Great otter shrew

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Great otter shrew
Great otter shrew, specimen in the Natural History Museum in London

Great otter shrew, specimen in the Natural History Museum in London

Systematics
Superordinate : Afrotheria
without rank: Afroinsectiphilia
Order : Tenrecus (Afrosoricida)
Family : Otter shrews (Potamogalidae)
Genre : Potamogale
Type : Great otter shrew
Scientific name of the  genus
Potamogale
Du Chaillu , 1860
Scientific name of the  species
Potamogale velox
( Du Chaillu , 1860)

The great otter shrew ( Potamogale velox ) is a species of mammal that, together with the small otter shrews, forms the family of the otter shrews (Potamogalidae), the closest relatives of the Tenreks (Tenrecidae). It represents the largest member of the family and is characterized by an otter-like appearance with thick fur and a long, laterally flattened tail. The beard-like ring of stiff whisker hairs on the upper lip is also striking . The species is endemic to central Africa , where it inhabits the tropical rainforests of the Congo Basin and adjacent areas. Preferred habitats consist of forest areas with small and clear streams, rivers or ponds. The otter shrew is a good swimmer that moves in the water by wiggling its tail sideways, largely without using its limbs. The animals live solitary and nocturnal, the main food consists of fish and crabs . Overall, however, little is known about the way of life of the great otter shrew. The species was scientifically introduced in 1860, due to the incomplete first finds, the exact genus and assignment to a specific animal group was initially unclear. The population is currently not considered endangered, but its significant decline would justify a higher endangerment category.

features

Habitus

The great otter shrew is the largest representative of the otter shrew. It has a head-torso length of 30.5 to 33.7 cm and a tail length of 23.5 to 29.0 cm. The tail thus takes up around 80% of the length of the rest of the body. The body weight is 517 to 780 g, other data amount to 340 to 397 g. Outwardly, the animals have a distant resemblance to otters . Their body is slender and streamlined, the muzzle appears spatulate due to its broad and flattened design. The body is covered by a dense, white undercoat, which consists of 3000 to 3500 hairs per square centimeter. Compared to the small otter shrews ( Micropotamogale ), this is much thinner. This is overlaid by slightly coarse, but overall soft and shiny outer hair. The coat is chocolate to tobacco brown on the head and top, the hair has white bases and brown tips. The whitish color of the undercoat does not shine through the topcoat. On the underside, the animals are colored whitish, the undercoat has a cream-colored tint. The clear separation of the dark top and the lighter bottom is clearly visible on the sides. The tail is flattened on the sides, but very thick at the base, about as high as the trunk. The circumference is about 100 mm. It shows the same coloration as the back. The front quarter is covered with long hair that becomes shorter and tighter towards the back.

A leathery nasal mirror is formed on the muzzle , its heart-shaped outline is divided by a vertical central furrow. The nostrils above the side can be closed by small flaps during diving. On both sides of the upper lip, stiff vibrissae appear in several rows, which form a conspicuous wreath of beard. The individual whiskers reach lengths of up to 70 mm. The eyes are small with a diameter of 2.5 mm. The externally visible auricles are 15 to 23 mm long and have a rounded to elongated shape. The short legs each have five rays on the hands and feet, the outer and inner rays are shorter than the three inner ones. All rays have claws that are pressed and bent on the sides. There are no webs between the individual fingers and toes. As with all otter shrews, the second and third toe rays form a unit ( syndactyl ). There is a fold of skin on the outside edge of the foot. The entire rear foot measures 39 to 46 mm in length. Females have two pairs of teats in the chest area and one each in the abdomen and groin area.

Skull and dentition features

The skull reaches a length of 60.5 to 66.3 mm with a maximum width at the cranium of 25.1 to 27.5 mm. Overall, it is elongated and narrow, the forehead line is straight. There is a noticeable constriction behind the eyes. The nasal bone is clearly stretched and can be up to 21 mm long. The large central jawbone does not protrude beyond the foremost teeth. A low crest is formed on the pair of parietal bones . The zygomatic arches are not as closed at all otter shrews. The lower jaw measures between 40.9 and 41.6 mm in length. The high crown process is striking here, which is over 13 mm high and sits well above the articular process.

