The Asian small-clawed otter (''Aonyx cinereus''), also known as the oriental small-clawed otter and the small-clawed otter, is an
otter species native to
South and
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...
. It has short
claws
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
that do not extend beyond the pads of its webbed digits. With a total body length of , it is the smallest otter species in the world.
The Asian small-clawed otter lives in riverine habitats,
freshwater wetlands and
mangrove
A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...
swamps. It feeds on
molluscs,
crabs and other small
aquatic animal
An aquatic animal is any animal, whether invertebrate or vertebrate, that lives in water for most or all of its lifetime. Many insects such as mosquitoes, mayflies, dragonflies and caddisflies have aquatic larvae, with winged adults. Aquatic ani ...
s. It lives in pairs, but was also observed in family groups with up to 12 individuals.
It is listed as
Vulnerable on the
IUCN Red List
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...
, and is threatened by
habitat loss
Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
,
pollution
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
, and in some areas also by
hunting
Hunting is the human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products ( fur/ hide, bone/tusks, horn/antler, ...
.
Taxonomy
''Lutra cinerea'' was the
scientific name proposed by
Johann Karl Wilhelm Illiger
Johann Karl Wilhelm Illiger (19 November 1775 – 10 May 1813) was a German entomologist and zoologist.
Illiger was the son of a merchant in Braunschweig. He studied under the entomologist Johann Hellwig, and later worked on the zoological colle ...
in 1815 for an otter collected in
Batavia
Batavia may refer to:
Historical places
* Batavia (region), a land inhabited by the Batavian people during the Roman Empire, today part of the Netherlands
* Batavia, Dutch East Indies, present-day Jakarta, the former capital of the Dutch East In ...
. In the 19th and 20th centuries, several
zoological specimen
A zoological specimen is an animal or part of an animal preserved for scientific use.
Various uses are: to verify the identity of a (species), to allow study, increase public knowledge of zoology.
Zoological specimens are extremely diverse. Exampl ...
s were described:
*''Lutra concolor'' proposed by
Constantine Samuel Rafinesque in 1832 was a uniform coloured otter from
Assam
Assam (; ) is a state in northeastern India, south of the eastern Himalayas along the Brahmaputra and Barak River valleys. Assam covers an area of . The state is bordered by Bhutan and Arunachal Pradesh to the north; Nagaland and Manipur ...
. Rafinesque also proposed ''Amblonyx'' as name for a subgenus for otters with short, obtuse claws.
*''Lutra leptonyx'' proposed by
Thomas Horsfield
Thomas Horsfield (May 12, 1773 – July 24, 1859) was an American physician and naturalist who worked extensively in Indonesia, describing numerous species of plants and animals from the region. He was later a curator of the East India Company ...
in 1824 were two adult small-clawed otters collected in
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mos ...
. It was subordinated to the genus ''
Aonyx
''Aonyx'' is a genus of otters, containing three species, the African clawless otter, the Congo clawless otter, and the Asian small-clawed otter.
The word ''aonyx'' means "clawless", derived from the prefix '' a-'' ("without") and ''onyx'' ( ...
'' by
John Edward Gray
John Edward Gray, FRS (12 February 1800 – 7 March 1875) was a British zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray (1766–1828). The same is used for ...
in 1843.
*''Amblonyx cinerea nirnai'' proposed by
Reginald Innes Pocock in 1940 was a dark brown small-clawed otter from
Virajpet
The town of Virajpet also spelled as Virajapete is the second town of the district of Kodagu (Coorg), in Karnataka. It is the main town of the ''Virajpet taluka'', south of the district, in the Kerala-Karnataka border. The name is an abbreviati ...
in South India.
Phylogeny
Results of a mitochondrial
cytochrome B
Cytochrome b within both molecular and cell biology, is a protein found in the mitochondria of eukaryotic cells. It functions as part of the electron transport chain and is the main subunit of transmembrane cytochrome bc1 and b6f complexes.
