Distinguishing between seals and sea lions can be challenging due to their shared aquatic habitats and similar appearances. This article clarifies their size differences and explores other defining characteristics.
Unpacking the Size Difference
Sea lions are generally larger than seals. While some smaller sea lion species may be comparable to larger seals, the most substantial sea lions significantly exceed the largest seals in mass and length. For instance, a male California sea lion can weigh 300 to 800 pounds and be 7 to 8 feet long, while a female might be 6 feet long and weigh around 225 pounds. This size disparity often stems from pronounced sexual dimorphism, with males considerably larger than females.
Seals are often more streamlined for aquatic life and generally possess a smaller overall body size compared to many sea lion species. Their body shapes are adapted for efficient movement in water, enabling them to be swift swimmers. Despite this general trend, some seal species can grow quite large, blurring the lines in casual observation.
Beyond Size: Key Distinctions
Beyond their general size, several physical and behavioral traits differentiate seals from sea lions. Sea lions, categorized as “eared seals,” possess small, visible ear flaps. In contrast, true seals, or “earless seals,” lack these external flaps, having only small, difficult-to-see ear openings.
Their methods of movement, both in water and on land, also differ. Sea lions use large, muscular front flippers for propulsion while swimming, moving them in an oar-like motion. Their hind flippers can rotate forward, allowing them to “walk” or gallop on land with agility.
Seals primarily use their hind flippers for propulsion in water, moving them side-to-side like a fish tail. Their front flippers are smaller and used for steering. On land, seals cannot rotate their hind flippers forward, moving instead by undulating their bodies in a “caterpillar-like” or “galumphing” motion.
Vocalization also provides a clue for identification. Sea lions are more vocal, known for loud, distinct barking sounds, especially when congregating in large groups. Seals are quieter, communicating through softer grunts, hisses, or moans.
Notable Giants of the Pinniped World
The Steller sea lion is the largest species of sea lion. Adult male Steller sea lions can reach lengths of up to 11 feet and weigh as much as 2,500 pounds. Females are smaller, typically growing to about 9.5 feet in length and weighing up to 1,000 pounds.
Among seals, the southern elephant seal holds the record as the largest pinniped. Males exhibit extreme sexual dimorphism, reaching 16 to 20 feet and weighing 5,000 to 8,800 pounds, with some exceptionally large males estimated to weigh over 11,000 pounds. Female southern elephant seals are considerably smaller, ranging from 9 to 12 feet long and weighing 900 to 2,200 pounds. While the southern elephant seal is an outlier in size among seals, its massive dimensions highlight the diversity within the seal family, often surpassing many sea lion species.