Overall, there is a bite of 40 teeth dental formula is: . Both the first upper and the second lower incisor are enlarged, they are reminiscent of canines and act as opponents when grasping the prey. The subsequent teeth, including the canine and the anterior premolars, are simple and roughly the same size. The molars show a zalambdodontic occlusal surface pattern, which is composed of three main cusps: the para-, meta- and protoconus (in relation to the maxillary teeth). The protoconus is well developed; in contrast to the small otter shrews ( Micropotamogale ), the metaconus and paraconus are clearly separated. For this reason, the tooth structure of the great otter shrew is sometimes referred to as primitive zalambdodont to dilambdodont . The paraconus forms the main cusp of the molars. The rearmost upper molar is significantly reduced in size. The upper row of teeth is 29.2 to 32.5 mm long.

distribution and habitat

Distribution area of ​​the great otter shrew (brown)

The great otter shrew is endemic to central Africa . Its distribution area extends from Nigeria east of the Cross River eastwards across the entire Congo Basin to the west of Uganda and south to the north of Angola and Zambia . There is frequent evidence from the east of the Democratic Republic of the Congo , for example from the okapi game reserve , the Ituri rainforest , the Itombwe Mountains and the upper reaches of the Lualaba . An isolated occurrence of the species has been documented from the area around Kakamega in western Kenya . With a few exceptions, the animals inhabit the tropical rainforest zone . The altitude distribution ranges from sea level to mountain regions around 1800 m. Preferred habitats consist of forests with small, slow flowing and clear rivers or streams that are sometimes only 1.5 m wide and 30 cm deep. As a rule, the animals can cope with natural cloudiness of the water as a result of rainfall. In addition, they can be observed in forest ponds and mountain streams, and occasionally also in muddy swamps in relative proximity to clear water. Prerequisites for their presence are banks in which they can dig their nest chambers. As a rule, the animals avoid larger currents, but there have also been sightings of animals from the Ivindo River in Gabon , which is several hundred meters wide. In beneficial habitats there is one individual for every 100 m river length, but the population density is usually lower and includes one animal for 500 to 1000 m river length.

Way of life

Territorial behavior

As with all otter shrews, the way of life of the great otter shrew has also been little researched; individual studies were carried out in Gabon in the 1960s and in Cameroon in the 1980s . The main activity of the animals is limited to the night. In Gabon the animals were active between 8.30 or 9 p.m. until 5.30 a.m. at the latest, in Cameroon they left their shelter between 6.50 p.m. and 7.20 p.m. and also returned around 5.30 a.m. The activities at night are cyclical and are interrupted by several rest periods. The first phase of activity usually lasts the longest at around three hours. During this time, the great otter shrew takes on its main food, it ends with a rest of around an hour. This is followed by a series of active, but shorter phases, which usually last between 15 minutes and an hour and a half. The conclusion is another longer activity phase. During the night the great otter shrew searches rivers up to 800 m in length.

The great otter shrew is adapted to a life in water. She swims with rapid, sideways winding movements. These are initiated by the gluteal muscles (Musculus gluteus) and transferred to the muscular tail. As a result, the swimming style is reminiscent of that of fish or crocodiles . The legs, especially the front ones, are not used for locomotion in the water, but attached to the body, which is unique among mammals. All in all, the animals are quick and effective swimmers who hit numerous hooks in the water. The head stays in line with the body when swimming, but it is sometimes raised. Dives are rather short and usually only last around 10 seconds, they are limited to foraging for food. Frightened or startled animals can jump up to 20 cm high out of the water. Occasionally the animals rest for a short time in the water with their bodies motionless, but they also seek out sandbanks and low banks. On land they move slowly on the soles, longer distances are generally covered over water, and escape usually takes place in the water.

The animals are considered solitary animals that do not come together with other conspecifics except during the mating season. Most of the animals have so far been sighted individually, researchers from Cameroon recorded two animals that swam in the same body of water for around ten minutes. During the day, the great otter shrew can be found in underground burrows that are dug into the bank slopes and are up to 4 m long. Often the burrows are under trees. They have two entrances, one of which leads into the building from the surface of the earth and the other from below the water level. In front of the above-ground entrance there is usually a heap of ejecta. Inside there is a round nest chamber, which is padded with leaves and wood fibers. It serves as a sleeping and resting chamber, the animals mostly rest on their stomachs, rarely curled up on their backs. As a rule, the individual structures are not used for a long time. The great otter shrew may be territorial. For defecation she seeks out special latrines, which consist of small depressions 10 to 15 cm in diameter and 4 to 5 cm deep. The latrines are located on small hills high above the water level and are protected by fallen trees or other natural ways. It is believed that they also mark territorial boundaries. The comfort behavior includes scratching with the syndactyl claws of the rear foot, which often interrupts food intake.

nutrition

The great otter shrew feeds primarily on prey that live in water. Analyzes of stomach contents showed mainly fish , crabs and insects . Among the fish, carp fish , cichlids and catfish such as gill sacs or spiny catfish are particularly preferred. In addition, include subordinated to amphibians like frogs to diet. The great otter shrew mainly uses whiskers and the sense of smell to locate its prey , the eyes play no role. The prey is attacked with bites and thrown to the side, the hands are hardly used to acquire food. The great otter shrew eats small prey up to 10 mm in length head first, larger prey up to 15 cm in length cuts it up from the side. However, it disdains crabs with a carapace of more than 6 to 7 cm. Sometimes it has been observed that the great otter shrew brings its prey ashore and eats it there. A single individual can eat 150 to 200 g of food per night, according to other reports on captured animals it is more than 70 g or 15 to 20 crabs.

