Bovids are the largest of 10 extant families within Artiodactyla, consisting of more than 140 extant and 300 extinct species. Designation of subfamilies within Aepycerotinae (impalas), Alcelaphinae (bonteboks, hartebeest, wildebeest, and relatives), Antilopinae (antelopes, dik-diks, gazelles, and relatives), Bovinae (bison, buffalos, cattle, and relatives), Caprinae (chamois, goats, serows, sheep, and relatives), Cephalophinae (duikers), Hippotraginae (addax, oryxes, roan antelopes, sable antelopes, and relatives), and Reduncinae (reedbucks, waterbucks, and relatives). Wild bovids can be found throughout Africa, much of Europe, Asia, and North America and characteristically inhabit grasslands. Their dentition, unguligrade limb morphology, and gastrointestinal specialization likely evolved as a result of their grazing lifestyle. All bovids have four-chambered, ruminating stomachs and at least one pair of horns, which are generally present on both sexes. (Alder, et al., 1995; Feldhamer, et al., 2007; Gentry, 2011; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)has been controversial and many experts disagree about whether is monophyletic or not. While as many as 10 and as few as 5 subfamilies have been suggested, the intersection of molecular, morphological, and fossil evidence suggests 8 distinct subfamilies:
Species in the subfamily Bovinae are native to Africa, North America, Eurasia, India, and southern Asia. Bovinae is generally considered to include 24 species from 8 different genera, including nilgai, four-horned antelope, wild cattle, bison, Asian buffalo, African buffalo, and kudu. Sexual dimorphism is highly prevalent in this subfamily, with the males of some species weighing nearly twice as much as their female counterparts. Bovines have played an important role in the cultural evolution of humans, as numerous species within this subfamily have been domesticated for subsistence purposes. (Estes, 1991; Gentry, 2011; Shackleton and Harested, 2010a; Shackleton and Harested, 2010b)
The subfamily Antilopinae includes antelopes, dik-diks, gazelles, and relatives. Small to medium-sized, cover-dependent antelope are found throughout a majority of Africa but occur in particularly high densities in east Africa. Dwarf antelope, steenboks, and dik-diks occur in a variety of different habitats but are also restricted to the continent of Africa. Finally, true gazelles include the genera Eudorcas, Gazella, Nanger, and Procapra, among others. In general, bovids within the subfamily Antilocapinae occur throughout much of Asia and Africa. (Estes, 1991; Gentry, 2011; Shackleton and Harested, 2010a; Shackleton and Harested, 2010b)
Bovids within the subfamily Reduncinae are primarily distributed throughout parts of Eurasia and Africa. Reduncinae is comprised of only three genera, including Redunca (reedbucks), Pelea (rhebok), and Kobus (waterbucks). Species in Reduncinae are medium to large-sized grazers that often have strong ties to water. They also have long hair, and all species exhibit sexual dimorphism, as horns are only present in males. (Estes, 1991; Gentry, 2011; Shackleton and Harested, 2010a; Shackleton and Harested, 2010b)
Bovids in the subfamily Hippotraginae consist primarily of large grazing antelopes with large horns. Hippotraginae species are restricted to Africa and middle-east Asia and are primarily grazers. Most species in this subfamily live in arid habitats and have an erect mane along the nape of the neck. Recent accounts include 8 species from 3 different genera. (Estes, 1991; Gentry, 2011; Huffman, 2011; Shackleton and Harested, 2010a; Shackleton and Harested, 2010b)
Ancelaphinae, consisting of 10 species from 4 genera, includes bonteboks, hartebeest, wildebeest, and relatives. All of the species in this subfamily are nomadic grazers that are native to Africa. Most species are size-dimorphic, with males being 10 to 20% larger than females, and both males and females possess double-curved horns, also known as lyrate. (Estes, 1991; Gentry, 2011; Huffman, 2011; Shackleton and Harested, 2010a; Shackleton and Harested, 2010b)
The subfamily Caprinae consists of goats, sheep, muskox, and relatives. This subfamily of bovids consists of 12 genera, however, the organization of Caprinae is complex and several classifications have been suggested. The International Union for Conservation of Nature (IUCN) currently has a Taxonomy Working Group within their Caprinae Specialist Group to help alleviate some of the outstanding issues within Caprina taxonomy. Caprinids are especially adapted to montane and alpine environments, which explains why this is the only subfamily that is more diverse in Eurasia than Africa. In general, both genders have horns, however, horn morphology in many species is sexually dimorphic. (Estes, 1991; Gentry, 2011; Huffman, 2011; Mallon, 2010)
The subfamily Aepycerotinae consists a single species, the imapala. Aepycerotinae is endemic to Africa and is thought to have diverged from other bovids during the early Miocene, around 20 million years ago. Impala are sexually dimorphic, as only males possess horns.. (Estes, 1991; Huffman, 2011; Kingdon, 1982a; Kingdon, 1982b)
Cephalophinae consists of 18 species of duiker from 3 genera. Duikers are highly specialized and are resident to the tropical forests of Africa. All species are easily recognizable as they have the same basic body plan but differ significantly in size from one species to the next. Duikers are size-dimoprhic, however, unlike most bovids, females are slightly larger than males. Also unlike most other bovids, duikers are primarily frugivorous. (Estes, 1991; Huffman, 2011; Nowak, 1999)
Bovids first evolved as grassland species, and most extant species are open grassland inhabitants. Bovid species richness is highest in the savannah of east Africa and the family has radiated to fill an enormous variety of ecological niches resulting in a wide range modifications to dental and limb morphology. For example, Bohor reedbuck and lechwe inhabit riparian and swampy landscape; springbok and oryx are found in deserts; bongo and anoa occupy dense forests; mountain goats and takin reside at high elevations; and musk ox are restricted to arctic tundra. (Danell, et al., 2006; Feldhamer, et al., 2007; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
