Bears, Cats, and Civets
Bears (family Ursidae) are widely distributed in Eurasia and North America, but only a few forms live in tropical areas of Asia and South America (the sloth and the sun and spectacled bears). At one time, a large predatory bear of the genus Agriotherium lived in Africa, but currently no wild ursids exist on this continent or in Australia. Today, the largest living ursid is the polar bear, with a body mass of 320 kilograms. Many Ursidae share with some of the Mustilidae a unique reproductive physiology, called delayed implantation, in which the fertilized egg may take many months to implant in the uterus and continue its development. This may be an adaptation to hibernation and wintertime shortages of food in temperate regions. Bears in cold climates spend much of the winter hibernating in a protected den. During this time, their heart rate and metabolism slow to conserve energy. Most bears are omnivorous, but the polar bear is a specialist hunter of seals. Cats (family Felidae) are distributed throughout the world, from the heights of the Himalayas (the snow leopard) to the Amazon (the jaguar). The cats are among the most carnivorous of their order and the most adaptable. The earliest felids evolved in forested areas, and most retain adaptations for tree-climbing and use of cover as concealment. Millions of years ago, much larger forms of felids existed, including the extinct sabertooths whose long, bladelike upper canines were specialized for delivering killing bites to the necks of large prey, such as mammoths. Cats are a diverse family, ranging from the group-living lion (body mass 135.5 kilograms) to the solitary Geoffroy's cat (body mass 2.2 kilograms). Virtually all cats can hunt day and night, but nocturnal habits predominate. The cheetah is the only living cat that hunts exclusively by day. Often habitats will contain several species of cats, differing in size and specialized for different prey. For example, certain areas of the Amazon may contain jaguars, pumas, ocelots, and one or more forms of smaller cat, such as jaguarundi or margay. Civets (family Viverridae) are restricted to tropical and subtropical areas in Africa and Asia. Civets retain many ancestral morphological features of the first carnivores. They are small (body mass range 1.2 to 13 kilograms), with adaptations for climbing trees and no specializations for pursuit or ambush of prey. Civets are nocturnal and, with one exception, arboreal. They eat both animals and fruits, although the fossa is almost exclusively predatory and the binturong eats almost only fruit.Viverrids are closely related to the mongooses.
Dogs, Hyenas, and Mongooses
Dogs (family Canidae) are almost as widely distributed as felids, being found fromthe Arctic and to the South American rainforest. However, canids evolved in open country habitats of North America and few have adapted to life in rain forests. The wolf was once the most widely distributed carnivore in the world. It evolved in east Asia and fromthere spread throughout Eurasia and the Arctic Circle, including migrating down into North America as far south as Mexico. Canids have reached their highest diversity in North American woodland-plains habitats (wolves, coyotes and foxes) and African savannahs (wild dogs and jackals). The dog family is diverse, but the domestic dog shows as much variation in body form (from tiny dachshunds to Great Danes) as all of the wild dog species put together. The smallest wild dog is the North African fennec (body mass 1.5 kilograms), and the largest is the wolf (body mass 31.1 kilograms). Although some canids, such as the gray fox, can climb trees to a limited extent, the dog family is highly adapted to fast running in open ground. Canids are characterized by complex social systems, often involving cooperative care of the young by older juveniles or nonreproducing adults. Dogs hunt animals by day and night, but many forms supplement their meat diet with fruit. Hyenas (family Hyaenidae) are found mainly in Africa, with one species, the striped hyena, living in southern and western Asia. However, in the Miocene and Pliocene (two to twenty-two million years ago), the hyenas were numerous, diverse, and widespread through Africa, Eurasia, and North America. Only four species of hyaenids exist today: the spotted hyena at 55.3 kilograms, the striped hyena at 35 kilograms, the brown hyena at 43.9 kilograms, and the aardwolf at 7.7 kilograms. The rise of the dog family has occurred in parallel with the decline of the hyenas. The unusual aardwolf eats termites and often digs a den in a termite mound. The other hyenas are specialized hunter-scavengers, adapted for bone-crushing with their