The body temperature of a great otter shrew that was actively swimming in the water was 35.2 ° C with a water temperature of 21.1 ° C. In contrast, two animals resting during the day had body temperatures of 29.9 and 31.0 ° C, respectively, with outside temperatures of around 24 ° C. On average, the body temperature of active animals is lower than that of most other higher mammals. The great otter shrew can probably lower its body temperature during the resting phase, comparable to some representatives of the tenreks .

Reproduction

Little is known about reproduction. Four pregnant females were caught in Gabon in the 1960s and carried one or two embryos . Whether the reproduction is seasonally dependent cannot currently be determined; the pregnant females were observed both during the rainy and dry seasons. One of the females was accompanied by two young animals with a total length of 18 to 19 cm. The offspring may remain with the mother until the next litter is born. This suggests that the great otter shrew mate at least twice a year. The natural life expectancy is unknown, most animals kept in captivity died after 9 to 14 days, mostly due to the loss of the water-repellent properties of the fur and a subsequent reduction in body temperature and pollution.

Parasites

External parasites are mainly ticks of the genus Ixodes . Roundworms are known to be internal parasites, such as the genera Molineus , Galeiceps , Parastrongyloides , Procamallanus and Spinitectus . Most of the roundworms use fish and amphibians as intermediate hosts.

Systematics

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

 Micropotamogale lamottei


   

 Micropotamogale ruwenzorii



 Potamogale  

 Potamogale velox



   

 Tenrecidae



Template: Klade / Maintenance / Style

The great otter shrew is a species of the genus Potamogale . The genus is regarded as monophyletic and thus contains only one representative. Together with the small otter shrews ( Micropotamogale ), the great otter shrew forms the family of otter shrews (Potamogalidae). The otter shrews are smaller mammals that are endemic to equatorial Africa . They are adapted to a semi-aquatic way of life. Characteristic features of the family are the overgrown second and third toe rays, the missing collarbone and the zalambdodontic chewing surface pattern of the molars. The tenreks (Tenrecidae) are considered to be the closest relatives of the otter shrews, which in turn are largely only found in Madagascar . According to molecular genetic studies, the separation of the otter shrews and the tenreks occurred in the Lower Eocene around 48.3 million years ago. In the transition from the Upper Eocene to the Lower Oligocene around 33.8 million years ago, the otter shrews split into the two current genus lines. No subspecies of the great otter shrew are distinguished.

Paul Belloni Du Chaillu

The first scientific description of the great otter shrew comes from Paul Belloni Du Chaillu in 1860. He carried it out under the name Cynogale velox and referred the new species to the crawling cats , in the narrower sense of the close relatives of the otter civet , which actually only occurs in Asia . For his description Du Chaillu only had the skin with fur, the skull and the skeleton were destroyed. The specimen had been caught by Du Chaillu himself during an expedition to central Africa, as type locality he gave mountains of the interior, or in the hilly country ... north and south of the equator ("mountains in the interior, or hilly terrain ... north and south of the equator ”). In his publication he presented various new animal species from western Central Africa, today the Ogooué river in Gabon is generally referred to as the terra typica of the great otter shrew. Du Chaillu gave the species name velox because of the rapid swimming movements of the animals in the water, which astonished him (from Latin velox for "fast" or "quickly"). He also emphasized that he would prefer the generic name Potamogale , for which he did not create a definition. Since only the fur was available to him, he left it with Cynogale .

Historical representation of the great otter shrew from 1867 after Barbosa du Bocage

The fur then came to the British Museum in London and was re-examined by John Edward Gray the following year. Gray declined the reference to Cynogale , instead he created the genus Mythomys , which he defined via the fur design and the shape of the tail. According to his assumption, the genus belonged more to the Glires (rodents and rabbits), where he saw similarities with the muskrat ( Ondatra ; he assigned the old synonym fiber ) or the beaver ( Castor ). At the same time, Gray spoke out against the designation Potamogale , since Du Chaillu had not given a characteristic diagnosis. He repeated his position in an essay that appeared almost at the same time, but referred to the new genre as Mystomys . In 1865, José Vicente Barbosa du Bocage analyzed a very well-preserved fur with skeletal parts of an adult female and a fetus from Angola who were in Lisbon. Barboga du Bocage recognized from the now complete set of teeth that it is an insectivore-like animal that most closely resembled the tenreks and shrews from the point of view of skeletal structure . He referred the finds to the genus Bayonia , in his main publication, which appeared two years later, he also published a graphic representation of the animal.

