Namib short-eared elephant
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Namib shorthaired elephant ( Macroscelides flavicaudatus ) in the Namib |
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| Macroscelides flavicaudatus | ||||||||||||
| Lundholm , 1955 |
The Namib macroscelides proboscideus ( macroscelides flavicaudatus ) or Namib round ear elephant shrew is a mammalian species in the genus Macroscelides within the family of shrews (Macroscelididae). It lives endemically in the Namib desert in western Namibia where it inhabits barren and scree-rich landscapes. For a long time, the Namib short-eared elephant was considered a subspecies of the short-eared elephant ( Macroscelides proboscideus ), which occurs in the Karoo of South Africa. It was not raised to species status until 2012, for which there were both genetic and geographical reasons. Their stock is classified as not endangered.
description
Like other species of the genus Macroscelides, the Namib short-eared elephant has a rounded body and head as well as long, thin legs. The total length is 19.9 to 23.5 cm, the tail takes 9.8 to 13.0 cm. Thus, the tail is about the same length or slightly longer than the rest of the body. The weight varies between 22 and 46 g. In terms of body size, the Namib short-eared elephant is only slightly smaller than the short-eared elephant ( Macroscelides proboscideus ), but significantly larger than the Etendeka short-eared elephant ( Macroscelides micus ). In terms of weight, the Namib short-eared elephant appears slightly lighter with an average of 31 g than M. proboscideus , which weighs 39 g on average. More northern populations of the Namib short-eared elephant are sometimes noticeably larger than more southern populations . The rest of the appearance of the two species differs only slightly from one another. Characteristic is the trunk-like elongated nose that protrudes a few millimeters. The eyes are small, the ears, which are between 20 and 32 mm long, protrude over the head in contrast to the Etendeka short-eared trumpet, but are typically rounded for Macroscelides . Due to the sparse hair, a darkly pigmented skin, comparable to the short-eared elephant, appears on the ears, while the Etendeka short-eared elephant lacks this pigmentation, which makes the skin appear pink. The body fur is dense and soft. The coat color of the Namib short-eared elephant usually has a light, yellowish hue, but sometimes the darker, brown-gray shades of the short-eared elephant also occur. The tail is only sparsely hairy in the front part, towards the back the coat becomes significantly thicker, so that the tail end appears bushy. Scent glands are formed on the underside of the tail, but these are not always visible in the Namib short-eared elephant. If they are externally visible, they reach lengths of 8 to 11 mm, which is less than a tenth of the tail length. The Etendeka short-eared elephant has more pronounced scent glands, the length of which takes up almost a third of the tail. The length of the rear foot, which is reinforced with claws, varies between 32 and 37 mm.
distribution
The distribution area of the Namib short-eared elephant is limited to the western part of Namibia . The species inhabits the areas of the Namib here . The region is characterized by a hot, dry climate with average annual temperatures of 17 to 21 ° C and annual precipitation of 15 to 27 mm. The vegetation is mostly sparse and consists of lichens , the growth of which is encouraged by the frequent coastal fog, as well as grass perennials and bushes of various sizes. The underground consists partly of rubble and rocks. The altitude distribution of the species ranges from sea level up to 1400 m in the southwest of Namibia. The total distribution area covers about 38,000 km². In northern Namibia in the area of the Etendeka plateau , the Namib short-eared elephant appears sympatric with the Etendeka short-eared elephant, but the latter largely uses higher habitats . The short-eared elephant, on the other hand, has a distribution area further south, which mainly includes the semi-deserts of the Karoo and is separated from that of the Namib short-eared elephant by a 50 km wide corridor.
Way of life
In general, the representatives of Macroscelides are twilight-active and move forward quickly, running and sometimes jumping. Their diet is omnivorous , with the majority comprising invertebrates. They enter into monogamous relationships, newborns flee from the nest . Self-dug caves, bushes or boulders serve as shelters, but no special nests are created. Particularly in the barren landscapes such as the Namib, the individual animals' areas of activity can be over a square kilometer. It was observed that the Namib short-eared elephant in areas with very stony subsoil creates clearly straight, sometimes very long paths between boulders or rocky outcrops by clearing away stones with its forefeet.
