Ruwenzori otter shrew

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Ruwenzori otter shrew
Systematics
Superordinate : Afrotheria
without rank: Afroinsectiphilia
Order : Tenrecus (Afrosoricida)
Family : Otter shrews (Potamogalidae)
Genre : Small otter shrews ( Micropotamogale )
Type : Ruwenzori otter shrew
Scientific name
Micropotamogale ruwenzorii
( de Witte & Frechkop , 1955)

The Ruwenzori otter shrew ( Micropotamogale ruwenzorii ), also known as the middle otter shrew , is a small species of mammal from the family of the otter shrew (Potamogalidae) that occurs only in central Africa west of the East African rift . It lives in a small area from the Ruwenzori Mountains on the border between the Democratic Republic of the Congo and Uganda to the west bank of Lake Kiwu . There it occurs in tropical rainforests and mountain forests with streams and swamps. The animals are very well adapted to a life in the water due to their otter-like physique with strikingly large whiskers and a powerful tail. Unlike the other otter shrews, they have webbed fingers and toes and swim with paddling movements of the limbs. The main diet consists of invertebrates and smaller vertebrates , otherwise very little is known about the way of life of the Ruwenzori otter shrew. The species was described in 1955. Some scientists assign them to the independent genus Mesopotamogale . The stock is currently not considered endangered.

features

Habitus

The Ruwenzori otter shrew is slightly larger than the dwarf otter shrew ( Micropotamogale lamottei ) and, based on around two dozen individuals, reaches a head-torso length of 13 to 20 cm, a tail length of 12.3 to 15 cm and a weight of 75 to 135 g. The tail is about 84% of the length of the rest of the body. In general, the animals are characterized by an otter-like external appearance, the body is more compact than the other otter shrews. The soft fur has a dark brown to gray-brown color on the back, the belly appears gray, light brown or whitish. It consists of a very dense undercoat of gray, brown-tipped hair. About 5000 to 6500 hairs are formed on every square centimeter, which is not quite as dense as that of the pygmy otter shrew. The outer hairs are characterized by short, firm awns, which are up to 15 mm long on the body. The tips are flattened and create a silky sheen. On the feet, on the upper face and on the tail, however, the hair is significantly shorter at 1 to 4 mm. Similar to the body, the bulwark has a darker upper and lighter underside, and individual scales are randomly distributed, which are missing in the dwarf otter shrew. At the base, in contrast to that of the dwarf otter shrew, with a circumference of 35 mm, the tail is significantly more massive; it is also slightly flattened on the sides and thus highly oval in cross-section. But towards the end it becomes round.

The head is characterized by a flat snout. Eyes and ears are very small, the rounded ears protrude only slightly from the fur with a length of 10 to 14 mm. The leathery, heart-shaped nose mirror , which is divided in two by a vertical central furrow, is striking . The snout is covered with numerous, very long whisker hairs. On the upper lip in particular, they are arranged in up to a dozen rows of six to nine vibrissae, creating a beard-like hairline. The whiskers can be up to 18 mm long. The limbs are short and end in five rays in front and behind. The first and fifth fingers or toes are about the same length, they are significantly elongated compared to the other otter shrews, but form the shortest rays as with these. In contrast, the rays two to four on the hands and feet are generally longer. In contrast to the other two species, the individual rays are connected to one another by webbed feet, and there is also a line of stiff, bristly hair on the outer and inner edges. In addition, the palms and feet reach larger dimensions compared to the other otter shrews. The second and third toes are typically fused together for all otter shrews ( syndactyl ). The entire rear foot is 26 to 29 mm long.

