The Carnivores

All kinds of animals eat meat. One-celled amoebas eat other one-celled animals, A praying mantis eats another praying mantis. Lions eat the flesh of a zebra. A man eats a steak.

      Animals that eat other animals are called carnivores (from the Latin carne, meaning ”Meat”). Amoebas, praying mantises, lions, and men are all carnivores. But only one particular group, or order, of mammals has the scientific name Carnivora. Technically speaking, the term “carnivore” refers to members of this order. Included in this group are lions, tigers, seals, bears, skunks, and many other familiar animals. It is these animals that we will discuss in this article. Other meat-eaters not in this order may be said to be carnivorous, but they are not true carnivores.

Introducing the Meat-eaters

The earliest vertebrates, even jawless ones that sucked food from the ooze of pond bottons, were injesting animal protein. The jawed fishes differentiated into a variety of plant- and animals-eaters. As vertebrates emerged onto land, feeding habits became even more specialized. By the heyday of the reptiles some 215 million years ago, carnivorous and herbivorous vertebrates were highly adapted to their food types.

      We know that different kinds of reptiles preferred different kinds of food. A study of fossils reveals differences in the structure of reptile bodies, especially in the structure of their jaws and teeth. Plant-eaters were generally bulky, since they had to take in and process a great quantity of vegetations to obtain the nourishment they needed. Meat-eating reptiles, with their protein-rich diet, required less food. The teeth of plant-eaters were adapted for grinding and chopping green plants; meat-eaters had teeth suited for stabbing, slicing, and tearing.

      During the Age of Reptiles, when dinosaurs dominated the land (between 181 and 135 million years ago), the distinctions between plant-eaters and animals-eaters were already quite marked. Giant flesh-eaters, such as the 35-foot-long Allosaurus, preyed on even larger plant-eaters, such as the 70-foot-long Brontosaurus.

      Mammals – animals whose young suckle milk from the mammary, or milk glands of the mother – already existed in those reptilian times. However, they played a relatively unimportant role. It was not until that still mysterious event, the extinction of the great dinosaurs, that mammals evolved into the many carnivorous and herbivorous species known today.

      This evolution began with small insect-eaters. Some of the early carnivorous mammals were very similar to the insect-eaters, except that they were larger and their teeth were modified. As vegetation-eating mammals evolved, there also evolved flesh-eating mammals to prey on them. Herbivorous and carnivorous mammals rapidly filled the ecological vacuum left by the extinction of the dinosaurs.

     The first carnivorous mammals are called creodonts. Slow-moving and rather stupid, they preyed on herbivores called condylarths. From then on, there was a constant evolutionary give-and-take between the meat-eaters and the animals upon which they preyed. As the herbivores adapted so that they could run faster and think more quickly, so did the carnivores, in the order to catch them. The brains, brawn, and teeth of the carnivores became increasingly better suited for success in hunting. Some carnivorous animals even took to the water and adopted a completely aquatic life.

      Today’s carnivores include some of the most alert and intelligent of mammals. They have well-developed brains and quick, coordinated movements. One or more of the senses of smell, vision, and hearing is keen. The carnivores live on the ground, in trees, or in the water. They range from the playful raccoon to the lion and back to the tabby cat, and from river otters to sea lions. They also include the unjustly despised hyena and the much-loved dog. 

What Are the Carnivores?

The animals that are technically called carnivores are all mammals. They can best be described in terms of the anatomical characteristics they have in common. They generally have lithe, powerful bodies and powerful jaws. Their feet each have four of five toes equipped with sharp claws. Most are completely carnivorous and eat only meat. But some also eat plants.

      The carnivorous way of life is shared by a large number of animals that are not mammals and not even vertebrates. For instance, carrion beetles finish the meat left by hyenas; are they not equally carnivorous? Hawks and eagles are great hunters, and even chickens pick at meat.

      All this demonstrates that a shared preference for a certain kind of food does not necessarily indicate a closer relationship. It is only by tracing evolutionary lineages that we can arrive at a good definition of what constitutes a group of related animals. For instance, among the placental mammals (those whose young develop within the mother’s body). There are a number of subgroups whose members share certain teeth and body features. Such subgroups are called orders. The distinguishing characteristics, or hallmarks, of an order are not shared by any other order. Carnivores make up one order of mammals. Rodents (rats, mice, etc.) make up another.

