ABOUT SEALION

Picture Source From Wikipedia

 

Sea lions are pinnipeds characterized by external ear flaps, long fore flippers, the ability to walk on all fours, short, thick hair, and a big chest and belly. Together with the fur seals they make up the family otariidae, eared seals, which contains six extant and one extinct species (the Japanese sea lion) in five genera.

Their RANGE extends from the subarctic or tropical waters of global ocean in both northern and southern hemispheres, with the notable exception of the northern Atlantic Ocean.

AVERAGE LIFE SPAN: 20-30 years.

WEIGHTS OF AVERAGE SEA LION: A Male seal lion weights on average about 300kg (600lb) and is about 2.4 m (8ft) long, while the female sea lion weighs 100kg (220lb) and is 1.8 m (6ft) long.

LARGEST AND SMALLEST SEA LION:  The largest sea lion is STELLER SEA LION which can weighs 1000kg (2200lb) and grow to a length of 3m (10ft). The smallest sea lion is GALAPAGOS SEA LION which can weighs 80kg (177lb) compared to California sea lion, the next smallest species, whose females weigh around 95 kg (209lb).

CONSUPTION OF FOOD: Sea lions consume large quantities of food at a time and are known to eat about 5-8% of their body weight (about 6

.8-15.9 kg (15-35lb)) at a single feeding.

SPEED OF SEA LION: Sea lions can move around 16 knots (30km/h; 18 mph) in water and at their fastest they can reach a speed of about 30 knots (56km/h; 35 mph).

GESTATION PERIOD: 9 months.

ENDANGERED SPECIES: The Australian sea lion, Galapagos sea lion and the New Zealand sea lion.

SENSES OF SEA LION

The special sensory organs in pinnipeds include the eyes, ears, nose and vibrissae. Marine mammals especially pinnipeds have quite a challenge to overcome because they have to function in air, in water, in bright light, and in low light. There are 5 good senses of sea lion hearing, sight, smell, taste, touch.

HEARING: Sea lions hear both above and below the water’s surface, although they hear better under water. Studies show sea lions can hear frequencies up to 70,000 Hz, but tend to vocalize within a range of 100 to 10,000 Hz. This is comparable to humans who have a hearing range of 20 to 20,000 Hz. Sea lion vocalizations include barks, clicks, moans, chirps, growls, and squeaks. There is no concrete evidence to suggest that sea lions use echolocation.

SIGHT: Sea lions like many marine mammals, can see well both above and below the surface of water. Unlike humans, sea lions may not see in colour. They can possibly discriminate colours in the blue- green spectrum. All pinnipeds have a membrane at a back of each eye called a tapetum lucidum to aid in the night vision. Cats also have a tapetum lucidum, which is why the eyes of both cats and sea lions glow at night. On the land, their eyes are protected by a nictitating membrane, which wipes away sand and debris.

SMELL: Sea lions cannot smell underwater but, above water, smell is a highly developed sense. Females use smell for pup recognition and males use it for breeding purposes to locate females in estrus.

TASTE: Sea lions have a limited sense of taste, similar to other marine mammals.

TOUCH: Sea lions are tactile mammals. Their whiskers contain nerve fibres, which make them sensitive. They may use their whiskers to aid in navigation or to detect vibrations from prey in water

SLEEPING POSITION OF SEA LION

On land, sea lions will sleep in a variety of positions, often on top of their friends. California sea lions have been seen interacting with other species of pinnipeds, such as northern elephant seals, harbor seals, Northern fur seals and Steller sea lions. In the water, they will sink to the bottom of shallow areas, and occasionally rise to the surface of air. In deeper water, they will float upright with the tip of their noise out of the water.

Sleeping Sea lion

DIVING ADAPTATION OF SEA LION

A sea lion’s body is well equipped to make such deep dives. Their heart rate slows on long dives and blood is shunted away from areas that are not as dependent on oxygen to areas like the heart and central nervous system that need oxygen to function. Unlike dolphins, sea lion exhale before diving. Naturally, their nostrils are closed, but they have special muscles to open them in order to breathe. Sea lions can dive to depths between 450 and 900 feet (135-272) m. On land, sea lions breathe through their nostrils. Their nostrils instinctively shut when they dive underwater. They have special muscles that open the nostrils when they need to breathe. When sea lions are swimming underwater their nostrils remain closed.

