Nyala angasii (Angas, 1849)

Don E. Wilson & Russell A. Mittermeier, 2011, Bovidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 444-779 : 593-594

17.

Nyala

Nyala angasii

French: Nyala / German: Nyala / Spanish: Niala

Taxonomy. Tragelaphus angasii Angas, 1849 ,

KwaZulu-Natal, S Africa.

The Nyala is often placed in the genus Tragelaphus , but variations in skull measurements (e.g. lateral nasal tips virtually absent and malar-maxillary suture deeply penetrating anteriorly in angasi but not in other tragelaphines) and no inversion of the Y-chromosome suggest that placement of angasii in its own genus Nyala is appropriate. Monotypic.

Distribution. S Malawi, Mozambique, N & S Zimbabwe, E South Africa, and Swaziland (extinct but reintroduced). Introduced on private ranches in Namibia and South Africa, from which they have escaped and spread to E Botswana.

Descriptive notes. Head-body 159-198 cm (males) and 132-146 cm (females), tail 37-47 cm (males) and 34-40 cm (females), shoulder height 104-121 cm (males) and 82-106 cm (females); weight 92-126 kg (males) and 55-68 kg (females). Tragelaphines are typified by their sexual dimorphism, and the Nyala is reportedly the most extreme and comparable to the Nilgai ( Boselaphus tragocamelus ) in India. The weight of males can be 171% that of females. Both sexes are born a chestnut color of varying degrees of intensity and with lateral stripes on their torso. With maturity at about four years of age, males become a spectacular dark brown to charcoal gray, often with a bluish hint and have contrasting chestnut-tan lower legs. Males are rather bulky and become shaggy as they age. They have pronounced fringes of long hair around the neck and ventrally from the throat to the hindquarters and a whitish-gray, erectile dorsal crest. Unlike females, lateral white stripes are reduced or absent on males. Only males possess loosely spiraled, yellow-tipped horns that reach lengths of 60-83 cm; the hairs between them and in the inner ears are chestnut-tan like the lower legs, providing a sharp contrast to the dark face. Adult females are a smooth-coated chestnut throughout the body and lack ventral hair fringes. They have 8-13 vertical stripes on their shoulders, sides, and hindquarters and white spots scattered on their hindquarters and torso. Both sexes have a white chevron between their eyes (of variable intensity on the female), a black muzzle with white upperlips and chin, 2-3 white cheek spots on each side, a white crescent on their chest (shaggy in males), a white stripe down the anterior ridge of the upperrear leg (shaggy in males), black rings above the hooves, and a bushy tail that is whitish underneath and black tipped. The male’s tail is bushier than the female's. Nyalas lack head and inguinal glands but do have pedal glands. At birth, young are striped and the same pale-to-bright chestnut as the females; the male pelage begins to darken after about four months of age and horns are evident at seven months. Dental formulais10/3,C0/1,P3/3,M 3/3 (x2) = 32. Permanent dentition is attained at two years of age, with permanent molars beginning to erupt at six months. Aging of Nyala is possible with a combination of cementum annuli counts and permanent tooth eruption and wear, but it is not as precise as in other species. Diploid numbers for the Nyala are b5 for males and 56 for females, much large than the closely related tragelaphines.

Habitat. In its native range, the Nyala is now confined to the Lowveld of the southern savanna in extreme south-eastern Africa, but now naturalized in Namibia and eastern Botswana. It prefers low-lying dense woodlands, open thickets, and woodland mosaics in close proximity to water. In Zinave National Park, Mozambique, Nyalas use closed and open tree-savannas dominated by Acacia, Ostyoderris, and Bolusanthus, with shrub thickets as tall as 2: 5 m. Over a two-year period in Zinave, 40-91% of the observations of Nyala were in shrub thickets interspersed throughout Acacia woodlands. Habitat preferences are disparate between males and females; males tend to confine themselves more to wooded habitats than females.

Food and Feeding. The Nyala is considered to be a generalist browser, or intermediate feeder, selecting leaves of at least 108 plant species in Zinave Nationall Park. Fruits from 39% of those plant species, twigs from 13%, and flowers from 10% also were eaten, along with bark of the baobab tree (Adansonia digitata). In some areas, woody species preferred by Nyalas and other ungulates have pronounced browse lines 1-3-2 m high. During the rainy season when vegetation is lush, Nyalas consume a greater variety of herbaceous vegetation such as legumes. In Zinave, grasses were found in stomach samples during most of the year, as high as 65% wet weight, but on average, no more than 12% mixed grass and herbaceous species. During the rainy season in Mkhuze and Ndumo game reserves, KwaZulu-Natal, Nyalas consume over 80% monocotyledons. Food preferences are disparate between males and females; females tend to forage more in the low herbaceous layer and males select more woody species higher above the ground. Because oftheir largersize, males require 62% more kcal/day than females. The nutritional status of Nyalas in KwaZulu-Natal, South Africa, is related to rainfall in the previous month, which is associated with current forage availability. Nyalas will drink daily, particularly during the dry season, often at night where human presence is high, but during midday elsewhere. Early reports suggested that Nyalas can go extended periods without free water, and they have been observed 16-24 km from known free water.