      The order of placental carnivores is set apart from all other mammals by a number of characteristics common only to it. One of its most important features is the arrangement of teeth. The eyeteeth, or canines, are lengthened into sharp fangs. Along the sides of the jaw, one upper and one lower tooth (the last upper premolar and the first lower molar) are shaped like blades, making them very effective shearing tools. These are the carnassials teeth.

      Carnivores also have a distinctive system for opening their jaws. The lower jaw is attached in such a way that it is difficult to move it from side to side. However, a large gape, or top-to-bottom opening, is possible. This is needed for the stabbing and slicing of meat. It is quite different from the arrangement found in herbivores, where side-to-side movements of the jaws help in grinding up plants.

      Some carnivores walk on their toes; others walk on their soles. In both kinds, certain bones in the wrist are fused. Therefore, this joint can only move up and down, not side-ways. This anatomical construction ties in with the small size or even absence of a collar bone, another feature related to a mainly forward-and-backward movement of the front limbs. Animals that use sideways movements of the hands and limbs while climbing, such as monkeys, all have un fused wristbones and well-developed collar bones.

      The carnivore brain is distinguished by its relatively large size and the considerable development of its higher centers. These are neurological feature related to the high degree of alertness and intelligence necessary for the hunting of fast-moving game.

      By grouping carnivores according to their characteristics, the order can be broken down into subgroups called families. Each family is distinguished by its anatomical peculiarities. The families of the order Carnivore are the weasels, the dogs, the hyenas, the bears, the raccoons, the civets, the cats, the hair seals, the fur seals, and the walruses.

      Carnivorous animals will evolve where there is sufficient game on which they can prey. Thus they have also evolved on the marsupial side of mammalian stock, among the animals that carry their young in external pouches. Such was the case in Australia, which was invaded by opossum like marsupials while the continent was still connected to other parts of the world. About 70 million years ago the land connection was broken; Australia became isolated before it had been populated with placental mammals. Thus marsupials reigned uncontested. They evolved into many different types. One group became carnivorous; to this day Australia harbors catlike marsupials, the wolf-like Tasmanian wolf, and the wolverine like Tasmanian devil.

      There were also marsupials in South America. These flourished because they were isolated in the same way as the Australian marsupials. They developed carnivorous forms such as the saber-toothed marsupial cats. Then the land bridge connecting Panama and North America was reestablished; South America was invaded by placental dogs and cats from North America, these animals gradually replaced the carnivorous marsupials.

Carnivores of the Past

Having listed the main characteristics of the order carnivore as it exists today, we shall now examine how these various adaptations, which turned certain mammals into efficient hunters of moving prey, came about.

      As we have seen, the basic stock of placental mammals from which all the modern orders are derived lived very much in the shadow of the dominant reptiles. This continued until most of the reptiles became extinct some 70 million years ago. Among the surviving mammals were a group called insectivores, which include shrews, moles, and hedgehogs among their modern representatives. The ancient insectivores evolved into many kinds of mammals, many of which are now extinct. These mammals filled ecological niches left vacant by the reptiles. Among mammals were the creodonts, the primitive flesh-eaters, and the condylarths, which included most of the first herbivores.

      Creodonts and condylarths were actually quite closely related. It appears from the fossil evidence that an early, mainly flesh-eating stock, derived from an insectivore ancestry, gave rise to both these kinds of archaic mammals. The modern even-toed hoofed mammals (pigs, deer, sheep, cattle) seem to have evolved from the early creodonts. Odd-toed hoofed mammals (horses, tapirs, and rhinos) form an entirely separate lineage descended from the condylarths. Strange as it may seem, a cow, for example, is just as closely related to a lion as it is to a horse.

     The development of carnivores was a logical consequence of the evolving habits of the ancestral insectivores. Once large plant-eating forms had come into being, it was only to be expected that other forms should prey upon them and should evolve various structures favorable to a flesh-eating existence.

