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The name Otariidae may not be as familiar as what it represents: the family of "eared" seals and sea lions. These are marine mammals with visible ear flaps, and a few other characteristics that are detailed below.
The Family Otariidae contains 13 species still living (it also contains the Japanese sea lion, a species that is now extinct). All of the species in this family are fur seals or sea lions.
These animals can live in the ocean, and feed in the ocean, but they give birth and nurse their young on land. Many prefer living on islands, rather than the mainland. This gives them better protection from predators and easier access to prey.
Characteristics of Eared Seals and Sea Lions
All of these animals:
- Are marine mammals.
- Are in the Infraorder Pinnipedia, making them related to "earless" seals and walruses.
- Have fur (mostly coarse hairs in sea lions, and a dense underfur in fur seals).
- Have long front flippers that can be more than one-quarter the length of the animal's body. These flippers are leathery and hairless with small claws and are used primarily for swimming.
- Have large hind flippers that can be rotated under the animal's body and used to support it so the animal can move relatively easily on land. Otariids can even run on land, which is something that earless seals cannot do. In the water, the otariid hind flippers are used primarily for steering.
- Have a small tail.
- Have a visible ear flap that has a middle ear similar to that of terrestrial mammals, and an air-filled auditory canal.
- Have excellent eyesight that allows them to see well in the dark.
- Have well-developed whiskers (vibrissae) that help them sense their surroundings.
- Have males that are between 2-4.5 times larger than the females of their species.
- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Vertebrata
- Superclass: Gnathostoma
- Order: Carnivora
- Suborder: Caniformia
- Infraorder: Pinnipedia
- Family: Otariidae
Otariidae Species List
- Cape fur seal (Arctocephalus pusillus, includes 2 subspecies, the Cape fur seal, and Australian fur seal)
- Antarctic fur seal (Arctocephalus gazella)
- Subantarctic fur seal Arctocephalus tropicalis
- New Zealand fur seal (Arctocephalus forsteri)
- South American fur seal (Arctocephalus australis, includes 2 subspecies, the South American fur seal, and Peruvian fur seal)
- Galapagos fur Seal (Arctocephalus galapagoensis)
- Arctocephalus philippii (includes 2 subspecies: the Juan Fernandez fur seal and Guadalupe fur seal)
- Northern fur seal (Callorhinus ursinus)
- California sea lion (Zalophus californianus)
- Galapagos sea lion (Zalophus wollebaeki)
- Steller sea lion or Northern sea lion (Eumetopias jubatus, includes two subspecies: the Western sea lion and Loughlin's Steller sea lion)
- Australian sea lion (Neophoca cinerea)
- New Zealand sea lion (Phocarctos hookeri)
- South American sea lion (Otaria byronia)
As mentioned above, a fourteenth species, the Japanese sea lion (Zalophus japonicus), is extinct.
Otariids are carnivores and have a diet which varies depending on the species. Common prey items include fish, crustaceans (e.g., krill, lobster), cephalopods and even birds (e.g., penguins).
Otarrids have distinct breeding grounds and often gather in large groups during the breeding season. Males arrive on the breeding grounds first and establish as large a territory as possible, along with a harem of up to 40 or 50 females. The males defend their territory using vocalizations, visual displays, and by fighting with other males.
Females are capable of delayed implantation. Their uterus is Y-shaped, and one side of the Y can hold a growing fetus, while the other can hold a new embryo. In delayed implantation, mating and fertilization occur and the fertilized egg develops into an embryo, but it stops development until conditions are favorable for growth. Using this system, females may become pregnant with another pup just after they give birth.
Females give birth on land. The mother may nurse her pup for 4-30 months, depending upon the species and availability of prey. They are weaned when they weigh about 40 percent of their mother's weight. Mothers may leave the pups on land for extended periods to go on foraging trips in the ocean, sometimes spending as much as three-quarters of their time at sea with the pups left onshore.
Many otariid populations were threatened by harvesting. This started as early as the 1500's when animals were hunted for their fur, skin, blubber, organs or even their whiskers. (Steller sea lion whiskers were used for cleaning opium pipes.) Seals and sea lions have also been hunted because of their perceived threat to fish populations or aquaculture facilities. Many populations were nearly wiped out by the 1800s. In the U.S., all otariid species are now protected by the Marine Mammal Protection Act. Many have been on the rebound, although Steller sea lion populations in some areas continue to decline.
Current threats include entanglement in fishing gear and other debris, overfishing, illegal shooting, toxins in the marine environment, and climate change, which may affect prey availability, available habitat, and pup survival.
Sources and Further Reading
- Australian Fur Seals. Climate Change. Phillip Island Nature Parks. Accessed January 8, 2014.
- Berta, A. and Churchill, M. 2013. Otariidae. Accessed through: World Register of Marine Species, January 8, 2014
- Committee on Taxonomy. 2013. List of marine mammal species and subspecies. Society for Marine Mammalogy, www.marinemammalscience.org, January 8, 2014
- Gentry, R.L. 2009. Eared Seals: . In Encyclopedia of Marine Mammals, ed. by W.F. Perrin, B. Wursig, and G.M. Thewissen. pages 340-342.Otariidae 200
- Mann, J. 2009. Parental Behavior 200. In Encyclopedia of Marine Mammals, ed. by W.F. Perrin, B. Wursig, and G.M. Thewissen. pages 830-831.
- Myers, P. 2000. Otariidae, Animal Diversity Web. Accessed January 8, 2014.
- Office of Naval Research. Ocean Life - California Sea Lion: Status and Threats. Accessed January 8, 2014.
- The Seals of Nam. Eared Seals (Otariids). Accessed January 8, 2014.