Sea lions are carnivorous marine mammals present in nearly all of the world’s oceans. They are frequently seen in the colder waters surrounding both the North and South Pole, but certain species can be found in warm, tropical waters, as well. They are pinnipeds, meaning that despite being mammals not far off from dogs in terms of their biology, they have the key difference of featuring fins instead of feet and toes. This specific adaptation makes them ideal hunters in their preferred sea habitat.
Sea lions are rather opportunistic carnivores that will eat nearly any living thing smaller than them. For most species, this means a diet consisting overwhelmingly of fish, and, for the polar varieties, penguins. Sea lions, especially the polar variety, consume large amounts of food in order to maintain their internal body temperature – it is not unusual for an adult sea lion to consume 5-8% of its own body weight in a single meal. Sea lions tend to be very muscular and bulky creatures, even small ones can use a great degree of force and have very powerful jaws and swimming appendages.
Being included in the suborder Caniformia, sea lions are very similar to dogs and bears in terms of their interior biology, including their intelligence and ability to communicate. They are receptive to training and often featured in zoos, public aquariums and circuses. The United States Navy has even successfully trained them for military use, such as the detection of water mines, although the program is highly controversial and soon to be closed in favor of modern robotic methods. Sea lions exhibit a number of unique vocalizations and communication strategies that they use in large rookeries where hundreds of individuals will meet, especially during the mating season.
In the warm summer months of every year, sea lions gather at large rookeries where males will establish territory and invite females to mate. Hunting generally ceases at this time, and males will rely on their stores of blubber for up to a month to survive without feeding. This places a premium on size for the sea lion mating season- larger sea lions will fare better because they can hold on to their territory for longer periods and consequently mate more often. After mating, female sea lions will give birth after a 12-month long gestation, during the following summer.
Australian Sea Lion
The Australian sea lion, also known by its scientific name Neophoca cinerea, is an eared seal belonging to the Otariidae family alongside other sea lions and fur seals. They are related to earless seals or true seals and walruses, with which they form the Pinnipedia suborder. This sea lion subspecies inhabits the western and southern parts of Australia.
This sea lion species presents sexual dimorphism. Males are much larger than males, with sizes of up to 2.2 meters and weighs of up to 250 kg. Females can grow to 1.85 meters and weigh up to 100 kg. Sea lions have bulky bodies with muscular chest and neck, and large foreflippers which are not only efficient at propelling them in water, but also for walking and running on land.
The hindflippers do not aid in swimming, but they can be turned to the front and help the sea lion propel itself on land with help from the front flippers, neck and body movements. The fur of these sea lions is shorter than in other species, with colors ranging from dark brown to light and cream, especially for pups before molting.
Just as the name suggests, this sea lion lives on islands and off the coast of Australia. Populations are distributed from the Houtman Abrolhos Islands, in the western part of Australia, to the Pages Islands in the south of the continent.
These sea lions are opportunistic foragers, meaning that they do not have a specialized diet. They consume a wide range of marine animals, from squid and octopuses to crustaceans such as rock lobsters, fish, including cuttlefish, small sharks and even penguins.
Australian sea lion females have an abnormal breeding cycle which can range from 5 months to 17 or 18 months. Breeding is also not synchronized between colonies. Bulls do not have territories to defend, as is the case with other species. They fight from a young age in order to establish a dominance hierarchy. Once domination has been established, dominant males will guard females and prevent other males from mating. Females come into season within 7 to 10 days of giving birth to pups.
Females care for their newborn only, and the older pups are aggressively fought off. Alloparental care has been observed in Australian sea lion populations, where other adults can adopt pups which have lost their parents.
California Sea Lion
The California sea lion is an eared seal that lives predominantly on the coasts of the North American continent. It belongs to the Otariinae subfamily of the Pinnipedia suborder, which includes true seals and walruses.
This California sea lion bears the scientific name Zalophus californianus. It belongs to the Otariidae family along with other sea lions and fur seals. These sea lions differ from true seals by having short ears or external ear flaps, and they can use their fore and hindflippers for locomotion on land.
The species is sexually dimorphic, with males being much larger than females. Males can reach 2.4 meters in length and weigh as much as 350 kg. Females are much
shorter, measuring up to 1.8 meters and weighing 100 kg. The males present a large crest which provides the head with a dominant and domed forehead. Individuals have robust necks, shoulders and chests which they use, along with their flippers, to swim as well as to move on land. The spine is flexible and allows sea lions to perform sharp turns in water.
They mostly use their foreflippers to propel themselves in water, arching between strokes. On land, these sea lions can run at speeds of up to 10 km per hour. They can dive at depths of over 270 meters, with most dives being no deeper than 80 meters. They can hold their breath underwater for up to 10 minutes, but they usually spend no more than 3 minutes holding their breath.
The habitat of this sea lion ranges from southeast Alaska to the central coastal waters of Mexico. There are many large populations in the temperate areas of the western coast near California, from Baja California to the Gulf of California. Sea lions typically forage under water and then retreat to cliffs or beaches to rest, sleep, mate or give birth.
These sea lions usually consume a wide range of seafood, from squid to fish and clams. Fish species that are most commonly consumed are salmon, herring, anchovies, hake and dogfish. Sea lions are usually preyed upon by killing whales and sharks, the latter usually ambushing individuals resting on shores.
Breeding occurs in rookeries, which are gatherings on shores. Males guard their territory where females can enter and leave without being coerced. Females reproduce every 12 months, with a gestation of 9 months. California sea lion pups are weaned within a year, but they may suckle for an extra year.
