Southern Grant Gazelle

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Southern Grant Gazelle
Southern Grant Gazelle (Nanger granti) in the Masai Mara

Southern Grant Gazelle ( Nanger granti ) in the Masai Mara

Systematics
without rank: Forehead weapon bearer (Pecora)
Family : Horned Bearers (Bovidae)
Subfamily : Antilopinae
Tribe : Gazelle-like (antilopini)
Genre : Mirror Gazelles ( Nanger )
Type : Southern Grant Gazelle
Scientific name
Nanger granti
( Brooke , 1872)

The southern Grant's gazelle ( Nanger granti ) is a species from the genus of the mirror gazelles within the family of horned gazelles . It occurs in East Africa , mainly in northwestern Tanzania and southwestern Kenya , and lives in open savannah landscapes . It is a large representative of the gazelles . Characteristic features can be found in addition to the strikingly curved horns, among other things, in the laterally wedge-shaped light body spot. Social life is complex and consists of varying herd groups of different gender compositions plus solitary male individuals. The animals feed mainly on hard grass and soft plant parts. Reproduction takes place all year round, and a mother usually only gives birth to one young. The Southern Grant Gazelle was scientifically introduced in 1872. Originally, all Grant's gazelles were considered to belong to one species. Genetic studies from the beginning of the 21st century divided these into three independent lines. The entire population of Grant's gazelles is considered safe.

features

Southern Grant Gazelle in Ngorongoro Crater

The southern Grant's gazelle is a comparatively large species of gazelle. It reaches a head-trunk length of 134 to 153 cm in males and around 127 cm in females, plus a 27 to 34 cm long tail. The shoulder height is 84 to 94 cm in males and 75 to 83 cm in females. Accordingly, the weight of male individuals varies between 58 and 81.5 kg and that of women between 38 and 67 kg. The back as well as the sides are colored red-brown, the belly side and additionally the inner sides of the limbs appear whitish. Other white spots appear on the throat and back of the trunk. The latter, called " mirror ", extends over the base of the tail, is undivided and wedges something into the body at the sides. Additional narrow black and vertical stripes separate the reddish-brown basic color from the white spot. The underside of the tail and the bushy tail end are also black. The upper side of the tail is white and differs from the reddish brown of the Eastern Grant's gazelle ( Nanger petersii ). In this case, the hull patch is also divided. A horizontal band runs along the sides, although this is not very pronounced in males as in females. In contrast, the males of the Northern Grant's gazelle ( Nanger notata ) have a more prominent shoulder. The head sits on a strong neck. A black stripe frames the eyes on the face, and a dark, triangular spot covers the nose. The pre-eye glands are small. The ears are 16 to 18.5 cm long. Horns occur in both sexes. They are strongly curled and designed more gracefully in females than in males. Their shape is roughly reminiscent of a lyre , at first they rise steeply on the head, then bend clearly to the side and point backwards with the tip. The length is 50 to 80 cm in males and 30 to 45 cm in females. The horn tips are 26 to 66 cm apart.

distribution and habitat

The southern Grant's gazelle is found in East Africa . The distribution area extends from Lake Elmenteita in the East African Rift eastwards via Nairobi to the Tsavo West National Park , due to individual spreading movements, the gazelle species can also be found in the west of the Tsavo East National Park . In the southwest, the habitat includes the Serengeti ecosystem. The animals live in open, dry savannah landscapes , but sometimes also in more closed habitats , where they mostly use bushy valleys. They may also be found in cooler high altitudes. As a rule, the Southern Grant's gazelle does not tolerate soft soils.

Way of life

Territorial behavior

Southern Grant Gazelle in the Serengeti

The social behavior of the Southern Grant Gazelle is complex. Different herd structures form the basic stock, but they are relatively unstable in themselves. Herds of all-female animals comprise an average of 6.1 individuals, while harems, including one dominant male, have an average of 9.6 individuals. Bachelor groups of only males consist of an average of 4.6 individuals. Mixed associations of both male and female animals can sometimes become large and include an average of 46.5 individuals, the upper limit can be 400 and more. In the latter case, there are congregations of several associations that disintegrate again within a few hours. In addition, individual bucks also appear, which then show territorial behavior. All known herd structures of the Southern Grant's gazelle are larger in more wooded landscapes than in the open savannah. In contrast to this, the mixed groups in more closed areas are smaller and consist of only around a dozen to a maximum of 40 animals. In general, the mixed associations in the Serengeti make up about half of all herd forms, in more wooded landscapes they decrease to about 12% and the harems dominate with around a third of the herds. Variations can also be found over the year. The group size of the herds decreases in the rainy season, at the same time the territoriality of the male animals increases. In the dry season, the territoriality decreases again, while at the same time the mixed associations increase.