Historical representation of the great otter shrew from 1866 after Allman

In the early 1860s, George James Allman received a complete individual from Nigeria that had been captured by Archibald Hewan near Calabar . Allman, unknown to the species, was made aware of the publications by Du Chaillu and Gray by Philip Lutley Sclater . With the help of the individual, Allman was able to present a complete description of the external characteristics and the skeleton for the first time; the corresponding report was completed in 1863, but did not appear until three years later. Like Barboga du Bocage, he noticed the similarity with other insectivores (in the view of the time). In his critical analysis, Allman highlighted the term Potamogale as valid and referred the genus and species to the independent family of Potamogalidae. He put these to the side of the slot weevils ( Solenodon ) as closest relatives. Before Allman's report was published, Gray turned to him in an open letter and again rejected the name Potamogale . In this repeated Gray's earlier arguments put forward, but also criticized the name creation, as Potamogale his opinion, contrary to the actual relationships a " weasel-like would imply" animal ( Potamogale : Greek ποταμός ( potamos ) for "river" and γαλἑη ( gale ) for "Wiesel"). In his very comprehensive study on the insectivores entitled A monograph of the Insectivora , George Edward Dobson corrected the systematic position of Potamogale in 1883 and classified the great otter shrew as closely related to the Tenreks.

Barbosa du Bocage correctly stated the number of teeth as 40 in his description, Allman on the other hand as 36, he could not identify a canine. Fredericus Anna Jentink therefore renamed the shape from Allman to Potamogale allmani in 1895 and distinguished it from Poatmogale velox by the differences in the structure of the teeth and also by deviations in the color of the fur. Almost ten years later, Guillaume Grandidier also differentiated between animals with 36 and 40 teeth when examining specimens from the Muséum national d'histoire naturelle in Paris. From Oldfield Thomas, on the other hand, comes the name Potamogale velox argens , which he introduced in 1915 based on two animals from the upper reaches of the Congo. He justified the new subspecies with deviations in the color of the fur. New examinations of Allman's individual later showed that the canine was there, but the last molar was not yet formed and so it was obviously a young animal. In addition, over 50 individuals were collected during the American Museum of Natural History's Congo expedition from 1909 to 1915. This brought new knowledge about the range of variation in the great otter shrew. The two forms named later are therefore today synonymous with Potamogale velox .

threat

The greatest threat to the population of the great otter shrew is the loss of habitat due to forest clearing in the course of wood removal or the creation of agricultural land. The associated soil erosion and reduction in water quality due to sediment input leads to a decline in local populations , which is a major problem in Cameroon , for example . In addition, the animals are hunted locally for their fur, while other animals get caught in fish traps. However, it is unknown to what extent this actually affects stocks. Until 1996 the species was considered endangered, since 2006 until today (last status 2015) it has been classified by the IUCN in the category “not endangered” ( least concern ) due to its large distribution area. However, the organization points out that due to the sharp decline in stocks, a higher hazard category is justified. The great otter shrew is present in several nature reserves. Overall, only little information is available on the way of life, habitat needs and distribution in general. The IUCN therefore urges the need for field studies and monitoring programs .

literature

  • 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 (p. 179) ISBN 978-84-16728-08-4
  • Ronald M. Nowak: Walker's Mammals of the World . The Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9
  • Peter Vogel: Genus Potamogale Giant 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. 220–222

