Bovid
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| Bovids Fossil range: Early Miocene to Recent |
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Bovinae |
A bovid is any of almost 140 species of cloven-hoofed mammals belonging to the family Bovidae. The family is widespread, being native to all continents except South America, Australia and Antarctica, and diverse: members include buffalo, bison, antelopes, gazelles, both wild and domesticated cattle, sheep, goats, and water buffalo.
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[edit] Characteristics
The largest bovids weigh well over a ton and stand 2 metres high at the shoulder; the smallest weigh about 3 kg and stand no taller than a large domestic cat. Some are thick-set and muscular, others lightly built with small frames and long legs. Many species congregate into large groups with complex social structures, but others are mostly solitary. Within their extensive range, they occupy a wide variety of habitat types, from desert to tundra and from thick tropical forest to high mountains.
Most members of the family are herbivorous, except most duikers, which are omnivorous. All bovids have a four-chambered stomach which allows most of them to digest foods that are too low in nutriment for many other animals, notably grasses. No higher animal directly digests cellulose, but like kangaroos, termites and others, bovids rely on micro-organisms living in their stomachs to break down cellulose by fermentation.
Because of the size and weight of their complex digestive systems, many bovids have a solid, stocky build; the more gracile species tend to have more selective diets, and be browsers rather than grazers. Their upper canine teeth and incisors are missing, and are replaced with a hard, horny pad, that the lower teeth grind against to cut grass or other foliage. The canines are either missing or modified to act as extra incisors. The cheek teeth are low-crowned and selenodont, and are separated from the forward teeth by a wide gap, or diastema. [1] The dental formula for bovids is similar to that of other ruminants:
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All bovids have four toes on each foot – they walk on the central two (the hooves), while the outer two (the dew-claws) rarely touch the ground. All males and many females have horns (except in some domesticated breeds); the size and shape varies greatly but the basic structure is always a single bony protrusion without branches and covered in a permanent sheath of keratin.
[edit] Evolution
The bovid family is known through fossils from the early Miocene, around 20 million years ago. The earliest bovids, such as Eotragus, were small animals, somewhat similar to modern gazelles, and probably lived in woodland environments. The number of bovid species greatly expanded by the late Miocene, when many adapted to more open, grassland, habitat.[2]
The largest number of modern bovids is found in Africa, while substantial but less diverse populations are in Asia and North America. It is thought that many bovid species that evolved in Asia could not survive predation by humans arriving from Africa in the late Pleistocene. By contrast, African species had many thousands or a few million years to adapt to the gradual development of human hunting skills. Yet many of the commonly domesticated bovid species (goats, sheep, water buffalo and yak) originated in Asia. This may be because Asian bovids had less fear of humans and were more docile.[who?]
The small number of modern American bovids are relatively recent arrivals over the Bering Land Bridge, but they long predate human arrival.
[edit] Classification
- ORDER ARTIODACTYLA: even-toed ungulates
- Suborder Suina: pigs and allies
- Suborder Tylopoda: camels and llamas
- Suborder Ruminantia: ruminants
- Infraorder Tragulina
- Family Tragulidae: chevrotains, 6 species in 4 genera
- Infraorder Pecora
- Family Moschidae: musk deer, 4 species in one genus
- Family Antilocapridae: pronghorns, one species in one genus
- Family Giraffidae: giraffes and okapi, 2 species in 2 genera
- Family Cervidae: deer, 43 species in 16 genera
- Family Bovidae
- Subfamily Bovinae: cattle and spiral-horned antelopes, 26 species in 10 genera
- Subfamily Cephalophinae: duikers, 19 species in 2 genera
- Subfamily Hippotraginae: grazing antelopes, 6 species in 5 genera
- Subfamily Antilopinae: gazelles, dwarf antelopes and the saiga, 34 species in 13 genera
- Subfamily Caprinae: sheep, goats, 33 species in 10 genera
- Subfamily Reduncinae: reedbucks, lechwe, 8 species in 2 genera
- Subfamily Aepycerotinae: impala, 1 species in 1 genus
- Subfamily Peleinae: rhebok, 1 species in 1 genus
- Subfamily Alcelaphinae: wildebeest, topi/tsessebe, 7 species in 4 genera
- Subfamily Pantholopinae: Chiru
- Infraorder Tragulina
[edit] References
- ^ Janis, C. & Jarman, P. (1984). in Macdonald, D.: The Encyclopedia of Mammals. New York: Facts on File, 498-499. ISBN 0-87196-871-1.
- ^ Savage, RJG, & Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File, 232-235. ISBN 0-8160-1194-X.
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