Nyala

Appearance

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 in head-and-body length. The male stands up to 110 cm, the female is up to 90 cm tall. Males weigh 98–125 kg, while females weigh 55–68 kg. Life expectancy of the nyala is about 19 years.

The coat is rusty or rufous brown in females and juveniles. But 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 less or absent in males. Both males and females have a white chevron between their eyes, and a 40–55 cm 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 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 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.

Naming

The nyala was first described by George French Angas, an English naturalist, in 1849. The scientific name of nyala is "Nyala angasii" or "Tragelaphus angasii". The name "angasii" is attributed to Angas, who said "Mr. Gray has named this species after my father, George Fife Angas, Esq. 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 Swahili name for this antelope, which itself comes from the Zulu "inyala". Its first known use was in 1899. The word has a Bantu origin, similar to the Venda word "dzì-nyálà".

The nyala is the second taxon to branch off of the spiral-horned antelope family tree just after the lesser kudu. As the nyala line has remained separate for a considerable amount of time, it has now been placed in its own monotypic genus "Nyala". "Nyala", like "Ammelaphus", was proposed by Edmund Heller, an American zoologist, in 1912 but not widely recognized, and was only re-established as a valid genus in 2011 by Peter Grubb and Colin Groves. But it is still considered as a species of "Tragelaphus".

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 provision of fresh water. They also inhabit 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 Swaziland.

The geographic distribution of the nyala may be based on the genetic variation. According to a study of the nyala in South Africa, Mozambique, Malawi and Zimbabwe, a great difference was marked among the gene frequencies at three microsatellite loci. Mitochondrial DNA analysis revealed the presence of a unique haplotype in individuals from each location. The conclusions were that the geographic variation in the nyala may be due to a distribution pattern based on the habitat specificity.

Today the nyala are found in South African protected areas in the KwaZulu-Natal Game Reserves of Ndumo Game Reserve, uMkuze Game Reserve and Hluhluwe-Umfolozi Game Reserve, and in Kruger National Park. According to statistics of 1999, 10-15% of the nyala occur on private land. Currently efforts are being made to retain the populations of nyala in Gorongosa National Park and Banhine National Park in Mozambique.

The nyala have never been observed showing signs of territoriality. Territories overlap extensively, let it be of any sex. The home ranges of males are approximately equal to that of females, about 10 km2. in area.

Status

The major threats to the population of the nyala are hunting, habitat loss, agriculture and cattle grazing. This species is currently of Least Concern, and the population is considered stable by both the IUCN and CITES. As of 1999, the total population of the nyala was around 32,000 individuals. More recent estimates show that South Africa has at least 30,000 nyalas, with 25,000 in KwaZulu-Natal. There are now more than 1,000 on protected areas and ranches in Swaziland. In Mozambique there are not more than 3,000, in Zimbabwe there are over 1,000 while numbers in Malawi have fallen from 3,000 to about 1,500. Namibia has the least population, about 250.

Today over 80% of the total population is protected in national parks and sanctuaries, mostly in South African protected areas. These are the Ndumo Game Reserve, uMkuze Game Reserve and Hluhluwe-Umfolozi Game Reserve and Kruger National Park. 10 to 15% occur on private land. They mostly occur in South Africa due to the high demand for adult males as game trophies.

Behavior

The nyala is active mainly in the early morning and late afternoon. It browses during the day if temperatures are 20–30 °C and during the night in 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 like remaining hidden rather than coming out in the open. Most sightings of the nyala in the wild are at water holes. But now-a-days they are becoming less shy and often come out in the sight 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 at 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. It was also seen that herds often broke up and formed again. Generally adult males remain alone. Females often remain near their mothers when they have their offspring, so the relationships in female herds may be considered relatively closer than that of males.

Alert and wary in nature, the nyala use a sharp, high, dog-like bark to warn others in a group about 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 too. The main predators of nyala are lion, leopard and Cape hunting dog, while baboons and raptorial birds are the predators of juveniles.

Habitat

The nyala is active mainly in the early morning and late afternoon. It browses during the day if temperatures are 20–30 °C and during the night in 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 like remaining hidden rather than coming out in the open. Most sightings of the nyala in the wild are at water holes. But now-a-days they are becoming less shy and often come out in the sight 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 at 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. It was also seen that herds often broke up and formed again. Generally adult males remain alone. Females often remain near their mothers when they have their offspring, so the relationships in female herds may be considered relatively closer than that of males.

