The lowland nyala or simply nyala (Tragelaphus angasii) is a spiral-horned antelope native to southern Africa. It is a species of the family Bovidae and genus Tragelaphus, previously placed in genus Nyala. It was first described in 1849 by George French Angas. The body length is 135–195 cm (53–77 in), and it weighs 55–140 kg (121–309 lb). The coat is maroon or rufous brown in females and juveniles but grows a dark brown or slate grey, often tinged with blue, in adult males. Females and young males have ten or more white stripes on their sides. Only males have horns, 60–83 cm (24–33 in) long and yellow-tipped. It exhibits the highest sexual dimorphism among the spiral-horned antelopes. It is not to be confused with the endangered mountain nyala living in the Bale region of Ethiopia).
The nyala is mainly active in the early morning and the late afternoon. It generally browses during the day if temperatures are 20–30 °C (68–86 °F) and during the night in the rainy season. As a herbivore, the nyala feeds upon foliage, fruits, and grasses, and requires sufficient fresh water. A shy animal, it prefers water holes rather than open spaces. The nyala does not show signs of territoriality, and individuals’ areas can overlap. They are very cautious creatures. They live in single-sex or mixed family groups of up to 10 individuals, but old males live alone. They inhabit thickets within dense and dry savanna woodlands. The main predators of the nyala are lion, leopard, and African wild dog, while baboons and raptorial birds prey on juveniles. Mating peaks during spring and autumn. Males and females are sexually mature at 18 and 11–12 months of age respectively, though they are socially immature until five years old. After a gestational period of seven months, a single calf is born.
The nyala’s range includes Malawi, Mozambique, South Africa, Eswatini, Zambia, and Zimbabwe. It has been introduced to Botswana and Namibia and reintroduced to Eswatini, where it had been extinct since the 1950s. Its population is stable and it has been listed as of Least Concern by the International Union for Conservation of Nature (IUCN). The principal threats to the species are poaching and habitat loss resulting from human settlement. The males are highly prized as game animals in Africa.
Taxonomy and naming
The nyala was first described by George French Angas, an English naturalist, in 1849. The scientific name of nyala is Tragelaphus angasii. The name angasii is attributed to Angas, who said that John Edward Gray had named this species after Angas’ father, George Fife Angas of South Australia. But, according to Article 50.1.1 of the International Code of Zoological Nomenclature and International Commission on Zoological Nomenclature, this is insufficient to state Gray as the author. The name “nyala” is the Tsonga name for this antelope, which is likely the source of the English, along with Zulu “inyala”. Its first known use was in 1899. The word has a Bantu origin, similar to the Venda word dzì-nyálà (nyala buck).
The nyala is the second taxon to branch off from the tragelaphine family tree just after the lesser kudu. As the nyala line has remained separate for a considerable amount of time (over 5 million years), some authorities have placed it in its own monotypic genus Nyala. Nyala was proposed in 1912 by American zoologist Edmund Heller, who also proposed Ammelaphus for the lesser kudu, but it was not widely recognized. It was re-erected as a valid genus in 2011 under the classification of Peter Grubb and Colin Groves but has not been embraced by taxonomic authorities such as the Mammal Diversity Database.
In 2005, Sandi Willows-Munro (of the University of KwaZulu-Natal) and colleagues carried out a mitochondrial DNA analysis of the nine Tragelaphus species. Mitochondrial DNA and nuclear DNA data were compared. The results showed the tribe Tragelaphini to be monophyletic, with the lesser kudu (T. imberbis) basal in the phylogeny, followed by the nyala. On the basis of mitochondrial data, studies have estimated that the lesser kudu separated from its sister clade around 13.7 million years ago. However, nuclear DNA data shows lesser kudu and nyala forming a clade, which collectively separated from the sister clade 13.8 million years ago.
Genetics and evolution
The nyala has 55 male chromosomes and 56 female chromosomes. The Y chromosome has been translocated onto the 14th chromosome, as in other tragelaphids, but no inversion of the Y chromosome occurs. Cranial studies have shown that the mountain nyala and nyala, though sharing a common name, are actually distant relatives.
Fossil evidence suggests that the nyala has been a separate species since the end of the Miocene (5.8 million years ago). Genetic evidence suggests that the proto-nyala had some early hybridization with the proto-lesser kudu, but the two have remained separate long after this crossing.
The nyala is a spiral-horned and middle-sized antelope, between a bushbuck and a kudu. It is considered the most sexually dimorphic antelope. The nyala is typically between 135–195 cm (53–77 in) in head-and-body length. The male stands up to 110 cm (43 in), and the female is up to 90 cm (3.0 ft) tall. Males weigh 98–125 kg (216–276 lb), while females weigh 55–68 kg (121–150 lb). The life expectancy of the nyala is about 19 years.
The coat is rusty or rufous brown in females and juveniles. It grows a dark brown or slate grey in adult males, often with a bluish tinge. Females and young males have ten or more white vertical stripes on their sides. Other markings are visible on the face, throat, flanks, and thighs. Stripes are very reduced or absent in older males. Both males and females have a white chevron between their eyes, and a 40–55 cm (16–22 in) long bushy tail white underside. Both sexes have a dorsal crest of hair running right from the back of the head to the end of the tail. Males have another line of hair along the midline of their chest and belly.
Only the males have horns. Horns are 60–83 cm (24–33 in) long and yellow-tipped. There are one or two twists. The spoor is similar to that of the bushbuck but larger. It is 5–6 cm (2.0–2.4 in) long. The feces resemble round to spherical pellets. The nyala has hairy glands on its feet, which leave their scent wherever it walks.
