Order Carnivora
carnivores

Members of the mammalian order Carnivora are the descendants of a successful late Paleocene radiation of mammals whose primitive food habits were carnivorous. The name "Carnivora" is sometimes taken to mean that members of this group are all carnivorous or that all carnivorous mammals are members of this group. This is not so. Members of Carnivora have diverse food habits, although many are primarily carnivorous, and carnivory is widely distributed in mammals, being found in many other orders including bats, marsupial mammals, primates, and dolphins and whales.

We recognize 13 extant families and around 270 species of Carnivora. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Carnivores are distributed across the world, on all major land masses (except possibly Australia, where the only terrestrial member of Carnivora, dingos (Canis lupus dingo), may have been brought by man) and in all oceans. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Carnivores occupy just about every type of terrestrial habitat, and many aquatic habitats as well, from the tropics to the poles. They live in forests, deserts, mountains, grasslands, scrublands, tundra, and on open ice. Aquatic and semi-aquatic species live in freshwater rivers, lakes, and marshes, in marine coastal areas, and in the open ocean. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Most systematists agree that carnivorans can be divided into two groups, the dog-like (caniform or Caniformia) and cat-like (feliform or Feliformia) families. However, there is considerable disagreement over how carnivoran families are related to each other, especially with respect to pinnipeds (the seals, sea lions, and walruses). Currently, the most strongly supported pattern of relationships places pinnipeds as a monophyletic group within the caniform lineage. The sister group to this clade is the superfamily Musteloidea, which includes red pandas (Ailuridae), skunks (Mephitidae), raccoons (Procyonidae), and weasels (Mustelidae). Canids appear as an early offshoot of the caniform lineage (Flynn et al. 2005). Some authorities, however, consider pinnipeds a monophyletic lineage sister to all other living carnivores (Feliformia and Caniformia), and place it in a separate order, Pinnipedia. Others suggest that marine species were derived at least twice, with one lineage (perhaps derived from ursids) leading to sea lions and walruses, and the other (perhaps derived from mustelids) giving rise to true seals. Feliform carnivorans include cats, hyaenas, mongooses, viverrids, and Malagasy carnivorans (Flynn et al., 2005; Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Most members of the order Carnivora can be recognized by their enlarged fourth upper premolar and first lower molar, which together form an efficient shear for cutting meat and tendon. These teeth are referred to as the carnassial pair. The exceptions are a few forms, such as bears, raccoons, and seals, in which these teeth are secondarily modified. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Besides usually having carnassials, almost all Carnivora retain the primitive number of incisors (3/3); an exception is the sea otter, which has 2/3. The outer (3rd) incisor is often relatively large and canine-like. The canines are large and conical. The number of teeth behind the carnassials varies considerably, from 1/1 in some cats to 2/2 in bears. All teeth are rooted and diphyodont. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

The skulls of carnivorans are varied in form. Most have a well-defined, transverse glenoid fossa, and the dominant motion of the jaw is in the dorsal-ventral direction. The primary muscle powering the jaw is the temporal, and sagittal crest associated with the temporal is commonly a conspicuous part of the surface of the skull. Carnivores also have a strong zygomatic arch and a relatively large braincase. The auditory bullae and the turbinals also tend to be large and complex. Carnivores are fairly intelligent animals and most have relatively large brains. All members of Carnivora have simple stomachs. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Pinnipeds are large, perhaps because water conducts heat well and large animals have a low surface area to body mass ratio, which minimizes heat loss due to conduction. Their bodies are insulated by a thick layer of fat called blubber. In all species, the external ears are small or absent, the external genitalia and nipples are hidden in slits or depressions in the body, and the tail is very small. The forelimbs and hindlimbs are transformed into paddles. In both, the proximal limb elements (humerus and femur) remain within the body, and other aspects of the limbs, limb girdles, and spine are highly specialized for swimming. Most species have a relatively short rostrum, and the orbits are large. The cheek teeth are usually homodont (no differentiation along the toothrow), and the teeth are usually shaped like simple cones. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Carnivores tend to be medium-sized animals; too small and they couldn't find enough within their capacity to kill; too large and they wouldn't be able to satisfy their appetites. However, as a group, carnivores span a wide range of body sizes. Least weasels (Mustela nivalis), the smallest carnivores, can weigh as little as 35 grams, and male southern elephant seals (Mirounga leonina), the largest carnivores, can weigh more than 3,600 kg. Many carnivore species are sexually dimorphic in size. Usually males are larger than females (as with fishers, lions, and wolves) but in a few species females are larger than males (as with spotted hyenas). Additionally, males of some species have ornamentation that females lack (as is the case with the inflatable probosci of male elephant seals). (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Many carnivores have thick, luxurious coats, though some, like walruses, have coats that are quite sparse. Their fur comes in various colors, including black, white, orange, yellow, red, and almost every imaginable shade of gray and brown. In addition, many carnivores are striped, spotted, blotched, banded, or otherwise boldly patterned. Some species, such as gray wolves, are polymorphic for coat color. Domesticated cats and dogs exhibit thousands of combinations of coat colors and body shapes as a result of selective breeding by humans. (Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Carnivores are relatively long-lived mammals, with most species living at least a decade. The main exceptions are small weasels (Mustela), which live up to six years in captivity but usually do not make it past one year in the wild. In general, pinniped carnivores live longer than fissiped carnivores, with several species (walruses, gray seals, ringed seals, Caspian seals, and Baikal seals) reported to live 40 or more years in the wild. (Carey and Judge, 2002; King, 1989)