Galapagos Sea Lion
The Galapagos sea lion is an eared seal that lives exclusively near the Galapagos Islands. Also known by its scientific name Zalophus wollebaeki, it belongs to the same genus as the California sea lion. Members of this species are highly social and playful, and they can often be seen bathing under the sun, on beaches and rocky cliffs.
The Galapagos sea lion is smaller than its relative, the California sea lion. Males are larger than females, and they also develop a crest on the forehead, forming a bump-like projection. Males can grow to 2 meters or more and weigh 250 kg, while females may be 1.5 meters long and weigh 50 kg. Males have thicker necks, chests and torsos, as well as well-developed shoulders and a thin abdomen. Females have a generally slender body but thicker abdomens.
These sea lions have long, thick, pointy and whiskered muzzles. Just like other sea lions, they have pinnae or ear-like flaps. The slender bodies and flexible spines allow these sea lions to swim at high speeds underwater, as well as to take sharp turns to catch prey or to avoid predators. They can also move agilely on land, and, opposed to many other sea lions, they can move their flippers independently.
These sea lions inhabit most of the islands in the Galapagos archipelago. There are also colonies near the offshore of Ecuador on the Isla de la Plata as well as on Isla Gorgona in Columbia. There are reports of colonization on Isla del Coco, which is 500 km to the southwest of Costa Rica.
The diet of these sea lions consists mainly of sardines. Individuals can be observed traveling for 10 or even 15 kilometers from the coast, where they may spend several days hunting. If sea lions are safe on the ground, during these trips they are vulnerable to attacks from orcas and sharks, their main predators. During specific El Nino events, sea lions may feed on other fish due to the decrease in the number of sardines.
Bulls fight for territory, where they can host and guard a harem of up to 25 females. Breeding can take place from January to May, with no synchronization between colonies being observed. Gestation takes about 12 months. After giving birth, females will look after the pups for a week and then go on foraging trips in the ocean. Galapagos sea lion pups are weaned after around 11 months, after which they will rely on their hunting skills.
Japanese Sea Lion
The Japanese sea lion is an eared seal which is thought to have become extinct in the 1970s. It inhabited the Sea of Japan and was perhaps one of the largest sea lions in the world.
This species, known by its scientific name Zalophus japonicus, belongs to the Zalophus genus alongside the California sea lion and the Galapagos sea lion. It was included in the subfamily Otariinae and the family Otariidae alongside fur seals. Until 2003, the Japanese sea lion was considered a subspecies of the California sea lion. Further studies, as well as the differences in habitat and behavior, have prompted scientists to name Zalophus japonicas a distinct species. By 1915, there were only 300 specimens left, and in 1974, the last juvenile specimen from Rebun Island died.
This species closely resembled the California sea lion, which still exists today. Males were larger than females and presented a mane as well as a sagittal crest which gave them a bumped forehead appearance. Males reached 2.5 meters in length and could weigh between 450 and 560 kg. Females could grow to 1.64 meters in length. The bodies of the males were stockier, with broader necks, chests and shoulders than females which had a wider abdomen. Males were darker in color than females and pups, which were lighter and orange.
These sea lions inhabited the offshores and islands of the Sea of Japan. Populations were also found on the coast of the Korean Peninsula and could extend up north to the southern tip of the Kamchatka Peninsula. There are also some old Korean accounts which describe these seals to have inhabited the Bohai Sea and the Yellow Sea. Populations could be found breeding on sandy beaches, but were also present on gravel or pebble beaches and rarely on rock groups. A distinct characteristic of this species is that, opposite to other sea lions that rested on the same grounds where they bred, they preferred to rest inside caves.
Little is known about the reproduction habits of these sea lions. Given the morphological similarities between the Japanese and California sea lions and the size of adult males of the former, it is reasonable to suspect that bulls fought for territories and tried to maintain control of as many females as possible. Japanese sea lion pups were most likely intensely looked after for a few weeks and weaned after a year.
South American Sea Lion
The South American sea lion, also known as the Patagonian sea lion or, by its scientific name, Otaria flavescens, is an eared seal that lives on the eastern and southern coasts and islands of South America. It is one of the larger species of sea lions, and by its general appearance, perhaps the archetypal representative.
These sea lions are sexually dimorphic, just like other similar species. Females may reach 2 meters in length and weigh 150 kg while males can grow to be 2.7 meters long and weigh 350 kg. Males of this sea lion species have a dominant mane, which rightfully earned them their name. Colors range from orange to dark brown, with pups being born more grayish only to turn to a chocolate color after molting.
This sea lion inhabits the coasts and offshore islands of the southern part of South America, from Peru to Chile, Ecuador, Argentina, Brazil and Uruguay. There are many breeding colonies on notable islands such as Lobos Island, Beagle Channel and Falkland Islands. The preferred habitat for breeding is sandy beaches, but these sea lions may also breed on gravel and even rocky groups.
The South American sea lion consumes a wide range of fish species, from anchovies to hake. They also feed on cephalopods such as squid and octopuses, and they have been seen attacking and preying on birds such as pelicans and penguins. There are reports of sea lions even feeding on fur seals. These sea lions either hunt slow prey alone, or they might group and hunt schools of fish in packs. They are also known to take advantage of the hunting strategies of other animals such as dusky dolphins, where the sea lions feed on fish which have been herded by the former. Sea lions are also preyed upon by large sharks and killer whales.
During the breeding season, which can occur from August to December, males establish a territory and defend it against other males. Any female that might enter their territory will be guarded, and the dominant male may also restrain access of females to the sea. Most males can keep up to 4 females, but some might be able to hold up to 18 females. Females give birth after around 12 months and, for the first 4 weeks, will look after their pups on land. South American sea lion pups will first enter the water after this period and will be weaned after 12 months.