     A good set of front teeth (the incisors) for biting off flesh and a pair of piercing eyeteeth (canines) were already present in the insectivores. These required little modification, other than additional emphasis on the canines. The cheek teeth, however, were greatly changed.

     To eat flesh, some sort of shearing apparatus is needed to slice off the meat and cut through sinews. Insectivores have some shearing action between the back edge of each upper cheek tooth and the front edge of the following lower one. However, the carnivores evolved a highly efficient shear between a pair of very specialized cheek teeth called carnassials. In the most proficient of the meat-eating mammals, these carnassials teeth became high, narrow, and elongated.

      In the early carnivores, the creodonts, the particular pair of cheek teeth that developed into carnassials varied. Evolution, through natural selection, was “experimenting.” In modern carnivores and their direct ancestors, it is always the last premolar in the top jaw and the first molar on the bottom that form the carnassials set. In some creodonts the carnassials developed between.

      Cheek teeth further back in the jaw. Some ancient forms never developed carnassials at all. Some modern carnivores lost the ability to use the carnassials, as these teeth became modified for eating foods other than meat.

      The teeth behind the carnassials are small or nonexistent in animals eating only meat. In bears, which have diversified eating habits, the carnassials have become low-crowned crushing teeth, good for chewing berries, fruits, and nuts.

      Carnivores use their claws for seizing prey. During the purse of evolution, hand and foot bones never grew very long,. The digits did not become highly specialized as in hoofed animals except in some of the simmers that evolved flippers.

      We can imagine the earliest carnivores as small, probably tree-climbing animals, much like opossums in their general habits. They walked like bears, on five-toed feet planted flat on the ground. Both the body and limbs were flexible; the skull was long; and the brain was small.

      From this beginning carnivores evolved in three stages. First, creodonts evolved from the early insect-eaters. Second, an early family of creodonts branched out into the modern land carnivores, or fissipeds – animals whose feet had separated toes and were adapted for walking. Finally, from some of these highly specialized land mammals, there evolved the seals, sea lions, and walruses.

     Creodonts were the earliest members of the order carnivore. Adapting and evolving successfully in their environment, they were the principal flesh-eating animals of the northern continents during the Paleocene and Eocene epochs, from about 60 million to 40 million years ago. As the early hoofed herbivores that served as prey began to disappear, creodonts were replaced by more advanced carnivores.

      The oldest creodont family, the arctocyonids, probably represent the transition from primitive insectivores to carnivores. Its members were mostly small. Two large forms were the European Arctocyon and the American Claenodon. Both were the size of bears, with flattened claws and wolflike shapes.

      Two other creodont families were the civetlike hyaenodonts and the wolverinelike oxyaenids. Both were derived from the earlier arctocyonids and both had specialized shearing teeth. The hyaenodonts survived longer than the other creodonts, from the early Eocene well into the Oligocene, 35 million years ago, and some even into the Pliocene, 10 million years ago. By then they had evolved into animals built like a wolf and ranging from 2 to 4 feet in length. Another family, the mesonychids, had blunt upper teeth and lower teeth that were good for shearing.

      The largest known carnivore, the giant Andrewsarchus, was a creodont that lived in Mongolia during the late Eocene. Its skull was 3 feet in length. In overall size it was larger than the Alaska brown bear.

     The Miacids were the first real family of carnivores and gave rise to the modern families. Small, forest-dwelling hunters about the size of weasels, they had long bodies and tails and flexible limbs. The most important characteristic of the miacids was their relatively large brains. This development may have been due to the rapid evolution of the herbivores, which forced the miacids to rely more on brain than on brawn for catching prey. From these miacids developed the intelligent, agile, modern carnivores that populate our planet.

      Early in the Oligocene epoch, 35 to 25 million years ago, miacids such as Cynodictis and Pseudocynodictis had the characteristics that were later of prime importance to the modern fissipeds. These animals had skeletal structures much like those of today’s civets and weasels. Their short, spreading feet had five toes, apparently with retractile claws. With such physical characteristics, these miacids can be placed at the ancestral base pf almost any of the families of modern land carnivores.