Carnivora includes terrestrial, aquatic, and semi-aquatic species. Aquatic species (pinnipeds) are excellent swimmers, more at home in the water than on land. These animals are capable of diving to extreme depths (600 m in the case of Weddell seals) and remaining under water for astonishing periods (over an hour, although most dives are much shorter). Some carnivores, such as procyonids, are skilled climbers and spend much of their time in trees. Many terrestrial carnivores are excellent runners. A few are good long-distance runners, but more commonly, carnivorans are rapid sprinters that use stealth to approach their prey, then overcome it with a short, violent rush. A few, like bears and raccoons, seem relatively slow or clumsy, but even these species are capable of remarkable bursts of speed. Even those specialized for long-distance running don't have the highly modified and relatively inflexible skeletons and movement patterns of cursorial herbivores like artiodactyls; this is probably related to the often unpredictable demands that catching and killing large prey place on their skeletons. (Gittleman, 1989; Sandell, 1989; Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Carnivores exhibit varying degrees of sociality, ranging from solitary (bears, for example) to colonial (California sea lions, for example). Some carnivore species are difficult to place in a single category, as their degree of sociality varies over their geographic range or even among sex and age classes within a population. For example, red foxes (Vulpes vulpes) breed cooperatively in some regions and are largely solitary in others, and female coatis (Nasua nasua) live in close groups, whereas male coatis are solitary. It is estimated that about 10 to 15% of carnivore species regularly live in groups beyond the breeding season (this estimate does not include pinnipeds). For social carnivores, group living often entails the formation of strictly-enforced dominance hierarchies. Social bonds among group members can be very strong, with individuals showing affection for one another and keeping each other out of trouble. (Gittleman, 1989; Sandell, 1989; Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Some carnivore species undergo seasonal long-distance migrations in concert with the migrations of their prey. Others stay within one home range year round. Home ranges tend to be large, and often vigorously defended, as each carnivore's home range must encompass the home ranges of many prey animals. Carnivora includes both diurnal and nocturnal species. When resting, many carnivorans den in tree hollows, burrows, or caves. A few species, such as those in the family Ursidae, undergo long periods of torpor through the winter. (Gittleman, 1989; Sandell, 1989; Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Most carnivorans have acute senses. Vision and hearing are excellent in many, often far surpassing the capabilities of humans. Domestic cats and other carnivores that hunt small rodents can hear ultrasounds emitted by their prey. Most carnivorans come equipped with tactile hairs (vibrissae) on the face and legs, which they use to feel their way through narrow, dark surroundings. The sense of smell is often remarkable. Carnivorans make extensive use of chemical signals excreted in urine and feces and produced by glands in the skin and anal region. They use these chemical signals for scent-marking territories and for conveying information about identity, social status, and reproductive status. Carnivorans also communicate acoustically with a variety of yips, howls, barks, growls, roars, and purrs. These sounds have various functions, including strengthing social bonds, advertising for mates, defending territories, and communicating alarm, distress, and contentment. Social carnivores such as lions sometimes erupt into choruses of loud roars as a means of calling one another to assemble. Visual signals, mainly in the form of body posturing, are also used by carnivorans to communicate, and tactile signals, as when a wolf licks and bites the muzzle of a dominant individual to show submission, are used as well. (Ewer, 1973; Gorman and Trowbridge, 1989; Peters and Wozencraft, 1989; Vaughan, Ryan, and Czaplewski, 2000)

Animal matter makes up a substantial portion of the diet of most carnivorans. However, not all members of Carnivora are carnivorous. Some, such as bears and raccoons, are decidedly omnivorous, and giant pandas are primarily vegetarian. Foods consumed by carnivorans include mammals, birds and eggs, reptiles, amphibians, fish, carrion, insects and other arthropods, earthworms, mollusks, crustaceans, fruit, nuts, tubers, leaves, shoots, and plankton (on which crabeater seals specialize). (Ewer, 1973; Reeves et al., 2002; Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Carnivorans have various means of capturing their prey. Some ambush prey, overtaking it in a sudden burst of speed, others chase prey over long distances and slowly tire it out. Some (such as skunks) simply shuffle about and eat whatever they happen to come across. Still others scavenge from carcasses or, in urban areas, from garbage cans. Some carnivores, such as arctic foxes (Vulpes lagopus) are known to cache their kills for later consumption. Crabeater seals (Lobodon carcinophaga) are unique among carnivores in that they are filter feeders. They have specialized teeth which allow them to strain tiny zooplankton, their staple food, from the water. (Ewer, 1973; Reeves et al., 2002; Stains, 1984; Vaughan, Ryan, and Czaplewski, 2000)

