The West African giraffe, Niger giraffeor Nigerian giraffe (Giraffa camelopardalis peralta) is a subspecies ofgiraffe distinguished by its light colored spots, which is found in the Sahel regions of West Africa. In the 19th century it ranged from Senegal to Lake Chad yet in 2011 this subspecies only survives in a few isolated pockets containing about 310 individuals in total. Its last self-sustaining herd is in southwest Niger, supported by a series of refuges in Dosso Region, and the tourist center at Kouré, some 80 km southeast of Niamey. All captive supposed "West African giraffe" are now known to be Kordofan giraffe (G. c. antiquorum).
Decline
Before World War I, at the time of European colonial administrations, West African giraffe lived in pockets across theSahel and savanna regions of West Africa. Population growth, involving more intensive farming and hunting, a series of dramatic droughts since the late 19th century, and environment destruction (both natural and human made) have all contributed to their dramatic decline. As late as the 1960s, prior to the Sahel drought that lasted to the early 1980s, populations identified asG. c. peralta existed in Senegal, Niger, eastern Mali, northern Benin, northernNigeria, southwest Chad and northernCameroon. However, recent geneticresearch has shown that the populations from northern Cameroon and southern Chad actually are the Kordofan giraffe (G. c. antiquorum).Therefore the giraffes that remain in Waza National Park (Cameroon) belong to the Kordofan giraffe, while the only remaining viable population of the West African giraffe is in Niger. In Niger, herds have been reported from the Agadez Region, and across the west and south of the country. Herds regularly traveled into the Gao Region of Mali as well and throughout the Niger River valley of Niger. Drought struck again in the 1980s and 1990s, and in 1991 there were less than 100 in the nation, with the largest herd in the western Dosso Region numbering less than 50, and scattered individuals along the Niger River valley moving from Benin to Mali, and clinging to the W National Park and nearby reserves.
Subspecies definition
Older studies on giraffe subspecies have caused some researchers to question the separate status of G. c. peralta and the Kordofan giraffe (G. c. antiquorum). Genetic testing published in 2007 confirmed the distinctiveness of the West African giraffe. One of these publications revealed results, that have been interpreted to show that there may be at least six cryptic speciesof giraffe that are reproductively isolated and not interbreeding, even though no natural obstacles, like mountain ranges or impassable rivers block their mutual access.
Most captive giraffes from northwestern Africa are in French zoological parks, a result of the history of French colonialism in what was French West Africa. Those giraffes were formerly treated as G. c. peralta. However, since genetic analysis revealed that only giraffes to the west of Lake Chadbelong to this subspecies, the populations in European zoos are in fact Kordofan giraffes (G. c. antiquorum). The West African giraffe is more closely related to the giraffes of East Africa than to those of Central Africa. Its ancestor may have migrated from East to North Africa during theQuaternary and then to West Africa with the development of the Sahara desert. At its largest, Lake Chad may have acted as a barrier between West African and Kordofan giraffes during theHolocene.
Conservation
Conservation efforts since the 1990s have led to a sizable growth in population, though largely limited to the single Dosso herd. From a low of 50 individuals, in 2007 there were some 175 wild individuals, 250 in 2010, and 310 in the Nigerien government's 2011 count. Intensive efforts have been made within Niger, especially in the area just north of the Dosso Partial Faunal Reserve. From there, the largest existing herd migrate seasonally to the drier highlands along theDallol Bosso valley, as far north as Kouré, some 80 km southeast of Niamey. This area, though under little formal regulation, is the centre for Nigerien and international efforts to maintain habitat, smooth relations between the herd and area farmers, and provide opportunities for tourism, organised by the Association to Safeguard Giraffes in Niger.
