Grey wolves (Canis lupus), coyotes (Canis latrans), and red foxes (Vulpes vulpes) all belong to the mammalian order Carnivora, which also contains the ursids, viverridae, procyonidae, and others.

They belong to the family Canidae, which extends to jackals, grey foxes and the Cape hunting dog. Wolves and coyotes are among the eight species of the genus Canis, and foxes belong to the genus Vulpes, which contains 10 species, including kit and fennec foxes.

The grey wolf is the largest of the three canids, with an average mass of 45-60 kg (up to 80 kg in the male) and an average nose-tail length of 150-170 cm. Their bodies are dense and heavily laced with muscle; their muzzles are (relatively) short, broad and blunt, their ears relatively small and rounded. Wolves range in boreal and coniferous forests, mountains, and open brushy areas in widely scattered areas of the Northern hemisphere. They are the most social of the canids, living in relatively stable hierarchically organised packs of between two and twenty animals (averaging five or six), and utilising a wide range of communicative behaviours. The most common colour is grey (or agouti), as in the photograph above, but "grey" wolves also appear in all shades from white to black, with pups of different colours being born in the same litter. Wolves hunt in packs of from two to twenty animals (the average being 4 or 5), preying on deer, antelope, caribou and bison as well as smaller animals such as rabbits, mice and birds.

The coyote is a much lighter version of the wolf, averaging between 11 and 21 kg and 90-120 cm. The body structure is much lighter than that of the wolf, the facial bones finer and the ears more pointed. Latrans has the largest range of any species of wild animal, living in forests, clearcuts, farms or woodlots from Central America, all of the U.S. and Alaska and all but the northernmost portions of Canada -- as humans killed off the native North American wolves, coyotes moved in to take their place and have done quite well. Coyotes are more solitary than wolves, but may form packs of two to three individuals to hunt or raise young, especially in areas where game is plentiful. Coyotes generally hunt smaller animals such as mice, rabbits and insects but when hunting in packs may take down young deer or small livestock such as sheep. Colour is generally ticked grey to yellow but may range, though not as often nor as extensively as in the fox and wolf.

The red fox is found in a wide range of habitats (from tundra to prairie) throughout Canada, Alaska, the U.S., Europe, Britain and almost all of Asia including Japan. They were introduced into Australia by man in the nineteenth century to help curb the exploding introduced rabbit population. They average 4 to 6 kg and 50-70 cm, with extremely elongated muzzles (the tooth row may be more than half the length of the skull), and relatively shorter legs than the wolf or coyote. Foxes come primarily in red, but also in shades from white to black (the "silver" fox), and intermediates such as the "cross" fox, which is pale orange with a black dorsal stripe and a stripe over the shoulders (forming the bar of the "cross"). Foxes may form small "harems" of one male and several (often related) females which may cooperate in rearing the young, but generally hunt alone, catching mice, small birds, rabbits, and insects, amongst other things. They are the most omnivorous canids and will also eat fruit or carrion.

Although all three canids (especially Vulpes and Latrans) are opportunistic hunters, they are all adapted for running (cursorial) hunting, this being most marked in C. lupus, which is primarily a carnivore and often relies on tiring larger prey with a relentless chase.

The chest and hips of canids are narrow, the legs long and slender (shorter in V. Vulpes), the tail thick and bushy (in V. vulpes, it reaches past the hocks; in Canis, it reaches to the hocks). The feet have individually moveable toes with heavy pawpads and blunt, keratinic, nonretractile claws; hindfeet have four toes and forefeet have five, with the first toe greatly diminished and no longer touching the ground ("dewclaw"). The dewclaw may be absent in some individuals.

All three species exhibit countershading (lighter underbelly). The coat is thick and multi-layered, with a sparse, wiry overcoat of long, coloured and banded hairs and a dense, monochromatic fluffy undercoat of "wooly" grey, black or white hairs which is shed annually in a spring moult. Hair is erectile over the back of the neck and shoulders (hackles); this is raised primarily as a conspecific aggression gesture.

Eyes are usually yellow, although some wolves have startling maroon irises; in Canis the pupil is round but in V. vulpes the pupil is vertically elliptical. The skin around lips and eyes is black and often strikingly marked (especially in the wolf), to aid in communication by facial expression and also to reduce glare. A scent gland (the "violet" gland) is present in both sexes approximately 5-10 cm down the dorsal side of the tail and is often marked by a spot in the fur.

The primary hunting senses are those of hearing and smell, which is markedly acute in the Canidae; all three species use scent for tracking prey and for conspecific communication. Scent glands are found in paired anal sacs, the corners of the mouth and between the toes of both sexes as well as on the tail.

Vision is usually the least acute of the senses, although canids use a great deal of visual communication signals and can probably see at least two colours (red and green) besides black and white.

All three species are primarily nocturnal or crepuscular but are known to hunt occasionally during daylight hours.