every year but the process is gradual and not visually apparent. Adult females and juveniles molt during the fall and winter. Adult males molt in the winter.
Shape: Juvenile and adult female sea lions have slender shapes. They have long dog-like noses and tiny external ears. The front flippers are long in comparison to the harbor seal or elephant seal. Around age 5 the males develop a bony bump, called a sagital crest, on top of their skulls. Adult male sea lions have a thickened shoulder, chest, and neck area.
Weight and length: Mature males are much larger than mature females, weighing up to 880 pounds while females weigh up to 240 pounds. Newborn pups weigh 13-20 pounds, male pups are larger. Maturemales are up to 8 feet in length and mature females up to 6.5 feet long. Pups weigh about 13 pounds at birth and are about 30 inches long.
Feeding: California sea lions eat a variety of fish, including anchovies, mackerel, and rockfish. They also prey on squid and octopus. They prefer to feed in areas of cool upwelling along the continental shelf and around seamounts. They may eat 5-10% of their body weight each day. Feeding can occur at any hour. They can be seen engaged in feeding frenzies, along with large numbers of sea birds.
Territorial males fast while maintaining their territories (1-45 days.) Nursing females spend the first week with their pup and then alternate feeding trips at sea (averaging 2-3 days) with nursing bouts when they are fasting (averaging 1-2 days).
Because females must forage while nursing their pups, the breeding areas are in regions where there is usually high food productivity. Warm El Nino waters can cause a reduction in food availability. Females tied to the breeding sites face the greatest challenge. During a strong El Nino, pup production can decrease and pup mortality can increase. El Nino events can also cause a shift in diet. Pelagic red crabs, which are rarely consumed otherwise, become a more common food item during El Nino years.
Breathing and diving: The typical dive for a California sea lion is about 2 minutes long, but they can dive up to 12 minutes. The average dive is between 80-300 feet but they can dive much deeper – over 900 feet. Their nostrils close in the resting state and while diving.
Movement/Behavior: Sea lions use their front flippers to propel themselves through the water and their back flippers to steer. The word “pinniped” is Latin for “wing-footed” or “fin-footed” and the sea lion does appear to fly underwater using its front flippers like wings. They are fast swimmers and reach 25 mph for short bursts.
On land they can rotate the hind flippers forward, under the body. That ability, in addition to the long fore flippers, allows them to “walk” on land with agility, using all 4 appendages. At sea they are frequently seen leaping out of the water in a behavior referred to as “porpoising.” Sometimes large groups of young sea lions are seen porpoising between the Piedras Blancas rocks – a joyful sight. Presumably this speeds up swimming because there is less resistance in air than in water. Another delightful sight is that of sea lions bodysurfing!
Sea lions may spend several days to several weeks at sea, diving almost continuously, resting briefly at the surface. The position in which they rest at the surface with one foreflipper and both rear flippers extended above water is referred to as “jugging” or the “jug-handle” position. Jugging helps regulate body temperature by conserving heat, which dissipates faster in water than in air.
Because sea lions are easily trainable, and can move well on land, they are seen in “seal shows” at zoos and aquariums. They can learn a simple sign language in captivity. When most people hear the word “seal” they probably think of the California sea lion. They are also known for their playfulness, sometimes approaching divers underwater.
Sounds: California sea lions are noisy, doing a lot of barking and crying out while they are hauled out on land. Make that barking noise and slap your arms together and most people will immediately know what animal you are talking about!
Reproduction: Sexual maturity occurs at 4-5 years but males aren’t big enough to hold a territory for several more years. Breeding occurs at the Channel Islands off Santa Barbara and at islands off Baja California and in the Gulf of California . They usually prefer sandy beaches for breeding. They may move inland or up slopes at night and when it’s cool but during warm weather they stay close to the water’s edge.
From May through July the males maintain breeding territories using visual displays and frequent barking. When fighting occurs they lunge at each other’s chests and bite the opponent’s flippers or hindquarters. Most males do not hold a territory for longer than 2 weeks but some have lasted to 45 days. They are either displaced by another male or forced to leave because their fat supplies have been exhausted. The broad neck and chest of the adult male contains fat to sustain him through a limited fasting period. Even though a male may lose his territory when he is forced to sea to feed he may regain it again when he returns.