Numerous bovid species have been domesticated by humans. Goats and sheep were domesticated for subsistence purposes around 10 thousand years ago (KYA) in the near east, followed by the domestication of cattle around 7.5 KYA. While wild relatives of goats and sheep can still be found in their native habitat, the wild ancestors of domesticated cattle, aurochs, have been extinct in the wild for nearly 300 years. Currently, domesticated aurochs are kept on farms and as pets throughout parts of Eurasia. (Danell, et al., 2006; Feldhamer, et al., 2007; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
Bovids display the characteristic long limbs and unique foot and unguligrade stance of artiodactyls. They are paraxonic, as the line of symmetry of the foot runs between the third and fourth digits. In most bovids, the lateral digits are either reduced or absent and the animal's weight is born on the remaining central digits. The third and forth metapodials are completely fused in bovids, resulting the cannon bone. The joint between the cannon bone and proximal phalanges includes four sesamoid bones that act as joint stops. The ulna and fibula is reduced and fused with the radius and tibia respectively. This arrangement provides for a wide angle of flexion and extension, but restricts lateral movement. (Alder, et al., 1995; Danell, et al., 2006; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
As a members of the suborder Ruminantia, bovids possess the trademark multi-chambered fore-gut adapted for cellulolytic fermentation and digestion. Thus, they are obligate herbivores, which is also reflected by their hypsodont and selenodont tooth morphology. Their upper incisors are absent and their upper canines are either reduced or absent. Instead of upper incisors, bovids have an area of tough, thickened tissue known as the dental pad, which provides a surface for gripping plant materials. The lower incisors project forward and are joined by modified canines that emulate the incisors. Their modified incisors are followed by a long toothless gap known as a diastema. Bovids have a generalized dental formula of I 0/3, C 0/1, P 2-3/3, M 3/3. (Alder, et al., 1995; Danell, et al., 2006; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
The distinguishing characteristic of the Bovidae family is their unbranching horns. The horns originate from a bony core known as the the cornual process (os cornu) of the frontal bone and are covered in a thick keratinized sheath. Horns are not shed like the antlers of cervids and most grow continuously. Except for Indian four-horned antelopes, horns occur in pairs and in a fascinating array of unique forms from curved daggers in mountain goat to the thick, rippled coils of greater kudu. (Alder, et al., 1995; Danell, et al., 2006; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
Bovids exhibit a wide range of sizes and pelage coloration and patterns. For example, gaurs have a maximum shoulder height of 3.3 m (10.82 ft) and a maximum weight of more than 1000 kg (2200 lbs), and pygmy antelope have a maximum shoulder height of 300 mm (1 ft) and a maximum weight of 3 kg (6.6 lbs). Forest and bush species tend to have shorter limbs and more developed hindquarters and cryptic pelage that helps them blend into their surroundings. Open habitat species have long, forelimbs that increase stride length and occasionally bold color patterns or stripes. These adaptations help bovids evade potential predators through the various mechanisms of hiding (cryptic coloration), escaping (increased stride length), or confusion (striped pelage). (Alder, et al., 1995; Danell, et al., 2006; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
Most bovids are sexually dimorphic. Males always have horns, which are used in ritualized fighting during the mating season. The horns of males tend to be more complex in design and more robust than those of females, which tend to be straighter, thinner, and simpler in design. Horns are present in females in approximately 75% of genera over 40 kg in mass and are usually absent in those less than 25 kg. This could be the result of differing life history strategies or the physiological cost of growing horns. Larger species are more likely to defend themselves against potential predators, and smaller species tend to retreat when threatened. In addition to sexual dimorphism in morphological characteristics, males also have better developed scent-glands than females, which are reduced or absent in species from the subfamily Bovinae. (Alder, et al., 1995; Danell, et al., 2006; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
Most bovids are polygynous, and in some of these species males exhibit delayed maturation. For example, male blue gnus do not reach sexual maturity until 4 years of age, while females become reproductively active between 1.5 to 2.5 years of age. Sexual dimorphism is more prevalent in medium to large bovid species, particularly in members of the subfamily Reduncinae. In general, males of sexually dimorphic artiodactyls become sexually active later in life than females, which is probably due to male-male competition for mates. In some species, males may fight for and defend territory, which gives them breeding rights to females residing within each territory. It is not uncommon for territorial males to try and prevent resident females from leaving (e.g., impalas). Alternatively, males of other species fight for and defend small groups of females known as harems. Adult males that successfully defend their harem often breed with each member of the group, therefore increasing there reproductive fitness. Some bovid species also form leks, a small collection of males that compete for territory or mating rights. Successful males win occupation rights to high quality habitats and thus are able to mate with a greater number of high quality females. Once an individual gains territorial rights, individuals guard their territory and the females within. For example, waterbuck males defend areas of less than 0.5 km2, puka maintain areas of less than 0.1 km2, and lechwe and Uganda kob guard areas of about 15 to 30 m^2. Some species live in large groups consisting of both males and females in which males compete for mating opportunities (e.g., water buffalo). This behavior is somewhat common among members of the subfamily Hippotraginae. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982b; Kingdon, 1982a; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
