Pygmy otter shrew

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Pygmy otter shrew
Systematics
Superordinate : Afrotheria
without rank: Afroinsectiphilia
Order : Tenrecus (Afrosoricida)
Family : Otter shrews (Potamogalidae)
Genre : Small otter shrews ( Micropotamogale )
Type : Pygmy otter shrew
Scientific name
Micropotamogale lamottei
Heim de Balsac , 1954

The pygmy otter shrew ( Micropotamogale lamottei ), also known as the little otter shrew , is a small species of mammal from the family of otter shrews (Potamogalidae). It occurs only in the West African Nimbabergen , in the border area of Liberia , the Ivory Coast and Guinea and at two other points a little southeast and northeast of it. Tropical rainforests , which are interspersed with streams and swamp areas, serve as the habitat . The animals are good swimmers and can dive for long periods of time. The diet is based on crustaceans and fish . The semi-aquatic way of life of the dwarf otter shrew is also expressed through its otter-like appearance. The fur is shiny and the head is characterized by strikingly large whiskers . Due to its thin tail with a rounded cross section and the lack of webbed membranes, the species is not quite as well adapted to aquatic life as the Ruwenzori otter shrew. The species was first described in 1954. The stock is considered to be potentially endangered.

features

Habitus

The pygmy otter shrew is a small mammal that looks similar to otters . After a total of fifteen examined animals from the Ivory Coast , the head-trunk length is 12.0 to 15.5 cm and the tail length 9.5 to 13.4 cm. The tail has around 77% of the length of the rest of the body. The weight varies from 32 to 95 g. Three other animals from Liberia had a body length of 13.5 to 15.1 cm and a tail length of 10.9 to 11.1 cm. The two larger individuals were males and weighed 60 to 68 g. In general, females are built somewhat smaller than males. The fur is dark gray-brown in color, the belly side not lighter than the sides and back. The very dense undercoat consists of about 6500 to 8000 hairs per square centimeter, which is noticeably more than that of the Ruwenzori otter shrew ( Micropotamogale ruwenzorii ). The top hairs have a silky sheen, which is caused by flattened tips. The hair is up to 11 mm long on the back, and up to 15 mm near the tail. Their bases usually show a whitish gray tint, the tips are blackish brown. Due to the lack of pigments, individual hairs have colorless tips, which gives the fur a silvery sheen, which is more noticeable when dry than when it is wet. Such hairs occur increasingly at the transition from the peritoneum to the hairless hands and feet and on the underside of the head, and also on the base of the tail. The tail itself shows the same coloration at the base as the rest of the body, after about 1.5 cm the hair becomes stiffer and, at 5 mm, significantly shorter. It then has a darker color on the top than on the underside. In general, the tail has a round cross-section, the circumference at the base is 25 mm. It is therefore noticeably thinner than that of the Ruwenzori otter shrew. He also lacks the typical horn scales that occur in the latter.

The high muzzle with the stiff vibrissae is striking on the head. These are arranged in up to a dozen rows on either side of the upper lip, creating a beard-like fringe of hair. They increase in length towards the rear, the longest whisker hair becomes 28 mm long. Other vibrissae appear above the eyes and on the lower jaw. The leathery nose mirror is characteristic of otter shrews . In the dwarf otter shrew it becomes 6.2 to 6.5 mm long and 4.8 to 5 mm high. The nostrils are above behind the nasal mirror and can be closed if necessary. The ears show a rounded shape, with a length of 9 to 12.5 mm they only protrude slightly from the fur. In contrast, the eyes are rather small, the eyeball is only 1.5 mm in diameter. The limbs are short and sturdy; the hands and feet each consist of five rays. Of these, the first and fifth rays are the same length and significantly shorter than rays two to four. The second and third rays of the feet typically form a unit for otter shrews and are fused together (syndactyl) . In contrast to the Ruwenzori otter shrew, there are no webs between the toe rays . The entire rear foot becomes 19 to 21 mm long. Females have four pairs of teats , two in the chest and one each in the abdomen and groin.

