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Aonyx capensisAfrican clawless otter

By Daniel Kowalsky

Geographic Range

Aonyx capensis is the most widely distributed otter species in Africa. Their home range is limited to the African continent, stretching along the coast from South Africa to Ethiopia and across the continent to Senegal. Unlike their close relative Aonyx capensis congica, Aonyx capensis does not occur in the central African rainforest region of the Congo basin. Aonyx capensis and A. capensis congica are sympatric in Uganda and Rwanda. (Hoffmann, 2010; Larivière, 2001)

Habitat

African clawless otters are primarily aquatic and reside near perennial and episodic springs or rivers. Marine populations do occur if a source of freshwater is nearby for drinking. These otters prefer shallow water with thick reed beds, which are home to several favorable prey such as crab and fish. On land, African clawless otters take shelter in underground burrows, under rocks, roots, or dense vegetation. Dens have been found from sea level to 1200 m in elevation. Dens are used for resting, playing, eating, defecating, and giving birth and are shared by multiple otters. African clawless otters have been known to dig burrows in the sand up to 3 m deep, with entrances to the den above and below the water surface. Burrows typically contain a nest made of grass or other vegetation. Dens are never farther than 50 m from shore or 15 m from freshwater. They are usually close to abundant food supplies and densely vegetated areas. African clawless otters do not typically dive farther than 1.5 m below the surface of the water. (Larivière, 2001; Nel and Somers, 2007)

  • Range elevation
    0 to 1200 m
    0.00 to 3937.01 ft
  • Average depth
    1.5 m
    4.92 ft

Physical Description

African clawless otters are the largest Old World otter species and 3rd largest species of otter overall. Their head and body length ranges from 762 mm to 880 mm. Their tail measures 465 mm to 515 mm long and is typically stout and tapered. They weigh between 10 and 22 kg. Males are slightly heavier and longer than females. Their thick shiny coats are colored dark brown except for distinctive white coloring on the upper lips, the sides of the face, neck, throat, belly, and lower ears. Otter pelage consists of two kinds of hair. The outer hairs, or guard hairs, measure up to 25 mm in length. The undercoat, or fur, is white to off-white and is made of short (10 mm), fine, wavy hair. African clawless otters have long white whiskers on their cheeks, chin, and brows, which are used to detect prey in murky waters. They are clawless except for small grooming claws on hind digits 2, 3, and 4. Although their hind feet are partially webbed, they have the least amount of webbing of all otter species. They have nimble forefeet with opposable thumbs. Rough skin lines their palms and fingers and helps to grip slippery prey. African clawless otters have large skulls, measuring 125 to 136 mm in length. They have a broad, flattened brain case and a small sagittal crest. Brain size is large compared to skull size, the rostrum is short and broad, and zygomatic arches are slender. African clawless otters have large molars, specialized for crushing crustaceans and fish skulls, and no cutting teeth. The shape of their molars varies geographically. They possess a pair of anal scent glands are used for scent-marking. Males’ foreskin protrudes from their body but the penis resides beneath their thick skin. Females have two pairs of mammary glands on their abdomen. (Larivière, 2001; Nel and Somers, 2007)

  • Sexual Dimorphism
  • male larger
  • Range mass
    10.6 to 21 kg
    23.35 to 46.26 lb
  • Range length
    730 to 880 mm
    28.74 to 34.65 in

Reproduction

Little is known about the mating system of Aonyx capensis. (Larivière, 2001)

Little is known of the mating system of African clawless otters. Breeding occurs during the dry season, which varies depending on location, and parturition coincides with the beginning of the rainy season. Gestation lasts approximately 63 days. Litters range in size from 1 to 3 pups, but as many as 5 pups per litter have been reported for animals in captivity. At birth, pups weigh about 200 g and can grow to more than 1,400 g within 14 days. Pups are born altricial but open their eyes and leave their den after 16 to 30 days, and weaning occurs by 45 to 60 days after birth. They become independent and sexually mature by 1 year old. (Nel and Somers, 2007; Somers and Nel, 2003)

  • Breeding interval
    A. capensis breeds once a year.
  • Breeding season
    Breeding occurs mainly during the dry season, though copulations may take place year round. .
  • Range number of offspring
    1 to 5
  • Average gestation period
    63 days
  • Range weaning age
    45 to 60 days
  • Average time to independence
    1 years
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Little is known of parental care in African clawless otters. Mothers nurse their pups until they are 45 to 60 days old. Pups reach independence by the end of their 1st year. (Larivière, 2001)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

