What's the Difference Between Seals and Sea Lions?

Seals and sea lions are commonly mistaken for one another. While rarely confused with their fellow pinniped relative, the walrus—easily identified by its telltale tusks—these torpedo-shaped sea dwellers share many similarities, including their sweet, doglike faces. A few key differences, however, set them apart.

So, which animal is it that you find shuffling around along the California coast, setting boundaries with beachgoers with their signature barks? Here's how to tell the difference between seals and sea lions.

Seal and Sea Lion Classification

Both seals and sea lions are pinnipeds, or members of the order Pinnipedia, which are described as carnivorous, fin-footed, mostly marine (but technically semiaquatic) mammals. They share this order with walruses.

Sea lions are technically seals but not true seals. That's because sea lions and fur seals have ears and true seals are earless. True (earless) seals belong to the family Phocidae, which includes two subfamilies (Phocinae and Monachinae). Eared seals belong to the family Otariidae.

There are 33 extant seal species, which includes six sea lion species, 18 true seals, and nine eared seals.

Characteristics of Seals vs. Sea Lions

You can tell a true seal from a sea lion from its lack of ear flap. Additionally, sea lions have much longer front flippers that help them assume an upright position while ashore. Rotating hind flippers allow sea lions to "walk" on land, whereas seals use their stubbier hind flippers only for swimming and their front flippers to move on land. If you see a seal on the beach, it will be lying horizontally on its belly.

Seals and sea lions also have very different vocalizations: Seals communicate with soft grunts, and sea lions with loud barks.

The location differs widely based on species, but many seals and sea lions coexist in a range. Sea lions occur in every ocean except the Northern Atlantic, while seals are found in the Northern Atlantic as well as the Pacific but are most abundant in polar seas.

Sea Lions vs. Fur Seals

Knowing the difference between sea lions and other eared seals is a little trickier. Both have hair—hence the name "fur seal"—while true seals are hairless and spotted. Sea lions are generally larger than seals, and while there are exceptions (such as the southern elephant seal, the largest of all pinnipeds), this is a good way to tell the two apart.

Additionally, fur seals have longer back flippers and larger ear flaps than sea lions. They can appear black when wet, whereas sea lions look brown.

Conservation Status

Of the six total species, three sea lions are endangered: Australian (population 6,500), Galápagos (population 9,200 to 10,600), and New Zealand sea lions (population 3,031), all of which have decreasing populations. The other three are near threatened (the Steller sea lion) or of least concern (California and South American sea lions) with stable or increasing populations.

Of the nine fur seals, one is endangered (the Galápagos fur seal, with 10,000 individuals remaining), one is vulnerable (the northern fur seal), and seven are of least concern. With the exception of Galápagos, northern, and Antarctic fur seals, populations are generally stable or increasing.

Three true seals are endangered: Caspian (population 68,000), Hawaiian monk (population 632 and decreasing), and Mediterranean monk seals (population 350 to 450 and increasing). The hooded seal is vulnerable, and 14 species are of least concern.

Extinct is one sea lion (the Japanese sea lion) and the one seal (the Caribbean monk seal), both last seen in the '50s.

Threats

Both seals and sea lions have a history of being hunted for their pelts, meat, and oil. Although the sealing industry was curtailed by the North Pacific Fur Seal Convention way back in 1911, it took decades for formal protections to take effect. Hunting was banned in the U.S. under the Fur Seal Act of 1966 and the Marine Mammal Protection Act of 1972, but seals and sea lions had already suffered from the mass slaughter. The IUCN points to hunting as the leading cause of extinction of the Japanese sea lion and Caribbean monk seal.

The animals are still being hunted, and now they face the additional challenge of surviving climate change. Due to rising ocean temperatures, certain fish species have abandoned the areas where they once were abundant, leaving the seals and sea lions hungry.