Carnivores of Today

All the carnivores that have survived to the present day may be grouped as canoids or feloids. All, as we have seen, can be considered descendants of miacids. The feloids are represented by three families: cats, hyenas, and mongooses. There are seven families of canoids: dogs, bears, raccoons, weasels, seals, sea lions, and walruses. The last three were once thought to be a separate order, pinnipedia. But recent studies show that sea lions and walruses evolved from bearlike ancestors and seals arose from the weasel family. However, the term pinniped, which means “fin-foot,” is still a useful one in discussing these three families of marine carnivores.

      During the Miocene, mammals flourished and evolved as never before and never since. As the modern world began to take shape, many living things evolved into the familiar form we know today.

      As we look at the two groups of modern carnivores, we see that the visible differences between them are slight. Most differences occur in the anatomy of the skull and reproductive system. There are many parallels between the two groups. The weasel. A canoid, is similar in appearance and habits to the mongoose, a feloid. Raccoons are similar to civets, and wolves parallel hyenas. Nevertheless, these resemblances in appearance and habits have evolved in response to similar ways of life. The true relationships are shown by the long fossil record of each group.

      Another example of similar appearance and adaptation is seen in the seals and sea lions. These animals are so well adapted to life in the sea that they seem to have more characteristics in common than either have with other carnivores. Even in their teeth, these pinnipeds are less like other carnivores than like each other. They do not have carnassials; most of their teeth are relatively simple and conical, and are good for holding slippery prey. Such similarities, of course, are what originally led to their classification as a separate group. However, recently discovered fossils and minute details of the anatomy of existing species, show that seals and sea lions had different ancestors.

The Teeth of Mammals

One of the most important ways of identifying fossil mammals is by the number and type of teeth. Therefore, before we continue our discussion of the carnivores, let us see how mammalian teeth are described for scientific purposes.

      The description of an animal’s dental pattern always follows the same formula. Since the pattern of teeth is the same on both the right and left sides of the mouth, the formula gives the number of each type of tooth found on one side. Because the number of each type of tooth is not necessarily the same in the upper and lower jaws, the formula includes two figures – one figure is for the upper jaw and the other one for the lower jaw.

      Each type of tooth is indicated by an initial: I for incisor, C for canine, Pm for premolar, and M for molar. Except for the canines, there may be more than one of each type of tooth of each side of the jaw. In order to identify any given tooth, each tooth is numbered. The numbers begin with the teeth closest to the front center of the mouth. For the upper teeth, the tooth initial is followed by a number above; for the lower teeth, the number goes below. Thus the first upper incisor I1, and the first lower incisor is I1. The successive incisors in the upper and lower jaws are shown as I2 and I2 respectively.

      In practice, when the whole dental formula is written out, the abbreviations for the various teeth are followed by fractions in which the top number refers to the number of that kind of tooth in one side of the upper jaw, and the bottom number refers to the number of that kind of tooth in one side of the lower jaw.

      As a specific example, let’s look at the dental formulas of the canids. Animals of this group usually have three incisors on each side of both the upper and lower jaws (six top and six bottom, or twelve altogether); this is represented as I3/3. They have one upper and one lower canine on each side (two top and two bottom, or four altogether), or C1/1. They have four premolars on each side of both the upper and lower jaws (eight top and eight bottom), or Pm4/4. Finally, there are two upper molars and three lower molars on each side (four top and six bottom), or M2/3. Thus the canids have a total of 42 teeth and the dental formula of these animals reads: I3/3, C1/1, Pm4/4, and M2/3 = 42.

Land Carnivores

One of the first ways of distinguishing between the major groups of land carnivores is to consider the types of teeth. Another method involves the way in which the animal’s foot rests on the ground. Certain animals, such as bears, are plantigrade. That is, when they walk, they put both the sole and the heel of the foot on the ground.

      Other animals, such as the cat, are digitigrades. They place only the bottom side of their toes on the ground; the heel never touches the ground. The relative toughness of the skin on the lower surface of each animal’s foot demonstrates the difference. This method was accepted by early naturalists as a highly important element in classification. However, it was later realized that this was a superficial way of distinguishing among the major groups of carnivores and that more basic anatomical differences would have to be used to separate them into proper subdivisions.