Individual evidence

  1. ↑ a b c d e f g h i j k l m n Peter Vogel: Genus Potamogale Giant 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. 220–222
  2. ↑ a b c d e f g h Martin E. Nicoll: The biology of the Giant otter-shrew Potamogale velox. National Geographic Society Research Report 21, 1985, pp. 331-337
  3. ↑ 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
  4. ↑ a b c d Hans-Jürg Kuhn: On the knowledge of Micropotamogale lamottei. Zeitschrift für Mammalskunde 29, 1964, pp. 152-173
  5. ^ A b c George J. Allman: On the characters and affinities of Potamogale, a genus of insectivorous mammals. Transactions of the Zoological Society of London 6, 1866, pp. 1–16 ( [1] )
  6. ↑ a b c d e f g h 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 (p. 179) ISBN 978-84-16728-08-4
  7. ^ A b George Edward Dobson: A Monograph of the Insectivora, systematic and anatomical. Part II. London, 1883, pp. 97-107 ( [2] )
  8. ^ A b Robert J. Asher and Marcelo R. Sánchez-Villagra: Locking Yourself Out: Diversity Among Dentally Zalambdodont Therian Mammals. Journal of Mammalian Evolution. 12 (1/2), 2005, pp. 265-282
  9. ↑ Ch. Guth, Henri Heim de Balsac and M. Lamotte: Recherches sur la morphologie de Micropotamogale lamottei et l'evolution des Potamogalinae. I. Ecologie, denture, anatomie crânienne. Mammalia 23, 1959, pp. 423-447
  10. ^ Wilhelm Leche: On the history of the development of the mammalian tooth system, at the same time a contribution to the tribal history of this group of animals. Part two: phylogeny. Second booklet: Families of the Centetidae, Solenodontidae and Chrysochloridae. Zoologica 20, 1906/1908, pp. 1–157 ( [3] )
  11. ↑ a b c d e f Gérard Dubost: Quelques renseignements biologiques sur Potamogale velox. Biologia Gabonica 1, 1965, pp. 257-272
  12. ^ A b Peter J. Stephenson, Steven M. Goodman and Voahangy Soarimalala: Potamogale velox. The IUCN Red List of Threatened Species 2016. e.T18095A97203526 ( [4] ); last accessed on September 30, 2017
  13. ^ A b Paul Belloni Du Chaillu: Descriptions of new species of mammals discovered in western equatorial Africa. Proceedings of the Boston Society of Natural History 7, 1860, pp. 296-304 and 358-367 (pp. 361-363) ( [5] )
  14. ^ Alain G. Chabaud, Odile Bain and Firmin Puylaert Description de trois nouveau Nématodes Molineinae et considération sur la systématiques et le caractére archaique de cette sous-famille. Bulletin du Muséum national d'histoire naturelle 2ème série 38, 1966, pp. 904–920 ( [6] )
  15. ^ Jean-Pierre Hugot: Description de cinq nouveaux Nématodes d'un Tenrecoidea africain: Potamogale velox du Chaillu. Bulletin du Muséum national d'histoire naturelle 4ème série, section A 4, 1979, pp. 1057-1073
  16. ↑ 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
  17. ^ Paul Belloni Du Chaillu: Explorations and adventures in Equatorial Africa. London, 1861, pp. 1–479 (p. 422) ( [7] )
  18. ^ John Edward Gray: Observations on Mr. Chaillu's paperson "The new species of Mammals" discovered by him in Western equatorial Africa. Proceedings of the Zoological Society of London, 1861, pp. 273-278 ( [8] )
  19. ^ John Edward Gray: Zoological notes on perusing M. Du Chaillu's "Adventures in Equatorial Africa". Annals and Magasin of Natural History 8, 1861, pp. 60–65 ( [9] )
  20. ↑ José Vicente Barbosa du Bocage: Sur quelques Mammifères rares et peu connus, d'Afrique occidentale, qui se trouvent au Muséum de Lisbonne. Proceedings of the Zoological Society of London, 1865, pp. 401–404 ( [10] )
  21. ↑ José Vicente Barbosa du Bocage: Un novo genero de memmiferos d'Africa occidental Bayonia velox (Potamogale velox Du Chaillu). Memorias da Academia Real das Sciencias de Lisboa. Classe de sciencias mathematicas, physicas e naturaes, 1867, pp. 1–19 ( [11] )
  22. ^ John Edward Gray: On the names of the Genus Mystomys (In a letter to Professor Allman). Annals and Magasin of Natural History 16, 1865, pp. 425-428 ( [12] )
  23. ↑ Fredericus Anna Jentink: On Potamogale velox Du Chaillu. Notes from the Leyden Museum 16, 1895, pp. 234–236 ( [13] )
  24. ↑ Guillaume Grandidier: Note on the Potamogale du Muséum de Paris. Bulletin du Muséum d'histoire naturelle 10, 1904, pp. 45–51 ( [14] )
  25. ↑ Oldfield Thomas: List of mammals (exclusive of Ungulata) collected on the Upper Congo by Dr. Christy for the Congo Museum Tervueren. Annals and magazine of natural history 8 (16), 1915, pp. 465–481 ( [15] )
  26. ^ JA Allen: The American Museum Congo expedition collection of Insectivora. Bulletin of the American Museum of Natural History 47, 1922, pp. 1–38 ( [16] )

Web links

Commons : Potamogale velox  - collection of images, videos and audio files