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.

Mammals are able to make enough internal body heat to keep their bodies at a relatively constant, high temperature. Endothermy (endo= inside; thermic= heat) makes mammals less dependent on outside temperatures, freeing them to be active in a wide range of conditions. Mammals may be active at night (nocturnal) or in the day (diurnal), in climates as extreme as the cold poles or the hot tropics. Adaptations to warm up or cool off, such as shivering and sweating, allow mammals to maintain their preferred body temperatures in the face of these extremes. Mammals also regulate body temperature with behavior: elephants flapping ears to cool off, humans wearing coats to warm up, dogs panting to cool down. The hairs making up mammal fur are raised or lowered to provide more or less insulation as needed.