      For instance, the method of dividing the carnivores into two large groups, the dog like canoids and the catlike feloids, resulted form observation of the tympanic bulla. This is a bony structure found toward the rear of the skull. It encloses part of the middle ear. This bony chamber is undivided in canoids, but in feloids it is separated into two portions by a bony wall. In addition, there are other more technical points of distinction between the two groups.

      The canoids include canids (dogs, wolves, and foxes), mustelids (weasels, martens, otters, and skunks), ursids (bears), procyonids (raccoons), otariids (eared seals), phocids (earless seals), and odpobenids (walruses). Like their ancestors, the miacids, these animals have long jaws and a large number of teeth. They have large snouts and, except for the pinnipeds, an excellent sense of smell

      The other group, the feloids, consists of viverrieds (civets, genets, and mangoose), hyaenas (hyenas), and felids (all cats). Some of these animals have shortened jaws, which give them greater biting power than the elongated jaws of canoids. However, most of the differences between feloids and canoids are highly technical.

      It is relatively easy to divide living carnivores into two natural groups on the basis of the structure of the tympanic bulla. However, it is much more difficult to discover the exact pattern of kinship among the living families within each of the two groups.

      It is agreed by most zoologists that miacids were the ancestors of both groups. But then the ancestry began to diverge. Ursids and procyonids may have come from forms similar to the canids. Among the feloids, viverrids and hyaends probably shared a common ancestor.

      At the dawn of the Oligocene period there were species that zoologist have not been able to classify definitely. These could have been mustelids, viverrids, of relids. This shows that at that time these groups were not clearly differentiated. While it is easy to assign an existing species to its proper “pigeonhole,” it is less feasible and, in fact, it is often impossible to do so for the early carnivores.

Dogs, wolves and Foxes – Canidae

The canids are a very homogeneous family. In addition to dogs, wolves, and foxes, this group includes coyotes and jackals, the maned wolf of South America, and the raccoon-dog of Asia. Including the domestic dog, canids are found throughout the world. Canids other than the dog are found every-where except large islands, such as New Zealand, New Guinea, and Madagascar. Most species of canids are social animals; they often live and hunt in packs.

      The most ancient forms of canids date back to the early Oligocene epoch, when a genus of canidlike animals, psedocynodictis, lived in North America. It was in the Miocene period, however, that this group reached its peak, branching out into many forms. Most of these forms became extinct well before recent times.

      One interesting exception that has long puzzled scientists is the dingo, the wild dog of Australia. The dingo is peculiar because it is the only placental teerstrial carnivore on a continent of meat-eating marsupilals. Most likely, it represents an early breed of domestic dog brought to Australia by primitive people who migrated from the south-eastern part of Asia. This might have happened about 20,000 years ago. Now those few dingos that still run wild, live and hunt in packs and feed on kangaroo meat. Dingo pups are sometimes tamed for hunting by the Australian aborigines.

Bears – ursidae

Bears appeared during the Miocene period, although some forms of Oligocene carnivores, Cynodon and Cynodictis, might possibly be related to the bears of today. The direct ancestor of the bear was probably Ursavus, which has been found fossilized in rocks of the lower Miocene. This genus already showed reduced premolars, a feature of modern bears.

      The most famous fossil bear is the giant cave bear. Its remains have been found in caves and rocky cliffs in many parts of the world. In spite of its huge canines, great size, and fierce appearance, the cave bear probably was like most bears – not wholly carnivorous. From a functional point of view, its molar teeth were not very different from those of omnivores. Even the carnassials were not specialized, but formed a part of the entire large chewing complex.

      Modern bears have flattened molars suitable for grinding up many different kinds of food rather than just meat. There are no carnassials teeth and the bear uses its canines as both offensive and defensive tools. The total number of teeth is about the same as in the canids, but often some front premolars are lacking or rare very small. The usual loss of premolars is from the front of the mouth backward, and the last of the upper teeth of this type one tends to be a long and flattened one.