African clawless otters live 10 to 12 years in the wild and approximately 15 years in captivity. (Larivière, 2001)

  • Range lifespan
    Status: wild
    10 to 12 years
  • Range lifespan
    Status: captivity
    15 (high) years
  • Typical lifespan
    Status: wild
    10 to 14 years
  • Average lifespan
    Status: captivity
    15 years

Behavior

African clawless otters are solitary and can be found in both freshwater and marine habitats. Groups composed of 4 to 6 individuals, with 2 to 3 adults and 2 to 3 young, are occasionally spotted and larger clans sometimes form to forage. These otters are most active during dawn and dusk (i.e., crepuscular). Daytime is spent sleeping in burrows or dens. Nearly half of all dens are formed by natural depressions or sheltering landscape with the other half of dens constructed by otters digging through soft substrates such as sand or mud. The floor of the den is often lined with vegetation. They spend a majority of their waking hours swimming, hunting, foraging, playing, and basking in the sun. On land, these otters either walk slowly or trot like a seal, sometimes walking over 7 km between bodies of water. They swim by using their hind legs and tails for propulsion while using their tails as rudders. (Larivière, 2001; Nel and Somers, 2007; Somers and Nel, 2003)

African clawless otters do the majority of their hunting in water. Shallow water, approximately 1.5 m deep, is preferred for hunting. They begin hunting by submerging their heads underwater and scanning for prey while using their forefeet to feel under rocks. They grab prey with their forefeet and bring it to the surface to eat. Small crabs are eaten while the otter is perpendicular to the water’s surface, and large crabs are eaten while the otter lies on its back in order to catch pieces of food falling from its mouth. African clawless otters also dive for fish. Dives can last from 6 to 49 s, averaging 18 s per dive. Small fish are eaten in the water, and large fish are brought to shallow water or the shore for consumption. Directly after eating, African clawless otters clean their faces with their forefeet. After hunting bouts they may exit the water and dry off or spend time playing. They dry themselves off by rolling and rubbing their bodies against grass, rocks, or sandbars and basking in the sun. Young African clawless otters spend a significant amount of time playing and have been observed play-fighting, swimming, sliding on rocks, playing with their food, and even fetching small pebbles thrown into the water before they hit the ground. (Larivière, 2001; Nel and Somers, 2007; Somers and Nel, 2003)

  • Range territory size
    49000 to 10625000 m^2

Home Range

African clawless otters have home ranges from 4.9 ha to 1062.5 ha. Most of their time is spent in a smaller core area ranging from 1.1 ha to 138.9 ha. (Nel and Somers, 2007)

Communication and Perception

African clawless otters make complex vocalizations, including low and high pitched whistles, grunts, and “hah” sounds thought to express anxiety. They also squeal, moan, and mew. The purpose of different vocalizations is not well understood. These otters demarcate territorial boundaries with scant-marked fecal droppings called "spraints." Spraints are commonly found surrounding dens and occur most frequently during the mating season. A pair of anal scent glands are also used to communicate through scent. (Larivière, 2001; Somers and Nel, 2003)

Food Habits

African clawless otters are primarily carnivores. In freshwater habitats, their diet consists primarily of crabs (Potamonautes); however, they also eat frogs (Xenopus), insects (Coprinae, Cyclorhapha, Dytiscidae, Nepidae, Odonota, Scarabaeidae), and various species of fish, which make up more of the diet during winter when they are slowed by cold temperatures and are easier to catch. In marine habitats, the diet of African clawless otters is mainly composed of fish. Marine inhabitants also eat crab, Cape rock lobsters, and abalone. African clawless otters have also been known to eat ducks, geese, coots, swans, dragonfly larvae, mollusks, reptiles, small birds, and shrews. (Larivière, 2001; Nel and Somers, 2007; Somers and Nel, 2003)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • mollusks
  • aquatic crustaceans

