Seal vs Sea Lion: What’s the Difference?
The main difference between seals and sea lions is that sea lions have small external ear flaps and can walk on all four flippers, while true seals have only ear holes and wriggle on their bellies on land. Sea lions swim with long front flippers and bark loudly. True seals, such as the harbor seal, swim with their hind flippers and are much quieter.
| Harbor Seal | California Sea Lion | |
|---|---|---|
| Scientific name | Phoca vitulina | Zalophus californianus |
| Lifespan | 25–30 years in the wild; males about 20–25 years, females 30–35 | 15–25 years in the wild |
| Weight | 55–170 kg (120–375 lb) | 100–350 kg (220–770 lb) |
| Size | 1.5–1.9 m (4.9–6.2 ft) (length) | 1.8–2.4 m (5.9–7.9 ft) (length) |
| Top speed | about 19 km/h (12 mph) | up to 40 km/h (25 mph) |
| Gestation / incubation | 9–11 months, including delayed implantation | about 11 months, including delayed implantation |
| Diet | Carnivore | Carnivore |
| Family | Phocidae | Otariidae |
| Habitat | Coastal waters, Estuaries and bays, Rocky shores, Sandbars and mudflats, Glacial fjords | Coastal waters, Rocky and sandy shores, Offshore islands, Harbors and marinas |
| IUCN status | Least Concern | Least Concern |
Figures shown are for the harbor seal (Phoca vitulina) and the california sea lion (Zalophus californianus).
Key differences
Ears
Sea lions and fur seals make up the family Otariidae, the 'eared seals,' named for the small, rolled ear flap visible on each side of the head. True seals, family Phocidae, have no external ear at all, just a small opening in the fur. On a clear photo, this one feature settles the identification.
Moving on land
A sea lion can rotate its hind flippers forward under its body, lift its chest and walk or even gallop on all fours, which is why it climbs rocks, docks and buoys so easily. A true seal's hind flippers point permanently backward. On land it hunches along on its belly like a caterpillar.
Swimming
Sea lions propel themselves with their large, wing-like front flippers, essentially flying underwater, and steer with the hind ones. True seals do the opposite: they tuck their short front flippers against the body and swim by sweeping the hind flippers side to side, like a fish's tail. Seals are often the better deep divers.
Front flippers
A sea lion's front flippers are long, hairless, and leathery, with only tiny nails. A true seal's front flippers are short, covered in fur, and tipped with obvious claws, which it uses for scratching, grooming and hauling itself over ice or rock. Flipper length alone often distinguishes the two at a glance.
Voice and social life
Sea lions are loud and gregarious. California sea lions pack tightly together on beaches and piers, and males bark almost constantly in the breeding season. Harbor seals are quieter, making soft grunts and growls, and they tend to keep some personal space even when many haul out on the same sandbar.
How to tell them apart
- Look for an ear flap. A visible external ear means sea lion or fur seal; a plain hole means true seal.
- If it is walking upright on its flippers or climbing onto a dock, it is a sea lion.
- If it is scooting along on its belly, it is a true seal.
- Loud, repeated barking from a crowded group is typical of sea lions, not seals.
- A spotted coat and short, round, cat-like face suggest a harbor seal; a plain brown coat and dog-like muzzle suggest a California sea lion.
What they have in common
Seals and sea lions are both pinnipeds, a group of fin-footed marine carnivores that also includes the walrus. They share streamlined bodies, thick blubber, sensitive whiskers for detecting prey, and large eyes suited to dim water. Both eat mainly fish and squid, hold their breath for long dives, and must return to land or ice to rest, molt and give birth.
Frequently asked questions
Are sea lions a type of seal?
In the broad sense, yes. Sea lions belong to the eared seal family, Otariidae, and they are pinnipeds like every other seal. They are not 'true seals,' which form the separate family Phocidae. The trained 'seals' in circuses and marine parks are nearly always California sea lions.
Can seals and sea lions interbreed?
No. True seals and sea lions belong to different families that diverged over 20 million years ago, and no hybrids between them are known. Hybrids have been recorded between closely related species within a family, such as different fur seals and sea lions.
Which is bigger, a seal or a sea lion?
It depends on the species. California sea lions are considerably larger than harbor seals, and males are much bigger than females. However, the largest pinnipeds of all, apart from the walrus, are true seals: the elephant seals, whose males dwarf any sea lion.
Are seals or sea lions dangerous to humans?
Neither normally attacks people, but both are wild predators with sharp teeth and can bite if approached, cornered or fed. Sea lions on docks can be bold and territorial. In the United States, it is illegal to harass marine mammals, and viewers should stay well back.