Showing posts with label Otaria. Show all posts
Showing posts with label Otaria. Show all posts

Friday, February 24, 2012

Human Interactions Of Sea Lion

Sea Lion
Some species of sea lion are readily trainable and are often a popular attraction at zoos and aquariums. The archetypal circus "seal" performing behaviors such as throwing and catching balls on its nose and clapping is almost always a sea lion.
Sea lions have been trained by the U.S. Navy's Marine Mammal Program, based in San Diego, to detain scuba divers.
Sea Lion
Sea lion attacks on humans are rare. In a highly unusual attack in 2007 in Western Australia a sea lion leapt from the water and seriously mauled a 13-year old girl surfing behind a speedboat. The sea lion appeared to be preparing for a second attack when the girl was rescued. An Australian marine biologist opined the sea lion may have viewed the girl "like a rag doll toy" to be played with. In San Francisco where an increasingly large population of California sea lion crowds dock along San Francisco Bay, there have been incidents in recent years of swimmers being bitten on the leg by large aggressive males, possibly as a territorial act.
The Moche people of ancient Peru worshipped the sea and its animals. They often depicted sea lions in their art.
Sea Lion
Sea lions have also been reported to assist or save humans who show signs of distress in the open waters. In June of 2000, Kevin Hines leaped into the San Francisco bay and it was reported that he was saved by a sea lion that kept him afloat and breathing till the paramedics arrived.

Thursday, September 15, 2011

Social behavior and reproduction of Sea Lion

Sea LionMating occurs between August and December, and the pups are born between December and February. Males arrive first and defend territories, but switch to female defense as they were joined by them. Males defend females from neighbours and intruders with threat displays and by fighting, and forcefully hold pre-estrous females near them. On rocky beaches, males defend small territories where females aggregate and herd them. On more open cobble or sandy beaches, males stay along the surf line and try to herd females going to sea to cool down or forage. The number of actual fights between males depends on the number of females in heat. The first males to arrive have the longest tenures and achieve the most copulations. Males are usually able to keep around three females in their harem, but some have as many as 18.
Sea LionDuring the breeding season, males that fail to secure territories and females (mostly subadults) will cause group raids in an attempt to change the status-quo and gain access to the females. These raids cause chaos in the breeding harems, often splitting mothers from their young. The resident males are unable to fight off all the raiders and keep all the females in their territorial boundaries. Nevertheless, raiders are often unsuccessful securing a female. Sometimes an invading male will abduct pups, possibly as an attempt to control the females. They may also take pups as substitutes for mature females. Pups are often severely injured or killed when this happens. Group raids are more common on sandy beaches than rocky ones.
Sea LionSea lion mothers remain with their newborn pups for nearly a week, and then start a routine of taking trips back into the sea for food and coming back to nurse the pups. They will act aggressively to other females who come close to their pups, as well as alien pups who try to get milk from them. Pups first enter the water at about four weeks and are weaned at about 12 months. This is normally when the mother gives birth to a new pup. Pups gradually spent more time in the nearshore surf and develop swimming skills.
South American sea lions are observed to make various vocalizations and calls which differs between sexes and ages. Adult males will make high-pitched calls during aggressive interactions, barks when establishing territories, growls when interacting with females, and exhalations which are made after agonistic encounters. Females who have pups make what is called a mother primary call when interacting with their pups, and grunts during aggressive encounters with other females. Pups make what are called pup primary calls. Some of those vocalizations and acoustic features may support individuality.
Sea Lion


South American Sea Lion

Sea LionThe South American sea lion (Otaria flavescens, formerly Otaria byronia), also called the southern sea lion and the Patagonian sea lion, is a sea lion found on the Chilean, Peruvian, Uruguayan, Argentine and Southern Brazilian coasts. It is the only member of the genus Otaria. Its scientific name was subject to controversy, with some taxonomists referring to it as Otaria flavescens and others referring to it as Otaria byronia. The former eventually won out. Locally, it is known by several names though the most common ones are lobo marino (sea wolf) and león marino (sea lion).
Sea LionThe South American sea lion is perhaps the archetypal sea lion in appearance. Males have a very large head with a well-developed mane, making them the most lionesque of the eared seals. They are twice the weight of females. Both males and females are orange or brown coloured with upturned snouts. The manes on males are lighter than females, and female fur on the head and neck is lighter than that of males. Pups are born greyish orange ventrally and black dorsally and moult into a more chocolate colour.
The South American sea lion's size and weight can vary considerably. Adult males can grow over 2.73 m (9 ft) and weigh up to 350 kg (770 lb). Adult females grow up to 1.8–2 m (6–7 ft) and weigh about half the weight of the males, around 150 kg (330 lb). These sea lions are the most sexually dimorphic of the five sea lion species.
Sea LionAs its name suggests, the South American sea lion is found along the coast and offshore islands of South America. It ranges from Peru south to Chile in the Pacific and then north to southern Brazil in the Atlantic. It generally breeds in the southern part of its range and travels north in winter and spring. Notable breeding colonies include Lobos Island, Uruguay; Peninsula Valdes, Argentina; Beagle Channel and the Falkland Islands. Some individuals wander as far north as southern Ecuador, although apparently they never bred there.
South American sea lions prefer to breed on beaches made of sand, but will breed on gravel, rocky or pebble beaches, as well. They can also be seen on flat rocky cliffs with tidepools. Sea lion colonies are more scattered on rocky beaches than sand, gravel or pebble beaches. The colonies make spaces between each individual when it is warm and sunny. They can also be found in marinas and wharves but do not breed there.
South American sea lions feed on a variety of fish, including Argentine hake and anchovies. They also eat cephalopods, such as shortfin squid, Patagonian squid and octopus. They have even been observed preying on penguins, pelicans and young South American fur seals. South American sea lions normally hunt in shallow waters less than five miles from shore. They often forage at the ocean floor for slow moving prey, but they will also hunt schooling prey in groups. When captured, the prey is shaken violently and torn apart. South American sea lions have been recorded to take advantage of the hunting efforts of dusky dolphins, feeding on the fish they herd together. The sea lions themselves are preyed on by orcas and sharks.


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