Canids are a family within order Carnivora and class Mammalia. The official name of the family is Canidae. It includes dogs, foxes, wolves, dingoes, jackals, coyotes, and African Wild Dogs. Canids are distinguished by high intelligence, exclusive carnivory, complex social structures, relatively long legs and lithe bodies adapted for chasing prey, bushy tails, claws, sharp teeth, the classic canid skull, and elongated snout with a sensitive sense of smell. Canids can be broken down into two clades, Canini (dogs and relatives) and Vulpini (foxes).
Canids evolved from primitive mammalian carnivores, miacids, in the late Eocene, about 40 million years ago. Rather than being ambush predators, a common predatory mode, canids are cursorial predators, pursuing their prey in long, open chases. Due to superior vision and smell, canids can detect prey as far as a mile away, or more. Their lithe bodies give them the stamina to travel long distances. When canids close in on their prey, they kill it with their high-powered bite. One canid, the African Wild Dog, has a bite force quotient (bite force to body mass ratio) that is supreme among all extant carnivores.
Canids are found on all continents except Antarctica, making their home in numerous habitats, including grasslands, deserts, mountains, and forests. They eat various animals for food, mostly small mammals like rabbits. Hunting in cooperative packs, canids can bring down all but the largest animals, including cattle, buffalo, and warthhog. Some canids, such as wolves, have historically even hunted humans, especially the young, weak, or solitary. Today, wolf attacks are very rare, the wolves with a propensity to attack humans probably having been selected out, in addition to depleted populations due to competition with humans and domesticated dogs.
The largest canids, such as the Dire Wolf, are now extinct. The Dire Wolf was as long as 6 ft (1.8 m) in length, weighing as much as 200 lbs. This is larger than most humans. The Dire Wolf is considered a typical member of the Pleistocene megafauna, large animals that went extinct in the recent evolutionary past, most likely due to human encroachment and defense. Numerous Dire Wolf skeletons are found in the La Brea Tar Pits in downtown Los Angeles.
Of course, the most famous of canids is the Domestic Dog, a domesticated version of the Grey Wolf. Dogs have been "man's best friend" for as long as 12,000 years, following us around the world and helping out on the hunt. It is now estimated that there are 400 million dogs worldwide.