Difference between revisions of "Plains zebra" - New World Encyclopedia

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Six subspecies are often recognized, including the [[extinct]] [[quagga]] (''E. quagga quagga''). At one point, the quagga and plains zebra were considered separate species, with the quagga classified as ''E. quagga'' and the plains zebra as ''E. burchelli''. While the various subspecies show morphological differences, genetic studies have found little genetic differentiation in the populations, possibly insufficient to indicate distinct taxonomic units, although the distinction among the groups is useful from a management standpoint.  
 
Six subspecies are often recognized, including the [[extinct]] [[quagga]] (''E. quagga quagga''). At one point, the quagga and plains zebra were considered separate species, with the quagga classified as ''E. quagga'' and the plains zebra as ''E. burchelli''. While the various subspecies show morphological differences, genetic studies have found little genetic differentiation in the populations, possibly insufficient to indicate distinct taxonomic units, although the distinction among the groups is useful from a management standpoint.  
  
The plains Zebra is much less numerous than it once was, largely because of human activities such as hunting it for its meat and hide, as well as encroachment on much of its former habitat, but it remains common in game reserves.  
+
The plains zebra is much less numerous than it once was, largely because of human activities such as hunting it for its meat and hide, as well as encroachment on much of its former habitat, but it remains common in game reserves.  
  
 
==Overview and description==
 
==Overview and description==

Revision as of 22:34, 29 April 2009

Plains Zebra
Grant's Zebra (E. quagga boehmi)
Grant's Zebra (E. quagga boehmi)
Conservation status
Status iucn3.1 LC.svg
Least Concern

(IUCN) [1]

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Genus: Equus
Subgenus: Hippotigris
Species: E. quagga
Binomial name
Equus quagga
Boddaert, 1785
Range map of The Plains zebra
Range map of The Plains zebra
subspecies

E. q. quagga
E. q. burchelli
E. q. boehmi
E. q. borensis
E. q. chapmani
E. q. crawshayi

Plains zebra is the common name for the most common and geographically widespread species of zebra, Equus quagga, characterized by vertical stripes on the forepart of the body, which tend towards the horizontal on the hindquarters. Also known as the the common zebra or the Burchell's zebra, it ranges from southern Sudan and southern Ethiopia to southern Angola, northern Namibia, and northern South Africa.

Six subspecies are often recognized, including the extinct quagga (E. quagga quagga). At one point, the quagga and plains zebra were considered separate species, with the quagga classified as E. quagga and the plains zebra as E. burchelli. While the various subspecies show morphological differences, genetic studies have found little genetic differentiation in the populations, possibly insufficient to indicate distinct taxonomic units, although the distinction among the groups is useful from a management standpoint.

The plains zebra is much less numerous than it once was, largely because of human activities such as hunting it for its meat and hide, as well as encroachment on much of its former habitat, but it remains common in game reserves.

Overview and description

The quagga (Equus quagga quagga) is a member of the Equidae, a family of odd-toed ungulate mammals of horses and horse-like animals. There are three basic groups recognized in Equidae—horses, asses, and zebras—although all extant equids are in the same genus of Equus.

Grévy's zebra is one of three or four extant species of zebras. The other extant species are the plains zebra (E. quagga), the Cape mountain zebra (Equus zebra) and the Hartmann's mountain zebra (E. hartmannae), which are placed together in the subgenus Hippotigris. The Cape mountain zebra and Hartmann's mountain zebra are sometimes treated as the same species. Grévy's zebra (E. grevyi) is placed in its own subgenus of Dolichohippus. In many respects, it is more akin to the asses (subgenus Asinus), while the other zebras are more closely related to the horses (subgenus Equus). Nevertheless, DNA and molecular data show that zebras do indeed have monophyletic origins. In certain regions of Kenya, the plains zebras and Grevy's zebras coexist.

Grévy's zebra differs from the other two zebras in its primitive characteristics and different behavior. Compared to other zebras, Grévy's zebra is tall, has large ears, and its stripes are narrower.

Zebra are wild members of the genus Equus, native to eastern and southern Africa and characterized by distinctive white and black (or brown) stripes that come in different patterns unique to each individual. The quagga is now recognized as an extinct subspecies of one of the three or four extant species of zebras, the plains zebra (E. quagga), which is also known as the common zebra, the painted zebra, and Burchell's zebra. The other extant species are Grévy's zebra (E. grevyi), the Cape mountain zebra (Equus zebra), and the Hartmann's mountain zebra (E. hartmannae), although the Cape mountain zebra and Hartmann's mountain zebra are sometimes treated as the same species. The plains zebra, Cape mountain zebra and Hartmann's mountain zebra are similar and placed in the same subgenus of Hippotigris. Grévy's zebra is placed in its own subgenus of Dolichohippus.