F ...
analysis published in 1998 indicated that it should be subordinated to the genus ''Aonyx''. Results of a molecular study published in 2008 showed that the Asian small-clawed otter is a
sister taxon
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
of ''
Lutrogale
''Lutrogale'' was proposed as generic name by John Edward Gray in 1865 for otters with a convex forehead and nose, using the smooth-coated otter '' L. perspicillata'' as type species.
The genus also contains the following extinct and fossil spec ...
'', lending support to retaining the genus ''Amblonyx'' or expanding ''Aonyx'' to make it
monophyletic. They
genetically diverged about .
The Asian small-clawed otter groups with the
African clawless otter
The African clawless otter (''Aonyx capensis''), also known as the Cape clawless otter or groot otter, is the second-largest freshwater otter species. It inhabits permanent water bodies in savannah and lowland forest areas through most of sub- ...
(''Aonyx capensis'') and the
smooth-coated otter
The smooth-coated otter (''Lutrogale perspicillata'') is an otter species occurring in most of the Indian subcontinent and Southeast Asia, with a disjunct population in Iraq. It is listed as Vulnerable on the IUCN Red List since 1996 and is threa ...
(''Lutrogale perspicillata'') into a
sister clade
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and t ...
with the genus ''
Lutra
''Lutra'' is a genus of otters, one of seven in the subfamily Lutrinae.
Taxonomy and evolution
The genus includes these species:
Extant species
Extinct species
*†'' Lutra affinis''
*†'' Lutra bressana ''
*†'' Lutra bravardi''
*†'' ...
''.
Hybridisation of Asian small-clawed otter females with smooth-coated otter males occurred in
Singapore
Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...
. The resulting offspring and their descendants bred back into the smooth-coated otter population, but maintained the genes of their small-clawed otter ancestors. Today, a population of at least 60 hybrid otters are present in Singapore.
Characteristics
![Oriental small-clawed otter teeth](https://upload.wikimedia.org/wikipedia/commons/f/f7/Oriental_small-clawed_otter_teeth.jpg)
The Asian small-clawed otter has deep brown
fur
Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...
with some rufous tinge on the back, but paler below. Its underfur is lighter near the base. The sides of the neck and head are brown, but its cheeks, upperlip, chin, throat and sides of the neck are whitish.
Its skull is short, and the naked
rhinarium
The rhinarium (New Latin, "belonging to the nose"; plural: rhinaria) is the furless skin surface surrounding the external openings of the nostrils in many mammals. Commonly it is referred to as the tip of the ''snout'', and breeders of cats and ...
rounded above. The muzzle has long coarse
vibrissae
Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser ...
on either side. Its eyes are located toward the front of the head. The small ears are oval-shaped with an inconspicuous
tragus and antitragus. Its
paw
A paw is the soft foot-like part of a mammal, generally a quadruped, that has claws.
Common characteristics
The paw is characterised by thin, pigmented, keratinised, hairless epidermis covering subcutaneous collagenous and adipose tissue, ...
s are narrow with short digits that are webbed to the last joint. There are short hairs on the lower sides of the interdigital webs. The four-lobed plantar pads are longer than wide. The
claw
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
s are short, almost erect, and in some individuals even absent.
Females have four
mammary glands.
The Asian small-clawed otter is the smallest otter species in Asia. In head-to-body length, it ranges from with a long
tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammal ...
. The tapering tail is thick and muscular, especially at the base, and more than half the length of the body. Hind feet are long. Length of skull ranges from . It does not have upper premolars and only four post
canine teeth
In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened howeve ...
above.
Adult captive otters range in weight from .
Distribution and habitat
The Asian small-clawed otter's native range comprises parts of India to Southeast Asia including the islands of
Sumatra, Java,
Borneo
Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...
and
Palawan
Palawan (), officially the Province of Palawan ( cyo, Probinsya i'ang Palawan; tl, Lalawigan ng Palawan), is an archipelagic province of the Philippines that is located in the region of Mimaropa. It is the largest province in the country in t ...
