All otariids bear young and suckle on land. All mate on land, but at least four species also mate to a small degree in the water. They prefer islands, possibly because these sites afford more freedom from land predators, winds and spray that provide better cooling, and a shorter transit time to offshore feeding areas (or a combination of these benefits) than mainland sites do. Nevertheless, large mainland breeding sites now exist in Africa, Argentina, and Peru, and historically existed along the Pacific Coast of North America. Animals prefer breeding on sand or rock, and tend to avoid mud. Most species breed on beaches or headlands, but when the northern fur seal is numerous its colonies extend several hundred yards (meters) up hillsides. Hooker's sea lion breeds under trees on at least two islands, and often suckles its young under dense brush. The Antarctic and northern fur seals can tolerate snow, but do not habitually breed on ice. Where cold water is available, several species live in very hot climates. Otariids can climb nearly vertical surfaces, an ability that gives them access to land areas that true seals cannot use.

Otariids tend to use very few of the many land sites available to them. All species have a long (more than four month) period of neonate dependency, which forces mothers to alternate between feeding themselves and suckling. Land sites must be located where the feeding/nursing pattern is energetically feasible, and this may reduce the number of sites they can use. True seals wean young at a few days to weeks of age, and suspend feeding while nursing. Thus, they are not constrained to breed on sites that permit commuting to feeding areas, and, as a group, tend to breed in smaller groups at more sites than eared seals.

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An Australian sea lion (Neophoca cinerea) nursing a pup. (Photo ┬ęTony Wu/www.silent-symphony.com. Reproduced by permission.)

Fur seals tend to feed in the open ocean; sea lions tend to forage on the continental shelf.

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