Bovine anatomy

Hides

Bovids come in a wide array of colours. Some utilize camouflage, such as the stripes on the bongo and kudu. Some bovids have unique markings, which individuals can use to tell their herdmates apart.^[1] Black cattle are more prone to heat stress than cattle with lighter colours, such as white^[7] or red,^[8] though colour does not seem to affect the respiration rate.^[7] Colour also affects growth, with white cattle growing faster than dark red cattle.^[9] Males are often darker than females.^[1]

Horns

Bovids have horns, which differ from antlers in that they are permanently attached to the skull, and their bony core is coated in keratin, while antlers shed every year and have no such coating. Horns grow throughout the bovid's life.^[1] Bovids in temperate climates have smaller bone cores and thicker keratin coatings than those in tropical climates, reducing surface area and allowing the temperate bovids to retain more heat. Temperate bovid horns also tend to be prostrate or curled in position, again reducing the surface area and thus retaining more heat.^[10]

Horn shape is also affected by fighting behaviors. Recurved horns are adapted for ramming behavior, horns with short reaches for stabbing, and horns with longer reaches for fencing.^[11] Some bovids, like the common eland, have spirals on their horns, which helps with attaining a grip and deflecting fractures while wresting.^[12] Generally, the more likely a species is to engage in fights, the longer its horns will be.^[11]

Male bovids always have horns, and these horns are thicker and more complex horns than females.^[1] A male's horn size is positively correlated with the size of his herd, likely due to the higher chance of sexual selection. Territoriality, in contrast, is negatively correlated to horn size, likely because territorial males have less access to females.^[13] A trade-off to large horns is heat loss; it has been argued that heat loss is a major countering force against sexual selection of horn size.^[14] When female bovids have horns, it is usually in species that are large in size or which live in open habitats. Thus, the female cannot hide as well as a less visible species. Females of small but territorial species, like duikers, are an exception to this rule.^[15]Female horn length is thought to be controlled by natural, rather than sexual, selection, as it is unaffected by mating system factors,^[13] and because the horns of female caprids (a subfamily of Bovidae) seem more affected by temperature.^[14]

Hooves

Bovids have cloven hooves, which means that the hoof is split into two digits, held together by the cruciate ligament.^[16] Each digit has 3 phalanx bones, a navicular bone, and 2 sesamoid bones, so that each hoof has a total of 6 bones.^[16]

The bovine hoof has a hard outer coating called a hoof wall, which is made of keratin. The hoof wall has a layered structure, making the hoof resistant to wear and protecting the animal from impact force when running.^[17] Below the wall is the corium, comparable to the dermis in humans, which consists of nerves and blood vessels. In some species, like yak, the tissue is also rich in adipose.^[18] The bottom of the external hoof is the sole, which is softer and more flexible than the hoof wall.^[19]

Skull

There is a much wider disparity between bovine skulls than there is between other ruminants, such as cervids.^[6] Snout width is tied to diet and the aridity of the animal's habitat. Grazing bovids have wide skulls for gathering large amounts of grass, with grazers living in humid climates having wider snouts than those in arid ones. This may be tied to grazers in arid climates having to be more selective in feeding. Conversely, the skulls of browsers and mixed feeders have more narrow snouts, as these animals are always more selective, and their snout size is more consistent across climates.^[23] Additionally, bovids in the tribe bovini are distinguished by wide, low skulls with short braincases.^[2]