The nyala (Nyala angasii or Tragelaphus angasii) is a spiral-horned antelope found in southern Africa. It is the antelope with highest sexual dimorphism. This means the male and female look very different. Only the male has horns, and he is also markedly bigger than the female. An adult male has a dark brown to slate gray coat, with faint vertical stripes on the sides. He has a line of white hair down the back, as well as yellow legs. The female is reddish-brown, with clear white vertical stripes on the sides. Females do also have a line of hair down their back, but it is less conspicuous. Both sexes have the look of females when young, but the male changes coat gradually as he matures. Adult animals with a female coat and male horns have been recorded, but are very rare. It is also not known if such individuals are females with horns, or males who never changed coat. A male nyala can reach a height of 110 cm (43 in) up to his shoulders, whereas a female can reach 90 cm (3 ft). General weight is 98-125 kg (216-276 lb) for males and 55-68 kg (121-150 lb) for females.
Nyalas are mixed feeders and will feed on grass, leaves, twigs, flowers and fruits. They tend to avoid open areas and will spend most of the day in thick bush. They are commonly seen at water holes as they will drink daily when water is available, although they can survive in drier environments. They are often known to be wary and shy animals, but in areas were the species does well and is numerous, they are quite common to see.
Nyalas live in social groups of 2-30 individuals. Mainly females and young live in large groups. Adult males often live solitary lives, but do form loose groups from time to time with both young and adult individuals. It is not uncommon for groups of males to join female groups over periods. Male nyalas often fight for dominance with their horns, like other species, but the nyala also has a second strategy to determine dominance between males. Male nyalas will often “tip-toe” next to a rival while showing off his size by erecting his back hair and tail. If done by a dominant male, the lesser rival will often leave without objection. This strategy is also deployed by the related bushbuck.
There is no breeding season for nyalas and they can mate throughout the year. Females normally get a single calf after a gestation period of seven months. Mating often peak in spring and autumn under normal circumstances. In Tembe Elephant Park, a reserve with an overpopulation of nyala, they are believed to breed a lot more under carnivore pressure. With a growing population of lions and leopards in the park it has caused somewhat of a population boom in nyalas, as they seem to counteract the frequency they are being preyed upon by breeding more. As they are able to breed throughout the year, this has caused the nyala to reach an astounding number in a short amount of time.
The nyala is a very common species throughout its range and 80% of the population is found within protected areas. A recent estimate has found that there are 30,000 nyalas in South Africa alone, with 25,000 of them in the province of KwaZulu-Natal, on the South African east coast. 1,000 animals are found in Swaziland, 3,000 in Mozambique, 1,500 in Malawi and over 1,000 in Zimbabwe. A small population of 250 are found in Namibia. Nyala numbers are stable or increasing and it is listed as least concern on the IUCN Red List. The males are popular targets for trophy hunters and this is one of the reasons for the popularity of introducing nyalas to reserves and ranches in South Africa.