Seals vs. sea lions: what’s the difference?

What’s the difference between seals and sea lions? 

Let’s look at some key differences between seals and sea lions. 

How they look 

Here are some key physical differences to help you tell seals and sea lions apart. 

Size 

Seals tend to be smaller than sea lions. But there are exceptions—and across both seal and sea lion species, there’s a lot of variation. 

Seals belong to the family Phocidae, within which there are 18 living species, including harbour seals, leopard seals, and elephant seals. Members of the Phocidae family range vastly in size, from huge southern elephant seals that weigh up to 4,000 kilograms (8,800 pounds) to small Baikal seals that weigh 50 to 100 kilograms (110 to 220 pounds).

Sea lions belong to the family Otariidae, which includes six living species of sea lions and eight living species of fur seals. The largest sea lion species—the Steller sea lion—can weigh as much as 1,133 kilograms (2,500 pounds), while the smallest—the Galapagos sea lion—only weighs about 80 kilograms (175 pounds).  

External ears 

Seals are also known as ‘true seals’ or ‘earless seals’. However, despite this name and their lack of external ear flaps, seals do in fact have ears. They just have small ear holes on the sides of their heads with no flaps. 

Sea lions are referred to as ‘eared seals’ and have visible external ear flaps. 

Flippers 

Body size and ears are not the only differences in appearance between seals and sea lions. You can also tell them apart by looking at their flippers. Seals have shorter front and hind flippers, all of which are fur-covered and have long claws on each toe.  

In contrast, sea lions have longer, skin-covered flippers with claws on only their hind flippers, which they use to scratch and groom themselves. Sea lions’ flippers are also much larger than those found on seals. Sea lions use their flippers to move around and for grooming.  

On land 

On land, there are also noticeable differences in how seals and sea lions move. Sea lions have much slimmer bodies and can rotate their hind flippers under their bodies to walk or even gallop quickly on all fours. This walking and galloping is aided by their large flippers, which they use to push themselves along on land. 

Seals have rounder bodies and move more awkwardly on land. They cannot rotate or walk on their much smaller flippers—a seal’s movement on land is more like a caterpillar’s. This combination of a rounder body and smaller flippers leads seals to inch their bodies along the ground in a movement known as ‘galumphing’.   

How they sound  

Both seals and sea lions produce vocalisations to communicate, though sea lions are the chattier of the two. A repertoire of barks, growls, and groans helps sea lions recognise each other, establish and defend territories, and engage in other social interactions.  

Sea lions also have exceptionally good hearing, both on land and under water. Despite speculation that sea lions can use echolocation, no good evidence suggests this. 

Seals tend to be much quieter than sea lions. They use growls, whistles, and moans to communicate, but they don’t bark. Scientists have observed that grey seals clap their flippers together to ward off rivals and attract a mate. This behaviour is different from the one seen in zoos, where seals clap because they have been trained to do so, rather than for a purpose, as seen in the wild. 

How they see  

One point of similarity between seals and sea lions is their exceptional eyesight. Both are equally adept at seeing both above and below the water. All pinnipeds have a membrane called the tapetum lucidum at the back of their eyes. This increases the amount of light taken in by the eye to aid with night vision and causes the eyes of seals and sea lions to glow, much like cats’ eyes. 

The tapetum lucidum is particularly useful for species that hunt at great depths, such as the elephant seal. These seals search for prey in deeper waters where the light does not penetrate, so they rely on their night vision and recognition of their target’s bioluminescence to hunt effectively. 

Sea lions are found on coastlines, islands with sandy beaches, and rocky ledges from the subarctic to tropical waters in the Northern and Southern Hemispheres (except in the northern Atlantic, where there are no sea lions).  

Conservation status 

Some species of both seals and sea lions are considered endangered by the IUCN Red List. The Caribbean monk seal and the Japanese sea lion have not been sighted in the past 50 years, leading researchers to believe that these species are extinct. 

The other species of seal range from least concern to endangered on the IUCN Red List. As of 2025, the Galapagos fur seal, Hawaiian monk seal, and Caspian seal are classed as endangered. The Mediterranean monk seal is classed as vulnerable. 

The Australian sea lion, the Galapagos sea lion, and the New Zealand sea lion are all classed as endangered, the Steller sea lion as near threatened, and the South American and Californian sea lions as least concern. 

Unfortunately, there are plans to extend the commercial seal hunt in Canada. The EU Seal Trade Regulation, introduced in 2009, is currently under evaluation, raising concerns that this regulation will be watered down. In 2025, seal and sea lion populations remain threatened by entanglement in fishing gear, plastic pollution, and climate change. 

How IFAW helps seals 

IFAW was founded on the mission of ending the commercial seal hunt in Canada. We travelled to the ice to observe and document the annual slaughter, bringing international media, politicians, and veterinary experts with us to observe the cruelty first-hand. 

Since then, our work has helped bring about monumental changes, like the 2009 EU ban on seal products. We continue to urge the Government of Canada to adopt sustainable alternatives to the commercial seal hunt—ones that can support the economy and local communities while protecting seals. 

On Cape Cod in the US, our marine mammal rescue team has developed safe and effective techniques to rescue entangled seals. One method, developed in partnership with the Marine Mammal Centre in California, involves using a sedative dart, which enables our team to capture, disentangle, and treat seals. We work to minimise the suffering of seals, release them back to the ocean, and share our expertise with marine mammal rescue networks around the world.  

IFAW also promotes coexistence with seals by working with communities on Cape Cod to ensure that beachgoers can appreciate the animals from a safe distance, minimising additional human impacts. We have distributed 100 informational seal signs to 14 towns and the Cape Cod National Seashore. Through greater awareness of seal behaviour and habitat, this initiative aims to inspire community conversations around coexistence with wildlife rather than conflict.