The condition of the nyala often varies between the sexes. According to a study, this can be attributed to the differences in their body sizes. It was noted that during nutritional stress, old adults died in more numbers, of which most were males. During an attempt of blood sampling in the nyala, it was found that Vitamin E levels varied during stress.
Ecology and behavior
The nyala is active mainly in the early morning and late afternoon. It browses during the day if temperatures are 20–30 °C (68–86 °F) and during the night in the rainy season. These antelopes rest in thick bushes during the hot hours of the day. The nyala is very shy and cautious in nature and often remains hidden rather than coming out in the open. Most sightings of the nyala in the wild are at water holes. But in protected areas, they become less shy and often come out in view of tourists.
Nyala groups are according to sex or mixed. Herds usually browse and drink water together. Each group consists of two to ten individuals. A study in Zinave National Park in Mozambique showed that 67% of the observations were of groups of one to three nyalas, and the rest of the herds consisted of up to 30 nyalas. Herds often broke up and re-formed. Generally, adult males remain alone. Females often remain near their mothers when they have their offspring, so the relationships in female herds may be closer than those of males.
Alert and wary in nature, the nyala uses a sharp, high, dog-like bark to warn others in a group of danger. This feature is mainly used by females. They also react to the alarm calls of impala, baboon, and kudu. The Impala has been found to react to the calls of the nyala as well. The main predators of nyala are lion, leopard, cheetah, spotted hyena, and African wild dog, while baboons and raptorial birds are predators of juveniles.
As a herbivore, the nyala’s diet consists of foliage, fruits, flowers, and twigs. During the rainy season, they feed upon fresh grass. They need a regular intake of water and thus choose places with a water source nearby. However, they are adapted to live in areas with only a seasonal availability of water. A study in Zululand showed that the nyala fed mainly in the early morning and the late afternoon. They feed at night during the rainy season.
A study in Mkhuze Game Reserve and Ndumu Game Reserve in Natal focused on the dietary habits of the impala and the nyala and showed that the number of dicotyledons in their diets varied seasonally. In the dry season, the nyala’s dicotyledon diet content was 83.2% and the impala’s 52%. During this season, the diet grew richer in fiber and dietary proteins were less. The reverse occurred in the rainy season. As the rainy season arrived, both species took to a diet of main monocotyledons, and the impala consumed more of them. The diet contained more proteins than fiber.
Another study was done to find whether the sexual dimorphism in the nyala influenced its foraging habits. Vegetation surveys were conducted at the end of each feeding bout. It was found that females spent equal periods of time foraging in all three habitats, but males preferred sand forests more. More differences were noted, as males ate woody species at a greater average height whereas females fed from the low herbaceous layer. It was concluded that the differences resulted from varying nutritional and energetic demands according to their diverse body sizes and different reproductive strategies.
The nyala breeds throughout the year, but mating peaks in spring and autumn. The reason for this is still unknown but attributed to the photoperiod and the feeding habits of the animal. Females reach sexual maturity at 11 to 12 months of age and males at 18 months (though they are socially immature until five years old), though they begin to show active spermatogenesis at 14 months.
Before ovulation, the Graafian follicles reach a length of at least 6.7 cm (2.6 in). A female’s estrous cycle is about 19 days long. Males will attempt to mate with the female for two days of the cycle, but she allows it for only six hours per cycle. When the male enters a female’s herd during mating, he makes a display by raising his white dorsal crest, lowering his horns, and moving stiffly. As in many other animals, the males fight over dominance during mating.
The kidney fat indices (KFIs) of impalas and nyalas have been studied to understand the influence of social class and reproduction on them. To determine the KFI, the kidney is removed and weighed with the fat and once again excluding the fat. The resultant difference is the amount of fat in the kidney. The more fat, the healthier the animal. In a rut, male nyalas had lower KFIs, which did not vary much with the season. Pregnant females of both nyala and impala had higher KFIs than non-pregnant ones.
There is a significant increase in corpus luteum in the last third of gestation. Gestation is of seven months. A single calf is born, weighing 5 kg (11 lb). Birth takes place generally away from the sight of predators, in places such as a thicket. The calf remains hidden for up to 18 days, and the mother nurses it at regular intervals. The calf remains with its mother until the birth of the next calf, during which males in rut drive it away from the mother.
Habitat and distribution
The nyala inhabits dense lowland woodlands and thickets, mainly in southern Malawi, Mozambique, Zimbabwe, and eastern South Africa. It chooses places with good quality grasslands as well as the provision of fresh water. It also inhabits a lush green river country. The nyala’s natural range stretches across southeast Africa from the Lower Shire Valley in Malawi through Mozambique and Zimbabwe to eastern South Africa and Eswatini.
The geographic distribution of the nyala may be based on genetic variation. According to a study of nyala in South Africa, Mozambique, Malawi, and Zimbabwe, there was a marked difference in the gene frequencies at three microsatellite loci. Mitochondrial DNA analysis revealed the presence of a unique haplotype in individuals from each location. Thus, the geographic variation in the nyala may be due to a distribution pattern based on habitat specificity.
Today nyala are found in South African protected areas in the Ndumo Game Reserve, uMkuze Game Reserve, and Hluhluwe-Umfolozi Game Reserve, all in KwaZulu-Natal, as well as in Kruger National Park. As of 1999, 10–15% of nyala occurred on private land. Efforts are being made to retain the populations of nyala in Gorongosa National Park and Banhine National Park in Mozambique. Nyala also thrives in Lengwe National Park in Malawi.
Nyala has never been observed showing territoriality. Territories of either sex overlap extensively. The home ranges of males are approximately equal to that of females, about 10 km2 in area.