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Aonyx capensis congicaCongo clawless otter

By Daniel MacArthur

Geographic Range

Congo clawless otters are found in the lower Congo basin, which lies between southeastern Nigeria and western Uganda. (Estes, 1991; Haltenorth and Diller, 1980; Kingdon, 1982; Nowak, 1999; Estes, 1991; Haltenorth and Diller, 1980; Kingdon, 1982; Nowak, 1999)

Habitat

Congo clawless otters reside exclusively in the small swamps, ponds, and streams of heavy rainforests. Due to their amphibious lifestyle, these otters are both excellent swimmers and skilled explorers of the shores (Kingdon, 1982). Their hair type, reduced vibrissae, and rather generalized dental morphology suggest that they may be more terrestrial than other otter species (Nowak, 1999). (Kingdon, 1982; Nowak, 1999)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Aonyx capensis congica is a large, powerfully built otter, though it is more slender in the neck and back than other populations of Aonyx capensis. Head and body length ranges between 78 and 97 cm, with the tail adding an additional 40 to 59 cm to the total length. Weights range from 15 to 25 kg in adult animals.

These otters have a dark, chestnut-brown coat with some silver frosting on the head and neck, contrasted by a white chest, nose and ears. A distinctive black patch is located between the eyes and nostrils (Kingdon, 1982). Aonyx capensis congica young resemble the adults except for a greater frosting of the coat. Unlike many other otter species, A. capensis congica has no claws, no webbing in the manus, and webbing only halfway down the digits in the pes. All are adaptations to improve dexterity and tactile sensitivity for foraging in the muddy waters of the lower Congo basin. The less specialized dentition of A. capensis congica, when compared to the broader species, A. capensis, serves as a distinguishing characteristic and suggests a broader carnivorous diet than other populations (Haltenorth and Diller, 1980). (Haltenorth and Diller, 1980; Kingdon, 1982)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    15 to 25 kg
    33.04 to 55.07 lb
  • Range length
    78 to 97 cm
    30.71 to 38.19 in

Reproduction

Very little has been recorded about the mating habits of Congo clawless otters. They remain enigmatic as their elusive nature and remote range have prevented many of their behaviors from being described (Estes, 1991). One could infer that the mating system is similar to other African otter species, where there is a short-lived monogamy followed by a return to a more solitary lifestyle (Chanin, 1985). (Chanin, 1985; Estes, 1991)

Nothing is known with certainty about the reproductive behavior of A. capensis congica. It has been suggested that the gestation period is around two months, that an average of two to three young are born per litter, and that young do not reach sexual maturity until about one year of age (Nowak, 1999). Although it is not known whether the breeding is seasonal or occurs throughout the year, births do seem to peak in the dry season in other Aonyx capensis populations, and it is predicted that A. capensis congica would be similar (Estes, 1991). (Estes, 1991; Nowak, 1999)

Despite a paucity of information on the development and reproduction of these otters, we can reasonably infer that they are similar to other members of the genus Aonyx. Aonyx cinerea has an estruous cycle that lasts between 22.4 and 30 days, and an estrus of 3 days. Because the gestation period is between 60 and 64 days, they can produce two litters per year. The young are altricial, and do not open their eyes until the age of 40 days. Young are able to swim by the age of 9 weeks, and eat solid foods after 80 days. (Nowak, 1999)

  • Breeding interval
    The breeding interval is not known at this time.
  • Breeding season
    It is not known whether or not these animals breed seasonally.
  • Range number of offspring
    1 to 6
  • Average number of offspring
    2-3
  • Average gestation period
    2 months
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Much of the parental behavior in Congo clawless otters is unknown. The mother is the primary care giver, but it is unclear to what degree the male is involved in rearing young (Nowak, 1999). Although we may infer that the mother provides young with milk, shelter, and grooming during their period of dependency, the duration of care is a mystery. Further, there is very little documentation on other members of the genus; observed males of the same subfamily, Lutrinae, show varying degrees of care. Though often solitary creatures, Congo clawless otters have been observed foraging as family parties. However, it is hypothesized that these associations are transient and based more on territory sharing and overlapping rather than a post-independence affinity for their family members (Haltenorth and Diller, 1980). (Haltenorth and Diller, 1980; Nowak, 1999)

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

Lifespan/Longevity

Lifespan range in A. capensis congica is unknown. Captive specimens of the larger species, A. capensis, and the related species, A. cinerea, have lived as long as 14 and 16 years respectively (Nowak, 1999). (Nowak, 1999)

  • Range lifespan
    Status: captivity
    16 (high) years

Behavior

Congo clawless otters are mostly nocturnal, but have been observed in undisturbed swamp lands during the daytime. Though mostly solitary, family groups have also been observed along the rivers of Cameroon (Kingdon, 1982). The social organization of A. capensis congica is not well understood. In other A. capensis populations, individuals defend territories of around twelve square kilometers that often overlap with three or more other adult males (Nowak, 1999). (Kingdon, 1982; Nowak, 1999)

