Bovids I: Kudus, Buffaloes, and Bison

(Bovinae)

Class: Mammalia

Order: Artiodactyla

Suborder: Ruminantia

Family: Bovidae

Subamily: Bovinae

Thumbnail description
Small to very large herbivores; males and often females bear unbranched horns on the head; limb structure is typical of the Artiodactyla, with two main toes terminating in hooves; all have a ruminant digestive system

Size
Length 30–170 in (80–435 cm); shoulder height 24–85 in (60–220 cm); weight 36–2,600 lb (17–1,200 kg)

Number of genera, species
9 genera; 24 species

Habitat
Forest, woodland, savanna, scrub, grassland, alpine meadows, prairie, and steppe

Conservation status
Critically Endangered: 2 species; Endangered: 7 species; Vulnerable: 4 species; Lower Risk/Conservation Dependent: 7 species; Lower Risk/Near Threatened: 3 species

Distribution
Africa, Asia, Europe, and North America

Evolution and systematics

The Bovinae is comprised of 24 extant species in three tribes: Boselaphini, Bovini, and Tragelaphini. Genetic evidence supports the idea that the Bovinae is a monophyletic group and a sister group to the subfamily Antilopinae. The tribe Bovini is also monophyletic and a sister group to the Boselaphini. The Boselaphini, today represented by only two living species, the nilgai (Boselaphus tragocamelus) and the chousingha (Tetracerus quadricornis), both of India, are probably the most primitive of the Bovinae and closest to the ancestors of this subfamily. The Bovini tribe includes yak (Bos grunniens), the various species of wild cattle (Bos), the European and American bisons (Bison), Asian (water) buffaloes and anoas (Bubalus), African buffalo (Syncerus caffer), and probably the saola (Pseudoryx nghetinhensis). The yak is sometimes placed into the genus Poephagus, while Bison have been suggested to belong to Bos, as has yak. Yaks appear from behavioral and genetic evidence to be intermediate between cattle and bison. The modern members of the tribe Tragelaphini are all African species, which have probably been separated from other Bovinae for 15 million years. Fossils attributed to nyala (Tragelaphus angasii) have been found in 6.5-million-year-old deposits. The mountain nyala (Tragelaphus buxtoni) is believed to be the precursor of kudu (Tragelaphus strepsiceros and T. imberbis). Other tragelaphines include the bongo (Tragelaphus eurycerus), bushbuck (T. scriptus), sitatunga (T. spekii), and elands (Taurotragus).

Physical characteristics

The smallest species of Bovinae is the chousingha, which weighs 36–45 lb (17–21 kg) and stands around 24 in (60 cm) at the shoulder. However, most species of Bovinae are medium to large ungulates, ranging up to 2,600 lb (1,200 kg), and several stand over 78 in (2 m) at the shoulder.

Males in all but one species of Bovinae have horns. In most of these species, females have smaller horns. This subfamily includes the only living artiodactyl with more than two horns. Male chousingha, also called the four-horned antelope, possess two pairs of short, sharp horns. Horn shape and relative size vary among species. Tragelaphines have long spiral-shaped horns with smooth surfaces, whereas the wild cattle, African buffalo, and smaller Asian (water) buffalo have shorter, smooth, curved, and often stout horns. Water buffalo have very large curved horns that are often ridged towards the base, while the saola's horns are straight and smooth.

Glands are limited in the Bovinae. The chousingha is the only member of this subfamily with pre-or ant-orbital glands in front of the eyes. Other Bovinae also lack pedal glands.

Most species of tragelaphins have a coat with several thin, white, vertical stripes, and some also have white spots. The contrasting white markings of tragelaphins probably act as disruptive patterns that help camouflage the animal by breaking up the body outline against the bush and forests they inhabit. In contrast, the eland, although a tragelaphin, is not striped and it inhabits open habitats where disruptive pelage would have little adaptive value. The largest members of the subfamily (e.g., American bison, water buffalo, African buffalo, and members of the genus Bos) have uniformly dark body pelage, although the lower legs of some species are light colored.

Distribution

Bovinae are native to both the New and Old Worlds and range from the north temperate regions south to the tropics. Africa, North America, Eurasia, India, and southern Asia are the main distribution regions. Bovinae are not native to either South America or Australia. The greatest species diversity of Bovinae is found in Africa and southern Asia, with the least in Europe and North America.

Habitat

Depending upon species, Bovinae inhabit a wide variety of habitats, ranging from open grasslands and savannas, thorn and scrubland, to swamps and dense tropical forests. Bovinae can be found at low elevations or above the tree line on the high mountain plateaus of Asia.

