Members of the Canidae (dog family) exhibit great flexibility in diet, opportunistic and adaptable behavior, and complex social organization with much variation both within and between species. Canids are among the most widely distributed carnivores, with at least one species present on every continent except Antarctica; one or more canids can be found from sea level to 5000 m. Sillero-Zubiri (2009) recognized 35 extant canid species (37 if the Dingo is treated as a distinct species rather than a subspecies of the Gray Wolf, Canis lupus dingo, and the Eastern North American Wolf is treated as a distinct species, Canis lycaon). South America has 11 species, including nine (mainly Pseudalopex foxes) endemic to the continent. Africa has 13 species, including eight endemics. Asia has twelve species, including three endemics. Two species, the Golden Jackal (Canis aureus) and Arctic Fox (Alopex lagopus) are native to three continents (Africa/Europe/Asia and North America/Asia/Europe, respectively)..
A few canids have extremely small ranges, the most extreme example being Darwin's Fox (Pseudalopex fulvipes): most of the world population of just a few hundred individuals is found on a single island off Chile, although a small number persist on the mainland. Ethiopian Wolves (Canis simensis) occur only in a few isolated pockets of Afro-alpine grasslands and heathlands above the treeline from around 3200 m to 4500 m, where they are found mainly in open areas with short vegetation and feed almost exclusively on Afro-alpine rodents such as Ethiopian African Mole Rats (Tachyoryctes macrocephalus) and Arvicanthis and Otomys murine grass rats, which can be very abundant. At the other extreme, the Red Fox (Vulpes vulpes) has the largest natural range of any carnivore (Lariviere and Pasitschniak-Arts 1996), covering nearly 70 million km2 and extending across the entire northern hemisphere from the Arctic Circle through Canada and the United States and most of Europe and Asia to North Africa; it was introduced to Australia in the 1800s and its range in the United States was extended through several introductions of European Red Foxes starting in the mid-1700s. The Gray Wolf (Canis lupus) has (or had) a similar distribution, occuring widely in North America, Asia, and Europe. Some canid distributions have changed substantially in historical times. For example, the Coyote (Canis latrans) used to be found mainly in arid parts of the western United States, but is now found in every state, province, and country north of Panama, an expansion that was clearly aided by the extirpation of Gray Wolves from most of the United States in the early 1900s. The Red Fox and Dingo are found in Australia and Oceania, but were brought there by humans. Red Foxes are known to coexist in one region or another with 14 other canid species, Golden Jackals (Canis aureus) with 13 other canids, and Gray Wolves with 11 other canids.
Although canids generally stick to the ground, Northern Gray Foxes (Urocyon cinereoargenteus) are very capable tree climbers and Blanford's Foxes (Vulpes cana) and Arctic Foxes regularly climb cliffs. Some carnivores have adaptations allowing them to live in extreme environments, e.g., the Arctic (Arctic Foxes, Alopex lagopus) and deserts. The Fennec (Vulpes zerda), Rüppel's (Vulpes rueppellii), and Pale Foxes (Vulpes pallida) are found in the Sahara and Sahel and Blanford's Fox occurs in the deserts and mountains of western Asia. Sechuran Foxes (Pseudalopex sechurae) live in the coastal desert of Peru and Ecuador. All these desert foxes are nocturnal and spend much of the hot day in burrows. The Fennec Fox is the smallest canid and the only Saharan carnivore that does not need to drink water. It is also so specialized to tolerate high ambient temperatures that it begins to shiver when the temperature drops below 20 C; it begins to pant only above 35 C and dramatically increases its breaths per minute. The Fennec Fox also has proportionately enormous ears, accounting for 20% of its body surface, that facilitate thermoregulation and are perhaps the most obvious of the suite of its anatomical, physiological, and behavioral adaptations to extremely hot and dry environments. More than 20 species of canids are associated with open habitats including temperate grasslands, shrublands, and montane habitats. Only four South American species—Bush Dog (Speothos venaticus), Short-eared Dog (Atelocynus microtis), Hoary Fox (Pseudalopex vetulus), and Crab-eating Fox (Cerdocyon thous)—are essentially restricted to tropical forest (the first three of these are among the most poorly known of all canids).
