The terms “seal” and “sea lion” are often used interchangeably, causing confusion. Both are marine mammals belonging to a group called pinnipeds, meaning “fin-footed.” While sharing an aquatic lifestyle, seals and sea lions have distinct differences in physical characteristics, behaviors, and preferred habitats. This article clarifies these distinctions.
Distinguishing Physical Traits
Sea lions possess visible external ear flaps, known as pinnae. True seals, conversely, lack these external ear flaps and instead have only small, inconspicuous ear holes. This fundamental difference also reflects their taxonomic classification: sea lions belong to the Otariidae family (eared seals), while true seals are part of the Phocidae family (earless seals).
Their flippers also present clear differentiating features. Sea lions are equipped with large, paddle-like fore flippers primarily used for propulsion when swimming. These robust fore flippers also provide significant support for their body weight, enabling them to lift themselves on land. In contrast, true seals have shorter, fur-covered front flippers mainly used for steering in water.
Differences extend to their hind flippers and overall body shape. Sea lions possess hind flippers that can rotate forward underneath their bodies, allowing them to support their weight and move effectively on land. True seals, however, have hind flippers that are fixed and point backward, making it impossible for them to rotate them forward. This anatomical distinction influences their terrestrial movement. Sea lions often have a more sleek, dog-like head and body, while seals tend to have a more rounded, cat-like head and a torpedo-shaped physique.
Behavioral Clues and Movement
The anatomical differences in their flippers directly influence how seals and sea lions move on land. Sea lions exhibit a more agile form of terrestrial locomotion, capable of “walking” or even galloping by rotating their hind flippers forward and using all four limbs to support their body. This allows them to raise their bodies off the ground.
True seals, with their fixed hind flippers, cannot achieve this upright posture. They move on land by undulating their bodies in a caterpillar-like motion. In the water, their primary methods of propulsion also differ. Sea lions propel themselves using powerful strokes of their large fore flippers. True seals, conversely, primarily use their powerful hind flippers, moving them from side to side for propulsion.
Distinct differences also emerge in their vocalizations. Sea lions are notably vocal animals, frequently emitting loud barks and roars, especially when communicating within their social groups. True seals are generally quieter than sea lions, typically communicating through softer grunts, growls, or hisses. Sea lions are also typically more gregarious, often found in large, noisy colonies, while seals can be more solitary or found in smaller, less densely packed groups.
Where They Live
While both seals and sea lions are marine mammals, their preferred habitats show some distinctions. Sea lions often favor warmer, temperate coastal waters and frequently haul out on accessible rocky shores, docks, and even buoys. Their ability to move effectively on land allows them to utilize various terrestrial resting sites.
True seals, on the other hand, demonstrate a wider range of habitat adaptability, thriving in environments from warmer temperate zones to the colder waters of the Arctic and Antarctic. They are more commonly found on ice floes, remote beaches, or isolated stretches of coastline. For instance, California sea lions are prevalent along the Pacific coast of North America, whereas species like the harp seal are abundant in the North Atlantic.