Females mate about 27 days after giving birth. Gestation is about 11 months, including a 3-month delayed implantation. Not all females give birth every year.
Pups: Most pups are born in May and June. Females give birth to a single pup a few days after coming ashore. Bonding occurs though sound and smell, necessary so the mother and pup can find each other after she returns from foraging. After giving birth the female stays with her pup for up to 8 days, then she leaves to find food. Most foraging trips are 2-3 days long but can vary according to the availability of prey. After the initial foraging trip, stays on land average 1-2 days with trips to sea in between. Pups begin to eat fish, along with milk, at 2 months of age. Most pups are weaned by 10-12 months, although some continue to suckle longer and some less. Pups can swim at birth, in a very uncoordinated fashion.
Young sea lions are playful, gathering in large groups when their mothers are away. They learn to swim in protected shallow water, engage in mock fights, chase each other, and even body surf. Sometimes older pups accompany their mothers on feeding trips.
California sea lion pups are occasionally born on the rocks off Piedras Blancas but they probably do not survive.
Longevity: Sea lions may live 20-30 years. Females live slightly longer than males. Pup mortality is about 15-20% during the first 6 months but it increases to about 40% for the next 6 months.
Social Dynamics: California sea lions are extremely gregarious. They come together in large groups, especially on the Channel Islands where thousands haul out. At sea they may travel in groups of a dozen or more. They can be seen resting at sea in groups referred to as “rafts.”
Some interesting behavior takes place at the breeding colonies. Males do not interfere with female movements. Extending her neck and swaying it side to side as she walks; a female indicates the desire for free passage. Females have to have access to the water, both to cool off and to leave on foraging trips. Furthermore, when it’s time to mate a female may leave the territory of the male where she has given birth and mate with another male. If a male is overly aggressive a female may abandon him. The only sustained relationship seems to be between mother and pup, until the time of weaning.
Distribution: Breeding age females remain in the areas around the breeding rookeries ( Baja California , Channel Islands ) all year. After the breeding season most adult and subadult males migrate north along the coast, some as far as British Columbia .
Predators: Sharks and orcas (killer whales) prey on sea lions.
Status: Hunting of California sea lions probably occurred for thousands of years before the arrival of Europeans without much effect on the population. However, during the commercial hunts of the 1800s and the early 1900s numbers were reduced. Sea lions were hunted for their hides, blubber, meat, and whiskers. The bacula (penile bone) was sold as an aphrodisiac. The U.S. Marine Mammal Protection Act of 1972 protects marine mammals today. The U.S California sea lion population is thought to be over 167,000 and growing at about 5% a year.
Currently, causes of death to sea lions include starvation, infection, disease, entanglement in nets, pollution, and shooting. Domoic acid, produced by toxic algae bloom, causes seizure and death in California sea lions. Domoic acid moves up the food chain and can cause poisoning to humans too.
El Nino weather conditions can affect sea lions by reducing prey availability. Animals that are able to migrate north to find food are not affected, but the adult females are not able to forage too far from the breeding sites. The lack of prey results in spontaneous abortions and in undernourished pups. Pup production can take several years to recover after an intense El Nino.
Some people view California sea lions as pests, competitors for marine resources. Occasionally fishermen shoot them. Sea lions have also made themselves at home on man-made resting areas, like docks. When they started hauling out on Pier 39 in San Francisco , they were viewed as a nuisance, but now it has become a popular tourist attraction.
Off Piedras Blancas: We are most likely to see young animals of either sex or adult males. Most mature males are in the Channel Islands area during the breeding season (May through July). During the month of August adult male sea lions that have been beaten up during territorial disputes may be seen hauling out to rest at Piedras Blancas. The number of California sea lions seen at Piedras Blancas varies during the year. They may occasionally be seen hauling on the beach to rest.Background photo by Carole Adams