In addition to polygynous mating systems, some species of bovid are monogamous, and male-male competition for mates is less common in these species. As a result, there is decreased selection for large males leading to little or no sexual dimorphism in monogamous bovids. For example, female dik-diks, are solitary and maintain large territories. Thus, male dik-diks are physically unable to defend more than one mate at a time resulting in monogamy. Unless there is a surplus of unmated males, male-male competition is unlikely leading to monomorphism between genders. In fact, females are slightly larger in some monogamous bovids (e.g., duikers and dwarf antelopes), which is probably the result of competition for high quality territories in which to raise their young. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
With the exception of hartebeests and topi, all bovids can detect estrus in females. Males sample the urine of potential mates, and high levels of sex hormones in the urine signal that a female is approaching estrus. Males then proceed with courtship behavior in an attempt to secure a mate. Typically, courtship begins with foreleg kicking, chest pressing and finally mounting. Females usually stand to be mounted only at peak estrus. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Bovids generally breed during fall or the rainy season. Estrus is generally short, usually lasting for less than a couple of days but is longer in non-territorial species. Bovids give birth to a single calf after a relatively long gestation compared to other mammalian families. For example, duiker gestation ranges from 120 to 150 days, while gestation in African buffalo ranges from 300 to 330 days. Calves are usually born synchronously each year during spring, when forage resources are abundant. Adult females reenter estrus within one to two months of parturition. Known as a tending bond, males of non-territorial species often form temporary, exclusive bonds with individual females. Gestation in bovids ranges from 6 months in smaller species to 8 or 9 months in larger species, and some smaller bovids can reproduce biannually. Usually a singe well-developed, precocial calf is born, but twins are not uncommon. Average birth weights vary depending on species. For example, dik-dik calves weigh between 0.5 and 0.8 kg with the males occupying the higher end of the spectrum. New-born eland antelope weigh between 23 and 31 kg. In many gregarious species, young are able to stand and run within one hour of birth. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Like all eutherian mammals, bovids are placental mammals and feed their young with milk. As a result, females are obligated to provide parental care. In polygynous bovids, females provide all parental care without aid from males. In monogamous bovids such as dwarf antelopes, males often defend their young. Weaning may occur as early as 2 months after birth (royal antelope) or as late as one year old as in musk ox. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
As calves, bovids can be classified either as hiders or followers. In hider species, mothers hide their young, during which time the mother is typically foraging nearby and on guard for potential predators. Hider mothers return to their calf several times a day for nursing. After nursing, the calf finds a new hiding place nearby. If the species is also gregarious, calves run ahead of their mother during herd movements and hide until their mother has passed. Calves then run ahead and hide again. Mothers with calves of similar age may form mother herds of 2-10 females which continues until the calf is one week to two months old, depending on the species. In follower species young join the herd either immediately or within two days of birth. Newborn wildebeest calves cling to their mother's side and the pair joins a nursery group within the larger herd. Female impalas leave the herd to give birth and rejoin in 1 to 2 days with their young. Upon returning, calves form small nursery groups, which are then guarded by herd females. Some species exhibit group or herd defense of young calves. Males and females alike encircle herd calves, thus protecting them from approaching predators. In many gregarious species, females remain in the herd while males often disperse after independence. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Bovid lifespans are highly variable. Some domesticated species have an average lifespan of 10 years with males living up to 28 years and females living up to 22 years. For example, domesticated goats can live up to 17 years but have an average lifespan of 12 years. Most wild bovids live between 10 and 15 years, with larger species tending to live longer. For instance, American bison can live for up to 25 years and gaur up to 30 years. In polygynous species, males often have a shorter lifespan than females. This is likely due to male-male competition and the solitary nature of sexually-dimorphic males resulting in increased vulnerability to predation. (Fowler and Miller, 2003; Toigo and Gaillard, 2003; Vaughn, et al., 2000; Walther, 1990)
Bovids are often classified as solitary, gregarious, territorial or non-territorial species. Solitary species are usually small bovids, like dik-dik, and klipspringer. Generally, these animals live in monogamous pairs and maintain a relatively small territory that excludes conspecifics. Many solitary species use a pheromone secreted from a pre-orbital gland to mark territorial boundaries while others use their own dung. Prior to mating, solitary males typically need to compete for and win a territory. Females then choose a mate based on the quality of the territory. In solitary species, offspring disperse during adolescence to seek out mates or establish a territory of their own. Typically, these bovids have cryptic or camouflaging pelage, which helps them avoid potential predators while hiding in dense cover. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Many bovids, including most antelopes, buffalo, bison, cattle, many goats and domestic bovids, are gregarious and form large herds. Generally, herds consist of females and their offspring and are led by a single, dominant male. Subordinate or juvenile males often gather in small bachelor groups consisting of 5 to 7 individuals. Female offspring remain with the herd after maturation, but males are forced to disperse upon the development of secondary sexual characteristics (e.g., bison mane). Dispersal has an increased risk of predation, which is why males will often form bachelor herds and have decreased survival rates compared to females. As a result, operational sex ratios of bovids are typically skewed towards females. Gregarious behavior in bovids is likely an antipredator defense. As the number of individuals in a group increase, the number of eyes scanning for potential predators increases and the per-capita time spent scanning for predators decreases. As a result, the per-capita time spent foraging increases. However, as group size increases, so to does intraspecific competition for food and mates. In gregarious bovids, dominant males can mate with any estrus female in their territory. Occasionally, satellite males follow herds and wait for the dominant male to die or become too old to defend their territory or mates. Some species, such as cape buffalo, follow a seniority system to determine male dominance. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Toigo and Gaillard, 2003; Vaughn, et al., 2000; Walther, 1990)
