Sea lions

What a sea lion looks like California sea lions - has a thick layer of blubber (fat), short, thick fur that is dark brown to buff-coloured, and a dog-like head. Males grow to 860 lb and 8 ft long, while females are significantly smaller, at 240 lb and 6.5 ft long. They have pointed muzzles, making them rather dog-like. Males are darker and bigger than females and grow a large crest of bone on the top of their heads as they reach sexual maturity. They also have thick furry manes, although they are not as well developed as the manes of adult male South American or Steller sea lions. Females are lighter in colour than the males and pups are born dark, but lighten when they are several months old. When it is dry the skin is a chocolate brown colour. The whiskers (called vibrissae) help the seal's sense of touch. The nostrils are closed in the resting state. The sea lion has small external ears and a good sense of hearing. It also has keen eyesight but no colour vision. The Steller sea lion are lighter in colour than most sea lions, ranging from pale yellow to tawny and occasionally reddish. Females tend to be slightly lighter than the males. Steller sea lion pups are born almost black, weighing around 50 lbs, and remain dark for several months. Females and males both grow rapidly until the fifth year, after which female growth slows down considerably, attaining on average 8 feet in length and 660 lbs. Males continue to grow until their secondary sexual traits appear in their fifth to eighth year. While only slightly longer than the females, males have much wider chests, necks and general forebody structure and weigh 1300-2500 lbs. Males are further distinguished by broader, higher foreheads, flatter snouts, and darker, slightly tuftier hair around their large necks, giving them a maned appearance. Indeed, their Latin name translates roughly as: "maned one with the broad forehead".

Were the different types of sea lions found Sea lions are pinnipeds characterized by external ear flaps, long fore flippers, the ability to walk on all fours, and short, thick hair. Together with the fur seals, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species (the Japanese sea lion) in five genera. Their range extends from the subarctic to tropical waters of the global ocean in both the Northern and Southern Hemispheres, with the notable exception of the northern Atlantic Ocean.[1] They have an average life span of 20–30 years. A male California sea lion weighs on an average about 300 kg (660 lb) and is about 8 ft (2.4 m) long, while the female sea lion weighs 100 kg (220 lb) and is 6 ft (1.8 m) long. The largest sea lion is the Steller's sea lion which can weigh 1,000 kg (2,200 lb) and grow to a length of 10 ft (3.0 m). Sea lions consume large quantities of food at a time and are known to eat about 5–8% of their body weight (about 15–35 lb (6.8–16 kg)) at a single feeding.

What they eat and what part of the food chain they are Sea lion

How they breed and where they breed The Australian sea-lion is different from other sea-lions because they have no set breeding season, and pups may be born at any time of year. The breeding takes place on rocky beaches. Pups are born and raised on land, fed on milk from their mother's body. California sea lions tend to breed on the same section of beach year after year. Sea lions generally favor beaches on the windward side of islands. California sea lion bulls establish breeding territories on the beach from May to August. The peak of mating activity is in late June and early July. Galápagos sea lions may mate from May to January.

Do they migrate and travel great distances? Pinnipeds' bodies are specially adapted to help them swim and dive. They are streamlined. The nostrils close underwater. The pupils of the eyes expand widely so they can see well in the darkness deep underwater. Seals are able to hold their breath for long periods of time. The deepest diving seals can stay underwater for up to 2 hours. Underwater, their heart rate slows down and arteries squeeze shut so that only the sense organs and nervous system get the normal blood flow. Their muscles store oxygen. Once they come up after a deep dive, seals need to recover, and rapid blood circulation through large veins helps their body chemistry return to normal.

What is happing to the sea life in our sea • Bycatch. Fish live in complex ecosystems and often when fishers are fishing for one species they catch other creatures may also be marine mammals, turtles or even birds that are diving to catch their fish dinner. If they become entangled in the nets or caught on fish hooks they may drown. Bycatch is a major global problem. 300,000 small whales, dolphins and porpoises die each year as a result of becoming entangled in fishing gear • Competition for food. Because fish are caught in complexecosystems, sometimes there are problems with too many fish being caught which disrupts the balance of the food supply for other species. For example, if seals mostly eat one type of fish, and humans catch a lot too, then the seals might struggle to find enough food to survive. This topic is discussed in more detail in the food chain section

What is happing to the marine life because of this change • Habitat destruction. Some fishing methods can destroy sensitive habitats like coral reefs, sea mounts and estuaries, which are essential breeding and feeding grounds for many different animals and birds. If this sensitive habitat is destroyed it can make it more difficult for the fish to find their food, hide from predators and reproduce • Competition for food. Because fish are caught in complex ecosystems, sometimes there are problems with too many fish being caught which disrupts the balance of the food supply for other species. For example, if seals mostly eat one type of fish, and humans catch a lot too, then the seals might struggle to find enough food to survive. This topic is discussed in more detail in the food chain section

What can be done to help the sea Your class can get stuck into other activities, such as beach clean-ups, to help improve the marine environment. See further resources at the back for contact details of MCS and Project AWARE, two organisations which run events like this. Introduce this section with the impact of fishing discussion card called ‘The downside of fishing’.

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