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); 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); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning