Grevy's zebra
| Grevy's zebra | ||||||||||||
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Grevy's zebra ( Equus grevyi ) |
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| Equus grevyi | ||||||||||||
| Oustalet , 1882 |
The Grevy's zebra ( Equus grevyi ) is a zebra from the horse family ( Equidae ) and belongs to the order of the odd ungulate (Perissodactyla). The species is named after the former French President Jules Grévy , who was given an animal by the Emperor of Abyssinia in the 1880s . The Grevy's zebra lives in northeastern Africa, mainly in Ethiopia and Kenya in dry areas and is rather solitary. The main food is grasses, and more rarely softer plants. In the wild, the Grevy's zebra is threatened with extinction due to hunting and habitat loss. Compared to other zebra forms, it has the densest stripe pattern and represents the largest of the horse species living in the wild today.
features
Habitus
The Grevy's zebra is the largest of the zebras living today and the largest wild representative of today's horses . It reaches a head-trunk length of approx. 300 cm, plus a tail length of 50 cm and a shoulder height of 125 to 150 cm. The weight of the adult Grevy's zebra is 350-430 kg. Male animals are slightly larger than females. The head is relatively large and elongated, the neck rather short. In addition, the Grevy's zebra has shorter and rounded ears compared to the donkey and the wild horse ( Equus ferus ). The legs are long and slender and end in relatively small, oval but horse-like wide hooves. The handle legs are significantly less reduced than in the other modern horse species. Chestnuts , callus-like elevations of a brownish color, are only formed on the front legs above the carpal joint and are small. As with all zebras, the mane of the Grevy's zebra has a dark middle hair corridor that continues as an eel line over the back to the base of the tail. The mane protrudes over the ears when erect. In the Grevy's zebra foals, the mane extends to the base of the tail. It disappears when the youth hairs molt.
Characteristic is the stripe pattern, which is individually shaped for each animal and is the narrowest and densest of all zebras. The stripes are black to black-brown in color and have an average width of 25 to 38 mm, while they are about 20 mm apart at the bottom. Between the shoulder and the rump there are usually 18 to 26 stripes, including half stripes, and 9 to 16 on the neck. They reach the tail to the highest point of the croup. Its rear part between the stripes on the torso and legs is filled with a system of very narrow, diagonal stripes that surround the base of the tail, the so-called rust. The basic color of the Grevy's zebra is white to yellowish-white or ash-gray. The belly has no stripes. In the Grevy's zebra, the “shadow stripes” are missing, but a broad, dark stripe runs along the spine. The stripe pattern already forms ontogenetically in the embryonic stage , with a total of 80 stripes appearing in a five-week-old embryo.
Skull and dentition features
The skull becomes 49 cm long and is rather narrow with the cheekbones not protruding very far . It has a characteristic elongated snout, which clearly distinguishes the Grevy's zebra from the African donkey ( Equus asinus ) or Asian donkey ( Equus hemionus ). The occiput is broad and clearly drawn out so that it protrudes over the articular surfaces ( condyles ) as the base of the cervical vertebrae. The weakly developed nasal bone has a slight curvature. The forehead line located between the two skull bones is clearly straight.
The 38 cm long lower jaw has a robust shape with protruding articulated branches. The teeth of the Grevy's zebras is not reduced and accordingly has the following dental formula . The incisors are elongated and chisel-shaped. The canine , separated from the incisors by a diastema , is rather small. This time there is also a larger diastema to the rear dentition. Its teeth, the premolars and molars each have high tooth crowns ( hypsodont ) with heavily folded enamel and a high proportion of dental cement . The premolars are clearly molarized and resemble the rear molars. In the molars of the lower jaw, the course of the tooth enamel at the rear edge between the two protrusions metaconid and metastylid is more V-shaped or angled, which means that the horse species belongs to the non-caballine or stenonine group of the genus Equus .
