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.

All mammals have hair, outgrowths of the skin, during at least some part of their development. While it evolved to insulate animals in cold climates, mammal hair has various functions. Long, stiff hairs (vibrissae, or whiskers) are found in all mammals but humans. Whether on the face, legs, or tail, vibrissae extend an animal's sense of touch. Some mammals, such as porcupines, have enlarged hairs that function as defensive spines. Defense is also achieved by raising individual hairs to make an animal look larger (such as an angry cat). Muscles in the skin make the hair stand up or lie down. Raising and lowering hair changes how much air is trapped under it, which also makes it more or less insulating. Mammals in cold climates tend to have an extra layer of insulating fur, or extra fat under their fur. Mammals in climates that change seasonally shed and replace their hair to create a thicker winter coat and a thinner summer coat.