  • Average territory size
    12 km^2

Home Range

The home range size of A. capensis congica is not known. In other A. capensis populations, home ranges are between four and six square kilometers (Chanin, 1985). (Chanin, 1985)

Communication and Perception

No form of communication has been specifically documented for A. capensis congica. Clawless otters, in general, communicate vocally with chirps, squeals, and purring noises when expressing affection or play. Often growls, snarls, and a screaming wail are signs of displeasure or apprehension. Clawless otters also use strong olfactory cues to communicate. They musk their coats and produce a sticky feces, capable of clinging to vertical surfaces, to mark the boundaries of their territory. The visual aspects of communication, including body language, are mostly undescribed (Estes, 1991). Tactile communication is undoubtedly of some importance in reproduction, especially between mates and between a mother and her offspring. (Estes, 1991)

Food Habits

Aonyx capensis congica is known to have a broad carnivorous diet, consisting of crabs, mollusks, fish, frogs, and other small vertebrates and invertebrates found in the shallow rivers and muddy shores of the Congo river basin. Its streamlined, powerful body propels it after the aquatic prey of rivers and ponds. Its specially adapted fingers are sensitive and dexterous, well suited for overturning stones, grasping prey, and sifting through the muddy shores of streams and swamps for invertebrates (Kingdon, 1982). Aonyx capensis congica has also been observed hunting in the tangled reeds and shoots of riverside vegetation, actively stalking small terrestrial vertebrates from cover (Haltenorth and Diller, 1980). (Haltenorth and Diller, 1980; Kingdon, 1982)

  • Animal Foods
  • mammals
  • amphibians
  • fish
  • eggs
  • mollusks
  • terrestrial worms
  • aquatic crustaceans

Predation

The dark chestnut coat of A. capensis congica acts as a form of camouflage within the muddy swamps and rivers of the Congo basin. The coloration may protect A. capensis congica from predation by the crocodiles, pythons, eagles, and leopards in this habitat (Kingdon, 1982). Although there is no documentation of predation on Congo clawless otters, other otter species are taken by large snakes, crocodilians, large cats, and birds of prey (Berry, 2000). It is reasonable to assume that similar predators take A. capensis congica.

Although it is not illustrated or described for A. capensis congica, the arched posture, snarled facial expressions, and harsh vocalizations of a defensive otter are commonly observed in the genus Aonyx (Estes, 1991). (Berry, 2000; Estes, 1991; Kingdon, 1982)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Within the rainforest ecosystem, A. capensis congica acts as a predator, preying on crustaceans, fish, frogs, and other small vertebrates and invertebrates. It is also a possible prey animal for pythons, leopards, eagles, and crocodiles (Kingdon, 1982). (Kingdon, 1982)

Economic Importance for Humans: Positive

If captured when young, their relatives, Aonyx cinerea have proven intelligent pets and have been trained to catch fish for Malay fishermen. Aonyx capensis congica has been commercially hunted for its beautiful coat as well. Though the fur quality is considered not as high as other otter species. (Nowak, 1999)

  • Positive Impacts
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Aonyx capensis congica has no known negative effects on the economy. However, if provoked, clawless otters have been known to sever fingers from the hands of humans with their bite. They have also attacked and drowned dogs that tread too closely to them (Estes, 1991). (Estes, 1991)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

The most likely causes for the endangered status of A. capensis congica are habitat loss and pollution due to development in the Congo basin as well as chronic over-harvesting for fur (Nowak, 1999). (Nowak, 1999)

Other Comments

Much of the natural history of A. capensis congica remains a mystery at this point. Most of what is currently help to be true of these animals has been constructed from fragmentary field observations and assumptions based on other populations of A. capensis, which are also poorly understood. Aonyx capensis congica was previously considered a species, A. congicus, but range overlap and similarities with A. capensis resulted in their being considered a population of A. capensis.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Barbara Lundrigan (editor, instructor), Michigan State University, Daniel MacArthur (author), Michigan State University.

Nancy Shefferly (editor), Animal Diversity Web.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

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.

fertilization

union of egg and spermatozoan

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).

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

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

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.

scent marks

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

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

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

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

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

Berry, K. 2000. "Animal Diversity Web" (On-line). Accessed April 09, 2005 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Lontra_longicaudis.html.

Chanin, P. 1985. The natural history of otters. London: Croom Helm.

Estes, R. 1991. The behavior guide to African mammals : including hoofed mammals, carnivores, primates / Richard Despard Estes ; drawings by Daniel Otte ; foreword by E.O. Wilson. Berkeley: University of California Press.

Haltenorth, T., H. Diller. 1980. A field guide to the mammals of Africa, including Madagascar / Theodor Haltenorth, Helmut Diller ; translated by Robert W. Hayman. London: Willliam Collins Sons and Co Ltd.

Harris, C. 1968. Otters: a study of the recent Lutrinae. London: Weidenfeld & Nicolson.

Kingdon, J. 1982. East African Mammals: an atlas of evolution in Africa. London, New York: Academic Press.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

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