Skull and dentition features

The skull of the Ruwenzori otter shrew reaches a total length of 33.8 to 39.4 mm and a maximum width measured at the cranium of 15.5 to 17.8 mm. Typically, there is no closed zygomatic arch , and a strong crest is formed on the parietal bone . The dentition consists of 40 teeth, the dental formula is: . As with all otter shrews, the first upper and second lower incisors are significantly enlarged and are reminiscent of canines , but the enlargements are not as advanced as in the dwarf otter shrew. The two incisors work together as opponents in the acquisition of prey. The subsequent teeth in both the upper and lower row of teeth including the canine and the anterior premolars are simple in design. The third upper incisor (I3) and the first upper premolar (P2) do not show quite as great reductions in size as in the dwarf otter shrew. The molars show a typical zalambdodontic occlusal surface pattern. The last molar of the upper row of teeth is noticeably reduced in size, even more clearly than that of the pygmy otter shrew. The entire upper row of teeth measures 17.7 to 18.5 mm in length.

distribution

Distribution area of ​​the Ruwenzori otter shrew (green)

The Ruwenzori otter shrew is endemic to central Africa . The distribution area is located west of the East African Rift and extends from Lake Kivu north to the western slopes of the Ruwenzori Mountains in the east of the Democratic Republic of the Congo . The species may also be found on the eastern slope of the mountain range in Uganda , but so far there are no clear indications. Another occurrence is in the Nyungwe Forest in Rwanda . The animals live on moats, streams and swamps in the tropical rainforests at an altitude of 800 to 900 m and in mountain forests up to an altitude of 2200 m. They have also been found in gallery forests of larger rivers with bordering savannah areas and altitudes of around 1000 to 1200 m. So far only a few individuals have been observed, the individual sites spread over an area of ​​around 72,000 km². The great otter shrew ( Potamogale velox ) also appears sympatric in the region.

Way of life

Territorial behavior

The way of life of the Ruwenzori otter shrew is little researched. The animals usually appear at night and then have several alternating phases of activity and rest. They retreat to self-built shelters on the banks of the water to rest. These are mostly located in dense vegetation and have a nest-like chamber at the end in which the animals sleep curled up on their side. The Ruwenzori otter shrew is well adapted to aquatic life thanks to its large webbed hands and feet. In the water it moves with paddling movements, the lateral bristle border on the edges of the hand and foot serve to enlarge the paddle surface. When swimming slowly, the front and rear legs are used alternately; when swimming quickly, the animals repel each other with all four limbs. The latter usually only takes place over short distances. Likewise, dives are always short. Like the great otter shrew and the pygmy otter shrew , the Ruwenzori otter shrew in the water makes meandering movements with the body and the tail, but these support swimming less strongly than with the first two. In addition, the rather round tail does not act as a control organ, unlike the great otter shrew with its clearly flattened tail. In the water, speeds of around 1.8 km / h are reached. The animals are also comparatively nimble on land, with the hind feet often stepping into the treads of the front feet. After each watering, the Ruwenzori shrew dries its fur by grazing through bushes and grasses. She also spends a lot of time grooming her, often scratching with her hind feet. The manure is usually deposited in certain places, this may serve as a kind of marking of the area.

nutrition

The animals feed on worms , insects , crustaceans , small fish and frogs . Depending on the food available, they prefer worms and insects. These are eaten directly in the water, which usually only takes a few seconds and is sometimes accompanied by a strong shake of the head. The Ruwenzori otter shrew brings larger prey to land and eats them there. These include crabs, often members of the Potamonautes genus , and fish such as predatory catfish and various carp fish . Above all, crabs are preyed from behind to avoid the claws and are eaten starting at the post abdomen. The size of the prey that can be captured is limited by the size of the mouth, so that those with a carapace of more than 5 cm are avoided. Only the mouth is used for all food intake, the prey is not manipulated with the front legs. An animal weighing around 135 g can eat 80 g of food in one night.

Reproduction

Not much is known about reproduction. A female examined carried two embryos of 45 mm crown-anus length, 22 mm head length and 32 mm tail length. The webbed feet and vibrissae were already developed, but the rest of the body hair was completely missing.

Parasites

So far, mites of the genus Gahrliepia and ticks of the genus Ixodes have been identified as external parasites . The latter usually only occur in common with the great otter shrew.