The bachelor groups of males include young and older bucks. There is an age-dependent hierarchy within the group. The animals fight numerous sparring fights with each other. During the migration of the bachelor group, the dominant male runs behind the subordinate individuals, the same applies to the harems. The territorial bucks occupy areas from 2.5 to 10 km² in size. In the Serengeti they reach a diameter of 1 to 2 km, in the Ngorongoro Crater they are 300 to 600 m. They are located in the tail areas of the larger herd groups, which extend to up to 20 km². Within this a herd makes daily migrations to the different feeding and resting places. She covers around 10 km a day, the train marches in a row. The action spaces can overlap with those of other herds at the borders, which also enables individual individuals to change groups. If, on the other hand, a territorial buck leaves his territory to move with a herd, he gains the status of a bachelor. On the other hand, a male of a harem can drive away the territorial goat and become territorial himself. In more wooded areas, all-female groups with young animals often stay in the area of ​​a territorial goat for several months, they then function as the harem of the occupier. In regions with large herd migration, such as the Serengeti, the goats' territories are largely unstable. The boundaries are defined by special landscape marks and are usually marked with urine or feces . In contrast to numerous other gazelles such as the Thomson gazelle, the only small pre-eye gland of the southern Grant's gazelle does not play a role in marking the territory . Males express claims to territory by wiping their horns through the grass. In addition, they present themselves on raised areas in a sideways position with their heads held high and swinging back and forth, showing their strong neck muscles; especially the swinging head movement is unusual for gazelles. They hold this position for up to a quarter of an hour. In territorial fights, the opponents slowly circle each other several times at a distance of up to 10 m and then come together with lowered horns up to 3 m. Then they crank their heads and present their throat patch. In almost half of the cases one of the opponents gives up, in about a quarter of the cases there is a fight. This consists of a ring competition in which the horns are wedged together.

The southern Grant gazelle often occurs simultaneously with the various representatives of the Thomson gazelles. Similar to these, the Southern Grant's gazelle makes annual migrations in the open landscapes of the Serengeti. However, these are partly opposite to those of the other large herbivores in the region. The animals mainly occupy dry landscapes, which may reduce competition. The Southern Grant's Gazelle is usually the last to leave a certain area during the migration.

Diet and energy balance

The diet of the Southern Grant's Gazelle consists of mixed feeding and consists of both hard grasses and softer parts of plants. The quality of the food is therefore dependent on the seasons; the proportion of soft vegetable food generally increases in the rainy season. Over the entire year, female animals get their food from the region around Arusha in Tanzania according to analyzes of stomach contents 69% from soft and 27% from hard vegetation. In male animals, the proportion of soft plant components is slightly higher at around 86%. The typical diet of the southern Grant's gazelle is also reflected in isotope analyzes . Due to the adaptation to a dry landscape, the animals hardly need any drinking water and they can do without water for a long time.

The Southern Grant's Gazelle is adapted to extremely dry conditions. At high external temperatures, the body temperature can rise to 46.5 ° C and exceed the ambient temperature by 0.5 to 2 ° C. Body heat flows from the inner to the outer region, avoiding panting or sweating and thus additional water loss due to surface evaporation on the skin.

Reproduction

Reproduction occurs all year round, but there is a higher birth rate from December to February and from August to September. The first phase falls in the short rainy season, the second in the dry season. Signs of willingness to mate in female animals can be found, among other things, in a rigid tail. Bucks follow rutting females in a typical posture with their tails raised and noses raised, and they utter stuttering sounds. The goat often tries to bypass the male, pushing back intrusive males. The goats are driven through the buck at moderate speed; when the female flees, the male rarely follows, but it occasionally tries to block the way with a sideways posture. Sometimes the male expresses a typical flehmen , which causes a provoked urine output in the female. In around four fifths of all cases, the male then stops making contact. The sexual act is repeated several times, with the male standing on its hind legs.