      Modern bears are found in a large part of the Northern Hemisphere. However, they do not range very far into the Southern Hemisphere.

Ranccoons, Coatis and Pandas – procyonidae

As a group, procyonids vary widely in appearance. However, they do share certain basic characteristics. In the procyonids the molars often lose their characteristic carnivorous appearance and grow to resemble the teeth of a specialized herbivore. However, with the possible exception of the giant panda, which appears to be entirely herbivorous, the diet of most procyonids frequently includes rodents and insects.

      Most species of procyonids, including raccoons, coatis, kinkajous, olingos, and cacomistles, live in North and South America. Two other species, the lesser panda and the giant panda, live in Asia near the border of India and China.

      The history of the procyonids is difficult to ascertain. Some zoologists contend that they developed from primitive tree-dwelling carnivores that produced both this group and the canids. Others believer that there is a kinship, which perhaps is more logical, between the ursids (bears) and the procyonids. In any event, it is known that the ancestors of the procyonids lived in Europe and Asia during the Miocene epoch.

      The procyonids include a number of carnivores that, in the past, were classified as members of the bear family because of the characteristics of their feet. The giant panda is considered by some authorities to be very closely related to the bears. Its teeth different from those of bears by the broadening of the molars to provide a large grinding surface for the tough bamboo that it eats. The skull is short and broad for good muscle attachment to powr the jaws. In the other existing genera of procyonids, the number of molars is even further reduced. In their dental formula there are two upper and two lower molars.

Weasels, Badgers, Otters and Skunks – Mustelidae

The mustelids include many diverse species of small and medium-sized animals. They are almost worldwide in distribution and are found everywhere except Australia, New Guinea, New Zealand, Madagascar, and the Antilles. Generally, these animals prey on small and medium-sized birds and mammlas. They do not really compete with the large canids and felids. Miustelids are fearless by nature and are great hunters. They track their prey into even the most hidden refuses. Only someone who has watched a weasel hunt, seen a polecat when it was angry, or defended a chickenhouse against martens can realize the capacity of mustelids for aggressiveness and savagery.

      Many mustelids have glands around the anus that emit odorous secretions. These may serve as mating signals. More often, however an animals uses these glands for marking off its territory; it sprinkles the ground with the secretion. The odor serves as a warning to another male of the same species; he knows that if he enters the scented area, he will have to fight its occupant. This is a primitive but common mammalian means of communicating “land ownership.”

      The small size of the mustelids occasionally leads to the use of weapons for survival that are different from the usual tooth-and-claw methods. For example, a skunk defends itself by spraying its enemy with the over whelming secretion form its anal glands.

      Another interesting phenomenon in mustelids is the changing of coat color with the seasons. This occurs in some species of weasel. In the ermine, for example, the coat is brown during the summer and then turns white in winter (except for the tip of the tail, which is black). This change provides a camouflage that remains effective with the changing seasons. Seasonal color variations are also found among other mammals.

      The dental formula of mustelids varies. There are generally three incisors and a single canine tooth followed by premolars. The premolars range from two to four on each side of both the upper and lower jaws. There is usually a single molar on each side of the upper jaw; there may be either one or two molars on each side of the lower jaw.

      To date, the evolutionary origins of mustelids have not been clarified. The miacid fissiped Cynodictis seems to be a possible ancestor for this group. The animals that existed during the Oligocene epoch cannot be accurately classified. As noted, there seems to be not clear distinction among mustelids, felids, and viverrids during that period.

      Unlike modern mustelids, which usually have only a single upper molar, some early types had a second upper molar. However, this molar is definitely of mustelid type. In other early mustelids, the second molar had already disappeared.

Hyenas – Hyaenidae

The hyaenids have a common ancestry with the viverrids, even though they look entirely different. Hyenas closely resemble large, awkward dogs. Today, hyenas are found only in Africa, part of Asia Minor, certain regions southeast of the Caspian Sea, Arabia, and India. Their dental formula is I3/3, C1/1, Pm3-4/3-1, and M1/1 = 28-34.

      The aardwolf (Proteles cristatus) is another member of the hyaenids. It is the sole species in its genus. Naïve to southern Africa, it looks like a small striped hyena.