Systematics

Internal systematics of the otter shrews according to Everson et al. 2016
 Tenrecomorpha  
 Potamogalidae  
 Micropotamogale  

 Micropotamogale lamottei


   

 Micropotamogale ruwenzorii



   

 Potamogale



   

 Tenrecidae



Template: Klade / Maintenance / Style

The Ruwenzori otter shrew is a species from the genus of the small otter shrews ( Micropotamogale ), which also contains the dwarf otter shrew ( Micropotamogale lamottei ). Together with the great otter shrew ( Potamogale velox ), both species form the family of otter shrews (Potamogalidae). The otter shrews are restricted to equatorial Africa and live semi-aquatic. Characteristic features can be found in the fused second and third toe rays and in the zalambdodontic chewing surface pattern of the molars. The closest relatives of the otter shrews are the Tenreks (Tenrecidae), which in turn only occur in Madagascar . According to molecular genetic analyzes, the otter shrews and the tenreks separated from one another in the Lower Eocene around 48.3 million years ago. The two species of small otter shrews split up in the Lower Miocene about 16.3 million years ago.

The first scientific description of the Ruwenzori otter shrew was carried out in 1955 by Gaston-François de Witte and Serge Frechkop under the name Potamogale ruwenzorii . It was carried out using three individuals that had been collected in February 1953 by de Witte on the western slope of the Ruwenzori massif. The holotype is a male and comes from the Talya River near Mutsora. The region, which belongs to the Virunga National Park in the Democratic Republic of the Congo , is located at an altitude of 1200 m and is to be regarded as a type area of ​​the species. De Witte, who was then head of Albert National Park (now part of Virunga National Park), sent his first captured specimen to Brussels, where Frechkop inspected it, but believed it was a juvenile of the great otter shrew. Only one more specimen convinced him that he was looking at a new species. At first no living specimen was known. It was only at the beginning of the 1960s that Urs Rahm was able to study the behavior of the Ruwenzori otter shrew on a captured individual. At this point in time, the known distribution area expanded considerably with new catches.

Only a year after the first description led Henri de Balsac home with Mesopotamogale a new generic name for the Ruwenzori Otter Shrew. He justified this with the formation of webbed hands and feet and the only slightly flattened tail, which reminded him more of the water trek ( Microgale mergulus ) from Madagascar . Heim de Balsac saw Mesopotamogale in a mediator role between the great otter shrew with its strongly flattened tail and the more generalized dwarf otter shrew with its thin, round cross-section tail. In contrast to the Ruwenzori otter shrew, the two other species lack webbed feet. Partly, this classification has been adopted, other authors saw Mesopotamogale however, due to the general morphological similarity to Nimba Otter Shrew only as a subgenus of Micropotamogale on. However, the formation of webbed feet in the Ruwenzori otter shrew would justify a position in its own genus. Independently of Heim de Balsac, Miklós Kretzoi referred the Ruwenzori otter shrew to the genus Kivugale he had created in 1961 , giving an almost similar reason. Kivugale is currently synonymous with Micropotamogale .

Threat and protection

The greatest threat to the Ruwenzori shrew population is the loss of suitable habitats through deforestation. Added to this are the increasing compaction of the soil structure in the immediate vicinity of the water ( colmation ) and the laying of fish traps in which the animals get caught. On the other hand, it is assumed that the glacier retreat of the high mountains of central Africa as a result of global warming has no direct impact on the population, since most of the water released falls to the earth as precipitation. The IUCN currently classifies the species as “not endangered” ( least concern ), but the narrowly limited range and the few known, highly fragmented occurrences of the Ruwenzori otter shrew would justify a higher endangerment classification. The species is present in several nature reserves, including the Virunga National Park and the Kahuzi-Biéga National Park , both of which are part of the UNESCO World Heritage Site of the Democratic Republic of the Congo , and the Nyungwe Forest National Park in Rwanda . Investigations into the distribution, frequency and ecological demands of the animals are necessary to maintain the population.

literature

  • Jonathan Kingdon: The Kingdon Pocket Guide to African Mammals. A&C Black Publishers Ltd., London, 2004, ISBN 978 0 7136 6981 7 .
  • Ara Monadjem: Potamogalidae (Otter-shrews). 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. 174-179 (pp. 178-179) ISBN 978-84-16728-08-4 .
  • Peter Vogel: Micropotamogale ruwenzorii Ruwenzori Otter-shrew. 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. 218-219.