. It lives in freshwater
wetland
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...
s such as
swamps, meandering rivers, irrigated rice fields as well as
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
, coastal
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...
s and
tidal
Tidal is the adjectival form of tide.
Tidal may also refer to:
* ''Tidal'' (album), a 1996 album by Fiona Apple
* Tidal (king), a king involved in the Battle of the Vale of Siddim
* TidalCycles, a live coding environment for music
* Tidal (servic ...
pools. It occurs in West Bengal, Assam and
Arunachal Pradesh
Arunachal Pradesh (, ) is a state in Northeastern India. It was formed from the erstwhile North-East Frontier Agency (NEFA) region, and became a state on 20 February 1987. It borders the states of Assam and Nagaland to the south. It shares ...
, and in coastal regions of
Odisha
Odisha (English: , ), formerly Orissa ( the official name until 2011), is an Indian state located in Eastern India. It is the 8th largest state by area, and the 11th largest by population. The state has the third largest population of ...
. In
Karnataka
Karnataka (; ISO: , , also known as Karunāḍu) is a state in the southwestern region of India. It was formed on 1 November 1956, with the passage of the States Reorganisation Act. Originally known as Mysore State , it was renamed ''Karnat ...
,
Nilgiri and
Palni hills
The Palani Hills are a mountain range in the southern Indian states of Kerala and Tamil Nadu. The Palani Hills are an eastward extension of the Western Ghats ranges, which run parallel to the west coast of India. The Palani Hills adjoin the hig ...
in
Tamil Nadu
Tamil Nadu (; , TN) is a state in southern India. It is the tenth largest Indian state by area and the sixth largest by population. Its capital and largest city is Chennai. Tamil Nadu is the home of the Tamil people, whose Tamil language ...
, it lives in shallow mountain creeks up to an elevation of .
In
West Java
West Java ( id, Jawa Barat, su, ᮏᮝ ᮊᮥᮜᮧᮔ᮪, romanized ''Jawa Kulon'') is a province of Indonesia on the western part of the island of Java, with its provincial capital in Bandung. West Java is bordered by the province of Banten ...
, it inhabits areas along slow-flowing irrigation channels, pond areas and rice fields surrounded by vegetation that offers shelter. It also occurs in
mangroves
A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...
.
In the 1980s, a few Asian small-clawed otters escaped from captivity in
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
and established a population in the wild.
Behaviour and ecology
![Aonyx cinerea - Zoo Frankfurt 1](https://upload.wikimedia.org/wikipedia/commons/0/00/Aonyx_cinerea_-_Zoo_Frankfurt_1.jpg)
The Asian small-clawed otter is mostly active after dark.
It lives in groups of up to 15 individuals.
[ In the Bangladesh ]Sundarbans
Sundarbans (pronounced ) is a mangrove area in the delta formed by the confluence of the Padma, Brahmaputra and Meghna Rivers in the Bay of Bengal. It spans the area from the Baleswar River in Bangladesh's division of Khulna to the Hooghly R ...
, 53 individuals were recorded in of water courses in 13 locations between November 2014 and March 2015. Group size ranged from one to 12 individuals.
Group members communicate using 12 or more distinct calls, and utter a variety of yelps and whimpers.[ When disturbed, they scream to rally the help of others.
When swimming on the surface, otters row with the forelimbs and paddle with the hind limbs. When diving under water, they undulate their bodies and tails. Captive otters swim at speeds of .][
Observations of wild Asian small-clawed otters revealed that they smear their ]spraint
Spraint is the dung of the otter.