Systematics
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Internal systematics of elephants according to Heritage et al. 2020
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The Namib short-eared elephant is a species from the genus Macroscelides . Today there are two other species in this genus. Macroscelides is referred to the elephant family (Macroscelididae), a group of smaller mammals native to Africa only . The elephants are divided into two subfamilies. The Rhynchocyoninae only contain the proboscis ( Rhynchocyon ) and are therefore monotypical . They predominantly inhabit forested habitats. The Macroscelidinae next be Macroscelides the elephantulus ( Elephantulus ), the proboscis rat ( Petrodromus ), the Somali elephant shrew ( Galeggeska ) and the North African elephant shrew ( Petrosaltator ) is assigned. These are more adapted to dry open landscapes to desert-like regions. According to molecular genetic studies, Macroscelides is more closely related to Petrodromus and Petrosaltator . The two subfamilies separated in the Lower Oligocene about 32.8 million years ago, the greater diversification of the Macroscelidinae occurred in the Upper Oligocene about 28.5 million years ago. The genus Macroscelides emerged in the Lower Miocene about 19.1 million years ago.
In the first half of the 20th century, the genus Macroscelides was divided into two species with up to 10 subspecies in use. A revision of the genus in 1968 resulted in the short-eared elephant ( Macroscelides proboscideus ) only one species, which was represented by two subspecies. Accordingly, M. p. proboscideus to the Karoo areas in South Africa , which are characterized by darker landscape tones and areas more strongly influenced by shadow. M. p. flavicaudatus, on the other hand, lived in the lighter and sunnier regions of the Namib further north. The sometimes varied fur drawings were seen as an adaptation to local habitat conditions. The occurrence and number of the subspecies was discussed, but the monotypical position of the genus Macroscelides was still valid until the beginning of the third millennium.
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Internal systematics of Macroscelides according to Dumbacher et al. 2014
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Molecular genetic studies carried out at the beginning of the 21st century combined with field research on site showed that the genus Macroscelides forms a diverse group with a diverse number of haplotypes . Accordingly, two groups could be distinguished, one more northerly, that of the subspecies M. p. flavicaudatus , and a more southerly, by M. p. proboscideus represented. According to the genetic studies, both groups had developed independently of one another for a long time. The field investigations also showed that the originally closed distribution area of Macroscelides in the area of the NamibRand nature reserve is interrupted over a width of at least 50 km and that both populations are separated from each other. In the areas of the smallest distance between the two populations, no hybrid forms could still be found, so there was no gene flow . In addition, the representatives of M. p. flavicaudatus in the southernmost distribution areas due to their small size considerably by the northernmost members of the subspecies M. p. proboscideus . Only to the north and further away from the southern population do larger forms of the northern group gradually appear. The different color variants did not turn out to be a pure range of variation of a characteristic, since the northern animals of the Namib were often a lighter color than the southern ones from the Karoo. For all these reasons, John P. Dumbacher , the scientific director of the investigation, and his research colleagues M. p. flavicaudatus in species status, making the Namib short-eared elephant the second recognized species of Macroscelides next to the short-eared elephant . In 2014 a third was added with the Etendeka short-eared elephant ( Macroscelides micus ), which appears regionally sympathetic to the Namib short-eared elephant and is also characterized by a darker coat color.
The first scientific description of the Namib short-eared elephant as a subspecies of the short-eared elephant was already in 1955 by Bengt Lundholm . The description was based on a 22 cm long male that was found 9.6 km from the mouth of the Omaruru River in western Namibia. Lundholm also stated this as a type area. The species name flavicaudatus refers to the yellowish gray tail color ( Latin flāvus for "golden yellow", "blond" and cauda for "tail").
