Like other marine mammals, pinnipeds evolved from ancestors that lived on land. Modern pinnipeds feed underwater, but regularly haul onto land to warm in the sun, sleep, and reproduce. Their eyes have to work underwater, while still having some use on land. For underwater vision, pinniped eyes are large with extra curvature of their lens to bend light (which is how images are formed). Also helping them see in dim, ocean light are lots of light-sensitive cells and a membrane that reflects light back to the retina that otherwise would escape. On land, the extra lens curvature makes pinnipeds nearsighted (myopic). In bright, sunny conditions, such as reflective ice, their pupils close to a vertical slit to partly counteract the myopia. Whiskers on their noses that are highly sensitive to touch help them explore on land. In water, the whiskers may serve as motion detectors, picking up vibrations from fish or other objects.

Although modern carnivores are a diverse group when it comes to diet, a typical carnivore feeds mostly on meat. Meat-eating carnivores tend to have a set of sharp-tipped teeth (carnassials), a characteristic of ancestral carnivores. Modified from molars, carnassials are specialized for slicing flesh. While meat is easier to digest, prey must be found, captured, and killed. Hunting collaboratively is sometimes more effective than hunting alone, and many large carnivores hunt in groups. Elaborate social behaviors have evolved around hunting, such as the dominance hierarchy in a pack of wolves. Even carnivores that do not hunt collaboratively, such as harbor seals and coatis, may live in social groups. Benefits of grouping may include sharing care of young or sharing defense of territory. Young carnivores must learn to hunt, which often means an extended training period. Carnivores have a high ratio of brain to body mass, allowing for the learning, coordination, and agility needed for hunting.