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.
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.
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.
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.
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.
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.
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.
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..
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.
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.
- Biogeographic Regions
- nearctic
- palearctic
- oriental
- ethiopian
- neotropical
- australian
- Other Geographic Terms
- holarctic
- cosmopolitan
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.
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.
- Habitat Regions
- temperate
- tropical
- polar
- terrestrial
- Terrestrial Biomes
- tundra
- taiga
- desert or dune
- savanna or grassland
- chaparral
- forest
- rainforest
- scrub forest
- mountains
- Other Habitat Features
- urban
- suburban
- agricultural
- riparian
Systematic and Taxonomic History
Evidence suggests that
bovids
evolved from
tragulid
ancestry in Eurasia. Eotragus, the earliest known bovid, appeared during the
Oligocene
in Asia, and molecular evidence suggests that rapid diversification early in their
evolutionary history resulted in a greater diversity of genera during the
Miocene
than exists today (78 versus 49). Currently 26 of 50 genera are endemic to sub-Saharan
Africa, representing the most diverse bovid assemblage of any continent. Toward the
end of
Pleistocene
, the ice-age forced most Eurasian bovids southward. However, a few cold-adapted species
traveled to North America via the Beringian Land Bridge.
Bovid synapomorphies include
horns
with a bony core covered by a keratinous sheath and large
foramen ovales
.
In addition, bovids exhibit dental and limb morphologies that reflect an evolutionary
specialization for open grassland habitats. For example,
bovid teeth
are
hypsodont
with upper
canines
that are either reduced or absent, which is likely the result of their grazing lifestyle.
The lateral digits of bovids are either severely reduced or completely absent making
them
paraxonic
and the third and fourth metapodials in their fore and hind feet are fused to form
a single bone, the
cannon bone
, which is considerably elongated. The ulna and fibula are greatly reduced in size.
The ulna is reduced distal to the body and fused with the radius, while all that remains
of the distal fibula is a knob on the tibia. Limb adaptations have allowed bovids
to become adept at escaping predators via fast and efficient movement in a variety
of habitat types. Finally,
bovid skulls
lack sagittal crests, the rear of the orbit is defined by a postorbital bar, and
the lacrimal canals have a single opening, which lies within the orbit.
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.
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.
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
.
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
).
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
.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- 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
.
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.
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.
- Mating System
- monogamous
- polygynous
- polygynandrous (promiscuous)
- cooperative breeder
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
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
.
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.
- Parental Investment
- precocial
- male parental care
- female parental care
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- male
- female
-
provisioning
-
pre-independence
-
protecting
- male
- female
-
protecting
- 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.
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.
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.
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.
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.
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.
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.
- Key Behaviors
- cursorial
- terricolous
- saltatorial
- diurnal
- crepuscular
- motile
- migratory
- sedentary
- solitary
- territorial
- social
- colonial
- dominance hierarchies
Communication and Perception
Members of the family
Bovidae
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.
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.
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.
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.
- Other Communication Modes
- scent marks
Food Habits
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.
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.
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.
- Foraging Behavior
- stores or caches food
Predation
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
.
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.
- Anti-predator Adaptations
- cryptic
Ecosystem Roles
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.
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.
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.
- Ecosystem Impact
- disperses seeds
- soil aeration
- zebra, Equus
- giraffe, Giraffa camelopardalis
- ostrich, Struthio camelus
- cattle egret, Bubulcus ibis
- cowbird, Molothrus
- rumen bacteria, Selenomonads
- rumen bacteria, Oscillospira
- rumen protozoa, Entodinium
- rumen protozoa, Dasytricha
- rumen protozoa, Diplodinia
- rumen protozoa, Isotricha
- rumen protozoa, Epidinia
- rumen fungi, Neocallimastix
- rumen fungi, Caecomyces
- rumen fungi, Pyromyces
- rumen fungi, Orpinomyces
- nematodes, Nematoda
- tapeworms, Cestoda
- flukes, Trematoda
- ticks, Ixodoidea
- lice , Phthiraptera
- flies, Diptera
- mites, Psoroptes and Sarcoptes
- keds, Hippoboscidae
- fleas, Siphonaptera
- mosquitoes, Culicidae
- parasitic protozoa, Trypanosomatida
- parasitic protozoa, Coccidia
- parasitic protozoa, Piroplasmida
- parasitic protozoa, Giardia
Economic Importance for Humans: Positive
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.
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.
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.
- Positive Impacts
- food
- body parts are source of valuable material
- ecotourism
- research and education
- produces fertilizer
Economic Importance for Humans: Negative
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.
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.
- Negative Impacts
-
injures humans
- carries human disease
- crop pest
- causes or carries domestic animal disease
Conservation Status
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.
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.
Additional Links
Contributors
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.
- Nearctic
-
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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Palearctic
-
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Australian
-
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- introduced
-
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
- holarctic
-
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.
- cosmopolitan
-
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.
- temperate
-
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).
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- polar
-
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.
- terrestrial
-
Living on the ground.
- tundra
-
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.
- taiga
-
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.
- desert or dunes
-
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.
- tropical savanna and grassland
-
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.
- savanna
-
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.
- temperate grassland
-
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.
- chaparral
-
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.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- rainforest
-
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.
- scrub forest
-
scrub forests develop in areas that experience dry seasons.
- mountains
-
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- urban
-
living in cities and large towns, landscapes dominated by human structures and activity.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- endothermic
-
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.
- bilateral symmetry
-
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.
- sexual ornamentation
-
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.
- monogamous
-
Having one mate at a time.
- polygynous
-
having more than one female as a mate at one time
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- cooperative breeder
-
helpers provide assistance in raising young that are not their own
- iteroparous
-
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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- young precocial
-
young are relatively well-developed when born
- male parental care
-
parental care is carried out by males
- female parental care
-
parental care is carried out by females
- saltatorial
-
specialized for leaping or bounding locomotion; jumps or hops.
- diurnal
-
- active during the day, 2. lasting for one day.
- crepuscular
-
active at dawn and dusk
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- sedentary
-
remains in the same area
- solitary
-
lives alone
- territorial
-
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
- social
-
associates with others of its species; forms social groups.
- colonial
-
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.
- dominance hierarchies
-
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- scent marks
-
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- stores or caches food
-
places a food item in a special place to be eaten later. Also called "hoarding"
- cryptic
-
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.
- soil aeration
-
digs and breaks up soil so air and water can get in
- food
-
A substance that provides both nutrients and energy to a living thing.
- ecotourism
-
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.
- causes or carries domestic animal disease
-
either directly causes, or indirectly transmits, a disease to a domestic animal
- herbivore
-
An animal that eats mainly plants or parts of plants.
- folivore
-
an animal that mainly eats leaves.
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