Mistaken Identities: Seals vs. Sea Lions

It can be tricky to tell marine animals apart—especially when looking at vaguely torpedo-shaped shadows shooting through the waves. Just as dolphins and porpoises have similar features, pinnipeds (the group of marine mammals made up of seals, sea lions and walruses) have a lot of physical characteristics in common with one another. Walruses stand out because of their size and huge tusks. But what about seals and sea lions? After all, they both have streamlined bodies and are flipper-footed. Luckily, several differences are visible even at a distance.

All pinnipeds are protected by the Marine Mammal Protection Act; in Maryland, the public is required to keep a minimum distance of 50 yards (about three school bus lengths) from these animals, both on the beach and in the water.

Other Differences

The presence or absence of external ear flaps and flipper form and function are some of the easiest ways to tell seals from sea lions, but there are other ways.

Social Dynamics

While you may see images of seals or sea lions congregating in large groups (colonies), most true seals have looser social and familial bonds with one another. They are often solitary hunters and rejoin larger groups during the breeding and pupping season. Sea lions, however, can routinely be spotted basking, resting, foraging and playing together. Herds of sea lions can even tally upward of a thousand individuals.

Range

These species overlap in a few regions, but it's less common than you might think. Seals dwell in the world's polar and subpolar ocean regions, with a few exceptions, such as the handful that reside in more tropical waters (and one that lives in a freshwater lake!). Sea lions venture into more temperate areas and can be found throughout and along coastlines of the northern Pacific, the coasts of southern South America and Africa, and around islands in the Southern Ocean. Notably, there are no sea lions in the northern Atlantic Ocean—so if you spot a pinniped on a Maryland or other mid-Atlantic beach, it's a seal, not a sea lion.

Protecting Seals and Sea Lions

Despite the protection afforded by the Marine Mammal Protection Act, seals and sea lions still face threats from entanglement, shifting food resources and climate change. Since pinnipeds routinely come ashore, these are often the best times to assess if they have stranded due to injury or illness.

If you're in Maryland and see a seal, please report it to the National Aquarium's Animal Stranding Hotline at 410-576-3880 so our Animal Rescue team can respond. Outside Maryland, please report a stranded or injured marine animal to the appropriate U.S. organization, notify the appropriate Canadian organization of a marine mammal incident or sighting, or contact the Mexico Marine Wildlife Rescue Center. You can also help protect them by joining beach cleanups to remove fishing debris or by reducing your carbon footprint.

All National Aquarium stranding response and seal rehabilitation activities are conducted under NOAA permit 18786-04.