Seals vs. Sea Lions: What's the Difference

Marine Mammal 101

California Sea Lion and Harbor Seals
California Sea Lion (left) and Harbor Seal and Pup (right). Jennifer Kennedy/Dr. Brandon Southall, NMFS/OPR

The term "seal" is often used to refer to both seals and sea lions, but there are several characteristics that set seals and sea lions apart. Below you can learn about the differences that set seals and sea lions. 

Seals, sea lions and walruses are all in the order Carnivora and suborder Pinnipedia, thus they are called “pinnipeds.” Pinnipeds are mammals that are well-adapted for swimming. They usually have a streamlined barrel shape and four flippers at the end of each limb.  As mammals, they also give birth to live young and nurse their young. Pinnipeds are insulated with blubber and fur. 

Pinniped Families

There are three families of pinnipeds: the Phocidae, the earless or true seals; the Otariidae, the eared seals, and the Odobenidae, the walrus. This article focuses on the difference between the earless seals (seals) and the eared seals (sea lions).

Characteristics of Phocidae (Earless or True Seals)

Earless seals have no visible ear flaps, although they still have ears, which may be visible as a dark spot or small hole on the side of their head. 

"True" seals:

  • Have no external ear flaps.
  • Swim with their hind flippers. Their hind flippers always face backward and are furred.
  • Have front flippers that are short, furry and stubby in appearance.
  • Have two or four teats.
  • Can be found in both marine and freshwater environments.

Examples of earless (true) seals: Harbor (common) seal (Phoca vitulina), grey seal (Halichoerus grypus), hooded seal (Cystophora cristata), harp seal (Phoca groenlandica), elephant seal (Mirounga leonina), and monk seal (Monachus schauinslandi).

Characteristics of Otariidae (Eared Seals, Including Fur Seals and Sea Lions)

One of the most noticeable features of eared seals is their ears, but they also move around differently than true seals. 

Eared seals:

  • Have external ear flaps.
  • Have four teats.
  • Are only found in marine environments. 
  • Swim with their front flippers. Unlike earless seals, their hind flippers can turn forward, and they are better able to walk, and even run, on their flippers. The "seals" you may see performing at marine parks are often sea lions.
  • May congregate in larger groups than true seals.

Sea lions are much more vocal than true seals, and make a variety of loud, barking noises.

Examples of eared seals: Steller’s sea lion (​Eumetopias jubatus), California sea lion (Zalophus californianus), and Northern fur seal (Callorhinus ursinus).

Characteristics of Walruses

Wondering about walruses, and how they differ from seals and sea lions? Walruses are pinnipeds, but they are in the family, Odobenidae. One obvious difference between walruses, seals and sea lions is that walruses are the only pinnipeds with tusks. These tusks are present in both males and females.

Other than tusks, walruses have some similarities to both seals and sea lions. Like true seals, walruses don't have visible ear flaps. But, like eared seals, walruses can walk on their flippers by rotating their hind flippers under their body. 

References and Further Information:

  • Berta, A. "Pinnipedia, Overview." In Perrin, W.F., Wursig, B. and J.G.M. Thewissen. Encyclopedia of Marine Mammals. Academic Press. p. 903-911.
  • NOAA National Ocean Service. . Accessed September 29, 2015.
  • NOAA Office of Protected Resources. 2008. (Online). NOAA. Retrieved November 23, 2008.
  • Waller, Geoffrey, ed. 1996. SeaLife: A Complete Guide to the Marine Environment. Smithsonian Institution Press. Washington, D.C.