This week's pinniped is an old friend of mine, as I used to look for them every time I went to the beach or the docks with my family as I was growing up in California.

The California Sea Lion (Zalophus californianus) can be found along the western coastline of North America, from the mid-coastline of Mexico to the southern coastline of Alaska. It can also be found in the Gulf of California. California Sea Lions are extremely intelligent, which allows them to quickly learn to perform certain behaviors on command. Trained California Sea Lions can be found in zoos, aquariums, research facilities and even military facilities as part of the U.S. Navy Marine Mammal Program. They can recognize and even perform simple sign language, although they do not typically sign in a way that would indicate they are forming sentences.

Sexual dimorphism in California Sea Lions is extremely pronounced, with males being much larger than females. Adult males average a total body length of 7.9 feet (2.4 meters) and weigh approximately 770 pounds (350 kg). Females grow up to 5.9 feet (1.8 meters) in body length and weigh only 220 pounds (100 kg). Young males and adult females have a tawny or silver-gray coat, while the big males are darker, and can range from brown to black. Females are streamlined, while males have very thick necks and shoulders, and a domed crest on their foreheads. Some of them even have short manes.

The diet of California Sea Lions varies depending on their range and availability of prey, but for the most part they feed on clams, crustaceans, squid and fish. They are known to participate in cooperative hunts of large schools of fish with other predators like sea birds, dolphins and porpoises. They will occasionally tag along with dolphins and take advantage of their hunting techniques to snag some of their prey. California Sea Lions are themselves preyed upon by orcas and large sharks, but they are amazing swimmers and are incredibly flexible - so much so that they can bend so far backward that their noses touch their tails.

The mating season of the California Sea Lion occurs between May and August, at which time the males will haul up and stay at the rookeries for as long as possible, increasing his chances to mate with as many females as possible. They will fast for this period, relying on their blubber to sustain them for about four months. They don't start fighting with each other until after the females have started to give birth and will be ready to mate again, at which point it can get bloody. After territories have been established, however, they mostly stick to dominance displays and vocalizations. Female California Sea Lions delay their implantation for three months, and then actively gestate for nine months, which makes their total gestation period to about year. Males don't have an active role in raising the pups, but they seem to be more tolerant and protective of them than other pinnipeds.

California Sea Lions are noisy. A rookery is full of animals barking at each other, which is their most common vocalization. Males are the loudest, and make prolonged calls especially during the breeding season. Females and their pups can distinguish each other's calls from the many other sea lions that share the rookery, which allows to find each other in what can be chaotic living conditions. Females will growl, squeal and belch, saving their barks for when they wish to put on an aggressive display. They can also vocalize under water. Due to their abundant populations, they are considered to be a species of least concern by the IUCN.