Bovidaeantelopes, cattle, gazelles, goats, sheep, and relatives

Diversity

Bovids are the largest of 10 extant families within Artiodactyla, consisting of more than 140 extant and 300 extinct species. Designation of subfamilies within Bovidae has been controversial and many experts disagree about whether Bovidae 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: 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)

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)

Geographic Range

Although the greatest diversity of Bovidae occurs in Africa, bovids are also found throughout parts of Europe, Asia and North America. A number of bovid species, particularly those domesticated for subsistence, have been globally introduced, including Australia and South America. (Danell, et al., 2006; Feldhamer, et al., 2007; Vaughn, et al., 2000; Walther, 1990)

Habitat

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)

Physical Description

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)

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • male larger
  • sexes shaped differently
  • ornamentation

Reproduction

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)

  • Parental Investment
  • precocial
  • male parental care
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • protecting
      • male
      • female
  • post-independence association with parents
  • extended period of juvenile learning

Lifespan/Longevity

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)

Behavior

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 kn