Nyala
The lowland nyala or simply nyala is a spiral-horned artiodactyl antelope native to Southern Africa. The species is part of the family Bovidae and the genus Tragelaphus. It was first described in 1849 by George French Angas and 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's range encompasses much of Southern Africa. As its population is relatively stable, it has been listed as of least concern by the International Union for Conservation of Nature. It generally browses during the day in warm weather 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 ten individuals, but old males live alone. They inhabit thickets within dense and dry savanna woodlands. The principal threats to the species are illegal poaching and habitat loss resulting from human settlement and livestock grazing. However, the large-horned, impressive males are highly prized as game animals by sport hunters.
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. According to Article 50.1.1 of the International Code of Zoological Nomenclature and International Commission on Zoological Nomenclature, though, 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.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 time, 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. Among its closest extant relatives are the forest-inhabiting bongo, the bushbuck, the large common and giant elands, the greater and lesser kudus, the mountain nyala and the swamp-dwelling sitatunga, all of which share similar characteristics, such as hornless females, vertical side-stripes and other unique white markings, and the spiraling horns and distinct "beard" or dewlap of males, often with a raised trail of fur extending down the back and underside.
In 2005, Sandi Willows-Munro 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 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. 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.
Physical description
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 in head-and-body length. The male stands up to, the female is up to tall. Males weigh, while females weigh. 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 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 long and yellow-tipped. There are one or two twists. The spoor is similar to that of the bushbuck, but larger. It is 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.
Parasites
A study of the helminths from 77 nyalas from four game reserves in Natal revealed the presence of ten nematode species and four nematode genera, a trematode species and paramphistomes, and two cestode genera. The research discovered new parasites that the nyala was host of - namely a Cooperia rotundispiculum race, Gaigeria pachyscelis, a Gongylonema species, Haemonchus vegliai, Impalaia tuberculata, an Oesophagostomum species, a Setaria species, Trichostrongylus deflexus, Trichostrongylus falculatus, the larval stage of a Taenia species, a Thysaniezia species and Schistosoma mattheei. Ostertagia harrisi and C. rotundispiculum were the most dominant nematodes in the antelope.Another study of 97 blood samples of South African nyalas revealed the presence of tick-borne hemoparasites. The methods used were polymerase chain reaction and reverse line blot hybridization. The dominant parasites were Theileria species, T. buffeli, T. bicornis, Ehrlichia species, Anaplasma marginale and A. bovis. Ten tick species, two louse species and a louse fly species were recovered in a study of 73 nyalas at Umfolozi, Mkuzi and Ndumu Game Reserves in northeastern KwaZulu-Natal in 1983 and 1984 and an additional six individuals in 1994. It was found that nyalas were hosts to all stages of development in Boophilus decoloratus, Rhipicephalus appendiculatus and R. muehlensi and the immature stages of Amblyomma hebraeum and Rhipicephalus maculatus. Adult males served hosts to more ticks and lice than adult females did. Also, a trypanosome was isolated from a nyala, wild-caught in Mozambique, which was diagnosed and found as akin to Trypanosoma vivax, based on biological, morphological and molecular data.
Diseases
The nyala can also suffer from myopathy. In between January 1973 and June 1981, 21 nyalas succumbed to the disease. The main symptoms were stiffness, inability to rise, and failure to suckle in newborns. Necrosis and mineralization were found in the skeletal muscle after a histological analysis. In the juveniles there was acute necrosis of the cardiac muscle. In adults, there was interstitial fibrosis of the cardiac muscle, along with arteriosclerosis.In a report published in 1994 entitled "Epidemiological observations on spongiform encephalopathies in captive wild animals in the British Isles", it was noted that spongiform encephalopathy had been diagnosed in one nyala captive in a zoo. The nyala was formerly affected by the disease rinderpest, although the viral disease is considered eradicated now.
Ecology and behavior
The nyala is active mainly in the early morning and late afternoon. It browses during the day if temperatures are 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 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 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. 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 use 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, African wild dog and nile crocodile while baboons and raptorial birds are predators of juveniles.