      Ictitherium was a genus that is now extinct. It is known only from fossil remains that are about 10 million years old. These animals possessed characteristics that placed them somewhere between viverrids and hyaenids. They seem to have evolved into large carnivores specializing in scavenging and feeding upon the carcasses of big game. The transition from Ictitherium to animals that were similar to modern species was relatively swift, and there has been comparatively little evolutionary change since.

Civets, Genets and Mongooses – Viverridae

Modern viverrids are native to the Old World. Only in Europe, where they are found from Spain to Germany do viverrids inhabit areas north of a latitude of 40o.

      Viverrids are small and medium-size carnivores characterized by a dental structure consisting of 40 teeth (I3/3, C1/1, Pm4/4, and M2/2). In some species some of the premolars are absent. It is easy to distinguish the skull of a viverrid from that of a mustelid; in modern mustelids the upper molars are always represented by a single tooth, while in the vivierrids there are two (an exception is the fossa of Madagascar). Mustelids and viverrids probably had an ancient common ancestor. Furthermore, some viverrids appear to be related to the felids. The fossa of Madagascar, for example, has claws that can be retracted and a rounded skull, both features that it shares with the cats. As always in these instances, it is hard o decide whether the shared characteristics are due to a direct relationship or evolved independently in the two groups.

Cats – Felidae

The cats – from trained lions and tigers in a circus to the family pet – are among the most popular of animals. Unfortunately, many of the larger wild cats are in danger of extinction because of the demand for their fur.

      The early history of the felids, like that of viverrids and mustelids, is for the most part lost. The first forms appeared between the end of the Eocene and the beginning of the Oligocene epoch in the drier areas of the Northern Hemisphere.

      Two major groups of felids are recognized. The first group is represented by the now extinct saber-toothed cats, which lived from the Oligocene to the Pleistocene epoch. The second group includes the true cats, the felines. This group also arose during the Oligocene. The felines are the group to which all living felids belong.

      From the beginning, felids fell into two clearly identifiable lines: one represented by animals having especially long upper canines, the other by animals with relatively normal-sized canines. In the evolution of the first line the canine development became further exaggerated and culminated in the saber-toothed “tigers” of later times. In the second line the proportion of the canine tooth has been more or less retained into the present.

      Today felids are present all over the world. However, no felids other than the domestic cat are native to Australia, New Zealand, Madagascar, Iceland, the extreme Arctic regions, the Antilles, Celebes, and New Guinea.

      The cat body is supple and lithe, permitting a silent approach to wary prey. Once within range of its prey, however, the cat replaces stealth with speed, moving very quickly toward its victim. The muscles are well developed. The strongest muscles are in the back, the hind legs (which propel the body in leaping), and the shoulders and neck (which are used for holding down the prey and in biting).

      Most cats have beautiful coats. Within the cat family there are coats of many different colors and designs which are important because they provide camouflage during hunting. As a stealthy hunter, the cat must approach its prey without being noticed. Cats that hunt in the open generally have coats of various shades of brown, which blend in with the surroundings. Cats that hunt in forested areas usually have spotted or striped coats, which blend in with the shadows cast by leaves and branches.

      Compared to many other mammals, cats are reasonably bright. Their brains are large and well developed. As with all mammals, innate patterns of behavior underlie many cat activities. However, learning from experience is also important in their behavior.

      Cats have very keen senses and large, well-developed eyes, ears, and noses. They have better vision than most other mammals. Although they are relatively colorblind, they are able to see quite well both in daylight and semidarkness. Their ability to judge distance is also excellent, and this is important for pouncing on prey.

      The teeth of felids are specialized for the killing and dismemberment of prey, an activity in which they are helped by short, strong jaws. The typical dental formula is I3/3, C1/1, Pm3/2, and M1/1, consisting of a total of 30 teeth. The cat’s incisor teeth are of little help in hunting or feeding and are used, rather, for grooming the fur. The canines, however, are very important. They, along with the claws, are the weapons used in a kill. They are also used in ripping and tearing the flesh of the prey. The carnassials cut through the meat, and the cat swallows small chunks of meat whole.