Many carnivorans are top predators in their ecosystems, and therefore do not face the threat of predation as adults, though their young may be vulnerable. Small terrestrial carnivorans face predation by larger carnivorans, and by diurnal and nocturnal birds of prey. Pinnipeds face predation by large cetaceans such as killer whales (Orcinus orca) and by sharks. Many carnivorans, large and small, terrestrial and aquatic, are hunted by humans. (Eaton, 1976; Gorman and Trowbridge, 1989; Korpimaki and Norrdahl, 1989; Ortolani and Caro, 1996; Reeves et al., 2002; Vaughan, Ryan, and Czaplewski, 2000)

Most carnivorans use their teeth and claws to fend off predators. A carnivore that feels threatened typically crouches and bares its teeth, hissing or growling at its attacker and biting and scratching if the attacker gets too close. Pinnipeds, on the other hand, rely largely on their speed and agility in the water to escape predators. Female carnivorans often hide their helpless infants in a den, and may switch the den location occasionally to avoid detection. Some carnivoran parents are also known to vigorously defend their offspring if necessary. Many carnivorans are the same color as their background (such as Arctic foxes, which turn white in winter to match the snow). They also frequently exhibit countershading or color patterns, such as spots and stripes, that break up their outline and make them difficult to see. A few carnivorans have special adaptations to defend themselves against predators. Skunks and some mustelids, herpestids, and viverrids have well-developed anal glands, which produce a foul-smelling musk that is released under stress. These animals usually bear aposematic coloration in the form of contrasting stripes and bands, warning would-be predators to stay away. Finally, it has been postulated that some carnivorans mimic others to avoid predation. For example, the coloration of cheetah cubs, which are highly vulnerable to predation, may mimic that of honey badgers, which are aposematic and highly aggressive. (Eaton, 1976; Gorman and Trowbridge, 1989; Korpimaki and Norrdahl, 1989; Ortolani and Caro, 1996; Reeves et al., 2002; Vaughan, Ryan, and Czaplewski, 2000)

Carnivorans are important predators in many ecosystems, acting as a "top-down" control on populations of their prey. Many are such an important control on their prey that they act as keystone species, and their removal has drastic consequences for the ecosystem. For example, wolves were recently reintroduced to Yellowstone National Park after being extirpated for nearly 70 years, and their predation on elk has allowed woody plants to recover from overbrowsing. (Ripple and Beschta, 2003)

Carnivores host a wide range of internal and external parasites, including protozoans, nematodes, trematodes, cestodes, fleas, lice, and ticks. (Roberts and Janovy Jr., 2000)

Carnivorans also have negative impacts on humans. They may compete with humans for game and prey on livestock. Occasionally, large carnivorans even attack and kill humans. Omnivorous species may raid fruit crops, and in urban areas carnivorans become pests when they raid garbage cans and take up residence inside chimneys and under porches. They also carry diseases and parasites, such as rabies, that can be transmitted to humans and domestic animals. (Roberts and Janovy Jr., 2000; Vaughan, Ryan, and Czaplewski, 2000)

Humans benefit from carnivorans in many ways. Humans have hunted them for thousands of years for sport and for their fur, meat, and other body parts. Bones and soft tissues of tigers (Panthera tigris) and other large carnivores have long been used in traditional Asian medicine. Millions of small carnivores such as red foxes (Vulpes vulpes) and mink (Neovison vison) are raised on farms for their fur. Carnivorans are also valuable to humans for their ability to control rodents and other pests, and domesticated cats, dogs, and other carnivorans are popular pets worldwide. (Schaller, 1996; Vaughan, Ryan, and Czaplewski, 2000)

Members of Carnivora have been feared, persecuted, and exploited by humans for centuries. There are currently 122 species on the IUCN's Red List of Threatened Species. Of these, 11 are near threatened, 9 are lower risk, 39 are vulnerable, 33 are endangered, 6 are critically endangered, 5 have recently gone extinct, and one, black-footed ferrets (Mustela nigripes), is extinct in the wild, although reintroduction efforts show promise. Another 18 are listed as data deficient. Major threats to carnivorans include habitat loss and degradation and hunting for sport and profit. Rare species often fetch top dollar on the black market, even though trade in these species is strictly regulated by CITES and by national laws. Captive breeding programs may be the last chance for the survival of some species, such as giant pandas (Ailuropoda melanoleuca). In some cases, reintroduction of species into areas where they were previously extirpated has been successful, as with the wolves of Yellowstone. In order to save carnivorans from extinction in the long term, large swaths of habitat and healthy populations of prey species must be preserved in all parts of the world, and humans must learn to coexist peacefully with these animals. (IUCN, 2004; Schaller, 1996)