Behavior

For most species, males and females generally live apart for most of the year. Adult males live either alone or in all-male groups. Females form groups of varying size, comprised of their young of one to two years age, other females, and sometimes including subadult males. The degree of social grouping varies within Bovinae and is related partly to habitat and to body size. Most tragelaphines, except elands, live solitarily or in small groups. The largest species inhabiting open habitats are highly social, forming large groups, although group size often declines when they occupy more visually dense habitat where group cohesion is more difficult to maintain. When Europeans first traveled across the North

American plains and before their populations were decimated, bison were reported to live in immense herds. These are probably rivaled today only by the migratory herds of wildebeest in the Serengeti of East Africa or of barren-ground caribou in the Arctic tundra of North America. In most species, the adult males form separate all-male groups apart from the females, young, and subadults.

Among males, fighting can occur over attendance at cows in heat and involves charging and ramming their horns together. More often, hierarchical disputes are settled by dominance displays that involve swinging the horns and head actively from the side, presumably to enhance their apparent size. The defeated subordinate may act like a juvenile by lowering its head and placing its nose beneath the dominant's belly as if it were to suckle, or it may simple run away.

Feeding ecology and diet

Bovinae include grazers, grazer-browsers (mixed feeders), and browsers. Some such as the bushbuck (Tragelaphus scriptus) also eat fruits and seed pods. Tragelaphines are primarily browsers feeding on twigs, leaves, fruits, and new shoots of woody species as well as forbs and sometimes grasses, especially when the latter are newly growing. Larger species such as members of Bos and Bison rely more heavily on grasses and forbs but will browse when fresh young growth of shrubs is available. In the African buffalo, the smaller forest subspecies relies on browse rather than grasses, while the larger Cape buffalo feeds almost exclusively on grasses in the savanna, open bush, and riverine habitats it occupies.

Reproductive biology

All species are polygynous, with males mating with several females, while females tend to mate with only one male per mating season. Single young are most common, although in some species twins are not uncommon. Among the Bovinae, gestation is shortest (7.5–8 months) in chousingha, longest in the water buffalo (10–11 months), and 8–9 months for most other species. Age at first reproduction is generally in the second year (i.e., mate first when 2.5 years old) for the larger species, but occurs during the first year (i.e., mate first when 1.5 years old) for many of the smaller species.

Conservation status

A total of 22 species are listed in the IUCN Red List of Threatened Species. However, listed as Endangered is the linh duong (Pseudonovibos spiralis); this species' existence is questionable as it is suspected of being a hoax. The listings for this subfamily are: Critically Endangered: 2 species; Endangered: 7 species; Vulnerable: 3 species; Lower Risk: 10 species. Excluding the linh duong, 11 of the accepted 21 species, or 52%, are listed in categories of conservation concern.

Most threats to Bovinae come from human activities, including hunting and loss of habitat through the encroachment of agricultural lands and loss of forests for timber harvesting. Increased road access is linked with both the latter activities, which enables hunters to reach previously isolated populations.

Both wisent (Bison bonasus) and American bison (Bison bison) are examples of the extent to which some Bovinae have been driven to the brink of extinction at the hand of humans. Wisent were all but wiped out, leaving just a few in Poland, while American bison once estimated to number over 60 million at the beginning of the nineteenth century had all but been eradicated through concerted hunting efforts by the end of that century. One of the most important conservation efforts to preserve wisent has been carried out in the Bialowieza Forest in Poland, while for American bison, there have been several centers of bison conservation across the continent.

Significance to humans

All species were hunted, and some such as wisent and bison were especially important for European and North American hunters from Paleolithic to historic times. Today, local peoples still hunt members of the Bovinae for food, and trophy hunters value the species with large horns.

Three species of Bovinae are important domestic species. The most common and widespread is cattle (Bos taurus), first domesticated probably some 6,000 years ago. Domestic cattle are represented by numerous breeds around the world and have been bred for meat, milk, hides, as well as draught animals. They are more suited to temperate than tropical regions, although zebu or humped cattle are well adapted to hot climates. Water buffalo is the next most common domestic Bovinae, and, like its wild form, is an animal best suited to tropical regions with high rainfall. Like domestic cattle, water buffalo are kept for their milk, meat, and hides, and provide power primarily for plowing. The yak is of major importance in the high mountain regions of Tibet, Northern India, Nepal, and Afghanistan, where it is well adapted to elevations above 10,000 ft (2,500 m) above sea level. It is also crossed with domestic cattle to create hybrids that are more suitable to lower mountain elevations. Yak and the hybrids are used as beasts of burden to carry loads and plow fields, but also supply milk and sometimes meat. Their hair is valued and is woven into material used for such purposes as making tents.

Species accounts

Resources

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[Article by: David M. Shackleton, PhD; Alton S. Harestad, PhD]

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