The Nigerian giraffe population relies upon seasonal migration between the relatively drought-resistant lowlands of the Niger River valley and the drier highlands near Kouré. In this area, Tiger bush habitat allows for bands of trees to thrive in climates which might otherwise become more typical desert. These giraffe survive primarily on a diet of leaves from Acacia albida and Hyphaene thebaica as well as Annona senegalensis, Parinari macrophylla, Piliostigma reticulatum, andBalanites aegyptiaca.In the late 1990s, an anti-desertification project for the area around Niamey encouraged the development of woodcutting businesses. An unintended effect of this was the destruction of much Tiger bush and giraffe habitat within the region. The Nigerien government has since moved to limit woodcutting in the area.
HABITAT
The Nigerian giraffe population relies upon seasonal migration between the relatively drought-resistant lowlands of the Niger River valley and the drier highlands near Kouré. In this area, Tiger bush habitat allows for bands of trees to thrive in climates which might otherwise become more typical desert. These giraffe survive primarily on a diet of leaves from Acacia albida and Hyphaene thebaica as well as Annona senegalensis, Parinari macrophylla, Piliostigma reticulatum, andBalanites aegyptiaca.In the late 1990s, an anti-desertification project for the area around Niamey encouraged the development of woodcutting businesses. An unintended effect of this was the destruction of much Tiger bush and giraffe habitat within the region. The Nigerien government has since moved to limit woodcutting in the area.
Neck
The giraffe has an extremely elongated neck, which can be up to 2 m (6 ft 7 in) in length, accounting for much of the animal's vertical height. The long neck results from a disproportionate lengthening of the cervical vertebrae, not from the addition of more vertebrae. Each cervical vertebra is over 28 cm (11 in) long. They comprise 52–54 percent of the length of the giraffe'svertebral column, compared with the 27–33 percent typical of similar large ungulates, including the giraffe’s closest living relative, the okapi.This elongation largely takes place after birth, as giraffe mothers would have a difficult time giving birth to young with the same neck proportions as adults.The giraffe's head and neck are held up by large muscles and a nuchal ligament, which are anchored by long dorsal spines on the anterior thoracic vertebrae, giving the animal a hump.
The giraffe's neck vertebrae have ball and socket joints. In particular, the atlas–axis joint (C1 and C2) allows the animal to tilt its head vertically and reach more branches with the tongue.The point of articulation between the cervical and thoracic vertebrae of giraffes is shifted to lie between the first and second thoracic vertebrae (T1 and T2), unlike most other ruminants where the articulation is between the seventh cervical vertebra (C7) and T1. This allows C7 to contribute directly to increased neck length and has given rise to the suggestion that T1 is actually C8, and that giraffes have added an extra cervical vertebra. However, this proposition is not generally accepted, as T1 has other morphological features, such as an articulating rib, deemed diagnostic of thoracic vertebrae, and because exceptions to the mammalian limit of seven cervical vertebrae are generally characterized by increased neurological anomalies and maladies.
There are two main hypotheses regarding the evolutionary origin and maintenance of elongation in giraffe necks. The "competing browsers hypothesis" was originally suggested by Charles Darwin and only challenged recently. It suggests that competitive pressure from smaller browsers, such as kudu, steenbok and impala, encouraged the elongation of the neck, as it enabled giraffes to reach food that competitors could not. This advantage is real, as giraffes can and do feed up to 4.5 m (15 ft) high, while even quite large competitors, such as kudu, can only feed up to about 2 m (6 ft 7 in) high. There is also research suggesting that browsing competition is intense at lower levels, and giraffes feed more efficiently (gaining more leaf biomass with each mouthful) high in the canopy. However, scientists disagree about just how much time giraffes spend feeding at levels beyond the reach of other browsers, and a 2010 study found that adult giraffes with longer necks actually suffered higher mortality rates under drought conditions than their shorter-necked counterparts. This study suggests that maintaining a longer neck requires more nutrients, which puts longer-necked giraffes at risk during a food shortage.
The other main theory, the sexual selection hypothesis, proposes that the long necks evolved as a secondary sexual characteristic, giving males an advantage in "necking" contests (see below) to establish dominance and obtain access to sexually receptive females. In support of this theory, necks are longer and heavier for males than females of the same age, and the former do not employ other forms of combat.However, one objection is that it fails to explain why female giraffes also have long necks
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