| Cattle | |
|---|---|
 | |
| Domestic cow | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Bovidae |
| Subfamily: | Bovinae |
| Tribe: | Bovini Gray, 1821 |
| Type genus | |
| Bos | |
| Subtribes and genera | |
| |
ThetribeBovini orwild cattle are medium to massivebovines that are native toEurasia,North America, andAfrica. These include the enigmatic,antelope-likesaola, the African and Asiaticbuffaloes, and a clade that consists ofbison and the wild cattle of the genusBos.[3][4] Not only are they the largest members of the subfamilyBovinae, they are the largest species of their familyBovidae. The largest species is thegaur (Bos gaurus), weighing up to 1,500 kg (3,300 lb).[5]
Bovins andhumans have had a long and complex relationship. Five of seven species have been successfully domesticated, with one species (cattle) being the most successful member of their lineage. Domesticated shortly after thelast ice age,[6] there are at least 1.4 billion cattle in the world.[7] Domestic bovines have been selectively bred forbeef,dairy products and leather, and serve asworking animals. However, many species of wild cattle are threatened by extinction due tohabitat loss to make room for cattle farming as well as unregulated hunting.[1][8] Some are already extinct like theaurochs, two subspecies ofEuropean bison and perhaps thekouprey.[9]
In 1821British zoologistJohn Edward Gray described the family, subfamily and tribeBovidae,Bovinae, and Bovini respectively.[10] The word "Bovini" is the combination of theLatin prefixbos (written asbov-, which isLate Latin frombovinus) and the suffix-ini refers to their ranking as a tribe.
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| Phylogenetic relationships of theBovinae (Bibi et al., 2013)[3] |
The wild cattle belong to the subfamilyBovinae, which also includes spiral-horned antelope of the tribeTragelaphini and two aberrant species of Asian antelope,four-horned antelope andnilgai, which belong to the tribeBoselaphini. The relationship between the tribes varies in research concerning their phylogeny. Most molecular research supports a Bovini and Tragelaphini subclade of Bovinae.[11][3][8] There are also some morphological support for this, most notably both groups havehorn cores with apedicle.[12]
The earliest known wild cattle originated from Asia south of theHimalayas during theLate Miocene.[13][14] This is not only supported by the fossil record but also the fact thatSouth Asia has the highest diversity of wild cattle on planet, as well as the fact the southeast Asian saola is the basal most of the living species.[13][14][15] At some point after the divergence of the three subtribes around 13.7 million years ago, bovins migrated into Africa from Asia where they have diversified into many species.[16][17] During thePliocene epoch some bovines left Africa and entered Europe, where they have evolved into hardy, cold-adapted species.[15] During the Ice Age ancestors of thebison had colonized North America fromEurasia over theBering Land Bridge in two waves, the first being 135,000 to 195,000 years ago and the second being 21,000 to 45,000 years ago.[18][19]
Below is the list of fossil species that have been described so far listed in alphabetical order that currently do not fit in any of the existing subtribes:
| Phylogenetic relationships of the tribe Bovini (Hassanin et al., 2013)[4] |
The majority of phylogenetic work based onribosomal DNA,chromosomal analysis, autosomal introns andmitochondrial DNA has recovered three distinctive subtribes of Bovini: Pseudorygina (represented solely by thesaola),Bubalina (represented today by the generaSyncerus andBubalus), andBovina (represented today by the generaBison andBos).[20][21] According to the fossil record and the molecular work, Bubalina and Bovina have diverged from one and another from a common ancestor around 13.7 million years ago in theLate Miocene.[2][22][4][15]
The number of taxa and their evolutionary relationships with each other has been debated, mainly as there is several evidence of ancient hybridization events that occurred among the various species of wild cattle, obstructing any evidence of their relationships.[23][24][22][25][4]
Below is the taxonomy of extant genera that are classified as members of the tribe Bovini (more information regarding the species taxonomy is explained more in-depth in their respective subtribe articles):[25][4][15][8]
Wild cattle are usually massivebovids that are stout-bodied with thick, short legs.[26][1][27][8] Some species can reach impressive body-sizes such aswild water buffalo,wild yak,American bison, andEuropean bison, which can weigh between 700 and 1,200kilograms and these species can attain a shoulder height more than 1.9 meters.[27] The gaur can weigh up to 1,500 kilograms and attain a shoulder height up to 2.2 meters.[5] There are some breeds of domesticcattle that can be even larger than both wild species, one of them being theChianina, bulls of which can weigh from 1,200 to 1,500 kilograms and reach a similar height to the gaur.[28][29] There are, however, several species ofbuffalo that live on the various islands inIndonesia are dwarf species, such as thetamaraw and theanoa, that weigh between 200 and 300 kilograms.[27][8] Furthermore, not all species of bovin look like cattle, such as the saola which looks more likeantelope (a fact that caused some confusion among bovid biologists[21]). What all bovins or wild cattle do have in common is both sexes have the presence of smooth horns, instead of annulated horns seen in most other bovids.[27][12][8] Inbovinans the horns are round, while inbubalinans they are flattened.[26] Like thespiral-horned antelopes there is extremesexual dimorphism in bovins, though it is emphasis on the body size and the size of the horns.[26][27][8] Males are significantly larger than the females, which most of their features are exaggerated with massive humps, large necks, and in some species the presence of a dewlap.[26][8] Males and females exhibit sexual monochromatism (with the exception of thebanteng, where males are a dark chestnut while females are just chestnut), though the male coloration hues are darker than the females.[26] Coloration can be uniform or with some white markings, from black to brown.[26][8]
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The wild species of bovins are found inNorth America,Eurasia andsub-Saharan Africa, though domesticated species or variants have a global cosmopolitan range with the help ofhumans.[26][27] With the exception of the open-plains dwellingAmerican bison and the montane-dwellingwild yak, all species of wild cattle inhabit wooded or forested areas with someclearings.[26][27] The reason is that most species require muchroughage (often tall grass) in their diet and much water to drink.[26][27] In addition they are less efficient eaters than smaller herbivores, as they cannot selectively forage on relatively short grass due their stiff, immobile upperlips.[26] They commonly wallow in mud and water in swamps, especially withwater buffalo.[26][27] Forest-dwelling live indeciduous andtropical forests. With their large body-size, wild cattle have few natural predators aside from humans. Still they are often prey tocrocodiles,big cats,spotted hyenas,dholes, andwolves.[27] It is often the young and the weak that are commonly selected by these predators.
Wild cattle are very social animals, which they accumulate into large herds, with some individual sizes that can go into the hundreds.[26] Usually these herds consisted of females and their young, although in some species there are occasionally bachelor males among them.[26][27][8] Generally the larger and more experienced males tend to be solitary, though in the breeding season mixed-herds occur.[26][27][8] There is a strict hierarchy among males based on size dominance.[26]
All species of bovin arepolyandrous. During therutting period males engage in ramming against each other in order to obtain the breeding rights for females as well as territory.[26] Thegestation period occurs once the female has been inseminated from the male successfully. In most species it lasts approximately nine to ten months.[26][8] They only give birth to a single calf. Once the young are born, they will not wean until they are around six to 10 months depending on the species.[8] Females of most species sexually mature by four years while for males it is seven years.[26]
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The chromosome number varies by species, and sometimes even by subspecies, which warrants further research for taxonomic purposes.[25] The ancestralY chromosome was probably a smallacrocentric, but evolved into several distinct characteristics.[30] The subtribe Bubalina have the acquisition of X-specific repetitive DNA sequence on their Y chromosomes;Bos has derivativemetacentric Y chromosomes, and share the presence of shared derivativesubmetacentricX chromosomes withBison.[30] Below is a listing of the diploid number 2n of selected species as follows:[30][31]
Bovin hybridization is most common in the subtribeBovina, the most well known of these is thebeefalo (a cross between cattle and American bison). Most of these hybrids are deliberate from humans wanting to improve the quality of various cattle breeds (in particular for beef production). All bovinan hybrids producesterile males andfertile females followingHaldane's rule. In addition for theagricultural purposes, bovin hybridization was used in the past to save several species such as the American bison in the past.[32] This has caused problems for wild cattle conservation as hybrids pollute thegenetic diversity of genetically-pure animals.[32] Bovin hybridization was also a major factor behind the evolution of Bovini, as some species have evidence of ancient hybridization in theirgenome.[33]
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