Seals and sea lions, along with walruses, belong to a group of marine mammals called “pinnipeds.” Pinniped means fin or flipper-footed in Latin. These animals spend the majority of their time in the ocean, but come on shore for long periods of time. Although seals and sea lions have similarities, they also have several distinct characteristics and adaptations that distinguish them from one another.
What Are the Differences Between Seals and Sea Lions?
“True” seals, also known as “earless” seals or simply “seals,” belong to a group of pinnipeds that have ear holes, but lack an external ear flap. This includes species such as the harbor seal, endangered Hawaiian monk seal, and harp seal.
On land, seals use their bellies to move around because they have small front flippers that are thinly webbed with a claw on each small toe. In the water, seals swim easily, moving their rear flippers back and forth, similar to how a fish uses its caudal fin (tail) to propel itself through the water.
In general, seals tend to be quiet, and vocalize through noises such as soft grunts, growls, or hisses. Many are less social than sea lion species, especially in the water, but seals can be found on land together to avoid predators, rest, mate, and nurse their pups.
Sea lions, such as the California sea lion and Steller sea lion, belong to a group of pinnipeds that have external ear flaps. This group also includes fur seals like the threatened Guadalupe fur seal.
On land, they use their large, elongated front flippers and rear flippers rotated underneath their bodies to “walk.” In the water, sea lions propel themselves by paddling their front flippers and use their rear flippers to help steer, like a boat’s rudder.
Sea lions can be noisy, and recognized by their loud and distinct “bark.” They commonly congregate in large groups called “herds” or “rafts.” They can be seen hauled out together on offshore rocks, sandy beaches, and sometimes human-made structures such as jetties and piers.
All seals and sea lions are protected under the Marine Mammal Protection Act and some are also listed under the Endangered Species Act. It is important to view these wild animals from a safe and respectful distance for their safety—and yours. If you see a sick or injured seal or sea lion, please call your nearest marine mammal rescue organization.