Skull and dentition features

The skull reaches a length of 32.4 to 38.1 mm and a width at the cranium of around 16 mm. It is generally elongated and narrow, the zygomatic arch does not form a closed arch. Males have on average more robust skulls than females, they are equipped with a crest in the former as well as a stronger occipital bulge. The dentition consists of 40 teeth with the following dental formula together: . As with all otter shrews, the first upper and second lower incisors are each enlarged and resemble canine teeth . Both act as opponents in grabbing the prey. The enlarged root of the upper first incisor causes the snout of the pygmy otter shrew to be greatly raised. The following teeth, including the canine and the anterior premolars, are simple in design, but the last incisor (I3) and the anterior premolar (P2) in the upper dentition are greatly reduced in size. The molars have a typical zalambdodontic occlusal surface pattern. The last upper molar is made smaller. The upper row of teeth is 14.2 to 16.2 mm long.

distribution

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

The pygmy otter shrew is endemic to western Africa and inhabits a small area in the Nimbabergen in the border area of Liberia , the Ivory Coast and Guinea . In addition, it has been found from the Putu Mountains southeast and from the Sérédou region northwest of the Nimbab Mountains, both Liberia. The entire distribution area is narrowly limited, the individual sites are distributed over an area of ​​57,400 km² with a maximum distance of 380 km from one another. The actually inhabited area covers around 10,850 km², 14,725 km² or 22,540 km², depending on the source. The preferred landscape areas consist of hilly, wooded areas interspersed with small moats, streams and swampy areas. The animals use both primary and secondary rainforests , and they also occur in agricultural areas, for example on cocoa or coffee plantations or on rice fields. In an investigation between 2013 and 2015 on the terra typica of the species, the Nimbabergen, most of the animals were found at an altitude of 449 to 651 m, the average annual precipitation here is 2000 mm. The population density is rather low. In the Nimbabergen, an average of one animal per 10 km² is caught in fishing nets.

Way of life

Territorial behavior

So far, only limited data are available on the lifestyle of the pygmy otter shrew. The animals are nocturnal as well as solitary and probably behave territorially. In captivity, individual couples lived together for several months without aggression. They inhabit the banks of streams and rivers or swampy terrain. The individual individuals often prefer bodies of water around 27 cm deep, rarely shallower, which may be related to the presence of prey. The pygmy otter shrew is an excellent swimmer and diver, even if it is not as well adapted to the water as the Ruwenzori otter shrew or the great otter shrew ( Potamogale velox ) due to the lack of webbed feet and the round and thin tail . Possibly it is more of a generalist with a broader ecological niche. When swimming, the winding movements of the tail and body provide propulsion, the limbs are only used occasionally. The paddling then takes place with the diagonally opposite legs at the same time, thus reminding of the cloister on land. To hunt prey in the water, the animals undertake dives that usually only last for a short time. However, the pygmy otter shrew can dive for up to 15 minutes. The upper limit is high for relatively small animals. Experiments with individuals living in captivity showed that staying under water for such a long time usually occurs in the event of external disturbances and that the animals seek protection at the bottom of the water. The duration of the dives can probably be controlled by slowing down the metabolism . Searching for shelter underwater is rather unusual, as other semi-aquatic mammals flee into the water, but go to the land to breathe in order to avert further danger. The dense fur is intensively cared for by the dwarf otter shrew. In addition to licking, this is also done by cleaning with the syndactyl toe of the rear foot. During their forays almost a dozen individuals equipped with radio transmitters overcame between 113 and 649 m (373 m on average) per night, which is only about half the distance that the distantly related water trek covers every day. Their swimming speed was 12.2 to 55.1 m / h. The pygmy otter shrew mostly stays near the water and does not move further inland.

nutrition

The main food of the pygmy otter shrew consists of crabs , often of the genus Sudanonautes , and catfish . In addition, the remains of water-dwelling insects , ants and frogs were found in the stomach contents examined . In captivity, the animals also ate mussels and worms , but largely spurned smaller mammals. The food is mainly found with the very sensitive vibrissae both in the water and on land. The pygmy otter shrew brings captured crabs ashore and attacks them from behind, which reduces the risk of being cut by the claws. She then breaks the crab at the junction between the cephalothorax and the abdomen . An animal can eat 40 to 70 g of food per day, which is roughly equivalent to its body weight.