The gestation period lasts 198 to 199 days. One young is born at a time, twin births are not known. The offspring are hidden in the bushes. The mother animal calls the young with a bleating sound and nodding head to suckle. Sometimes several females meet to suckle their young. Young females reach sexual maturity with 420 to 450 days, with males it takes almost twice as long. Under certain circumstances, however, females can give birth to their own offspring after around 210 to 290 days. Life expectancy in the wild is unknown; animals in captivity can live up to 19 years.

Predators and parasites

The most important predators of the southern Grant's gazelle are lions , cheetahs , leopards and African wild dogs . However, the species only accounts for a small proportion of the predators' prey . This can possibly be attributed to the rare frequent use of water points, which are among the most important hunting grounds for predators. Young animals are sometimes provided by the African gold wolf and the black-backed jackal . Individual individuals of the latter predators are able to ward off the dams relatively well, and occasionally other animals in purely female herds are also helpful in repelling them.

Well-known external parasites include various types of ticks such as Rhipicephalus and Ornithodoros , while internal ones mainly include worms . It is noteworthy that territorial bucks are more infested with parasites than those who roam in bachelorette groups. Perhaps this is one of the reasons why males switch from territoriality to group life more often. A high parasite infestation causes additional energetic costs, which can then no longer be invested in the defense of the area.

Systematics

Internal systematics of the mirror gazelles according to Bibi 2013
 Nanger  

 Nanger granti type complex


   

 Nanger dama


   

 Nanger soemmerringii




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The Southern Grant's gazelle is a kind from the kind of mirror gazelles ( Nanger ; also called United gazelles) and the family of Bovidae (Bovidae). The genus is counted within the family to the subfamily of the Antilopinae , here it is in the tribe of the gazelle-like (Antilopini). The mirror gazelles are characterized by their relatively larger body shape from the other, closely related representatives of the genera Gazella , Eudorcas and Antelope , with which they form a closer family group within the Antilopini. Further differences can be found in the design of the back spot, the so-called " mirror ", which is wedged laterally in the Nanger species and according to which the genus bears its common German name . The nasal mirror does not go back as far as with Gazella , but further than with Eudorcas . A trend towards a reduction in the coat pattern can also be seen. From a skeletal anatomical point of view, the comparatively long skull, the poorly developed fore-eye region and individual other features of the horns and the dentition can be used.

Internal systematics of the Grant gazelle species complex according to Lorenzen et al. 2008
 Nanger granti type complex  

 Nanger petersii


   

 Nanger granti


   

 Nanger notata




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In most classifications the mirror gazelles addition to Grant's gazelles are assigned to two other types: the soemmerring's gazelle ( Nanger soemmerringii ) and the Dama Gazelle ( Nanger at that ). Consistent in numerous molecular genetic studies, the latter two are closer, while the Grant's gazelles form the sister group. However, individual analyzes see the Grant gazelles more closely related to the Sömmerring gazelle. For a long time, the Grant gazelles were considered to be members of a single species. This was known in German as " Grant gazelle " and scientifically under the binomial Nanger granti . The species contained several subspecies, of which the Eastern and Northern Grant's gazelle with the respective scientific names N. g. petersii or N. g. notata were the most famous. In 2008, molecular genetic studies revealed that Grant's gazelles form three monophyletic lines, of which at least two (the Southern and Northern Grant's gazelles) showed no intermingling. Because of this, the authors of the study recommended that both lines be treated as separate species, and they suspected the same for the Eastern Grant's gazelle due to its geographical isolation and significant morphological differences. Accordingly, the Grant gazelles form a species complex . In a revision of the ungulates in 2011, Colin P. Groves and Peter Grubb raised the three lines of Grant's gazelles to the species level. Over time, other authors followed this assessment.

In some cases, further subspecies are distinguished within the Southern Grant's Gazelle:

  • N.g. granti ( Brooke , 1872); Nominate form from the larger part of the distribution area; with lyre-like horns that span between 26 and 48 cm
  • N.g. robertsi ( Thomas , 1903); northwestern Tanzania and southwestern Kenya immediately east of Lake Victoria ; more curved horns with spans from 34 to 66 cm

While the Northern and the Eastern Grant Gazelle can be separated from the Southern Grant Gazelle well according to genetic data, this does not apply to N. g. robertsi . Although some research results suggest a separation of the southern Grant's gazelle into a western ( N. g. Robertsi ) and an eastern ( N. g. Granti ) population, this has not yet been clearly proven, for example by a characteristic geographical distribution of the Haplotypes .