Breeding. Breeding and subsequent births of the Nyala can occur throughout the year, but births in Zinave were somewhat concentrated in August-September, at the end of the dry season and beginning of summer rains. Births in Ndumo Game Reserve, South Africa, were somewhat bimodal with peaks in autumn and spring. At Ndumo, the fewest births occurred in June—September and December. Breeding may be cued more by photoperiod than changes in forage availability, but neither effect is strong enough to establish pronounced breeding peaks. Sexual maturity of malesis attained at 4-5 years of age, with no indication of senescence offertility with advanced age. There is no evidence that breeding adult males are territorial or form harems, but rather, they establish a hierarchy among themselves before and during rut, and seemingly with a limited repertoire of display sequences. Male Nyalas will rub and thrash the ground and vegetation with their horns, but horn-to-horn combat appears to be very uncommon. Mature males display parallel to each other, often in a frozen position, with their dorsal crests erect, their tails lifted onto the back with hairs flared to expose the white undersides, and their heads lowered so that horn tips are held slightly forward. This posturing effectively increases a male’s visual surface area by 40%, and no doubt plays a role in establishing dominance without combat. Subordinate males will walk past such posturing males with a high-stepping walk that is considered submissive. Few observations of courtship and copulation exist, although males do perform a typical lip curl, but sparingly, in response to smelling an estrous female’s tail area and often without testing her urine. He also will push his head between the female’s legs prior to copulation. A male will tend an estrous female for up to 24 hours, but he may be replaced by progressively more dominant males during that period. As with most bovids, copulation is brief. Females breed at 14-20 months of age and become reproductively inactive at about 14 years old. Gestation is about 8-5 months, and a single young is born. Females can come into estrus one week after parturition, with calving intervals of 257-297 days. In Zinave, neonates are 4.1-5. 5 kg at birth, with a total length of81-93 cm and a shoulder height of 47.5-53 cm. They are left in hiding places for 10-18 days, and mothers are not particularly attentive. Unlike many other ungulates, they do not attempt to defend neonates from predators, which include Lions (Panthera leo), Leopards (P. pardus), and Spotted Hyenas (Crocuta crocuta). Maximum longevity in captivity has been 18-5 years; it is no doubtless in the wild.

Activity patterns. Nyalas are described as secretive and shy and generally stay close to cover. They tend to be crepuscular and nocturnal where persecuted, but active throughout the day where protected. During hot weather, even individuals in protected areas are probably more active at dawn, dusk, and throughout the night. During the dry season, Nyalas move more in search of food and water. Woodlands and shrub thickets are important during hot, dry weather for cover and protection from threats. As with all ruminants, peaks of foraging and resting/ruminating occur through the day, but little information exists on the specifics of daily activity patterns.

Movements, Home range and Social organization. The Nyala is non-migratory and gregarious. In Zinave National Park, densities peaked at about 10 ind/km?, and male and female non-exclusive home ranges were 1:3-9-5 km* (average 3-9 km?) and 0-4— 3-6 km* (average 2-9 km?®), respectively. Average densities where Nyalas are common are 7 ind/km?. Individuals may move up to 12 km /day, but typically less. Group dynamics of Nyala are fluid, and a mother and her offspring-of-the-year, and perhaps the previous year, form the most lasting bond. Group sizes were 1-30 individuals in Zinave, but 67% of the observations were of 1-3 individuals. Males were seen alone twice as often as females at Zinave, and it was uncommon to see many adult males in mixed groups. Vocalizations of the Nyala include an alarm bark described as dog-like, a distress bleat used between a mother and her calf, and soft clicking heard in captivity when in estrus and while tending a calf.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Populations of Nyala were severely depleted in the past, largely because of conversion of woodland savannas to agriculture uses such as cattle grazing but also overhunting and diseases such as rinderpest. Genetic divergence (e.g. unique haplotypes) is apparent among regional populations but no loss of genetic diversity is suggested. Currently, about 32,000 Nyalas remain, with 80% in protected areas and 10-15% on private ranches in South Africa and Namibia. Populations are considered stable to increasing, particularly with reintroductions and escapees from private land that are now populating areas even beyond the Nyala’s historical distribution (e.g. in eastern Botswana). In an early assessment in 1996 of the effects of climate change on ungulates in Lengwe National Park, Malawi, the Nyala was identified as the species with the greatest potential susceptibility to decreasing rainfall and subsequent reductions in forage availability. Droughts in Lengwe in 1980s were known to be particularly hard on the Nyala . Relocation of the Nyala to game ranges in South Africa and Namibia has resulted in well-regulated trophy hunting and has increased the number and range of the species. Ongoing management of the Nyala is important because it could become overpopulated, leading to significant mortality events. Current restoration of protected areas in Mozambique (e.g. Gorongosa and Banhine national parks) will benefit all savanna wildlife and may allow the Nyala , in particular, to regain its former abundance there.

Bibliography. Anderson (1978, 1979, 1980, 1984, 1985, 1986), Bro-Jorgensen (2008), Davison (1971), East (1999), Estes (1991a, 1991b), Grobler et al. (2005), Huffman (2004), IUCN/SSC Antelope Specialist Group (2008bd), Kazembe (2009), Kirby et al. (2008), Leslie (2008), Leuthold (1977), Lobao Tello & van Gelder (1975), Mentis (1972), Mkanda (1996), Mkanda & Munthali (1991), Richards & Shurter (2010), Roberts (1936), Rubes et al. (2008), Van Rooyen (1992, 1993), Volf (1991), Walther (1990b), Weigl| (2005).

Figures

14. Saola (Pseudoryx nghetinhensis), 16. Chowsingha (Tetracerus quadricornis), 17. Nyala (Nyala angasii)

Distribution. S Malawi , Mozambique , N & S Zimbabwe , E South Africa , and Swaziland (extinct but reintroduced). Introduced on private ranches in Namibia and South Africa , from which they have escaped and spread to E Botswana .