Sensory performances and vocalizations
Numerous vocalizations are known in the Grevy's zebra. Alarmed animals emit a loud hum that resonates widely and is reminiscent of lions . A whistle or squeak is emitted in similar situations or when there is pain and fear. This also gives off young animals that have been separated from the mother animal. Warnings are indicated by snorting, often associated with pounding forelegs, while the stallions roar in territorial fights. A sound similar to barking is used during sexual intercourse .
distribution
The distribution area of the Grevy's zebra is in East Africa and the Horn of Africa , but today it is largely limited to Ethiopia and Kenya ; data for Sudan have not yet been confirmed. However, the habitats are very fragmented. A small population lives in the Alledeghi Plain northeast of the Awash National Park in Ethiopia. Further stocks can be found in southern Ethiopia from Lake Chew Bahir to Mount Kenya and along the Tana . It is more common in northern Kenya east of the Great Rift Valley up to the Tana River. Here the Grevy's zebra lives in several game reserves. Originally the distribution area was much larger and reached from the rift valley system in Kenya to Somalia and northern Ethiopia.
The habitat includes semi-arid open landscapes up to an altitude of 1,700 m. Here the animals inhabit regions with low to half-high vegetation (1 to 4 m high), mainly bush and grasslands consisting of acacias , but where water must be accessible. They prefer flat or hilly terrain with a stony surface. However, there are individual differences in the preference for certain landscapes. Mares with suckling foals claim areas with green and fresh vegetation, as do stallions without their own territory. In contrast, mares without foals and territorial animals also tolerate regions with dry vegetation. Because of this and the droughts that regularly occur in some regions, the Grevy's zebra undertakes seasonal migrations. The population density in areas with a higher population density is a maximum of 0.1 to 0.2 individuals per km².
Way of life
Territorial behavior
Unlike the mountain zebra ( Equus zebra ) and the plains zebra ( Equus quagga ), the Grevy's zebra does not form any real herds. If the environmental conditions are favorable, a large number of individuals can come together in one area, which usually happens while eating. These groups consist of representatives of both sexes, but there are no leading animals and the associations quickly disintegrate. Close social ties only exist between mares and their offspring. Females with foals and bachelors each sometimes form loose associations. Older stallions often live solitary and maintain territories that they defend against their peers of the same age. These areas can be 2.5 to 10 km² in size and are created in areas with dry vegetation. The boundaries of the territories often follow natural barriers such as watercourses. Much traveled paths or meeting points with conspecifics are marked by urine and feces . A dominant stallion keeps the ground up to one year and tolerates other males there as long as no rutting mares are present. Then he defends his territory with bites in the neck, back or on the flanks. Occasionally, mares with foals enter into temporary relationships with stallions in order to avoid the chasing after several other males in the rearing phase.
nutrition
The Grevy's zebra feeds on hard, silica-rich grass food, to which it is adapted with its high-crowned molars with a high proportion of dental cement and the strong lower jaw. The main diet includes lamp-cleaner grass and finger millet , but also vetiver , prickly grass and other sweet grasses . Furthermore, are legumes as food plants known. However, this zebra species occasionally eats softer plant food such as leaves , twigs or flowers , but this makes up less than 30% of the total diet. Vegetable food contains most of the mineral substances necessary for metabolism , so the use of salt and mineral licks is not known. In contrast to the plains zebra, the Grevy's zebra needs far less water and can do without liquid for up to five days. This does not apply to nursing mothers that need water every two days.
Reproduction
A young male Grevy's zebra is sexually mature at three years of age, a female at three to six years. The rut begins every 19 to 33 days and initially lasts 2 to 9 days, after the first birth it extends to 9 to 14 days. Mares urinate frequently during the rutting season. A stallion willing to mate first approaches a female with measuring steps, smelling the feces and showing a pleading face . Then he draws attention to himself by pinching, jostling or fighting. A reluctant mare will often kick her hind legs and run away. The foreplay lasts up to 30 minutes. The sexual act takes only 3 to 10 minutes to complete, but is often interrupted for up to 3 hours. During the mating, the stallion rests with his front feet on the shoulders of the mare. The mating usually takes place in the rainy season .
After a gestation period of around 390 days, mostly a single foal is born. The birth usually takes place after the rainy season in August or September, but can also take place all year round. The cub has long ears and slender legs and long-haired, ocher-colored fur with brown stripes. It has a shoulder height of around 90 cm and weighs around 40 kg. It stands for the first time within an average of 14 minutes and begins to suckle milk a little later. Sometimes the mother and young animal join other mares with foals. The foal eats grass very early, after 2 months it already comprises around 40% of the food consumed. This is a much higher proportion than in other horse species, whose foals do not consume the same amount of grass until they are 5 months old. A young Grevy's zebra drinks water for the first time at the age of 3 months. At around four months of age, the short-haired coat develops with the black and white stripes of the old animals. After about a year and a half, the young animal is independent. The somewhat faster youthful development phase, especially the deviating development of food intake and sucking and drinking behavior, is explained by the adaptation of the Grevy's zebra to very dry areas. The maximum age in captivity was 22 years.