Graphic representation of the Southern Grant Gazelle from the first description by Victor Brooke in 1872

The first scientific description of the Southern Grant Gazelle was in 1972 by Victor Brooke . It is based on individuals collected by James Augustus Grant and John Hanning Speke on their expedition to search for the sources of the Nile between 1860 and 1863 near Ugogo in Tanzania. These had been shipped to London together with a letter from Speke, but the copies were lost; only Speke's letter with drawings of the horns and the head reached the destination. The letter was published in 1863 and also contained the drawing. Speke suspected a new species in this, but saw a close relationship with the Sömmerring gazelle. On their return to London, Grant and Speke gave Brooke some color drawings they had made of the gazelle shape. Brooke took this as an opportunity to scientifically introduce the Southern Grant Gazelle. With the specific epithet granti Brooke honored the African explorer Grant and pointed out that Speke with the Spekegazelle already acted as namesake. The form N. robertsi was established in 1903 by Oldfield Thomas as a subspecies of the Southern Grant's gazelle. Thomas was referring to two skulls with significantly more curved horns from Mwanza on the south bank of Lake Victoria in northwestern Tanzania.

Threat and protection

Currently, the IUCN does not differentiate the Grant gazelles according to their distinct species. The nature conservation organization sees the total population of Grant gazelles as "not threatened" ( least concern ) due to their wide distribution . However, only 25% of the population is considered stable while the rest are in decline. Threats to the population can be found in hunting for food or as a trophy and in the loss of habitat due to the expansion of agricultural land. Estimates for the Southern Grant Gazelle assume around 75,000 individuals, of which the largest population with possibly around 26,000 animals lives in the Serengeti . Other significant protected areas in which the Southern Grant Gazelle occurs are Tarangire National Park , Masai Mara National Park , Nairobi National Park and Amboseli National Park .

literature

  • Colin P. Groves and David M. Leslie Jr .: Family Bovidae (Hollow-horned Ruminants). In: Don E. Wilson and Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 2: Hooved Mammals. Lynx Edicions, Barcelona 2011, ISBN 978-84-96553-77-4 , p. 635
  • Hans R. Siegismund, Eline D. Lorenzen and Peter Arctander: Nanger (granti) Grant's Gazelle Species Group. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume VI. Pigs, Hippopotamuses, Chevrotain, Giraffes, Deer and Bovids. Bloomsbury, London, 2013, pp. 373-379