Bovids exhibit grooming behaviors that helps keep their coats and skin clean and parasite free. Some species have lower incisors that are specialized for combing through fur, which helps remove unwanted debris. Many species also nibble groom with their lips and other species, such as cattle, bushbuck, and many duikers, self-groom by licking their coats. In some long-horned bovid species, horn tips are used to scratch the back and rump. Most bovids shake their heads, wag their tails and stamp the ground in order to remove insect pests. Buffalo and wildebeest also wallow in mud to help fend off insects. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Bovids are notorious for fighting during mating season. Male’s use their horns and strength during competitive interactions, and kicking and neck swinging are not uncommon. Fighting is rarely fatal, as most blows are directed toward the horned portion of the opponent's head and not the body, reducing the likelihood of fatal injuries. During male-male competition opponents may lock or clash horns in a display of strength enacted to force opposing males into submission. Most fighting occurs between evenly sized individuals as undersized or outmatched opponents retreat almost immediately. Prior to physical confrontation, males may assess various aspects of one another's physical appearance. Based on this assessment, males determine whether to fight or flee. Despite the violent nature of male-male interactions during mating season, injuries are rare. On rare occasions victors have been known to chase down or attempt to gore defeated opponents. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Different fighting styles and techniques are used as displays of strength and are as diverse as the animals that employ them. Most bovids fight standing on all fours, yet hartebeests and the horse antelopes (Hippotraginae, Oryx and Addax) of East Africa fight on their knees. Many gazelle species box, which involves a series of low intensity nod-like head butts. In more intense combat, gazelle and oryx clash fight and fence, which consists of hard blows from short range where the animals jump back between head butts. Ibex and goats ram opponents by running at each other, rising on their hind legs, and clashing horns. Some species push fight, which involves unlocked horn-to-horn shoving. Some species use a side-to-side head butting technique where the animal forward presses its opponent in an attempt to knock their opponent down. If horns become entangled, animals may attempt to unlock horns by moving in a circular motion. The most intense battles of wildebeest and antelope involve thrust fighting, which is high energy jump thrusts and powerful head butting. In long horned species, horn pressing is used to force the opponent’s horns into its own neck. Members of the subfamily Hippotraginae are known to parallel fight, which consists of side-to-side fighting with locked horns and neck wrestling. Some bovids air fight where they go through the motions of several fighting techniques without ever touching the opponent in an attempt to intimidate their rivals. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Similar to many other artiodactyls, many bovid species migrate according to proximal cues, such as photoperiod. These proximal cues serve as indicators for various ultimate factors, such as changes in season, which can affect the abundance of pests, predators, and forage. Although the costs of migration can be great, benefits often include increased individual survival rates and increased reproductive fitness. One of the best-studied cases of bovid migration is that of Serengeti wildebeest, which travel an annual distance of more than 1700 km. Unfortunately, seasonal migrations of bovids are cued by photoperiod while plant-growing seasons are cued by temperature. If the growing season of species-specific resources is not precisely matched to the initiation of migration, changes in plant phenologies may detrimentally impact the long-term survival of migratory animals. For example, increasing mean spring temperatures in West Greenland appear to have resulted in a mismatch between caribou migratory cues and the onset of spring growing season for important forage plants. Evidence suggests that caribou migrations are not advancing at a comparable rate with forage plants, and as a result, calf production in West Greenland caribou has decreased by a factor of four. (Darling, 1937; Feldhamer, et al., 2007; Grzimek, 1990; Nowak, 1999; Post and Forchhammer, 2008; Scott, 1988; Vaughn, et al., 2000)
Members of the family Muskox frequently roar during male-male contests and hold a unique posture that maximizes the intensity of their roar. The ventrorostral ventricle, a vocal ligament that transforms into a large fat pad during maturation, increases the amplitude of the bellow by adding additional resonance space and by directing the sound through a unique pulsing structure. The posture of the male effects how his roar is delivered. Other bovids utilize their nasal passages to roar. Male saiga contract and extend their peculiar noses while forcing air through their nostrils to produce a roaring sound, which is used to deter rival males and attract females. Vocal communication between calves and their mothers help them recognize and locate each other when separated. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Frey, et al., 2006; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)communicate in a number of different ways. Some species are vocal, while others communicate via different body postures and displays. Although vocal communication is limited, during mating season mature males may bellow or roar to intimidate each other and to make their presence known to females.
