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Aonyx cinerea - Oriental small-clawed otter

Geographic Range

Aonyx cinerea is found in coastal regions from southern India to the Malay Peninsula and southern China. (Nowak, 1999; Timmis, 1971)

Biogeographic Regions: oriental (native); Indian ocean

Habitat

Aonyx cinerea individuals are commonly seen in the shallows of freshwater streams and rivers as well as coastal regions. There is often dense foliage nearby, which they use as defensive cover, and which restricts behavioral studies in the wild. Nesting burrows are dug into the muddy banks where they live. They have also been seen numerous times in rice paddies. (Hoogerwerf, 1970; Mason and Macdonald, 1986; Timmis, 1971)

Habitat Regions: tropical; saltwater or marine; freshwater

Aquatic Biomes: rivers and streams; coastal

Other Habitat Features: riparian

Physical Description

Aonyx cinerea weigh 2.7 to 5.4 kg, have a combined head and body length of 406 to 635 mm, and a tail length of 246 to 304 mm. They have dark, greyish-brown fur over most of their body, and a lighter cream coloration on their face and neck. Their claws are extremely reduced, and rarely extend past the digit. The paws are only partially webbed, which allows for more dexterity than otters with full webbing. (Mason and Macdonald, 1986; Timmis, 1971)

Other Physical Features: endothermic; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Range mass 2.7 to 5.4 kg5.95 to 11.89 lb

Range length406 to 635 mm15.98 to 25.00 in

Reproduction

Asian clawless otters form monogamous pairs for life. (Lancaster, 1975; Leslie, 1970)

Mating System: monogamous

The estrous cycle is 28 days with a 3 day period of estrus. Mated pairs can have two litters of 1 to 6 young (usually 1 or 2) per year. Gestation is approximately 60 days, and newborn young are relatively undeveloped. At birth, they weigh around 50 g and have closed eyes. Eyes open at around 40 days, and pups can be seen outside the den after ten weeks. Young begin eating solid food after 80 days, and start swimming after three months. (Lancaster, 1975; Leslie, 1970)

Key Reproductive Features: iteroparous; year-round breeding; gonochoric/gonochoristic/dioecious (sexes separate); sexual; viviparous

Breeding interval: Aonyx cinerea may produce two litters annually.

Breeding season: Mating may occur throughout the year.

Average number of offspring: 2

Average gestation period: 60 days

Average weaning age: 80 days

Males assist with nest building before birth and food procurement after parturition. (Lancaster, 1975; Leslie, 1970)

Parental Investment: male parental care; female parental care

Lifespan/Longevity

A captive specimen of A. cinereus lived about 16 years. (Nowak, 1999)

Range lifespan

Status: captivity16 (high) years

Behavior

Aonyx cinerea live in extended family groups of approximately twelve individuals. They are social and vocal animals. They are often seen playing on mud banks and in the water, and slides are quite obvious in regions where they either frequently visit or permanently live. In captivity they are often seen juggling pebbles and other small objects. They are mainly active during the day. (Hoogerwerf, 1970; Medway, 1969; Timmis, 1971)

Key Behaviors: natatorial; diurnal; motile; sedentary; social

Communication and Perception

Twelve different vocalizations have been identified in this species, not counting simple alarm vocalizations. Communication also occurs with visual, chemical, and tactile cues such as social grooming, hormonal changes, and posturing. (Timmis, 1971)

Communication Channels: visual; tactile; acoustic; chemical

Perception Channels: visual; tactile; acoustic; chemical

Food Habits

Unlike most otters, A. cinerea individuals use their forepaws to locate and capture items, rather than their mouth. Their incomplete webbing gives them a great deal of manual dexterity. They dig in sand and mud at the shoreline for various types of shellfish (clams and mussels) and crabs. To get at the meat they can either crush the shell manually or let heat from the sun open the shells. Their teeth are broad and robust, well-suited for crushing shells. (Timmis, 1971)

Primary Diet: carnivore (eats non-insect arthropods, molluscivore)

Animal Foods: amphibians; fish; terrestrial non-insect arthropods; mollusks

Predation

Predation on A. cinereus has not been described but it is likely that they are taken by large, primarily aquatic predators, such as crocodiles and snakes. Their amazing agility in the water may help them to avoid predation.

Ecosystem Roles

The role of A. cinereus in the ecosystem is not well understood. They impact the populations of shellfish and crustaceans in their area.

Economic Importance for Humans: Positive

Aonyx cinerea consume small crabs which are considered agricultural pests. (Mason and Macdonald, 1986)

Positive Impacts: controls pest population

Economic Importance for Humans: Negative

Rice farmers complain about Asian clawless otters uprooting plants in the paddies. (Mason and Macdonald, 1986)

Conservation Status

Clawless otters are managed under the Species Survival Program. While not endangered themselves, they are being used as a model for the management of other otter species. (Lankard, 2001)

IUCN Red List: Vulnerable

More information

US Federal List: No special status

CITES: No special status

Contributors

David Hamman (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University.

Glossary

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.

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.

Diurnal: 1.active during the day, 2. lasting for one day.

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.

Female parental care: parental care is carried out by females

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).

Male parental care: parental care is carried out by males

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.

Oriental:found in the oriental region of the world. In other words, India and southeast Asia.

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.

Sedentary: remains in the same area

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

Social: associates with others of its species; forms social groups.

Tactile: uses touch to communicate

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.

Year-round breeding: breeding takes place throughout the year

References

Hoogerwerf, A. 1970. Udjung Kulon. Leiden: E. J. Brill.

Lancaster, W. 1975. Exhibiting and breeding the asian small-clawed otter at Adelaide Zoo. International Zoo Yearbook, 15: 63-65.

Lankard, J. 2001. AZA annual report on conservation and science 1999-2000. Volume I: Conservation programs reports. Silver Springs, MD: American Zoo and Aquarium Association..

Leslie, G. 1970. Observations on Oriental short-clawed otter at Aberdeen Zoo. International Zoo Yearbook, 10: 79-81.

Mason, C., S. Macdonald. 1986. Otters: ecology and conservation. Cambridge University Press.

Medway, L. 1969. The wild mammals of Malaya. Kuala Lampur: Oxford University Press.

Nowak, R. 1999. Walker's Mammals of the World, Volume 1. Baltimore and London: The Johns Hopkin University Press.

Timmis, W. 1971. Observations on breeding the Oriental short-clawed otter, *Amblonyx cinerea*, at Chester Zoo. International Zoo Yearbook, 11: 109-111.

Unreviewed

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© University of Michigan Museum of Zoology, Animal Diversity Web

Supplier: J Medby

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