Seals vs Sea Lions: 5 Major Differences Explained

Written by AZ Animals Staff
Updated: July 23, 2021
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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.

SealSea Lion
Size110 to 8,500 lbs. (50 to 3,850 kg)150 to 2,200 lbs. (70 to 1,000kg)
Social BehaviorMostly solitary except in the breeding seasonLives in larger colonies
HabitatPolar, subpolar, and temperate waters; the Baikal seal is the only freshwater speciesSubpolar, temperate, and equatorial waters
Number of Species18 species, including the elephant seals and ringed seals16 species, including the California sea lion and Steller sea lion
BodyStreamlined body with backward-facing hind flippersSea 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. Both sea lions and fur seals have small external flaps on their heads.

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.

Seals vs Sea Lions: Social Behavior

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. 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.

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FAQs (Frequently Asked Questions) 

What is the difference between a seal and a sea lion?

The main difference is that the true seals are better adapted for a more solitary life of hunting and surviving for long periods of time out in the harsh sea. Its streamlined body is more ergonomic and lacks external ear flaps, and its hind flippers are unable to rotate around, which makes it clumsy on land.

Which is more aggressive, a seal or a sea lion?

It’s difficult to say which one is more aggressive because behavior can vary so much by species. Both seals and sea lions may become aggressive if they feel threatened or provoked in some manner. Since even the smallest Pinnipeds are the same size as a person, they should not be approached in the wild unless absolutely necessary.

Do sea lions kill seals?

Fatalities between seals and sea lions are normally quite rare. The Steller sea lion (the largest of all sea lions, weighing up to 2,200 pounds) has been known to kill and eat much smaller seals, but this is an exception rather than a rule. Given the similar size between a seal and a sea lion, one does not usually prey upon the other. Territorial disputes are a little more common, but even then, they very rarely result in death. One population usually just drives off the other.

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