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Aonyx capensis

Aonyx capensis

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Placentalia
Ordo: Carnivora
Subordo: Caniformia
Familia: Mustelidae
Subfamilia: Lutrinae
Genus: Aonyx
Species:
A. capensis
Subspecies: A. capensis congicus - A. capensis capensis - A. capensis hindei - A. capensis meneleki - A. capensis microdon - A. capensis philipssi

Name

Aonyx capensis Schinz, 1821

Vernacular names
Internationalization
Dansk: Afrikansk fingerodder
English: African Clawless Otter
Svenska: Klolös utter

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The African Clawless Otter (Aonyx capensis), also known as the Cape Clawless Otter or Groot Otter, is the second largest freshwater species of otter. African Clawless Otters are found near permanent bodies of water in savannah and lowland forest areas. They range through most of sub-Saharan Africa, except for the Congo basin and arid areas.[2] They are characterized by partly webbed and clawless feet, from which their name is derived.

Taxonomy

Aonyx capensis is a member of the weasel family (Mustelidae) and of the Order Carnivora. The earliest known species of otter, Potamotherium valetoni, occurred in the upper Oligocene of Europe: A. capensis first appears in the fossil record during the Pleistocene.[3] Aonyx is closely related to the extinct giant Sardinian otter, Megalenhydris.

Subspecies

Mammal Species of the World lists six subspecies of Aonyx capensis:[1]

* Aonyx capensis capensis (Schinz, 1821)
* Aonyx capensis hindei (Thomas, 1905)
* Aonyx capensis meneleki (Thomas, 1903)
* Aonyx capensis congica (sic) (Lönnberg, 1910)
* Aonyx capensis microdon (Pohle, 1920)
* Aonyx capensis philippsi (Hinton, 1921)

However some authorities[2][3] consider the Congo/Cameroon Clawless Otter to be a separate species (A. congicus). Under this view, only the first three of the above list would be subspecies of A.capensis.

Description

African Clawless Otters have thick, smooth fur with an almost silky underbelly. Chestnut in color, they are characterized by white facial markings that extend downward towards their throat and chest area. Paws are partially webbed with five fingers, and no opposable thumbs. All lack claws except for digits 2, 3, and 4 of the hind feet. Their large skull is broad and flat, with relatively small orbits and a short rostrum. Molars are large and flat, used for crushing of prey. Adults are 4-5' in length including tail, weighing 30-70 lbs.

Habitat

African Clawless Otters can be found anywhere from open coastal plains, to semiarid regions, to densely forested areas. Surviving mostly in southern Africa, the otters live in areas surrounding permanent bodies of water, usually surrounded by some form of foliage. Logs, branches, and loose foliage greatly appeal to the otter as this provides shelter, shade and great rolling opportunities. Slow and rather clumsy on land, they build burrows in banks near water, allowing for easier food access and a quick escape from predators. In the False Bay area of the Cape Peninsula they have been observed scavenging along beaches and rocks and hunting in shallow surf for mullet. They are mainly nocturnal in urban areas and lie up during the day in quiet bushy areas.

Reproduction

Females give birth to litters containing 2-5 young around early spring. Mating takes place in short periods throughout the rainy season in December. Afterwards, both male and females go their separate ways and return to a solitary life once more. Young are raised solely by the females. Gestation lasts around 2 months (63 days). Weaning takes place between 45–60 days, with the young reaching full maturity around one year of age.

Diet

The diet of Aonyx capensis primarily includes water dwelling animals such as crabs, fish, frogs, and worms. They dive after prey to catch it, then swim to shore again where they eat. Their hands come in handy as searching devices and are great tools for digging on the muddy bottoms of ponds and rivers, picking up rocks and looking under logs. Extremely sensitive whiskers (vibrissae) are used as sensors in the water to pick up the movements of potential prey.

Behavior

Though mostly solitary animals, African clawless otters will live in neighboring territories of family groups of up to 5 individuals. Each still having their own range within that territory, they mostly keep to themselves unless seeking a mate. Territories are marked using a pair of anal glands which secrete a particular scent. Each otter is very territorial over its particular range.

Awkward on land but acrobats in the water, these animals spend their days swimming and catching food. They return to underground burrows for safety, cooling or a nice rub down using grasses and leaves. Mainly aquatic creatures, their tails are used for locomotion and propel them through the water. They are also used for balance when walking or sitting upright.

Predation

Quick in the water and burrowing on land, A. capensis doesn’t have many predators. Their greatest threat comes from the python, which will often lay in wait near or in the water. Other predators would include the crocodile and fish eagles. If threatened, a high pitched scream is emitted to warn neighboring otters and confuse a predator.

Thermoregulation

Living in Africa, circumstances can become very hot. Staying cool means spending time in the water, and also using burrows as a way to escape the highest temperatures of the day. African clawless otters use their watery surroundings as a way of cooling down. During the day, they are usually found underground in their burrows to escape the highest temperatures. To stay warm on the other hand, the otters depend solely on their thick fur. Guard hairs cover the body acting as insulate. Since the otter lacks an insulating layer of body fat, their only means of warmth is provided by their thick coats of fur.

Economic Impact

The biggest threat imposed on African clawless otters comes from humans. Aonyx will often forage in man-made fisheries and may be hunted or become entangled in nets. Over-fishing by humans may reduce the food supply available to otters. They are sometimes hunted for their thick soft pelts, which humans use in forms of clothing. In forested areas, logging may be a major threat since erosion leads to greatly increased turbidity in rivers which can in turn greatly reduce the populations of fish on which the otters depend. This may well be a far greater threat to otters than hunting.

Conservation

Often hunted for their soft pelts, or killed by local competitive fishermen. The Otter Trail, is a hiking trail in South Africa named after the African Clawless Otter, which is found in this area. Otters along the trail are protected, as the trail falls within the Tsitsikamma National Park.

References

1. ^ a b Wozencraft, W. Christopher (16 November 2005). "Aonyx capensis". In Wilson, Don E., and Reeder, DeeAnn M., eds. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press, 2 vols. (2142 pp.). ISBN 978-0-8018-8221-0. OCLC 62265494. http://www.bucknell.edu/msw3/browse.asp?id=14001078.
2. ^ a b c Hoffmann, M. (2008). Aonyx capensis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2. Downloaded on 2 Aug 2010.
3. ^ a b Larivière, Serge (5 June 2001). "Aonyx Capensis". Mammalian Species 671: 1–6. http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/671_Aonyx_capensis.pdf.

* Michael J. Somers and Jan A. J. Nel. 2004. Habitat selection by the Cape clawless otter (Aonyx Capensis) in rivers in the Western Cape Province, South Africa, African Journal of Ecology 42: pg 298-305.
* Michael J Somers. 2000 Foraging Behavior of Cape Clawless Otters (Aonyx Capensis) in a marine habitat., Journal of Zoology, 252: pg 473-480.

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