Individual evidence

  1. ↑ a b W. N. Verheyen: Recherches anatomiques sur Micropotamogale ruwenzorii. 1. La morphologie external, les viscères et l'organe génital mâle. Bulletins de la Société Royale de Zoologie d'Anvers 21, 1961, pp. 1-16.
  2. ^ A b Hans-Jürg Kuhn: On the knowledge of Micropotamogale lamottei. Zeitschrift für Mammalskunde 29, 1964, pp. 152-173.
  3. ↑ a b c d e f g h i Peter Vogel: Micropotamogale ruwenzorii Ruwenzori Otter-shrew. 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. 218-219.
  4. ↑ a b c d e f Ara Monadjem: Potamogalidae (Otter-shrews). 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. 174-179 (pp. 178-179) ISBN 978-84-16728-08-4 .
  5. ↑ Peter Vogel: Genus Micropotamogale Pygmy Otter Shrew. 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. 216-217.
  6. ↑ Erik Thorn and Julian Kerbis Peterhans (with the participation of Jonathan Baranga, Michael Huhndorf, Rainer Hutterer and Robert Kityo): Small mammals of Uganda. Bats, shrews, hedgehog, golden-moles, otter-tenrec, elephant-shrews, and hares. Bonner Zoologische Monographien 55, 2009, pp. 1–164 (pp. 102–106).
  7. ↑ a b U. Rahm: Note sur les spécimens actuellement connus de Micropotamogale (Mesopotamogale) ruwenzorii et leur répartition. Mammalia 24, 1960, pp. 511-515.
  8. ↑ a b c d e f U. Rahm: Observations on the first captive mesopotamogal ruwenzorii (Mammalia-Insectivora). Revue Suisse de Zoologie 68 (4), 1961, pp. 73-90.
  9. ↑ a b Peter J. Stephenson: Micropotamogale ruwenzorii. The IUCN Red List of Threatened Species 2016. e.T13394A21287768 ( [1] ); last accessed on September 2, 2017.
  10. ↑ M. Nadchatram and A. Fain: Description of a new species of Gahrliepia from Zaire (Acari: Prostigmata: Trombiculidae). Revue de Zoologie Africaine 94 (3), 1980, pp. 521-524.
  11. ↑ a b Kathryn M. Everson, Voahangy Soarimalala, Steven M. Goodman and Link E. Olson: Multiple loci and complete taxonomic sampling resolve the phylogeny and biogeographic history of tenrecs (Mammalia: Tenrecidae) and reveal higher speciation rates in Madagascar's humid forests. Systematic Biology 65 (5), 2016, pp. 890-909 doi: 10.1093 / sysbio / syw034 .
  12. ↑ Gaston-François de Witte and Serge Frechkop: Sur une espèce encore inconnue de mammifère africain, Potamogale ruwenzorii, sp. n. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique 31, 1955, pp. 1-11.
  13. ↑ Serge Frechkop: A propos de novelles espèces de Potamogalinés. Mammalia 21, 1957, pp. 226-234.
  14. ^ Henri Heim de Balsac: Morphology divergente des Potamogalinae (Mammifères Insectkivores) en milieu aquatique. Comptes rendus hebdomadaires des séances de l'Académie des sciences 242, 1956, pp. 2257-2258 ( [2] ).
  15. ↑ Ch. Guth, Henri Heim de Balsac and M. Lamotte: Recherches sur la morphologie de Micropotamogale lamottei et l'evolution des Potamogalinae. II. Rachis, viscéris, position systématique. Mammalia 24, 1960, pp. 190-216.
  16. ^ WN Verheyen: Recherches anatomiques sur Micropotamogale ruwenzorii. 4. Observations ostéologiques et considérations générales. Bulletins de la Société Royale de Zoologie d'Anvers 22, 1961, pp. 1-7.
  17. ↑ Miklós Kretzoi: Two or three Potamogaline genera? Vertebrata Hungarica 3 (1/2), 1961, pp. 137-140 ( [3] ).
  18. ↑ Don E. Wilson and DeeAnn M. Reeder: Mammal Species of the World. A taxonomic and geographic Reference. Johns Hopkins University Press, 2005 ( [4] ).

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