In addition to communication that is used to increase reproductive success and offspring survival, bovids also vocalize in an attempt to ward of potential predators. Grunting and roaring, much like those used by competing males, are used to drive off predators and warn herd members. Domesticated bovids are known to vocalize in anticipation of food and native Korean cows vocalize before being fed. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990; Yeon, et al., 2006)
Unlike primates and many carnivorous mammals, bovids are fairly limited in their ability to convey information via facial expressions, thus they rely heavily on postural displays to communicate their intentions. When attempting to communicate dominance or aggression towards competitors or lower ranking individuals, most bovids make themselves look as large as possible. Slow rigid movement and occasionally posing in an erect posture with a level muzzle, is used to exhibit dominance over others. Common aggressive displays include mimic fighting, staring, or shaking their heads wildly to communicate they feel threatened and are ready to fight. Submissive communication includes a lowering of the head or raising the chin so horns rest along the top of the neck. When threatened, bovids often remain still. In some antelope, like impala, lesser kudu, and common eland, individuals may jump in place to signal a potential threat to conspecifics. (Feldhamer, et al., 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Although bovids are obligate herbivores, they occasionally supplement their diet with animal products, and feeding strategies are correlated with body size. In general, small bovids are solitary specialized feeders that forage in dense, closed habitat, whereas large bovids tend to be gregarious and feed in open grassland habitats. As generalist herbivores, large bovids consume high-fiber vegetation, which contains more cellulose and lignin than the diet of forest dwelling species. However, because all bovids are obligate herbivores they support microbial communities within their rumen (bacteria, protozoa, and fungi), which help break down cellulose and lignin and converts high fiber forage into an abundant energy source. (Feldhamer, et al., 2007; Krebs and Davies, 1997; Vaughn, et al., 2000; Feldhamer, et al., 2007; Krebs and Davies, 1997; Vaughn, et al., 2000; Buchholtz and Sambraus, 1990; Feldhamer, et al., 2007; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
In addition to the true stomach, or abomasum, all bovids have 3 additional chambers, or false stomachs, in which bacterial fermentation takes place. Bovids digest low-quality (i.e., low protein, high-fiber) food via four different pathways. First, gastric fermentation extracts lipids, proteins, and carbohydrates, which are then absorbed and distributed throughout the body via the intestines. Second, large undigested food particles form into a bolus, or ball of cud, which is regurgitated and re-chewed to help break down the cell wall of ingested plant material. Third, cellulose digestion via bacterial fermentation results in high nitrogen microbes that are occasionally flushed into the intestine, which are subsequently digested by their host. These high-nitrogen microbes serve as an important protein source for bovids. Finally, bovids can store large amounts of forage in their stomachs for later digestion. All bovids chew their cud, have four-chambered stomachs (1 true and 3 false stomachs) and support microorganisms that breakdown cellulose. (Grzimek, 1990; Prins, 1996; Van Soest, 1994)
Each bovid subfamily has a unique feeding strategy. For example, members of Antilopinae are arid land gleaners and feed primarily on unevenly dispersed food resources. Bovinae species rely on both scattered and abundant forage and are fresh grass bulk grazers. Members of Caprinae are more generalized and flexible feeders and can often be found foraging in low-productivity habitats. Hippotraginae species are arid adapted grazers that generally rely on an unstable food supplies. Bovids from Reduncinae are valley grazers and depend on an abundant unstable food supply. Unlike most other bovids, members of Cephalophinae are primarily frugivorous and are known to follow canopy dwelling primates to collect dropped fruit. (Buchholtz and Sambraus, 1990; Feldhamer, et al., 2007; Huffman, 2011; Kingdon, 1982a; Kingdon, 1982b; Krebs and Davies, 1997; ; Vaughn, et al., 2000; Walther, 1990)
Bovids are an important food source for a variety of natural predators, and in Eastern and Southern Africa bovids are the primary food source for many pradator species including lions and cheetahs. On the African continent nearly all bovids are vulnerable to predation by lions and African wild dogs, but young, old and sick individuals are particularly susceptible. Leopards, spotted hyenas, cheetahs, Nile crocodiles, and side-striped jackals are also major predators of smaller bovid species. In North America, bovids are vulnerable to predation by grey wolves, brown bears, and cougar. Packs of wolves and adult bears are typically the only predators capable of taking down the largest bovids in North America, like American bison. On the continent of Asia, grey wolves and tigers, are predators of bovids. Leopards, dholes and mugger crocodiles are also capable of taking bovids as prey. There are some cases of Komodo dragons consuming goats and even water buffalo. Many predators like wild dogs and large cats are notorious for taking domesticated livestock, including domestic goats, domestic sheep, and cattle. (Carbyn and Trotter, 1988; Feldhamer, et al., 2007; Grange and Duncan, 2006; Krebs and Davies, 1997; Rasmussen, 1999; Scheel, 1993; Vaughn, et al., 2000; Walther, 1990)
Bovids are formidable opponents and are capable of putting up an incredible fights against their predators. Strength in numbers, dangerous horns, powerful kicks, speed, and in some cases, sheer size are more than enough to deter most predation attempts. Muskox form tight knit circles of adults around their young, making an impenetrable wall against potential predators. Cape buffalo have been known to charge and kill lions. Many species of bovid are extremely fastest and use their speed to out maneuver predatory pursuers. Forest dwelling bovids, such as Bongo antelope have cryptic coats to help camouflage themselves in densely vegetated habitats. (Carbyn and Trotter, 1988; Feldhamer, et al., 2007; Grange and Duncan, 2006; Krebs and Davies, 1997; Rasmussen, 1999; Scheel, 1993; Vaughn, et al., 2000)