BREEDING METHODS AND HABITS OF SEA LION

They rarely breed more than once in a single season. Copulation have been observed on land and in shallow and deep water. Courtship and copulation may last from few minutes to few hours. The female terminates copulation by raising her head and shoulders and biting the male’s neck. Breeding season last from late June to early august; most pups are born from May through June. 3 to 4 weeks after giving birth, females are ready to mate again. California sea lions separate their nursing and feeding activities. Male sea lions reach sexual maturity from ages 5 to 7 and don’t become territorial until around 9 to 13 years of age. Female sea lions reach maturity from 3-5 Years. New born California sea lions weigh 13 to 20 pounds and stay with their mother for about a year as they nurse and learn important survival skills, like how to swim and find food on their own.

GEOGRAPHIC VARIATION

Geographic variation for sea lions have been determined by the observations of skulls of several Otariidae species; a general change in size corresponds with a change in latitude and primary productivity. Skulls of Australian sea lions from Western Australia were generally smaller in length whereas the largest skulls are from cool temperate localities. Otariidae are in the process of species divergence, much of which may be driven by local factors, particularly latitude and resources. Populations of a given species tend to be smaller in the tropics, increase in size with increasing latitude, and reach a maximum in sub-polar regions. In a cool climate and cold waters there should be a selective advantage in the relative reduction of body surface area resulting from increased size, since the metabolic rate is related more closely to body surface area than to body weight.

Image From Live Science

CONSERVATION

Until recently, sea lions were hunted for their meat, skin, and oil. Some people even used sea lion whiskers for pipe cleaners! Many sea lion populations were wiped out as a result. Steller’s sea lions are endangered, possibly due to the effects of commercial fisheries on their prey. They were also accidentally killed when caught in commercial fishing nets and were shot on purpose by fishermen who believed the sea lions damage their nets. Protective zones and other measures around known Steller’s sea lion rookeries have been implemented. Other sea lions are experiencing declines as well, for many of the same reasons. Today, all sea lions are under the protection of the Marine Mammal Protection Act. 

There were over 700 strandings of young sea lions from Washington State to Baja California, Mexico, in 2013, an indication that something unusual is going on in the ocean. Young sea lions typically leave their mother and go out on their own between eight months and one year of age, but if they are weaned early or orphaned, they may not have learned the skills needed to hunt for fish on their own. Scientists are looking at what role pollution may play in these strandings. 

A neurotoxin called domoic acid is produced by algae during algae blooms and is called a red tide. Fish eat the algae, and sea lions and other marine predators eat the fish. High levels of domoic acid can lead to lethargy, seizures, and death. And pollution may have a significant role in more of these toxic algae blooms occurring. That’s why it’s so important to keep pollution and trash out of the ocean, and to recycle plastic. There is a correlation between NOT recycling and the emergence of excess domoic acid in marine mammals, a documented connection between wildlife and pollution.

You've probably heard it before, but it's still true: you can help protect sea lions by keeping plastic items out of our oceans. For example, the plastic rings around six-pack cans can be deadly for sea lions and other wildlife that may swallow them or become entangled in them.

By supporting San Diego Zoo Wildlife Alliance, you are our ally in saving and protecting wildlife worldwide.

HUMAN INTERACTION

The Moche people of ancient Peru worshipped the sea and its animals. They often depicted South American sea lions in their art. Two statues of this species are the symbol of the city of Mar del Plata.

Indigenous peoples of South America exploited this species for millennia and by Europeans around the 16th century. The hunting has since gone down and the species is no longer threatened. The species is protected in most of its range. Numerous reserves and protected areas at rookeries and haul-out sites exist for the sea lions. Despite this, protection regulations are not effectively enforced in much of animals' range.

The overall population of sea lions is considered stable; the estimate is 265,000 animals. They are declining in the Falkland Islands, and in Argentina Patagonia, but are increasing in Chile and Uruguay. Many sea lions of the Peruvian population died in the 1997/1998 el Niño. They still are killed due to their habits of stealing fish and damaging fishing nets.

Moche Statue Of Sea Lion Pup