Interaction with other animal species
The predators of Grevy's zebra are lions , leopards , spotted hyenas and wild dogs . However, an adult Grevy's zebra can defend itself well against these animals with kicks, which occasionally leads to the death of the attacker. Young animals can also fall prey to cheetahs or crocodiles . The Grevy's zebra also lives partly sympathetically with the plains zebra, in Ethiopia partly also with the African donkey . Furthermore, there is some overlap with large animals used for agriculture.
Parasites
Numerous parasites are known in Grevy's zebra. The most external ones include lice and mites that cause mange , such as burial mites and ticks . It is noteworthy that the Grevy's zebra is not attacked by tsetse flies and is therefore not infected with sleeping sickness . Internal parasites include gastric dassels , which mainly lay their eggs in the stomach. Furthermore, there are nematodes , especially of the subclass Spiuria , which attack the lungs. The trichostrongyle and esophagostomy are particularly common among them . Tapeworms are also known. Anthrax , tetanus , herpes virus infections and rinderpest have been observed among dangerous diseases . Anemia as a result of poisoning can also occur in animals in captivity , as is known from the North American red maple .
Systematics
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Internal systematics of the genus Equus according to Jónsson et al. 2014
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The Grevy's zebra is a member of the genus Equus , which includes today's modern horses. The zebra form belongs to the group of stenonine or non-caballine horses within this genus. These are characterized by the special shape of the lower molars. The Grevy's zebra still belongs to its own subgenus Dolichohippus . Other synonyms that are no longer in use today are Sterrohippus , Kraterohippus and Kolpohippus . Some DNA analyzes show a close relationship to the plains zebra, while the mountain zebra is a little further out. The donkey and the wild horse also form outer groups. The relationships within the individual horse species have not yet been fully clarified. No subspecies are distinguished within the Grevy's zebra.
In earlier historical times the Grevy's zebra was widespread as far as Egypt and North Africa. Specimens of the Grevy's zebra were shown in the Colosseum of Rome by the then Roman emperor Caracalla (211 to 217 AD). At that time it was called Hippotigris (tiger horse), a name that is used today as a subgenus name for the steppe and mountain zebra. After that the knowledge of this zebra shape was lost. It was not known again until the 17th century when the Ethiopian King Assaghedus of Shewa sent three animals to the Ottoman Sultan. Menelik II , also King of Shewa and Emperor of Abyssinia , sent a Grevy's zebra to Jules Grévy , the then President of France . However, the animal died during the journey, was stuffed and exhibited in the Muséum national d'histoire naturelle in Paris . It served the French zoologist Émile Oustalet in 1882 as the basis for the first description , the name Grevyzebra is an honorary designation for the then President of France.
The first stenonine horses are recorded in Africa in the Pliocene , from them the zebras and the African donkey developed. An early representative, similar to Grevy's zebra, was Equus numidicus from the Old Pleistocene , which has been documented from northern to northeastern to eastern and southern Africa. Possibly it developed from the older Equus oldowayensis of East Africa. Another older form is represented by Equus capensis from South Africa. The Cape zebra reached roughly the size of today's Grevy's zebra, but was not as dependent on grass forage as it did. The Grevy's zebra itself was first detected around 500,000 years ago. Significant finds from the Holocene come from the Dakhleh Oasis in Egypt and date to the Neolithic there .