The quagga was distinguished from other zebras by having the usual vivid black marks on the front part of the body only. In the mid-section, the stripes faded and the dark, inter-stripe spaces became wider, and the rear parts were a plain brown. Overall, the coat was sandy brown and the tail white.


Closeup of zebra

The Plains Zebra is mid-sized and thick bodied with relatively short legs. Adults of both sexes stand about 1.4 meters (4.6 ft) high at the shoulder, are approximately 2.3 meters (8 ft) long, and weigh about 294 kg (646 lbs) however males may weigh 10% more than females. Like all zebras, it is boldly striped in black and white and no two individuals look exactly alike. All have vertical stripes on the forepart of the body, which tend towards the horizontal on the hindquarters. The northern populations have narrower and more defined striping; southern populations have varied but lesser amounts of striping on the underparts, the legs and the hindquarters. Southern populations also have brown "shadow" stripes between the black and white coloring. The first subspecies to be described, the now-extinct Quagga, had plain brown hindquarters. (Technically, because the Quagga was described first as E. quagga, the proper zoological name for the most common form of the Plains Zebra is E. quagga burchelli.. Rare albino zebras have been recorded in the forests of Mount Kenya.[2]

Ecology

Zebras grazing with wildebeest

Plains zebras live in eastern and southeastern Africa where there are only two seasons; wet and dry. Zebras rely on rainfall for food and water and thus have to go on great migrations to follow the rains. The zebras will migrate up to 700 miles (1,100 km) for food. Other grazers also must do the same thing. Plains zebras can not survive very long without water and are usually found within 25-30 kilometers of a water source.

Unlike many of the large ungulates of Africa, the Plains zebra does not require (but still prefers) short grass to graze on. It eats a wide range of different grasses, preferring young, fresh growth where available, and also browses on leaves and shoots from time to time. In consequence, it ranges more widely than many other species, even into woodland, and it is often the first grazing species to appear in a well-vegetated area. A zebra's digestive system works quickly and can extract more protein from the fibrous and poorest plant parts. Thus zebra are less picky in foraging but they do spend much time eating. Only after animals like zebras have cropped and trampled the long top grasses, which are low in protein, do the other grazers like Blue wildebeests and Thompson's gazelles move in to eat the newly exposed and more nutritional short grasses.

The Plains zebra's main predators are lions and spotted hyenas. Nile crocodiles are also great threats during river crossings. Wild dogs, cheetahs and leopards also prey on zebras, although the threats they pose are generally minor. For protection from land predators the Plains Zebra retreats into open areas with good visibility at night time.

Lifestyle

The Plains zebra is highly social and usually forms small family groups consisting of a single stallion, one, two, or several mares, and their recent offspring. The adult membership of a harem is highly stable, typically remaining together for months to years. Bachelor males either live alone or with groups of other bachelors until they are ready to start their own harems. Multiple harems and bachelor groups come together to form herds, although these aggregations are highly fluid.

A zebra harem

A stallion forms a harem by abducting young mares from their families. When a mare reaches sexual maturity she will exhibit the estrous posture which invites the males. Her father has to chase off stallions attempting to abduct her. Eventually a stallion will be able defeat the father and include the mare into his harem. In addition to the father, the stallion must also fight rival males to get the young mare.

Two zebras fighting

Mares exist in a hierarchy with the alpha female being the first to mate with the stallion and being the one to lead the group. When new mares are added to the group, they are met with hostility by the other mares. Thus the stallion must shield the new mares until the aggression subsides.

A stallion will defend his group from other males. When challenged, the stallion would issue a warning to the invader by rubbing nose or shoulder with him. If the warning is not heeded, a fight breaks out. Zebra fights often become very violent, with the animals biting at each other's necks, heads or legs, wrestling to the ground, and occasional kicking. Sometimes a stallion will lay still on the ground like he's surrendered but once the other male lets up the stallion will strike and continue the fight.

Zebras strengthen their social bonds with grooming. Members of a harem nip and scrape along the neck, shoulders and back with their teeth and lips. Mothers and foals groom the most often followed by siblings. Grooming shows social status and eases aggressive behavior.

