Eared seals are a group of marine mammals, showcasing unique adaptations for life in both aquatic and terrestrial environments. These animals are a significant part of coastal ecosystems worldwide, displaying remarkable agility and social complexity.
Defining Characteristics
Eared seals, belonging to the family Otariidae, are distinguished by several physical features that set them apart from “true seals” (Phocidae) and walruses. They have visible external ear flaps, known as pinnae, which gives them their common name and differentiates them from true seals.
Beyond their ears, eared seals possess unique locomotive abilities. They can rotate their large hind flippers forward and underneath their bodies, allowing them to “walk” on all four limbs on land. This adaptation grants them considerable agility on rocky shorelines and sandy beaches, enabling them to move much faster and more efficiently than true seals, which tend to wriggle on their bellies. Their long, powerful front flippers, often more than a quarter of their body length, are leathery and hairless with small claws, primarily serving as their main propulsion system in water.
Major Groups and Distribution
The family Otariidae encompasses 15 extant species, categorized primarily into two main subgroups: sea lions and fur seals. Fur seals possess a dense layer of soft underfur beneath coarser outer hairs, which historically made them a target for hunting. Sea lions, in contrast, have rougher, stiffer hair covering their bodies.
Eared seals are widely distributed across subpolar, temperate, and equatorial waters, predominantly in the Pacific and Southern Oceans, as well as the southern Indian and Atlantic Oceans. They are notably absent from the North Atlantic. Specific examples include the Galápagos fur seal, the smallest species, found in equatorial Pacific waters, and the Steller sea lion, the largest eared seal, inhabiting northern Pacific regions. They inhabit various coastal saltwater regions, often preferring rocky shorelines, sandy beaches, and estuaries for breeding and resting.
Daily Life and Social Behavior
Eared seals are carnivores and opportunistic feeders, with their diet varying based on species and location. Their primary food sources include fish, squid, and crustaceans, and some species may also consume krill or even penguins. They employ different hunting strategies; for instance, sea lions often hunt closer to shore in areas where nutrient-rich water rises, consuming larger fish, while smaller fur seals may undertake longer hunting trips farther out at sea to find smaller prey. Some female seals can dive to depths of up to 400 meters (about 1,300 feet) to pursue their prey, relying on their eyesight to locate food underwater.
These animals are sociable, frequently congregating in large numbers, particularly during breeding seasons, forming what are known as rookeries or harems. Males arrive at breeding grounds first, establishing and defending territories, sometimes containing up to 40 or 50 females, using vocalizations, visual displays, and occasional fights with other males. Eared seals communicate through various vocalizations, including barks and growls, and females can recognize their pups through specialized calls.