Threat and protection
Grevy's zebras were hunted to show off their attractive fur and because they were thought to be food competitors for cattle. However, Grevy's zebras eat particularly hard types of grass, which are rather indigestible for cattle. Further threats are a reduction in the distribution area due to the expansion of human settlements and economic areas and the associated poorer access to water. In the 1960s, the population still comprised around 15,000 animals. Today 1,970 to 2,440 animals are accepted. Between 1988 and 2007 alone, the population declined by over 50%. Larger stocks only live in Kenya , where effective protective measures have been adopted. 1,500 to 2,100 animals are suspected here. It is assumed that there has been a slight recovery in the population in recent years; locally, however, a decline in individual populations must also be expected. In addition, due to overlapping with the distribution area of the plains zebra, hybrid formations can occur, which in part has an influence on the population development. In Ethiopia , the population may be less than 130 animals, but a slight increase is expected here too. However, the population has almost collapsed, falling 94 percent since the 1980s. In Somalia , the Grevy's zebra has now been almost or completely wiped out. The Grevy's zebra is an endangered species and is protected by the Washington Convention on the Protection of Species ( CITES ). The IUCN lists it as endangered ("seriously threatened").
The Grevy's zebra is officially protected in both Ethiopia and Kenya. Ethiopian protected areas include the Alledeghi Game Reserve , the Yabello Conservation Area and the Chalbi Conservation Area , the Kenyan Meru and Shaba National Park and the Buffalo Springs and Samburu National Reserves . A small group of 30 animals was introduced into Tsavo East National Park . In Kenya, the Grevy's zebra is also found in private protective facilities and sometimes outside the borders of the protected areas. Further protective measures include observations in the wild or making food and water reserves accessible. Around 600 Grevy's zebras are kept in zoos around the world.
literature
- CS Churcher: Equus grevyi. Mammalian Species 453, 1993, pp. 1-9
Individual evidence
- ↑ a b c d e f g h i j k l m n o p C. S. Churcher: Equus grevyi. Mammalian Species 453, 1993, pp. 1-9
- Jump up ↑ Vera Eisenmann and Michel Baylac: Extant and fossil Equus (Mammalia, Perissodactyla) skulls: a morphometric definition of the subgenus Equus. The Norwegian Academy of Science and Letters. Zoologica Scripta, 29, 2000, pp. 89-100
- ^ A b c Patricia D. Moehlman, DI Rubenstein and F. Kebede: Equus grevyi . In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. last accessed on February 23, 2013
- ↑ Geoffrey L. Lelenguyah1, Callistus KPO Ogol and Paul K. Muoria: Historical distribution and threats to Grevy's zebra (Equus grevyi) in Samburu - an indigenous people perspective. African Journal of Ecology 49, 2010, pp. 258-260
- ↑ a b Siva R. Sundaresan, Ilya R. Fischhoff, Helen M. Hartung, Patrick Akilong, and Daniel I. Rubenstein: Habitat choice of Grevy's zebras (Equus grevyi) in Laikipia, Kenya. African Journal of Ecology 46 (3), 2007, pp. 359-64.
- ^ Siva R. Sundaresan, Ilya R. Fischhoff and DI Rubenstein: Male harassment influences female movements and associations in Grevy's zebra (Equus grevyi). Behavioral Ecology 18 (5), 2007, pp. 860-865
- ^ A b c Patricia D. Moehlman: Status and Action Plan for the Grevy's zebra (Equus grevyi). In: Patricia D. Moehlman (Ed.): Equids: Zebras, Asses, and Horses: Status Survey and Conservation Action Plan . IUCN / SCC Equid Specialist Group, IUCN (The World Conservation Union), Gland, Switzerland and Cambridge, 2002, pp. 11-27
- ^ Joshua R. Ginsberg and DI Rubenstein: Sperm competition and variation in zebra mating behavior. Behavioral Ecology and Sociobiology 26, 1990, pp. 427-434
- ^ C. Dustin Becker and Joshua R. Ginsberg, Mother-infant behavior of wild Grevy's zebra: adaptations for survival in semidesert East Africa. Animal Behavior 40, 1990, pp. 1111-1118.