As obligate herbivores, bovids can dramatically affect the abundance and diversity of plant communities. Predation, or the threat of predation, has been shown to decrease overgrazing by bovids. Bovids are host to a diverse array of endo- and ectoparasites. Many species of parasitic flatworms (Cestoda and Trematoda) and roundworms spend at least part of their lifecycle in the tissues of bovid hosts. Bovids are also vulnerable to various forms of parasitic arthropods including ticks, lice, mites (Psoroptes and Sarcoptes), keds, fleas, mosquitoes, and flies. Bovids also host various forms of parasitic protozoa, including trypanosomatids, coccidians, piroplasmids, and numerous species of Giardia. In addition, various forms of bacterial and viral pathogens play an important role in bovid health and population dynamics. For example, Brucella abortus, the bacteria that causes brucellosis, affects many bovid species and rhinderpest, also known as cattle plague, is a highly contagious viral disease caused by paramyxovirus that is especially prevalent in bovids. Unfortunately, evidence suggests that recent climate change is altering host-parasite dynamics across the globe, increasing transmission rates between populations of conspecifics and hybridization rates between host specific parasite forms. (Dagg and Foster, 1976; Escalante and Ayala, 1995; Kutz, et al., 2005; Whitaker and Hamilton, 1998)
Many bovids have mutualistic relationships with other animals. Cattle egrets and cowbirds regularly live amongst many bovid species, taking advantage of insects and parasites that feed on bovids, or feeding on insects and small animals that are forced out of hiding by movement and grazing. In addition to pest removal, mutualist species can alert them to the presence of predators. Bovids also create loosely formed interspecific groups with other large herbivores such as zebras, giraffes, and ostriches, which increases the chances for predator detection. (Alder, et al., 1995; Feldhamer, et al., 2007; Krebs and Davies, 1997; Vaughn, et al., 2000; Walther, 1990)
Although bovids can serve as host to numerous species of pathogenic bacteria and protozoa, in conjunction with anaerobic fungi, these organisms are one of the major reasons that bovids are as abundant and diverse as they are today. Bacteria help break down cellulose and comprise between 60 and 90% of the microbial community present in the gastrointestinal (GI) tract of bovids. Ciliated protozoa, which makes up 10 to 40% of the microbe community within the rumen, help bacteria break down cellulose, while also feeding on starches, proteins and bacteria. The presence of anaerobic fungi in the rumen has only been known since the early 1970's. These fungi make up between 5 to 10% of the rumen's microbial abundance and are thought to help break down the cell wall of ingested plant material. Bacteria and protozoa that pass from the upper to the lower regions of the GI tract represent a significant portion of the dietary nitrogen required by their host. (Van Soest, 1994)
The domestication of artiodactyls for subsistence purposes lead to one of the most important cultural changes in human history, the transition from a purely hunter-gatherer society to a predominantly agricultural society. In the near east, around 10 thousand years ago (KYA), goat and sheep were domesticated purely for subsistence purposes, followed by the domestication of cows (7.5 KYA). Economically, cattle are the most important domesticated animal world wide. In 2001, the global population of domestic artiodactyls was greater than 4.1 billion, more than 31% of which consisted of cattle. In the United States, one of the worlds top 4 beef producers, beef production is the country's fourth largest industry, and in 2006, per capita beef consumption in the United States was nearly 66 pounds. (Bates, 2005; Colby, 1966; Dagg and Foster, 1976; Feldhamer, et al., 2007; Fowler and Miller, 2003; Grzimek, 1990)
In addition to meat production, bovids are used for their milk, fur, skin, bone and feces. Goats and cattle are the primary producers of commercial milk and dairy products, sheep wool is used in the mass production of clothing, and manure is commonly used as fertilizer. For thousands of years humans have used bovids for hard labor tasks such as hauling materials, plowing fields, and transportation. Domestic bovids have also been used to control invasive plant species and enhance plant biodiversity through their selective feeding behavior. (Bates, 2005; Colby, 1966; Dagg and Foster, 1976; Feldhamer, et al., 2007; Fowler and Miller, 2003; Grzimek, 1990)
Sport hunting of bovids generates millions of dollars annually. However, trophy hunting can alter the evolutionary dynamics of wild populations by imposing unnatural selective pressures for decreased ornamentation. Finally, bovids play an important role in the global ecotourism movement as various species are readily observable throughout much of their native habitat. Wildlife related tourism is especially popular in Eastern and Southern Africa and Central North America at various National Parks. (Bates, 2005; Colby, 1966; Dagg and Foster, 1976; Feldhamer, et al., 2007; Fowler and Miller, 2003; Grzimek, 1990)
Bovids, despite their important economic contributions to humans, can also have important detrimental effects. Zoonotic diseases transmitted by bovids to humans and domestic animals can have significant negative consequences, both physically and financially. For example, in less developed counties bovine tuberculosis can pose a significant economic threat for cattle farmers, and brucellosis, a bacterial disease that affects sheep, goats, cattle, elk, and deer, can be transmitted to humans by consuming undercooked contaminated meat and contaminated milk and dairy products. Bovine spongiform encephalopathy (BSE), more commonly known as Mad Cow Disease, is an infectious disease caused by an unknown agent, currently believed to be a modified protein. Cattle become infected when they are fed meat-and-bone meal that contains infected cattle by-products. Humans can contract BSE by consuming animal products from infected animals. ("BSE (Bovine Spongiform Encephalopathy, or Mad Cow Disease)", 2008; "Bovine Tuberculosis", 2008; "Brucellosis", 2007; Fowler and Miller, 2003; Krebs and Davies, 1997; Rhodes, 1997)
Bovids have been introduced world wide and in some locations have had severe detrimental impacts on the local environment. For example, goats were introduced by whalers to the Galapagos Island during the 18th century and have since caused extensive damage to the native ecosystem. In addition, introduced bovids compete with native animals for both food and habitat and can cause soil erosion due to overgrazing. Bovids, native and domestic, present a potential threat to various forms of agriculture by damaging and consuming crops. ("Charles Darwin Reseach Station Fact Sheet: Goats in Galapagos", 2006; Fowler and Miller, 2003; Krebs and Davies, 1997; Rhodes, 1997)