Threat and protection
There are no known major threat factors for the Namib short-eared elephant. The species predominantly inhabits very dry habitats , which are rather unsuitable for human activities. There may be potential for conflict in the vicinity of river and water areas, so a local overprinting of the landscape there by human settlements or agricultural activities cannot be ruled out in the future. Regional mineral extraction can also have a greater influence. The IUCN therefore classifies the species as “not endangered” ( least concern ). It occurs in several nature reserves, including the NamibRand nature reserve and the Skeleton Coast National Park .
literature
- John P. Dumbacher, Galen B. Rathbun, Hanneline A. Smit and Seth J. Eiseb: Phylogeny and Taxonomy of the Round-Eared Sengis or Elephant-Shrews, Genus Macroscelides (Mammalia, Afrotheria, Macroscelidea). Plos ONE 7 (3), 2012, p. E32410
- Stephen Heritage: Macroscelididae (Sengis). In: Don E. Wilson and Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 206-234 (pp. 228-229) ISBN 978-84-16728-08-4
Individual evidence
- ^ A b Bengt G. Lundholm: Descriptions of new mammals. Annals of the Transvaal Museum 22, 1955, pp. 279-303
- ↑ a b c d e John P. Dumbacher, Galen B. Rathbun, Hanneline A. Smit and Seth J. Eiseb: Phylogeny and Taxonomy of the Round-Eared Sengis or Elephant-Shrews, Genus Macroscelides (Mammalia, Afrotheria, Macroscelidea). Plos ONE 7 (3), 2012, p. E32410
- ↑ a b c d e John P. Dumbacher, Galen B. Rathbun, Timothy O. Osborne, Michael Griffin and Seth J. Eiseb: A new species of round-eared sengi (genus Macroscelides) from Namibia. Journal of Mammalogy 95 (3), 2014, pp. 443-454
- ↑ a b c Stephen Heritage: Macroscelididae (Sengis). In: Don E. Wilson and Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 206-234 (pp. 228-229) ISBN 978-84-16728-08-4
- ^ A b Galen B. Rathbun and S. Eiseb: Macroscelides flavicaudatus. The IUCN Red List of Threatened Species. Version 2015.2. ( [1] ); last accessed on July 1, 2015
- ↑ a b Mike Perrin and Galen B. Rathbun: Genus Macroscelides - Round-eared Sengi. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume I. Introductory chapters and Afrotheria. Bloomsbury, London, 2013, pp. 276-278
- ^ Galen B. Rathbun: Why is there discordant diversity in sengi (Mammalia: Afrotheria: Macroscelidea) taxonomy and ecology? African Journal of Ecology 47, 2009, pp. 1-13
- ↑ a b Steven Heritage, Houssein Rayaleh, Djama G. Awaleh and Galen B. Rathbun: New records of a lost species and a geographic range expansion for sengis in the Horn of Africa. PeerJ 8, 2020, p. E9652, doi: 10.7717 / peerj.9652
- ↑ Hanneline Adri Smit, Bettine Jansen van Vuuren, PCM O'Brien, M. Ferguson-Smith, F. Yang and TJ Robinson: Phylogenetic relationships of elephant-shrews (Afrotheria, Macroscelididae). Journal of Zoology 284, 2011, pp. 133-143
- ^ Mike Perrin and Galen B. Rathbun: Order Macroscelidea - Sengis (Elephant-shrews). In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume I. Introductory chapters and Afrotheria. Bloomsbury, London, 2013, pp. 258-260
- ↑ John P. Dumbacher, Elizabeth J. Carlen and Galen B. Rathbun: Petrosaltator gen. Nov., A new genus replacement for the North African sengi Elephantulus rozeti (Macroscelidea; Macroscelididae). Zootaxa 4136 (3), 2016, pp. 567-579
Web links
- Macroscelides flavicaudatus in the endangered Red List species the IUCN 2015 Posted by: Rathbun & Eiseb, 2013. Retrieved on July 1, 2015.