- ↑ Paul K. Muoria, Philip Muruthi, Daniel Rubenstein, Nicholas O. Oguge and Elephas Munene: Cross-sectional survey of gastro-intestinal parasites of Grevy's zebras in southern Samburu, Kenya. African Journal of Ecology 43, 2005, pp. 392-395
- ↑ AS Blunden, KC Smith, KE Whitwell and KA Dunn: Systemic Infection by Equid Herpesvirus-1 in a Grevy's Zebra Stallion (Equus grevyi) with Particular Reference to Genital Pathology. , Journal of Comparabel Pathology 119, 1998, pp. 119, 485-493
- ↑ Paul K. Muoria, Philip Muruthi, Waititu K. Kariuki, Boru A. Hassan, Dominic Mijele and Nicholas O. Oguge: Anthrax outbreak among Grevy's zebra (Equus grevyi) in Samburu, Kenya. African Journal of Ecology 2007, 45, pp. 483-489
- ↑ Martha Weber and R. Eric Miller: Presumptive Red Maple (Acer rubrum) Toxicosis in Grevy's Zebra (Equus grevyi). Journal of Zoo and Wildlife Medicine 28 (1), 1997, Pharmacology and Toxicology, pp. 105-108
- ↑ a b Hákon Jónsson, Mikkel Schubert, Andaine Seguin-Orlando, Aurélien Ginolhac, Lillian Petersen, Matteo Fumagallic, Anders Albrechtsen, Bent Petersen, Thorfinn S. Korneliussen, Julia T. Vilstrup, Teri Lear, Jennifer Leigh Myka, Judith Lundquist, Donald C. Miller, Ahmed H. Alfarhan, Saleh A. Alquraishi, Khaled AS Al-Rasheid, Julia Stagegaard, Günter Strauss, Mads Frost Bertelsen, Thomas Sicherheitsitz-Ponten, Douglas F. Antczak, Ernest Bailey, Rasmus Nielsen, Eske Willerslev and Ludovic Orlando: Speciation with gene flow in equids despite extensive chromosomal plasticity. PNAS 111 (52), 2014, pp. 18655-18660
- ↑ Ann Forstén: Mitochondrial DNA time-table and the evolution of Equus: comparison of molecular and paleontological evidence. Annales Zoologici Fennici 28, 1992, pp. 301-309
- ↑ Ludovic Orlando, Jessica L. Metcalf, Maria T. Alberdi, Miguel Telles-Antunes, Dominique Bonjean, Marcel Otte, Fabiana Martin, Véra Eisenmann, Marjan Mashkour, Flavia Morello, Jose L. Prado, Rodolfo Salas-Gismondi, Bruce J. Shockey, Patrick J. Wrinn, Sergei K. Vasil'ev, Nikolai D. Ovodov, Michael I. Cherry Blair Hopwood, Dean Male, Jeremy J. Austin, Catherine Hänni, and Alan Cooper: Revising the recent evolutionary history of equids using ancient DNA . PNAS 106, 2009, pp. 21754-21759
- ↑ Samantha A. Price and Olaf RP Bininda-Emonds: A comprehensive phylogeny of extant horses, rhinos and tapirs (Perissodactyla) through data combination. Zoosystematics and Evolution 85 (2), 2009, pp. 277-292
- ↑ Thomas M. Kaiser and Tamara A. Franz-Odendaal: A mixed-feeding Equus species from the Middle Pleistocene of South Africa. Quaternary Research 62 (3), 2004, pp. 316-323
- ↑ Raymond L. Bernor, Miranda J. Armor-Chelu, Henry Gilbert, Thomas M. Kaiser and Ellen Schulz: Equidae. In: Lars Werdelin and William L. Sanders (eds.): Cenozoic Mammals of Africa. University of California Press, 2010, pp. 685-721
- ↑ Raymond L. Bernor, Omar Cirilli, Advait M. Jukar, Richard Potts, Maia Buskianidze and Lorenzo Rook: Evolution of Early Equus in Italy, Georgia, the Indian Subcontinent, East Africa, and the Origins of African Zebras. Frontiers in Ecology and Evolution 7, 2019, p. 166, doi: 10.3389 / fevo.2019.00166
- ↑ Belinda Low, Zeke Davidson, Guy Parker, Siva Sundaresan, Martha Fischer and Peter Lalampaa: Reassessing the status of Grevy's zebra (Equus grevyi), and other large mammals in the Marsabit region of northern Kenya. Preliminary report, 2010 ( PDF )
- ↑ JE Cordingley, SR Sundaresan, IR Fischhoff, B. Shapiro, J. Ruskey and DI Rubenstein: Is the endangered Grevy's zebra threatened by hybridization? Animal Conservation 12, 2009, pp. 505-513
Web links
- Equus grevyi in the endangered Red List species the IUCN 2012. Posted by: Equid Red List Authority, 2008. Accessed February 23, 2013.