Alert and wary in nature, the nyala use a sharp, high, dog-like bark to warn others in a group about 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 too. The main predators of nyala are lion, leopard and Cape hunting dog, while baboons and raptorial birds are the predators of juveniles.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 provision of fresh water. They also inhabit 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 Swaziland.

The geographic distribution of the nyala may be based on the genetic variation. According to a study of the nyala in South Africa, Mozambique, Malawi and Zimbabwe, a great difference was marked among the gene frequencies at three microsatellite loci. Mitochondrial DNA analysis revealed the presence of a unique haplotype in individuals from each location. The conclusions were that the geographic variation in the nyala may be due to a distribution pattern based on the habitat specificity.

Today the nyala are found in South African protected areas in the KwaZulu-Natal Game Reserves of Ndumo Game Reserve, uMkuze Game Reserve and Hluhluwe-Umfolozi Game Reserve, and in Kruger National Park. According to statistics of 1999, 10-15% of the nyala occur on private land. Currently efforts are being made to retain the populations of nyala in Gorongosa National Park and Banhine National Park in Mozambique.

The nyala have never been observed showing signs of territoriality. Territories overlap extensively, let it be of any sex. The home ranges of males are approximately equal to that of females, about 10 km2. in area.

Reproduction

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. Once sexually mature, a male's seminiferous tubules begin spermatogenesis, that is, the generation of sperm. In a study, males over 14 months old showed active spermatogenesis.

Before ovulation, the Graafian follicles reach a length of at least 6.7 cm. A female's estrus cycle is about 19 days long. Males 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 females' 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.

In a study, the Kidney Fat Indices of impalas and nyalas were studied to understand the influence of social class and reproduction on them. Kidney Fat Index is a technique in which the kidney is removed and weighed with the fat and once again excluding the fat. The resultant difference is the amount of fat on the kidney. The more the fat, the healthier the animal. In rut, the male nyalas had less KFIs, that did not vary much with the season. Pregnant females, both the antelopes nyala and impala, had higher KFIs than the 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. Birth takes place generally away from the sight of predators, in places like a thicket. The calf remains hidden for up to 18 days, and the mother nurses it in regular intervals. The calf remains with its mother till the birth of the next calf, during which males in rut drive it away from the mother.

Food

As a herbivore, the nyala's diet consists of foliage, fruits, flowers and twigs. During the rainy season they feed upon the 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 made in Mkhuze Game Reserve and Ndumu Game Reserve in Natal, focused on the dietary habits of the impala and the nyala, showed that the amount of dicotyledons in their diets varied seasonally. In the diet of nyala its content was 83.2% and impala's diet contained a lesser figure of 52% dicotyledons. The diet grew richer in fiber content and dietary proteins were less. The reverse occurred in the rainy season. As the rainy season arrived, both the species took to a diet of mainly monocotyledons, and the impala consumed more of them. The diet contained more proteins than fibers.

Another study was done to find whether the sexual dimorphism in the nyala influenced its foraging habits. Vegetation surveys were conducted with the end of each feeding bout. It was found that females spent equal periods of time foraging in all the three habitats, but males preferred sand forest 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 differing reproductive strategies.

Predators

The major threats to the population of the nyala are hunting, habitat loss, agriculture and cattle grazing. This species is currently of Least Concern, and the population is considered stable by both the IUCN and CITES. As of 1999, the total population of the nyala was around 32,000 individuals. More recent estimates show that South Africa has at least 30,000 nyalas, with 25,000 in KwaZulu-Natal. There are now more than 1,000 on protected areas and ranches in Swaziland. In Mozambique there are not more than 3,000, in Zimbabwe there are over 1,000 while numbers in Malawi have fallen from 3,000 to about 1,500. Namibia has the least population, about 250.

Today over 80% of the total population is protected in national parks and sanctuaries, mostly in South African protected areas. These are the Ndumo Game Reserve, uMkuze Game Reserve and Hluhluwe-Umfolozi Game Reserve and Kruger National Park. 10 to 15% occur on private land. They mostly occur in South Africa due to the high demand for adult males as game trophies.

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. 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.