Seals vs Sea Lions: 5 Major Differences Explained

Straddling a fine line between oceans and land, seals and sea lions belong to a group of closely related semi-aquatic mammals called the Pinnipeds (this is a Latin term that roughly translates to “fin-footed”). On an evolutionary timescale, it’s believed that the Pinnipeds split off from other carnivores (like canines and felids) around 50 million years ago. Their huge flippers, thick layers of blubber, and long whiskers enable them to survive harsh life in the cold ocean waters.

The taxonomy of this group can be a little hard to parse, but Pinnipeds are divided into three distinct families. The family of Phocidae contains all of the true seals; they are sometimes called crawling seals or earless seals to distinguish them from other types of seals. The family of Otariidae contains 16 species of fur seals and the sea lions (a third family, called Odobenidae, is devoted exclusively to the tusked walruses).

What confuses many people is that, despite their name, fur seals are anatomically and behaviorally closer to the sea lions than the true seals. Basically, fur seals and sea lions are distinguished from true seals by body shape and social behavior. But fur seals are further distinguished from sea lions by the presence of a thick layer of fur (not just hairless blubber) to protect them from the cold water. To clarify for this article, whenever the term “seal” is used, it generally refers to the true seals. The term “sea lion” may refer to both the sea lions and the fur seals as well.

Comparing Seals vs Sea Lions

Here’s a quick breakdown on the basic differences between the seal and the sea lion.

Category	Seal	Sea Lion
Size	110 to 8,500 lbs. (50 to 3,850 kg)	150 to 2,200 lbs. (70 to 1,000kg)
Social Behavior	Mostly solitary except in the breeding season	Lives in larger colonies
Habitat	Polar, subpolar, and temperate waters; the Baikal seal is the only freshwater species	Subpolar, temperate, and equatorial waters
Number of Species	18 species, including the elephant seals and ringed seals	16 species, including the California sea lion and Steller sea lion
Body	Streamlined body with backward-facing hind flippers	Sea lions have external ear flaps and rotatable hind flippers

The 5 Key Differences between Seals and Sea Lions

While seals and sea lions can be very difficult to tell apart for the untrained eye, there are five important differences between them that should aid in identification. These differences mostly come down to body shape and social organization. Body size or color alone will not help you determine which one is which (one exception is the truly massive elephant seal, the largest of all Pinnipeds).

Keep in mind that there’s enormous variation within families as well as between them. Some species may have certain adaptations that closely related species simply lack.

Seals vs Sea Lions: Adaptations for Land and Water

True seals are more adapted for aquatic life than life on land. Their more streamlined bodies enable them to cut swiftly through the water, while their hind flippers are angled backward to propel them forward. They move clumsily on land by crawling on their bellies and dragging themselves forward with their front flippers. Sea lions, by contrast, are generally better adapted for life on land, since their hind flippers rotate forward and function more like feet. Whereas the seals rely more on whole-body movements in the water, sea lions largely swim by rotating their hind flippers.

Seals vs Sea Lions: Ear Flaps

True seals have no visible ear flaps; instead, they have two holes in the sides of their heads. Ear holes enable seals to hear well in water and on land. This feature is especially crucial to their survival, for seals are the preferred meal of polar bears. If a seal can hear a polar bear up above, it may be able to escape the ferocious predator.

Both sea lions and fur seals have small external flaps on their heads. The flaps turn downward to prevent water from entering their ears whilst swimming.

Seals vs Sea Lions: Size of the Flippers

Seals tend to have shorter flippers than sea lions. They also have short claws surrounded by hairless skin, whereas sea lions have long claws on their front flippers with tufts of fur.

Sea lions are more likely to congregate together in large, boisterous colonies for the entire year. True seals, by contrast, prefer to live and hunt alone; they only tend to come ashore about once a year to mate.

Seals vs Sea Lions: Vocalizations

True seals make soft grunting sounds, sometimes emphasized by slapping the water, but otherwise, they’re pretty quiet. Since seals are solitary by nature, it makes sense that their vocalizations are minimal.

Sea lions, on the other hand, make loud barking noises to communicate. When a colony is riled up, it can be a sheer cacophony of barking and grunting sounds. They are social creatures, and verbal communication is a form of socializing the sea lion uses regularly.

Seals vs Sea Lions: Survival Status

Beyond the 5 key differences between seals and sea lions, there’s one more we wanted to add to the list. Seal populations around the world are normal, with millions of them living in Antarctica alone. They are classified as animals of least concern by the IUCN. But sea lions are currently not quite as lucky. Due to threats from climate change, pollution, and hunting, three species of sea lions have been listed as endangered by the IUCN.