Spraints are typically identified by smell and are known for their distinct odors, the smell of which has been described as ranging from freshly mown hay to putrefied fish. The Eurasian otter
The Eurasian ott ...
at latrine
A latrine is a toilet or an even simpler facility that is used as a toilet within a sanitation system. For example, it can be a communal trench in the earth in a camp to be used as emergency sanitation, a hole in the ground ( pit latrine), or ...
sites, using their hind feet and tails. Large groups smeared more than groups of three or fewer animals. The frequency of latrines with smeared scats varied in different locations, indicating a preference for certain sites. Spraint smearing most likely facilitates social ties among group members and is associated with territorial marking
In ethology, territory is the sociographical area that an animal consistently defends against conspecific competition (or, occasionally, against animals of other species) using agonistic behaviors or (less commonly) real physical aggression. A ...
displays. They use grassy or sandy banks for resting, sun bathing and grooming. In marshes, they use mostly islands.[
]
Diet
The Asian small-clawed otter feeds mainly on crabs, mudskippers and ''Trichogaster
''Trichogaster'' is a genus of gouramis native to South Asia from Pakistan to Myanmar. It is the only genus in the monotypic subfamily Trichogastrinae as set out in the 5th Edition of ''Fishes of the World'', although that book states that there ...
'' fish. Its diet varies seasonally. When and where available, it also catches snakes, frogs, insects, rats and ricefield fish like catfish
Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive ...
, ''Anabas testudineus
The climbing perch (''Anabas testudineus'') is a species of amphibious freshwater fish in the family Anabantidae (the climbing gouramis). A labyrinth fish native to Far Eastern Asia, the fish inhabits freshwater systems from Pakistan, India ...
'' and ''Channa striata
''Channa striata'', the striped snakehead, is a species of snakehead fish. It is also known as the common snakehead, chevron snakehead, or snakehead murrel and generally referred simply as mudfish. It is native to South and Southeast Asia, and h ...
''.[
The size of crabs found in spraints in ]Huai Kha Khaeng Wildlife Sanctuary
The Huai Kha Khaeng Wildlife Sanctuary ( th, เขตรักษาพันธุ์สัตว์ป่าห้วยขาแข้ง, ) is in Uthai Thani and Tak Provinces, Thailand. The park was established in 1974, and is part of the ...
ranged in carapace width from .
Captive Asian small-clawed otters were observed to leave shellfish in the sun, so that the heat causes them to open. That way, they consume the crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...
s without having to crush the shells.[
]
Reproduction
Information about the Asian small-clawed otter's mating
In biology, mating is the pairing of either opposite- sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reprod ...
and breeding behaviour has been studied in captive environments. Captive pairs are monogamous. The estrous cycle
The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestro ...
of females lasts 28 to 30 days with estrus
The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous ...
lasting between one and 13 days. Usually, mating takes place in the water.
Gestation lasts 62 to 86 days. Interval between births is at least eight months.
About two weeks before parturition
Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
, both female and male engage in building a nest. They collect grass, hay or straw and carry this material into the breeding chamber. Between one and seven pups are born in a litter
Litter consists of waste products that have been discarded incorrectly, without consent, at an unsuitable location. Litter can also be used as a verb; to litter means to drop and leave objects, often man-made, such as aluminum cans, paper cups ...
. Pups are born with closed eyes, which open in the fifth week.[
Newborn pups weigh between and reach a weight of after 60 days. They start exploring the environs of the breeding den at the age of ten weeks. At about three months, they enter and paddle in shallow water under the guidance of the mother. They become independent at the age of four to five months.][
]
Threats
The Asian small-clawed otter is threatened by poaching
Poaching has been defined as the illegal hunting or capturing of wild animals, usually associated with land use rights.
Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set a ...
for its fur, loss and destruction of habitats such as hill streams, peat swamp forests and mangroves for aquaculture projects. Threats in India include deforestation, conversion of natural habitat for tea and coffee plantations, overfishing of rivers and water pollution through pesticides.
It is the most sought after otter species for the illegal pet trade
Wildlife trade refers to the of products that are derived from non-domesticated animals or plants usually extracted from their natural environment or raised under controlled conditions. It can involve the trade of living or dead individuals, ti ...
in Asia. At least 711 Asian small-clawed otters were offered for sale through online websites by 280 traders in Indonesia, Thailand, Malaysia and Vietnam between 2016 and 2017.
Between December 2015 and October 2018, 49 Asian small-clawed otters were confiscated from wildlife traffickers in Thailand, