Cattle family (Bovidae)
Cattle family (Bovidae)
Cattle family (Bovidae)
The cattle family, Bovidae, is a widespread group of mammals which also includes the goats, sheep, gazelles, antelopes, and goat-antelopes. Of the 107 species currently recognized within this family, just 12 are wild cattle. Even the large muskox (Ovibos moschatus ), which looks quite cow-like, is more closely related to the goats than to cattle. Cattle are generally characterized by their large size and the single pair of non-branching horns growing from their forehead. The horns, which are not shed, are largely hollow and differ considerably among species: some of the largest are those of the wild yak (Bos mutus ) and African buffalo (Syncerus caffer ), while the smallest are those of the anoas or dwarf water-buffalo (Bubalus spp.). Both males and females develop horns as they mature, but those of the male are usually much longer. Wild cattle vary considerably in appearance—from the brown-black colors of the anoas to the banteng (Bos javanicus ), in which the females are reddish brown and the males shiny black. Both sexes are adorned with white stockings, a white rump patch, a white patch over the eyes, and a white band around the muzzle. The antithesis to these decorative cattle are wild yaks, whose unkempt, shaggy appearance and unpredictable temperament are an example of how one species has evolved to withstand extreme conditions which few other animals could exploit.
The precise origins of wild cattle are still unclear, but it is thought that they arose from species resembling the small four-horned antelope (Tetracerus quadricornis ) and larger nilgai (Boselaphus tragocamelus ), which today survive only in India. The ancestors of the modern-day cow (Bos taurus ) have been traced back to a species known as the auroch (Bos primigenius ), an extinct wild ox of Europe and Asia that reached more than 7 ft (2 m) at the shoulder. These were largely forest-dwelling cattle, feeding in open glades and around the fringes of woodlands. Adult males, or bulls, had long curving horns, a black coat with a white stripe down the middle of the back, and a patch of short tufts of white hair between the horns. Females, or cows, were smaller and a reddish brown color. The last known auroch died in Poland in 1627. Domestic cows, of course, are extremely abundant in captivity, with a worldwide population exceeding a billion animals.
Wild cattle have evolved to survive in a wide range of habitats, from Arctic to tropical conditions. Wild yaks are an example of a species that has adapted to living in a harsh climate, with their thick shaggy outer hair and densely matted undercoat providing insulation against the extreme cold in their native habitat in the high, wind- and snow-swept plateaus of the Himalayas. Species that live in the tropics have other physiological problems to overcome, such as avoiding becoming too hot. These species are typically forest-dwelling, and have short hair that does not retain body heat very effectively. Some species, such as the kou-prey (Bos sauveli ), have extended dewlaps, large fat-filled folds of loose skin that hang below the neck and serve as heat-radiating surfaces. Other species, such as water buffaloes, cope with the heat and ever-present flies by immersing themselves in water. By frequent wallowing, buffalo cover themselves with a layer of mud that also helps protect them from the piercing bites of insects. Most species feed at dawn and dusk in order to avoid the midday heat. Some of the shyer species, such as gaur, anoa, and tamaraw (Bubalus mindorensis ) may feed at nighttime in order to avoid detection by predators, including humans.
Over the centuries, several species of wild cattle have been domesticated, including the auroch, yak, gaur, banteng, and water buffalo. In some cultures, cattle are their owner’s most important possessions. In Africa, cattle are an important symbol of wealth and are used for trade purposes, as well as for their milk and blood, both of which feature in the diet of certain tribes. Their meat, of course, is also of importance, as are their valuable hides, but cattle are only butchered on special occasions. Even their dung is of considerable importance as it is dried and stored as a source of cooking fuel in many parts of the continent where tree cover is sparse. Domesticated yaks are equally important for the people of mountainous Nepal and Tibet in regions where roads are few and the climate extreme. Working at altitudes of up to 20, 000 ft (6, 000 m), yaks are capable of hauling heavy loads and surviving on a low-quality diet. In addition, they provide people with an essential supply of milk, meat, wool, and hides.
Cattle are grazing animals that feed mainly on grasses, herbs, and tree and shrub leaves. They feed by twisting grasses and stems around their tongue and cutting the vegetation off with the lower incisors, which protrude slightly forward. The jaw is designed to allow a circular grinding motion, which allows the food to be thoroughly crushed and masticated between the animal’s large teeth. Their plant food, however, is largely composed of cellulose, a tough carbohydrate that few animals are able to digest. Cows, however, have evolved a means of overcoming this problem and are able to benefit from the relatively abundant supplies of available plant biomass. Cows belong to a group of animals known as ruminants, which have a specialized system of digestion that enables them to break down the cellulose fibers and extract the energy from the plants they eat. One of the most significant features of this system is a specialized stomach which, in ruminants, consists of four distinct chambers: the rumen, reticulum, omasum, and abomasum. Another is the presence of large numbers of specialized bacteria that live within a sort of liquid broth in the stomach, and are essential in digesting cellulose. Without these symbiotic bacteria, no amount of chewing would render the plant material in a state from which nutrients can be absorbed.
Cattle are prodigious eaters; at any one feeding, large quantities of grasses are consumed and pass
directly into the large rumen. Here they are moistened and mixed with the bacteria that begin to attack the tough plant fibers. From the rumen, partly digested materials pass on to the reticulum, where a similar process continues. Most wild cattle have preferred feeding and resting grounds and, when not feeding or moving, they withdraw to protective cover to digest their food. At this time the animal will regurgitate this partly digested food once again into the mouth, where it is chewed a second time, mixed with salivary enzymes, and then swallowed again in a process commonly known as “chewing the cud.” When it is swallowed again, the food passes through the upper stomach to the omasum and abomasum, where normal digestive enzymes take over the process of breaking down the plant materials and freeing the nutrients, which can then be absorbed and used by the cow. In total, food takes from 70–100 hours to pass through the digestive system of a cow—one of the slowest passage rates in the animal kingdom. Although this passage is slow, it is extremely effective. A thoroughly masticated and digested food base allows a large fraction of the proteins and other nutrients to be absorbed.
Wild cattle play an important ecological role through their grazing habits, in particular by keeping grasslands open from invading shrubs and coarse grasses, and creating a habitat favorable for other grazing animals, such as deer and antelope. Their dung, which is widely scattered across the grasslands or throughout the forest, serves as an important fertilizer and is broken down by a wide range of beetles, fungi, and bacteria that release essential nutrients and minerals that promote further plant growth.
Cattle are naturally social animals and form small herds, the composition of which varies according to the species. Some species, like the anoa, may be solitary or travel in groups of just two to four animals. At the other extreme, herds of thousands of bison once ranged across the vast fertile prairies of North America, each massive herd separated into sub-units of several hundred animals.
The African buffalo displays a relatively advanced system of social behavior. The entire herd not only feeds and moves around as a colossal single unit, but individual animals will also gather around an injured or sick animal if it is threatened by predators. This is a non-territorial species that forms herds of 50–2, 000 animals, with an average of about 350 animals. Within the herd, a distinct social hierarchy is evident: dominant males are most successful in breeding with females. There is constant rivalry between these dominant bulls and transient males who do not belong to the local herd. Subordinate juvenile males are allowed to remain with the herd until they reach sexual maturity, at which time they are driven out and may remain solitary or form small bachelor groups with other males. Juvenile females remain with the herd and maintain a strong bond with their mother.
Breeding is a frantic time for all species of wild cattle, with adult males vying with other socially dominant males for the right to mate with receptive females. Dominant males must also keep a vigilant eye on sexually mature transient males, who may attempt to steal their cows and form their own herd. Adult bulls challenge others of similar status with loud roars and mock charges. On most occasions these displays of strength are sufficient to deter challenging males, but sometimes the challenging male refuses to back down and the situation escalates to fierce clashes in which one bull pitches his strength and agility against the power of another. The bull’s horns are one focus of attention in such battles, as males interlock their horns and try to wrestle their opponent into a vulnerable position where they may strike other parts of the body with their pointed horns. The winner of such conflicts is almost certainly guaranteed the rights of dominant male within the herd, until he, in turn, is deposed by another challenging male.
The gestation period of wild cattle varies considerably, from about 270 days to over 400 days. As the calving time approaches, most cows leave the herd, returning to join it again seven to 10 days later with their offspring. Most cows give birth to a single calf, which remains close to its mother until weaned. Following that, calves usually remain with the herd for a further three years until they reach sexual maturity. The fate of young cattle thereafter depends on the social system of the particular species, as described above.
Wild cattle have few natural predators, at least at the adult stage. Calves, however, are susceptible to predation from lions, tigers, leopards, and wild dogs. Predation is thought to have been one of the main reasons why wild cattle developed a herding life style, as the presence of large numbers of heavily armored animals is often enough to deter a predator from attacking. When feeding as a group, the animals are slightly spread apart, and it is advantageous to have many eyes on the lookout. Each animal takes its turn to scan the surrounding vegetation between feeding bouts. Through the centuries, however, wild cattle have suffered considerably at the hands of humans, as they have been hunted for their meat, hides, and as sport. Widespread herds of auroch were decimated by the sixteenth century; the European bison (Bison bonasus ) suffered a similar fate during the nineteenth century, and the once vast herds of American bison suffered heavily at the hands of European settlers in their quest to open up the American West.
The European bison is an example of a species that became extirpated in the wild, but then recovered somewhat through the breeding and release of captive animals. A sedentary, woodland-dwelling species, the European bison was reduced to a few scattered populations by the beginning of the twentieth century. Many of these were destroyed during World War I (1914–1918), and the last remaining wild herds died out in Lithuania and the Caucasus by the middle 1920s. Concentrated efforts by a few zoos led to the re-introduction of a small herd to natural habitat in the Bialowieza Forest in Poland. At first, these animals were retained in semi-captive conditions, but they were later released to form free-ranging herds. Although this species has been saved from extinction, present-day herds are closely inbred—they are all descended from just 17 animals. Additional conservation programs are underway to try and maximize the genetic exchange between breeding herds.
One of the least-known cattle species is the tamaraw, a small species that reaches just 3 ft (1 m) at the shoulder. This species inhabits forested parts of the island of Mindoro in the Philippines. It is thought to be nocturnal and quite aggressive, but almost nothing is known about its ecology. Overhunting, as well as loss of habitat and human encroachment on this species’ habitat, has resulted in a serious population decline from an estimated 10, 000 animals in the early 1900s, to fewer than 200 animals today. The majority of these free-living animals are confined to Mount Ilgo National Park. In view of the extent of deforestation on this island, the species is classified as endangered by conservation organizations. Several conservation initiatives have been attempted in the past, but these have met with little success so far.
Like the tamaraw, the kouprey is another highly endangered species. Once wide-ranging throughout Indochina, it is now thought to be extinct in countries such as Thailand. The last remaining herds may survive in the forested border countries of Laos, Cambodia, and Vietnam. A large species reaching a height of 6 ft (1.9 m) at the shoulder and measuring from 7–8 ft (2.1–2.3 m) in body length, males of this species are much larger than females. Young calves and females are generally a gray color (the species is locally known as the “gray ox”), with the undersides a lighter hue and the neck, chest and forelegs slightly darker. Mature males are a rich dark brown color, with white or gray coloring on the lower legs. The species may be recognized by its dewlap, which in some older males may even reach and drag along the ground. Apart from color differences, bulls are easily distinguished from cows by their horns: the latter generally have horns that spiral upwards, while those of a bull are more widely spaced and often frayed at the ends. The reason why these split at the ends is unknown, but some authorities believe kouprey use their horns for digging in the earth, perhaps in search of mineral salts.
Kouprey are animals of gently rolling hills in deciduous and semi-evergreen tropical forests that offer a wide range of open feeding and resting sites. They may, however, move to higher ground during the wettest periods of the year. Little is known about the ecology of this species. They are known to form small herds of cows and offspring, with separate bachelor herds of young males. Animals appear to be most active in the morning and again in late afternoon, and frequently travel at night. Mixed herds of kouprey, banteng, and feral water buffaloes have been reported. In 1949, there were thought to be around 1,000 kouprey surviving. This number is thought to have declined to 500 in 1951, and just 100 in 1969. No one is quite sure how many kouprey survive in the wild today, as this species’ habitat is at the center of almost constant human warfare. Authorities fear for its survival in view of the heavy hunting pressure in the region.
Recent analyses of kouprey DNA have added a surprising twist to the story of this species. Three biologists from Northwestern University and the Cambodian Forestry Administration have proposed that the kouprey is not a valid species at all, but rather is a hybrid of two domesticated species—the banteng and the zebu—that became feral, probably in the nineteenth century. Other scientists dispute this interpretation and maintain that the kouprey is a valid, natural species. Further DNA sampling and analysis is necessary to resolve this question, but no one disputes the fact that very few kouprey (if any) remain in the wild.
Other species, which are perhaps equally threatened, are the wild anoas, of which two species have been recorded: the mountain anoa (Bubalus quartesi ) and the lowland anoa (B. depressicornis ). Both species are only found in Sulawesi, Indonesia. In appearance, anoas resemble dwarf water buffaloes, measuring just 2–3 ft (0.7–1 m) at the shoulder and 5–6 ft (1.6–1.7 m) in body length, and weighing about 300–600 lb (150–300 kg). Adults are usually a dull brown color, but the shading pattern may vary, with some animals having lighter undersides. Calves are covered with woolly yellow-brown hair, but this is lost as they mature. Little is known about the ecology of these secretive cattle as few observations have been made in the wild. It is known that they are widely hunted for their meat, but another serious threat is continuing loss of forest habitat, which affects both species.
Wild cattle are of enormous importance for our present civilization, just as they have been in our past. They not only play a vital role in the local ecology of their diverse environments, but also represent an important genetic reservoir which is important for breeding purposes. Hybrids of cattle-yak origin are already of great importance in many parts of Nepal and China. Elsewhere in Asia, farmers in Laos and Kampuchea used to drive their cows into the forest in the hope that they would breed with wild kouprey bulls, as they found that such offspring were stronger than if the cows were mated with domestic cattle. All wild cattle therefore, have considerable potential in the breeding arena, since these species are often far better adapted to local climatic and forage conditions, as well as being stronger and more resistant to diseases, many of which are debilitating for domestic breeds.
If humans are to save these remaining species in the wild, however, there is not much time to lose. Most species are now severely threatened by hunting as well as habitat loss. As the habitat range of these species continues to shrink in the face of human encroachment, all wild populations of cattle risk becoming isolated and susceptible to disease, as well as inbreeding, as there will no longer be a possibility of genetic exchange between isolated populations. Future conservation efforts must continue to focus on preserving natural feeding and breeding ranges, as well as essential migration corridors of these species, in order to ensure the continued viability of the wild herds of cattle.
See also Livestock.
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