Plains zebra herds will mix and migrate together along with other species such as wildebeests. Wildebeests and zebras generally coexist peacefully and will alert each other to predators. However in one case, a gang of young zebra stallions isolated and harassed a wildebeest calf while keeping the mother at bay. The zebras chased and bit the young calf repeatedly. One zebra even trampled over it. The group eventually lost interest and the calf survived.[3] A similar incident happened when a lone wildebeest calf wandered too close to a gang of stallions and was kicked to death.[4]

Reproduction

Mother zebra and foal

Mares may give birth to one foal every twelve months. She nurses the foal for up to a year. Like horses, zebras are able to stand, walk and suckle shortly after they're born. Plains zebra foals are protected by their mother as well as the head stallion and the other mares in their group. Even with parental protection up to 50% of zebra foals are taken by predation, disease and starvation each year. It is possible that zebras practice infanticide and feticide, although such incidences have only been observed in captive individuals.[5]

Conservation

The Plains zebra’s range has diminished in modern times. While the population remains stable, zebras are threatened by hunting, for their hide and meat, and habitat change from farming. They compete with livestock for food. One subspecies, the quagga, is now extinct. Nevertheless, Plains zebras are protected in most of their range. They are an important economic source in tourism.

Taxonomy

In 2004, C.P. Groves and C.H. Bell did investigations on the taxonomy of the zebra's genus Equus, subgenus Hippotigris. They published their research in Mammalian Biology. They revised the subspecies of the Plains Zebra Equus quagga. Six subspecies are recognizable. The completely maneless Somali population may represent a seventh subspecies: Equus quagga isabella (Ziccardi, 1958). This subspecies may be valid, but at present there is no evidence that it is.

  • Quagga, Equus quagga quagga Boddaert, 1785
  • Burchell's Zebra, Equus quagga burchellii Gray, 1824
  • Grant's Zebra, Equus quagga boehmi Matschie, 1892
  • Selous' Zebra, Equus quagga borensis Lönnberg, 1921
  • Chapman's Zebra, Equus quagga chapmani
  • Crawshay's Zebra,Equus quagga crawshayi

The quagga was the first extinct animal to have its DNA studied and this revealed that it was not a distinct species from the plains zebra.

"Groves and Bell (2004) recognized six subspecies, based on coat patterns, skull metrics, and the presence or absence of a mane and of the infundibulum on the lower incisors (intergrades are observed). A recent genetic study ... found very little differentiation among populations. ... The five sampled Plains Zebra subspecies, which included the extinct Quagga, could not be distinguished with the genetic markers used and no genetic structuring was found indicative of distinct taxonomic units. The molecular data represented a genetic cline and was differentiated along an east-to-south gradient in agreement with the progressive increase in body size and reduction in stripes towards the south. This is consistent with the overlapping morphological parameters and geographical distribution of subspecies reported in literature. Hence, the subspecies splits based on the morphological cline may be arbitrary, but are useful from a management perspective."


Footnotes

  1. M. A. Hack and E. Lorenzen, Equus quagga. In IUCN, 2008 IUCN Red List of Threatened Species. Retrieved April 29, 2009. Database entry includes a brief justification of why this species is of least concern.
  2. http://www.animalorphanagekenya.org/members/bush_drums_2006_december.php
  3. Wilderness Safaris - Zebra attack Blue Wildebeest foal
  4. National Geographic Zebra: Patterns in the Grass (1991)
  5. Further evidence for male infanticide and feticide in captive Plains zebras


References
ISBN links support NWE through referral fees

  • Estes, R. (1991). The Behavior Guide to African Mammals, Including Hoofed Mammals, Carnivores, Primates. Los Angeles, The University of California Press.
  • Moss, C., Ed. (1982). Portraits in the Wild, Animal Behavior in East Africa. Chicago, The University of Chicago Press.
  • Duncan, P. (ed.). (1992). Zebras, Asses, and Horses: an Action Plan for the Conservation of Wild Equids. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland.
  • Groves, C.P. & Bell, H.B. 2004. New investigations on the taxonomy of the zebras genus Equus, subgenus Hippotigris. Mammalian Biology. 69: 182-196.
  • Hack et al 2002. [1]. 2006 IUCN Red List of Threatened Species., World Conservation Union. Retrieved on 17 June 2006.
  • Hack et al 2002. [2]. 2006 IUCN Red List of Threatened Species., World Conservation Union. Retrieved on 10 May 2006. (Extinct subspecies of the Plains Zebra.)
  • Higuchi et al. 1987. Mitochondrial DNA of the Extinct Quagga: Relatedness and Extent of Postmortem Change. Journal of Molecular Evolution 25:283-287.
  • Moelman, P.D. 2002. Equids. Zebras, Assess and Horses. Status Survey and Conservation Action Plan. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland. (http://www.iucn.org/themes/ssc/pubs/sscaps.htm#Equids2002)
  • Hack, M. A, and E. Lorenzen. 2008. Equus quagga. In IUCN, IUCN Red List of Threatened Species. Retrieved February 8, 2009.
  • Hack, M. A., R. East, and D. I. Rubenstein. 2008. Equus quagga ssp. quagga. In IUCN, 2008 IUCN Red List of Threatened Species. Retrieved February 8, 2009.
  • Hartwell, S. n.d. Hybrid equines. Messybeast.com. Retrieved February 8, 2009.

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