Reproduction

Births have so far rarely been observed in the pygmy otter shrew; a few could be studied in animals in captivity in the 1970s. Among other things, a female gave birth to a litter 51 days after being captured. The litter size is one to four young. The newborns are naked and blind. They get their first hair growth at eleven days and are fully hairy at 20 days of age. The eyes open after 23 days and the boys eat their first solid food around 40 days. One animal in captivity lived about 18 months.

Parasites

Mites of the genus Orycteroxenus appear as external parasites . The internal parasites include roundworms such as the genus Molineus .

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 pygmy otter shrew is a species from the genus of the small otter shrews ( Micropotamogale ), which also includes the Ruwenzori otter shrew ( Micropotamogale ruwenzorii ). Together with the great otter shrew ( Potamogale velox ) they form the family of otter shrews (Potamogalidae). The otter shrews only occur in equatorial Africa and are adapted to a semi-aquatic way of life. Its characteristic features include the fused second and third toe rays and the zalambdodonte chewing surface pattern of the molars. They represent the closest relatives of the Tenreks (Tenrecidae), which in turn are restricted to Madagascar . According to molecular genetic analyzes, the otter shrews and tenreks separated from each other 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 pygmy otter shrew shows only a few genetic variations between the three known find regions. This speaks for a certain gene flow, at least in the past. However, it is assumed that this is currently prevented by the current isolation of the three populations .

The first scientific description was carried out in 1954 by Henri Heim de Balsac . For this he had a not fully grown individual with an indeterminable gender. The animal came from Ziéla at the foot of the Nimbaberge in Guinea , where it had already been caught in 1951 at around 550 m above sea level. The area is considered a type region of the species. With the new species, Heim de Balsac introduced the genus Micropotamogale , which he separated from Potamogale on the basis of body size and the shape of the tail and the nasal mirror . He named his new species in honor of the French zoologist Maxime Lamotte , who discovered the holotype specimen during an expedition in 1951. Until the mid-1960s, only young animals of the dwarf otter shrew were known. Only with two fully grown animals from the Nimbabergen was Hans-Jürg Kuhn able to provide a more detailed description of the species in 1964.

Threat and protection

The habitat of the pygmy otter shrew is mainly threatened by mining . Parts of the Nimbaberge in Liberia and Guinea have already been destroyed as a result of the mining of iron ore . The same goes for the Putu Mountains. Another threat factor is the deforestation of the rainforests and the conversion of the land into rice fields . The increased fishing also has a negative impact on stocks. Overall, the population density has decreased significantly. Whereas in the 1970s individual animals were spotted near localities, the distance to human settlements in the 1990s was around 3 to 5 km. According to the IUCN , the range of the species is very limited, but more extensive than originally assumed. Therefore, the conservation organization lists the Nimba Otter Shrew in the "near threatened" ( near threatened ), in 2008 it was still considered "high risk" ( endangered ). Some researchers advocate categorization in a higher protection status, as the species has an extremely low population density. The animals can be found in the Réserve naturelle intégrale du Mont Nimba , a 17.5 km² UNESCO World Heritage Site in the border area of ​​Liberia and the Ivory Coast . The protective effect is not very strong, however, as the reserve borders directly on a mining region and the local population has a negative impact through artificially created fires and poaching. In addition, the region is currently attracting little interest from independent nature conservation organizations.

literature

  • Jonathan Kingdon: The Kingdon Pocket Guide to African Mammals. 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 (p. 178) ISBN 978-84-16728-08-4 .
  • Peter Vogel: Micropotamogale lamottei Nimba Otter-shrew (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. 217-218.

