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Ocean Life: California Sea Lion - Adaptation

Feeding

Not much is known about the feeding habits of the California sea lion. Sea lions are an opportunistic feeder, eating what is available. They are carnivores (animals who eat other animals) and eat fish, squid, octopi, crabs, clams, and lobsters. Their diet includes several fish species, such as anchovy, whiting and herring. Sea lions will eat 5-8% (15-35 pounds) of their body weight daily. They have 34-38 cone-shaped teeth that are specially designed for grasping slippery fish; however, sea lions do not chew their food, but swallow it whole or in large chunks. Most of their water intake comes directly from the fish they eat although they may drink small portions of sea water while fasting throughout the breeding season. Strangely, rocks have been found in the stomachs of sea lions. The exact reason is unknown, but one theory states that sea lions may swallow rocks to create a false sensation of feeling full during the period when they fast.

Photo of the face of Rocky, a sea lion.
Rocky, a trained Navy sea lion, shows off
his features that aid him with hearing,
smell, sight and touch
(courtesy of Dan Costa, UCSC)

Senses

California sea lions hear well both above and below the water’s surface. Studies have shown that sea lions can hear frequencies as low as 100 Hz and as high as 40,000 Hz, while humans have a hearing range of 20-20,000 Hz. Sea lions vocalize within a range of 100 to 10,000 Hz. Sea lions are very vocal and can bark, click, growl, squeak, and honk. Barking by male sea lions is related to social dominance, territorial defense, and alarm calling.

Sea lions cannot smell underwater, but above water their smell sense is highly developed. Females can recognize their pups by their distinctive scent and males use their sense of smell to recognize females in estrous during the breeding season. Mothers locate their pups on crowded rookeries through smell, sight, and distinctive vocalizations. Pups also learn to recognize and respond to the vocalizations of their mothers.

Sea lions have large eyes and excellent sight. Unlike humans, sea lions probably do not see in color. It is possible they can see colors in the blue-green spectrum. All pinnipeds have a membrane at the back of their eyes called a tapetum lucidum to aid in foraging while diving below the sunlit surface where there is little available light. Cats also have a tapetum lucidum and this is why the eyes of both cats and sea lions appear to glow at night. On land, their eyes are protected by a nicitating membrane, which wipes away sand and debris.

Sea lions are tactile mammals. Vibrissae, or whiskers, are stiff, thick hairs made of keratin (human fingernails are also made of keratin). These whiskers are found around the muzzle and are embedded in facial tissue rich in nerves and muscle fibers. This sensitive system functions to detect vibrations from sound or prey in the water and can be used to feel the shape and size of objects on land.

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