reinforced teeth, jaws, and crania. Once considered scavengers only, field studies since the 1970's have documented the extensive hunting done by the large hyenas in Africa. All hyenas are solitary except the spotted hyena, which lives in clans. Members of clans usually disperse to hunt but also hunt in small packs, especially for large prey. Spotted hyenas are unique among carnivores because the females are larger than males and the males give the females priority of access to food and space. Mongooses (family Herpestidae) are found only in Africa and warmer climates in Eurasia. They are closely related to viverrids but tend to be smaller (body mass range 0.5 to 1.5 kilograms), more terrestrial, and more often diurnal than the civets. Mongooses are renowned for their bravery in the face of snakes, but they generally hunt insects or small vertebrates, and may supplement their diet with fruits. Most mongooses are solitary, but Africa contains several forms of gregarious mongooses, such as meerkats, dwarf mongooses, and banded mongooses. These form long-lasting packs of up to thirty animals, using termite mounds or tunnels as dens during the night. It is believed that these mongooses have evolved highly social, gregarious habits because of the severe risk of predation by hawks, eagles, large carnivores, and snakes. The dwarf mongooses and meerkats show the most unusual social system, with one breeding male-female pair and multiple nonreproductive helpers feeding and protecting the young and the rest of the group. This system involves complex communication systems and a division of labor, including the use of sentinels to detect predators.
Pandas, Raccoons, and Weasels
The giant panda is the only member of its family (Ailuropodidae), although it is considered closely related to bears. Its habitat is restricted to the Tibetan plateau. The panda bear is large (body mass 96.8 kilograms) and specialized to eat bamboo, as well as some animal foods. The red or lesser panda has not yet been clearly related to other carnivores. Many scientists place it alone in its own family (Ailuridae), while others may group it with the raccoon family (procyonids). Its size (body mass 5.7 kilograms) and omnivorous diet is consistent with procyonids, but its distribution is not. The red panda is restricted to the Tibetan plateau, and part of its diet consists of bamboo, so it has sometimes been classified with the giant panda. Raccoons (family Procyonidae) are found only in the Americas. This family is rather uniform in size (body mass 0.9 to 6.7 kilograms) and in diet. Virtually all of them eat a mixture of fruit, insects, and small vertebrates. Along with the familiar, widespread raccoons, there are less well-known forms in tropical regions, including the arboreal kinkajou, distinguished by a prehensile tail that permits it to hang from branch tips in order to reach fruit at the ends. Also among the tropical procyonids is the coati, which forms large groups with complex social organization. In a coati band, adult males live alone for much of the year, while adult females and young form groups of thirty or more individuals. Weasels (family Mustelidae) are found everywhere except Australia. Scientists recognize four main subfamilies. The otters (body mass 5 to 40 kilograms) are adapted to aquatic life and eat fish and shellfish. The widely distributed badgers (body mass 0.6 to 10.9 kilograms) are adapted to digging and often specialize in eating earthworms. The true skunks of North America (body mass 0.4 to 2 kilograms) are terrestrial omnivores that have specialized anal scent glands used against predators. The weasel group (body mass 0.06 to 2.3 kilograms) includes a host of long, thin forms such as mink, ferrets, and martens. Mustelids are more numerous in temperate regions than in tropical ones, although otters are found around the world. Another tropical mustelid is the tayra, a weasellike semiarboreal predator that may attack monkeys in the trees. In summary, the order of carnivores is very diverse in body size, habits, social organization, geographic distribution, and basic ecology. Most members of this order are intelligent, predatory, adaptable, nocturnal, and solitary. However, among the exceptions to these general rules about carnivores are some of those species most familiar to humans: coyotes, lions, and wolves. Humans have long had a mixed view of carnivores. From the Egyptian reverence for cats and more recent romantic views of the noble wolf, positive impressions of carnivores have been countered by hatred for large predators, driven by economic concern over livestock-killing and attacks on humans.
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