Predation

African clawless otters are occasionally eaten by Nile crocodiles and fish-eagles. Their most dangerous predators are humans. Their bi-colored pelage helps camouflage them with in the water and on land. They are agile swimmers that can often escape potential predators while in the water. While on land, however, they are particularly vulnerable to predation. (Larivière, 2001)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators
    • Nile crocodile, (Crocodilus niloticus)
    • fish eagle, (Haliaetus vocifer)
    • humans, (Homo sapiens)

Ecosystem Roles

African clawless otters are predators of crabs, fish, frogs, and insects. They are parasitized by several species of flatworm, including Baschkirovitrema incrassatum, Clinostomum pyriforme, and Prudhoella rhodesiensis. In addition, various species of roundworm, including Cloeoascaris spinicollis, spend at least part of their complex life cycle in the tissues of African clawless otters . There are no known ectoparasites. (Larivière, 2001)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

African clawless otters are hunted for their pelts and other body parts, and they are occasionally kept as pets. (Hoffmann, 2010)

  • Positive Impacts
  • pet trade
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Due to their diet, fishermen view African clawless otters as competitors for fish and fish prey. African clawless otters are occasionally viewed as agricultural pests as they also sometimes kill poultry. (Hoffmann, 2010)

Conservation Status

Populations of African clawless otters are widespread and stable, and the IUCN Red List of Threatened Species lists them as "least concern". However, human-induced habitat change is a potential threat to some local populations. African clawless otters in Nigeria and Cameroon are listed under CITES Appendix I, while all others are listed under Appendix II. (Hoffmann, 2010)

Contributors

Daniel Kowalsky (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

piscivore

an animal that mainly eats fish

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Hoffmann, M. 2010. "Aonyx capensis" (On-line). IUCN Red List of Threatened Species. Accessed April 01, 2011 at http://www.iucnredlist.org/apps/redlist/details/1793/0.

Jacques, H., G. Veron, F. Alary, S. Aulagnier. 2009. The Congo Clawless Otter (Aonyx congicus) (Mustelidae: Lutrinae): A Review of Its Systematics, Distribution and Conservation Status. African zoology, 44/2: 159-170. Accessed March 14, 2011 at http://dx.doi.org/10.3377/004.044.0204.

Larivière, S. 2001. Aonyx capensis. Mammalian Species: 1-6. Accessed March 10, 2011 at http://dx.doi.org/10.1644/1545-1410(2001)671<0001:AC>2.0.CO;2.

Nel, J., M. Somers. 2007. Distribution and habitat choice of Cape clawless otters, in South Africa. South African Journal of Wildlife Research, 37/1: 61-70. Accessed March 10, 2011 at http://dx.doi.org/10.3957/0379-4369-37.1.61.

Parker, D. 2005. The diet of Cape clawless otters at two sites along the Bloukrans River, eastern Cape Province, South Africa. African zoology, 40/2: 330-334.

Perrin, M., C. Carugati. 2000. Food habits of coexisting Cape clawless otter and spotted-necked otter in the KwaZulu-Natal Drakensberg, South Africa. South African Journal of Wildlife Research, 30/2: 85-92.

Somers, M., J. Nel. 2003. Diet in relation to prey of Cape clawless otters in two rivers in the Western Cape Province, South Africa. African zoology, 38/2: 317-326.

Somers, M., J. Nel. 2004. Movement patterns and home range of Cape clawless otters (Aonyx capensis), affected by high food density patches. Journal of zoology, 262/1: 91-98. Accessed March 10, 2011 at http://sfx.lib.umich.edu:9003/sfx_local?sid=CSA%3Azooclust-set-c&pid=%3CAN%3EZOOR14005029188%3C%2FAN%3E%26%3CPY%3E2004%3C%2FPY%3E%26%3CAU%3ESomers%2C%20M.J.%20%7Ba%7D%3B%20Nel%2C%20J.A.J.%3C%2FAU%3E&issn=0952-8369&volume=262&issue=1&spage=91&epage=98&date=2004-01&genre=article&aulast=Somers&auinit=MJ%7Ba%7D&title=Journal%20of%20Zoology%20%28London%29&atitle=Movement%20patterns%20and%20home%20range%20of%20Cape%20clawless%20otters%20%28Aonyx%20capensis%29%2C%20affected%20by%20high%20food%20density%20patches.

Wotton, S., T. Morris, G. Anderson, G. Shorrock. 2010. Threatened species surveys in the Gola Forest Reserves, Sierra Leone. Ibis, 152/1: 205-206.

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