Individual evidence

  1. ↑ a b c d e f g Peter Vogel: Micropotamogale lamottei Nimba Otter-shrew (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. 217-218.
  2. ↑ a b c d e f g Hans-Jürg Kuhn: On the knowledge of Micropotamogale lamottei. Zeitschrift für Mammalskunde 29, 1964, pp. 152-173.
  3. ↑ a b c Hans-Jürg Kuhn: An Adult Female Micropotamogale lamottei. Journal of Mammalogy 52 (2), 1971, pp. 477-478.
  4. ^ WN 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.
  5. ↑ a b c d Ch. Guth, Henri Heim de Balsac and M. Lamotte: Recherches sur la morphologie de Micropotamogale lamottei et l'evolution des Potamogalinae. I. Ecology, denture, anatomy cranienne. Mammalia 23, 1959, pp. 423-447.
  6. ↑ a b c d e f g 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. 178) ISBN 978-84-16728-08-4 .
  7. ↑ 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.
  8. ↑ a b c d J. Decher, CR Gray, JC Garteh, CW Kilpatrick, HJ Kuhn, B. Phalan, A. Monadjem, B. Kadjo, F. Jacquet and C. Denys: New Evidence of the Semi-Aquatic Nimba Otter Shrew (Micropotamogale lamottei) at Mount Nimba and in the Putu Range of Liberia - Uncertain Future for an Evolutionary Distinct and Globally Endangered (EDGE) Species in the Face of Recent Industrial Developments. Journal of Contemporary Water Research & Education 157, 2016, pp. 46–57.
  9. ↑ Luigi Boitani, Iacopo Sinibaldi, Fabio Corsi, Alessio De Biase, Ilaria d'Inzillo Carranza, Maria Ravagli, Gabriella Reggiani, Carlo Rondinini and Patrizia Trapanese: Distribution of medium- to large-sized African mammals based on habitat suitability models. Biodiversity and Conservation 17, 2008, pp. 605-621.
  10. ↑ a b c d Ara Monadjem, Jan Decher, Wing-Yunn Crawley and Robert A. McCleery: The conservation status of a poorly known range-restricted mammal, the Nimba otter-shrew Micropotamogale lamottei. Mammalia 83 (1), 2019, pp. 1-10
  11. ↑ a b c Peter J. Stephenson: Micropotamogale lamottei. The IUCN Red List of Threatened Species 2016. e.T13393A21287657 ( [1] ); last accessed on August 25, 2017.
  12. ↑ a b c d e Ara Monadjem: Conservation Status of the Nimba Otter Shrew Micropotamogale lamoteii (Afrosoricida) within the ArcelorMittal Concession. Western Range Iron Ore Project, Liberia Biodiversity Conservation Program 2011–2015, 2013, pp. 1–17.
  13. ^ A b Peter Vogel: Contribution a l'écologie et a la zoogéographie de Micropotamogale lamottei (Mammalia, Tenrecidae). Revue d'Ecologie (Terre Vie) 38, 1983, pp. 37-49.
  14. ↑ Peter Vogel: Highlights and disappointments during 40 years of research on otter-shrews. Afrotherian Conservation 10, 2014, pp. 9-11.
  15. ↑ Alex Fain, Fritz S. Lukoschus and Gisela Rack: Notes on Parasitic Mites from some Small Mammals in Liberia. Messages from the Hamburg Zoological Museum and Institute 71, 1974, pp. 165–174.
  16. ^ Claude Vaucher, Marie-Claude Durette-Desset and Jean-Pierre Hugot: Molineus eburneus n. Sp. (Nematoda: Trichostrongyloidea), parasite de Micropotamogale lamottei Heim de Balsac. Bulletin de la Société Neuchâteloise des Sciences Naturelles 102, 1979, pp. 49-53.
  17. ↑ 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 .
  18. ^ Henri Heim de Balsac: Un genre inédit et inattendu de Mammifére (Insectivore Tenrecidae) d'Afrique Occidentale. Comptes rendus hebdomadaires des séances de l'Académie des sciences 239, 1954, pp. 102-104 ( [2] ).

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