Although many canids are highly carnivorous, they are mostly rather opportunistic (especially the foxes) and the typical diets of some species, especially those with smaller body sizes, may include less than 5% protein. Among the larger canids are several species that live in groups and prey on animals that may exceed their own body size: Gray Wolves across much of the Northern Hemisphere, Dholes (Cuon alpinus) in southern Asia, and African Wild Dogs (Lycaon pictus) in Africa. The Maned Wolf, which lives in South American savannas, is unusual for a large canid in that it feeds mostly on rodents and fruit . The Bat-eared Fox of eastern and southern Africa and the Hoary Fox of Brazil are the only canids that feed largely on insects rather than mammals, taking largely Synthermes and Cornitermes harvester termites that emerge from undergound colonies to forage on grasses, as well as on other insects such as adult and larval dung beetles (particularly during the rainy seasos when termites are less active).
The dog is believed to be the first domesticated animal, apparently derived from Gray Wolves at least 10,000-15,000 years ago—possibly far longer ago than this and pre-dating the emergence of agriculture. The Domestic Dog is now generally treated as a subspecies of Gray Wolf, Canus lupus familiaris. Dingo-like feral dogs were apparently associated with hunter-gatherer societies of Africa, Asia, and Europe and later with sedentary agricultural societies. Dingos were brough from mainland Asia to Australia and various Pacific islands as many as 10,000 years ago, perhaps for food, as guard animals, or for warmth and companionship. The Dingoes of Southeast Asia are often known as Pariah Dogs. On various islands, in particular, introduced Dingos, Red Foxes, and Arctic Foxes have decimated populations of some native birds and mammals.
A number of canid species face serious threats to their populations. Gray Wolves, African Wild Dogs, and Coyotes (Canis latrans) have often been actively persecuted by humans as a result of their predation of livestock (and, to a lesser degree, because of the perception that they pose a direct danger to humans). Some smaller canids—notably the Arctic Fox and some South American foxes—have historically been hunted extensively for the fur trade, although this pressure has declined with the decline of the fur trade. Some species that have been subjected to intense hunting pressure—such as Dingoes, Coyotes, Culpeos (Pseudalopex culpaeus), and Red Foxes—have nevertheless thrived. Today, many canid species seem to be maintaining stable populations and some have even expanded. Coyotes, for example, are more common and widespread than ever and Golden Jackals have expanded into Western Europe. Gray Wolves are slowly recovering in some portions of their once far greater range. However, nearly a dozen canid species are considered threatened or endangered, either because they are naturally rare, with limited geographic distributions, or because of human activities that have led to habitat loss, persecution, and disease. The Falkland Islands Wolf (Dusicyon australis) was eradicated by humans in the 19th century. Among the most vulnerable species are Darwin's Fox, Island Foxes (Urocyon littoralis, on the Channel Islands off southern California, U.S.A.), and the Red Wolf (Canis rufus, of the southeastern U.S.A.) (the taxonomic status of the Red Wolf remains controversial). Extinct in the wild by 1980, Red Wolf introduction efforts have been fairly successful, but many individuals are killed by cars each year and genetic dilution by hybridization poses a serious threat to the persistence of the species. Other endangered or threatened canids include the African Wild Dog (formerly found across much of sub-Saharan Africa excluding rainforests, but now in small scattered populations), the Dhole, and the Ethiopian Wolf, among others. Some species are very poorly known so their status is difficult to assess. Sillero-Zubiri (2009) suggests that the failure of attempts to locate and survey populations of some of these species (notably, Bush Dog and Short-eared Dog and Saharan Pale, Ruppell's, and Fennec Foxes) do not bode well.
Human impacts on canid populations may be direct (e.g., hunting of Indian Foxes) or indirect (e.g., the local extinction in the Negev Desert in Israel of Rüppell's Fox, which was abundant into the 1960s, possibly as a result of Red Fox populations increasing in association with incrreased agriculture). Rabies, canine distemper, anthrax, and other pathogens have all taken a severe toll on various canid populations (notably Island Foxes, Ethiopian Wolves, and African Wild Dogs) and in some cases these were likely transmitted from domestic dogs. Management efforts for the long-term conservation of several canids, such as the African Wild Dog and Ethiopian Wolf, have shown evidence of some success, but the remaining challenges are great. Although around half the species of canids are known to have some use in traditional medicine, demand for traditional medicine does not appear to pose a major conservation concern (as it does for many other types of animals) since harvesting for for medicinal uses is not believed to pose a significant threat to any endangered canid (Alves et al. 2010)
(Sillero-Zubiri 2009 and references)