What's the difference between a seal and a sea lion?

Seals and sea lions are right up there with otters and dolphins as some of the marine darlings that draw crowds of admiring fans to aquariums and beaches. But upon closer inspection, you may wonder which animal you're actually pointing and grinning at: a seal or a sea lion.

Seals are closely related to sea lions and another semiaquatic mammal -- the walrus -- but there are some distinct differences. Walruses are easy to point out, but seals and sea lions can get a little confusing, especially because of the terminology used for the two. Sea lions are classified with fur seals, and the remaining seals with ears are known as true seals. We'll discuss fur seals and true seals in much more detail on the next page.

Taxonomic discussions tend to be a bit muddled as scientists strive to classify all the different species on the planet. Both types of seals, sea lions and walruses are all considered to be in the suborder Pinnipedia, which is usually translated as "fin-footed" or "feather-footed." Pinnipeds (within the order Carnivora) consist of three families. The breakdown of these families looks something like this:

Before we look at what sets these animals apart, let's examine some features all pinnipeds share. For instance, they all have short fur (although in varying amounts), growing in different shades and patterns. Pinnipeds sport fine-tuned whiskers called vibrissae which, like with cats and mice, work as tactile sensors. These mammals also possess four flippers and great hearing. All three branches tend to be social butterflies, although at times individuals may crave some alone time.

Baby seals or sea lions are called pups, while baby walruses are known as calves. Pinnipeds can live in the womb for anywhere from 8 to 16 months, depending on how long the fertilized egg lies dormant.

As you probably guessed from the name of their order, pinnipeds are carnivores and eat a variety crustaceans and clams. Pinnipeds also vary greatly between family, genus and species in the amount of time they spend on land versus time in the water. They're believed to have evolved from animals similar to bears or weasels. As these creatures began spending long spans of time in the water, they eventually adapted to their marine environment and became semiaquatic.

Ready to discover what visual cues you can use to determine if the animal you're looking at is a sea lion or a seal? Find out how to tell these slick customers apart on the next page.

Seals and Sea Lions (and Walruses)

Seals and sea lions share many characteristics -- that's why they're in the same suborder after all -- but there are a few important features we can use to distinguish them. To examine where the subtle differences occur, let's look closer at these pinnipeds.

David Tipling/Lonely Planet Images/Getty Images

when looking at these pups.

Phocidae: This is the family where we find true or earless seals. Phocids have no external ears, although they do have ear holes. The seals' front flippers are generally furry, small and weak, so these marine mammals move on land by using their diminutive forward appendages to wiggle forward. They use their back flippers to generate powerful strokes when swimming in the water.Some common species of phocids include harp seals (the most populous species of seal) and harbor seals.
Otariidae: The otariids, sea lions and fur seals, have little external ear flaps that poke out of the sides of their heads (hence why members of this family are also referred to as eared seals). Another big difference between true seals and these guys is that sea lions and fur seals have larger, hairless flippers which they use more effectively on land. Sea lions and fur seals can rotate their hind flippers toward the ground so they're able to walk on all four appendages. Otariids make use of their fore flippers when propelling themselves through water.Well-known sea lion species include the California sea lion and the steller (or northern) sea lion. Fur seals, which tend to have thicker coats and longer flippers than sea lions, include the Guadalupe fur seal, the northern fur seal and the Galapagos fur seal.
Odobenidae: The sole surviving species of this family is the walrus. There are two walrus subspecies -- one living in the Pacific Ocean and one in the Atlantic. Embracing characteristics of both of the previously mentioned families, walruses have little fur and no external ears. What they do have is the otariid ability to move on land by using their hind flippers. They make use of both their fore flippers and hind flippers while swimming. They also possess tusks and can grow extremely large, with males weighing up to about 3,000 to 4,000 pounds (1,300 to 1,800 kilograms). For more information about odobenids, read How Walruses Work.

These Atlantic walruses relax on ice.
Paul Nicklen/National Geographic/Getty Images

Now that you know all about pinnipeds -- and how to tell them apart -- you're ready to seal the deal and impress your friends the next time you're at the beach. Go to the next page for some great links about seals, sea lions, walruses and other creatures of the sea.

Lots More Information

Sources

"2007 IUCN Red List." International Union for Conservation of Nature and Natural Resources. 2007. (7/1/2008)http://www.iucnredlist.org/search/search-basic
"Endangered Marine Mammals." The Marine Mammal Center. (7/1/2008)http://www.marinemammalcenter.org/learning/education/mammalinfo/endanger.asp#top
"Fur Seal." Encyclopedia Britannica. 2008. (7/1/2008)http://www.britannica.com/EBchecked/topic/222512/fur-seal
Higden, Jeff et al. "Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset." BMC Evolutionary Biology. 11/9/2007. (7/1/2008)http://www.biomedcentral.com/1471-2148/7/216"
Marine Mammal Classification." The Marine Mammal Center. (7/1/2008)http://www.marinemammalcenter.org/learning/education/mammalinfo/classification.asp
"Pinniped." Encyclopedia Britannica. 2008. (7/1/2008)http://www.britannica.com/EBchecked/topic/461139/pinniped
"Pinnipeds: Seals, Sea Lions, and Walruses." National Oceanic and Atmospheric Administration's National Marine Fisheries Service's Office of
Protected Resources. (7/1/2008)http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/
"Seal." Encyclopedia Britannica. 2008. (7/1/2008)http://www.britannica.com/EBchecked/topic/530868/seal
"Seals, Sea Lions, and Walruses." SeaWorld Education Department. (7/1/2008)http://www.seaworld.org/just-for-teachers/guides/pdf/s&sl-4-8.pdf
"Sea Lion." Encyclopedia Britannica. 2008. (7/1/2008)http://www.britannica.com/EBchecked/topic/530626/sea-lion
"Sea lions and seals--what's the difference?" San Diego Zoo's Animal Bytes. (7/1/2008)http://www.sandiegozoo.org/animalbytes/t-sea_lion.html
"The Pinnipeds: Seals, Sea Lions, and Walruses." The Marine Mammal Center. 1/2001. (7/1/2008)http://www.marinemammalcenter.org/learning/education/pinnipeds/pinnipeds.asp
"Walrus." Encyclopedia Britannica. 2008. (7/1/2008) http://www.britannica.com/EBchecked/topic/635052/walrus
"What's the difference between a seal and a sea lion?" North Carolina Aquariums. 10/15/2005. (7/1/2008)http://www.ncaquariums.com/askaquarium/seal.htm