Individual evidence

  1. a b c d e f g h Colin P. Groves and David M. Leslie Jr .: Family Bovidae (Hollow-horned Ruminants). In: Don E. Wilson and Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 2: Hooved Mammals. Lynx Edicions, Barcelona 2011, ISBN 978-84-96553-77-4 , p. 635
  2. a b c d e f g h i j k l Hans R. Siegismund, Eline D. Lorenzen and Peter Arctander: Nanger (granti) Grant's Gazelle Species Group. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume VI. Pigs, Hippopotamuses, Chevrotain, Giraffes, Deer and Bovids. Bloomsbury, London, 2013, pp. 373-379
  3. a b c Fritz R. Walther: Behavioral Studies on the Grant's Gazelle (Gazella Granti Brooke, 1872) in the Ngorongoro Crater. Zeitschrift für Tierpsychologie 22 (2), 1965, pp. 167-208
  4. ^ A b Richard D. Estes: The Comparative Behavior of Grant's and Thomson's Gazelles. Journal of Mammalogy 48 (2), 1967, pp. 189-209
  5. ^ Fritz R. Walther: Social Grouping in Grant's Gazelle (Gazella Granti Brooke 1827) in the Serengeti National Park. Zeitschrift für Tierpsychologie 31 (4), 1972, pp. 348-403
  6. Thure E. Cerling, John M. Harris and Benjamin H. Passey: Diets of East African bovids based on stable isotope analysis. Journal of Mammalogy 84 (2), 2003, pp. 456-470
  7. ^ C. Richard Taylor: Strategies of temperature regulation: effect on evaporation in East African ungulates. American Journal of Physiology 219 (4), 1970, pp. 1131-1135
  8. C. Richard Taylor: Dehydration and heat: effects on temperature regulation of East African ungulates. American Journal of Physiology 219 (4), 1970, pp. 1136-1139
  9. Lynette A. Hart and Benjamin L. Hart: Species-Specific Patterns of Urine Investigation and Flehmen in Grant's Gazelle (Gazella granti), Thomson's Gazelle (G. thomsoni), Impala (Aepyceros melampus), and Eland (Taurotragus oryx). Journal of Comparative Psychology 101 (4), 1987, pp. 299-304
  10. G. Hoffmann, G. Köhler and R. Sachs: Contribution to the knowledge of the tick fauna of the wild animals of the Serengeti. Acta Tropica 27 (3), 1970, pp. 193-207
  11. Vanessa O. Ezenwa and Matthew H. Snide: Reciprocal relationships between behavior and parasites suggest that negative feedback may drive flexibility in male reproductive behavior. Proceedings of the Royal Society B283, 2016, S. 20160423, doi: 10.1098 / rspb.2016.0423
  12. a b Fayasal Bibi: A multi-calibrated mitochondrial phylogeny of extant Bovidae (Artiodactyla, Ruminantia) and the importance of the fossil record to systematics. BMC Evolutionary Biology 13, 2013, p. 166
  13. Jürgen Lange: A contribution to the systematic position of the mirror gazelles (Genus Gazella Blainville, 1816 Subgenus Nanger Lataste, 1885). Journal for Mammalian Science 36, 1971, pp. 1-18
  14. ^ A b Colin Groves and Peter Grubb: Ungulate Taxonomy. Johns Hopkins University Press, 2011, pp. 1–317 (SS 160–161)
  15. ^ Colin P. Groves: Genus Nanger Greater gezelles. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume VI. Pigs, Hippopotamuses, Chevrotain, Giraffes, Deer and Bovids. Bloomsbury, London, 2013, pp. 372-373
  16. ^ A b c Eline D. Lorenzen, Peter Arctander and Hans R. Siegismund: Three reciprocally monophyletic mtDNA lineages elucidate the taxonomic status of Grant's gazelles. Conservation Genetics 9, 2008, pp. 593-601
  17. Alexandre Hassanin, Frédéric Delsuc, Anne Ropiquet, Catrin Hammer, Bettine Jansen van Vuuren, Conrad Matthee, Manuel Ruiz-Garcia, François Catzeflis, Veronika Areskoug, Trung Thanh Nguyen and Arnaud Couloux: Pattern and timing of diversification of Cetartiodactalia, Lauriala (Mammia ), as revealed by a comprehensive analysis of mitochondrial genomes. Comptes Rendus Palevol 335, 2012, pp. 32-50
  18. Halina Cernohorska, Svatava Kubickova, Olga Kopecna, Miluse Vozdova, Conrad A. Matthee, Terence J. Robinson and Jiri Rubes: Nanger, Eudorcas, Gazella, and Antilopeform a well-supported chromosomal clade within Antilopini (Bovidae, Cetartiodactyla). Chromosoma 124, 2015, pp. 235-247
  19. Juan P. Zurano, Felipe M. Magalhães, Ana E. Asato, Gabriel Silva, Claudio J. Bidau, Daniel O. Mesquita and Gabriel C. Costa: Cetartiodactyla: Updating a time-calibrated molecular phylogeny. Molecular Phylogenetics and Evolution 133, 2019, pp. 256-262
  20. ^ Eva Verena Bärmann, Gertrud Elisabeth Rössner and Gert Wörheide: A revised phylogeny of Antilopini (Bovidae, Artiodactyla) using combined mitochondrial and nuclear genes. Molecular Phylogenetics and Evolution 67 (2), 2013, pp. 484-493
  21. ^ John Hanning Speke: Letter from, relating to the zoology of Eastern Africa. Proceedings of the Zoological Society of London, 1963, pp. 1-6 ( [1] )
  22. ^ Victor Brooke: On a supposed new species of gazelle from Eastern Africa. Proceedings of the Zoological Society of London, 1872, pp. 601-602 ( [2] )
  23. Oldfield Thomas: Exhibition of, and remarks upon, the horns of a new form of Grant's Gazelle, proposed to be nemaed Gazelle granti robertsi. Proceedings of the Zoological Society of London, 1903, pp. 119–121 ( [3] )
  24. ^ IUCN SSC Antelope Specialist Group: Nanger granti. The IUCN Red List of Threatened Species 2016: e.T8971A50186774. ( [4] ); last accessed on May 24, 2019

Web links

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