page_title: Hirola
section_title: Social structure and reproduction
hierarchical_section_title: Hirola / Social structure and reproduction
caption_attribution_description: English: Nursery herd in Tsavo East National Park, 2011. (Copyright James Probert)
context_page_description: The hirola, Hunter's hartebeest or Hunter's antelope, is a critically endangered antelope species found on the border between Kenya and Somalia. They were discovered by Kenyans living in the area in 1888. It is the only member of the genus Beatragus. The global hirola population is estimated at 300–500 animals, there are no hirola in captivity and the wild population continues to decline. According to the International Union for Conservation of Nature Red List "The loss of the Hirola would be the first extinction of a mammalian genus on mainland Africa in modern human history."
context_section_description: Female hirola give birth alone and may remain separate from the herd for up to two months, making them vulnerable to predation.  Eventually the female will rejoin a nursery herd consisting of females and their young.  Nursery herds number from 5 to 40 although the mean herd size is 7-9. They are usually accompanied by an adult male.
  Young hirola leave the nursery herd at around nine months of age and form various temporary associations.  They may gather together in mixed or single sex herds of up to three individuals; sub-adult or subordinate adult males may form bachelor herds of 2-38 individuals; female sub-adults may join an adult male and; if no other hirola are present, young hirola may attach themselves to a herd of Grant's gazelles or simply spend most of their time alone.
  Adult males attempt to secure a territory on good pasture.  These territories are up to 7 square kilometres (2.7 sq mi) and are marked with dung, secretions from the sub-orbital glands and by stamping grounds where males scrape the soil with their hooves and slash the vegetation with their horns.  It has been suggested that at low population densities adult males abandon territory defence and will instead follow a nursery herd.  Nursery herds do not defend a territory but do have home ranges which overlap the territories of several adult males.  The size of a nursery herd's home range varies from 26 to 164.7 square kilometres (10.0 to 63.6 sq mi) with a mean size of 81.5 square kilometres (31.5 sq mi).
  Nursery herds are relatively stable but bachelor herds are very unstable with a fission fusion dynamic.  In the 1970s hirola were observed forming aggregations of up to 300 individuals to take advantage of scarce, but spatially clumped, resources during the dry season (Bunderson, 1985).
  Information is lacking on male territoriality and how it relates to mating success, how and when hirola join a herd and how new herds are established (Butynski, 2000).
  Hirola are seasonal breeders with young being born from September to November.  Data on age of sexual maturity and gestation period are not available for wild hirola however in captivity gestation was around 7.5 months (227–242 days) with one female mating at 1.4 years old and giving birth at 1.9 years.  Another pair of hirola mated when they were 1.7 years of age.  In captivity one of the main causes of mortality is wounds caused by intra-hirola aggression, including aggression between females.
caption: Nursery herd, Tsavo East National Park, 2011. (Copyright James Probert)
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