Currently, many bovid species enjoy sufficient numbers to ensure their survival for years to come. The ICUN red list of threatened species considers 67 of the 143 species listed as “least concern.” This is in part due to the protection of large tracts of land that help offset the detrimental effects of habitat loss. For instance, wildebeest and gazelles in the African Serengeti were fewer than 500,000 during the 1960’s, but had grown to more than a million by the 1990’s. Parks like Serengeti National Park provide ecotourism opportunities and serve as a significant source of income to local economies. As a result, ecotourism enhances the monetary value of wildlife in these countries. In some areas, however, bovids continue to be over exploited for meat and habitat loss due to overgrazing by domestic species, farming, and logging is a significant threat to the persistence of many species. Bovids with limited range and unique habitat requirements are even more at risk. As of 2009, four species of bovid have gone extinct in the wild: aurochs, Queen of Sheebas gazelle, Saudi gazelle, and bluebuck. Scimitar-horned oryx is extinct in the wild and now lives only in zoos. Eight others species are "critically endangered". Saola antelope and bighorn sheep are listed as "endangered". Another 21 species are listed as vulnerable and 16 species are considered "near threatened". CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, lists 71 species under appendix 1 and 1 species under appendix 2. (Alder, et al., 1995; CITES, 2010; Danell, et al., 2006; Feldhamer, et al., 2007; Fowler and Miller, 2003; Kingdon, 1982a; Kingdon, 1982b; Vaughn, et al., 2000; Walther, 1990)
Bovids are an important food sources for a number of different carnivores. As bovid populations decline, so too will those animals that depend on them. For example, the decline of cheetahs is often attributed habitat loss. However, cheetahs primarily prey upon small to medium sized bovids, specifically gazelle. According to the IUCN Red List of Threatened Species, 2 species of gazelle are extinct, while 10 more are listed as vulnerable, endangered or critically endangered. In north Africa, as preferred prey species have declined, more and more cheetahs are turning to livestock for prey. Consequently, these cheetahs are then killed as pests. As a result, one of the major directives for cheetah conservation is restoration of wild prey species, most of which are small to medium-sized bovids. (IUCN, 2010; Ray, et al., 2005)
Whitney Gomez (author), University of Michigan-Ann Arbor, Tamatha A. Patterson (author), University of Michigan-Ann Arbor, Jonathon Swinton (author), University of Michigan-Ann Arbor, John Berini (author, editor), Animal Diversity Web Staff, Phil Myers (editor), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
either directly causes, or indirectly transmits, a disease to a domestic animal
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
helpers provide assistance in raising young that are not their own
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
having more than one female as a mate at one time
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
specialized for leaping or bounding locomotion; jumps or hops.
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.
associates with others of its species; forms social groups.
digs and breaks up soil so air and water can get in
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
2008. "BSE (Bovine Spongiform Encephalopathy, or Mad Cow Disease)" (On-line). Centers for Disease Control and Prevention. Accessed March 11, 2009 at http://www.cdc.gov/ncidod/dvrd/bse/.
2008. "Bovine Tuberculosis" (On-line). Michigan Department of Natural Resources. Accessed February 16, 2009 at http://www.michigan.gov/dnr/0,1607,7-153-10319-99064--,00.html.
2007. "Brucellosis" (On-line). Centers for Disease Control and Prevention. Accessed March 11, 2009 at http://www.cdc.gov/NCIDOD/DBMD/DISEASEINFO/brucellosis_g.htm.
2006. "Charles Darwin Reseach Station Fact Sheet: Goats in Galapagos" (On-line). Charles Darwin Foundation. Accessed February 16, 2009 at http://www.darwinfoundation.org/files/species/pdf/goats-en.pdf.
2009. "National Cattlemen's Beef Association" (On-line). Accessed February 13, 2009 at http://beefusa.org/.
Alder, P., R. Estes, D. Schlitter, B. McBride. 1995. National Audubon Society Field Guide to African Wildlife. New York: Chanticleer Press.
Allard, M., M. Miyamoto, L. Jarecki, F. Kraus, M. Tennant. 1992. DNA systematics and evolution of the artiodactyl family Bovidae. Proceedings of the National Academy of Science, 89: 3972-3976.
Auffenberg, W. 1981. The Behavioral Ecology of the Komodo Monitor. Gainesville: University Press of Florida.
Bates, D. 2005. Human Adaptive Strategies: Ecology, Culture, and Politics (Third Edition). Boston, MA: Pearson, Allyn, and Bacon.
Buchholtz, C., H. Sambraus. 1990. Bovids: Cattle. Pp. 406-407 in S Parker, ed. Grzimek's Encyclopedia of Mammals, Vol. 5, 1 Edition. New York: McGraw-Hill Publishing Company.
CITES, 2010. "Convention on International Trade of Endangered Species of Wildlife Fauna and Flora" (On-line). CITES species database. Accessed April 12, 2011 at http://www.cites.org/eng/resources/species.html.
Carbyn, L., T. Trotter. 1988. Descriptions of Wolf Attacks on Bison Calves in Wood Buffalo National Park. Arctic, 41: 297-302.
Colby, C. 1966. Wild Deer. New York, NY: Duell, Sloan, and Pearce.
Dagg, A., J. Foster. 1976. The Giraffe: Its Biology, Behavior, and Ecology. New York, NY: Van Nostrand Reinhold and Company.
Danell, K., R. Bergstrom, P. Duncan, J. Pastor. 2006. Large Herbivore Ecology, Ecosystem Dynamics and Conservation. Cambridge: Cambridge University Press.
Darling, F. 1937. A Herd of Red Deer: A Study in Animal Behavior.. London: Oxford University Press.
Escalante, A., F. Ayala. 1995. Evolutionary origin of Plasmodium and other Apicomplexa based on rRNA. Proceedings from the National Academy of Science, 92: 5793-5797.
Estes, R. 1991. The behavior guide to African mammals: including hoofed mammals, carnivores, primates. Berkeley, CA: University of California Press.
Ezenwa, V., A. Jolles. 2008. Horns Honestly Advertise Parasite Infection in Male and Female African Buffalo. Animal Behavior, 75: 2073-2021.
Feldhamer, G., L. Drickamer, S. Vessey, J. Merritt, C. Krajewski. 2007. Mammalogy: Adaptation, Diversity, Ecology. Baltimore,MD: The Johns Hopkins University Press.
Fowler, M., R. Miller. 2003. Zoo and Wild Animal Medicine. St. Louis: Saunders.
Frey, R., A. Gebler, G. Fritsch. 2006. Arctic Roars: Laryngeal Anatomy and Vocalization of the Muskok (Ovibus moschatus Zimmermann, 1780 Bovidae). Journal of Zoology, 268: 433-438.
Frey, R., I. Volodin, E. Volodina. 2007. A Nose That Roars: Anatomical Specializations and Behavioral Features of Rutting Male Saiga. Journal of Anatomy, 211: 717-736.
Gentry, A. 2011. Bovidae. Pp. 363-465 in T Harrison, ed. Paleontology and Geology of Laetoli: Human Evolution in Context. Volume 2: Fossil Hominins and the Associated Fauna. New York, NY: Springer.
Gould, B. 2009. "Understanding Dairy Markets" (On-line). Accessed February 13, 2009 at http://future.aae.wisc.edu/.
Grange, S., P. Duncan. 2006. Bottom-up and Top-down Processes in African Ungulate Communities: resources and Predation Acting on the Relative Abundance of Zebras and Grazing Bovids. Ecography, 29: 899-907.
Grzimek, B. 1990. Artiodactyla. Pp. 1-639 in S Parker, ed. Grzimek’s Encyclopedia of Mammals, Vol. 5, 1st Edition. New York, NY: McGraw-Hill.
Huffman, B. 2011. "Ultimate Ungulate" (On-line). Accessed April 04, 2011 at http://www.ultimateungulate.com/index.html.
IUCN, 2010. "IUCN Red List of Threatened Species" (On-line). Mammals. Accessed April 12, 2011 at http://www.iucnredlist.org/initiatives/mammals.
Janis, C., K. Scott. 1987. The interrelationships of higher ruminant families with special emphasis on the members of the Cervoidea. American Museum Novitates, 2893: 1-85.
Kingdon, J. 1982. East African Mammals: Part C. Chicago: The University of Chicago Press.
Kingdon, J. 1982. East African Mammals: Part D. Chicago: The University of Chicago Press.
Krebs, J., N. Davies. 1997. Behavioural Ecology: An Evolutionary Approach. Australia: Blackwell Publishing.
Kutz, S., E. Hoberg, L. Polley, E. Jenkins. 2005. Global warming is changing the dynamics of Arctic host–parasite systems. Proceedings from the Royal Society B, 272/1581: 2571-2576.
Mallon, D. 2010. "Caprinae (Sheep, goats, and relatives)" (On-line). Grzimek's Animal Life. Accessed April 05, 2011 at http://animals.galegroup.com/web/grzimeks/animals/Caprinae?searchTerms=Caprinae.
Marty, J. 2005. Effects of Cattle Grazing on Diversity in Ephemeral Wetlands. Conservation Biology, 19: 1626-1632.
Nowak, R. 1999. Walker’s Mammals of the World. Baltimore, MD: The Johns Hopkins University Press.
Post, E., M. Forchhammer. 2008. Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch.. Philosophical Transactions of the Royal Society B, 363: 2367-2373.
Prins, H. 1996. Ecology and Behaviour of the African Buffalo. Great Britain: Chapman and Hall.
Rasmussen, G. 1999. Livestock Predation by the Painted Hunting Dog, Lycaon pictus, in a Cattle Ranching Region of Zimbabwe: a Case Study. Biological Conservation, 88: 133-139.
Ray, J., K. Redford, R. Steneck, J. Berger. 2005. Large Carnivores and the Conservation of Biodiversity. Washington D. C.: Island Press.
Rhodes, R. 1997. Deadly Feasts: The "Prion" Controversy and the Public's Health. New York, NY: Simon & Schuster Paperbacks.
Scheel, D. 1993. Profitability, Encounter Rates and Prey Choice of African Lions. Behavioral Ecology, 4: 90-97.
Scott, J. 1988. The Great Migration.. London: Elm Tree Books.
Shackleton, D., A. Harested. 2010. "Bovidae (Antelopes, cattle, bison, buffaloes, goats, and sheep)" (On-line). Grzimek's Animal Life. Accessed April 04, 2011 at http://animals.galegroup.com.
Shackleton, D., A. Harested. 2010. "Bovinae (Kudus, Buffaloes, and Bison)" (On-line). Grzimek's Animal Life. Accessed April 04, 2011 at http://animals.galegroup.com.
Toigo, C., J. Gaillard. 2003. Causes of sex-biased adult survival in ungulates: sexual-size dimorphism, mating tactic or environment harshness?. Oikos, 101/2: 376-384.
Van Soest, P. 1994. Nutritional Ecology of the Ruminant, Second Edition. Ithaca, NY: Cornell University Press.
Vaughn, T., J. Ryan, N. Czaplewski. 2000. Mammalogy. Philadelphia, PA: Saunders College Publishing.
Walther, F. 1990. Bovids. Pp. 288-324, 338-339, 354-355, 432-433, 444-445, 460-461, 482-483 in S Parker, ed. Grzimek's Encyclopedia of Mammals, Vol. 5, 1 Edition. New York: McGraw-Hill Publishing Company.
Whitaker, J., W. Hamilton. 1998. Mammals of the Eastern United States. Ithaca, NY: Cornell University Press.
Yeon, S., J. Jeon, K. Houpt, H. Chang, H. Lee. 2006. Acoustic Features of Vocalizations of Korean Native Cows (Bos taurus coreanca) in Two Different Conditions. Applied Animal Behavior Science, 101: 1-9.