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.
Rocky, a trained Navy sea lion, shows off
his features that aid
him with hearing,
smell, sight and touch
(courtesy of Dan Costa,
California sea lions hear well both above and below the waters
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.