Pinnipeds, a diverse group of fin-footed marine mammals, encompass seals, sea lions, and walruses. These animals share a common ancestry and a semi-aquatic lifestyle, spending time both in the ocean and on land. While they might appear similar at first glance, seals and sea lions possess distinct characteristics that allow for clear differentiation.
Physical Characteristics
One of the most noticeable differences between seals and sea lions lies in their ears. Sea lions, belonging to the family Otariidae (“eared seals”), have visible external ear flaps, or pinnae. In contrast, true seals, or “earless seals” (Phocidae), lack these external ear flaps and instead have only small, often difficult-to-see ear holes.
Their flippers also present clear distinctions. Sea lions have long, paddle-like front flippers, largely hairless and covered in skin, which propel them through water. Seals, however, possess smaller, fur-covered front flippers with claws, primarily used for steering rather than propulsion.
The hind flippers further differentiate these animals. Sea lions can rotate their hind flippers forward and underneath their bodies, enabling them to support themselves on land. Conversely, seals’ hind flippers extend straight backward and cannot rotate, impacting their terrestrial movement. Additionally, sea lions are generally brown, while seals often display varied, spotted coats ranging from white to dark brown.
Movement on Land and in Water
The anatomical differences in their flippers directly influence how seals and sea lions move. On land, sea lions exhibit agile locomotion due to their ability to rotate their hind flippers forward. This allows them to “walk,” “gallop,” or even run using all four limbs, navigating rocky shores and sandy beaches with ease. Their powerful front flippers aid in balance and propulsion during terrestrial movement.
Seals, with their fixed hind flippers, cannot achieve this upright posture on land. Instead, they move by “scooting,” “wiggling,” or “galumphing”—a caterpillar-like motion where they undulate their bodies to drag themselves across surfaces. While this appears awkward, some seal species, like elephant seals, can move surprisingly quickly in short bursts.
In the water, their methods of propulsion also differ significantly. Sea lions primarily use their large, muscular front flippers in powerful, wing-like strokes to propel themselves, with their hind flippers serving as rudders for steering. Seals, however, use their hind flippers for powerful side-to-side thrusts, much like a fish’s tail, to move through the water, while their smaller front flippers are used for steering and balance.
Sound and Social Life
Vocalizations provide another clear distinction between these marine mammals. Sea lions are notably vocal animals, recognized for their loud barks, roars, and honking sounds. They use a diverse range of vocalizations for communication, especially in crowded colonies, and males often bark incessantly during breeding season to defend territories. This noisiness is a hallmark of their presence.
In contrast, seals are generally much quieter. They typically produce softer sounds like grunts, growls, or hisses, often reserving more pronounced vocalizations for specific situations such as the breeding season. Their communication tends to be less overtly audible than that of sea lions.
Regarding social behavior, sea lions are highly gregarious creatures, frequently congregating in large, noisy groups called colonies, herds, or “rafts” on land and in the water. They often lie closely packed together, sometimes even on top of each other. Seals, while sometimes gathering in large groups for resting or breeding, are generally more solitary or form smaller, less densely populated aggregations. Their social interactions within these groups can be less intense compared to the active social dynamics of sea lions.
Habitat and Distribution
Geographic distribution and preferred habitats also differ. Sea lions are found in coastal waters and along coastlines, preferring temperate and tropical regions. They commonly haul out on sandy beaches or rocky shores for resting, mating, and giving birth. While found in the Pacific Ocean and parts of the Atlantic (off South America), no sea lions are native to the North Atlantic.
Seals have a more widespread distribution, inhabiting diverse marine environments globally. They can be found in waters ranging from arctic to tropical regions, including open ocean, coastal areas, and even some freshwater lakes, such as the Baikal seal in Siberia. Many seal species, particularly those in colder climates, rely on icy habitats for breeding and resting. Their ability to thrive in colder waters is supported by thick blubber layers. Seals tend to occupy a broader spectrum of aquatic and terrestrial environments compared to the more coastally-focused sea lions.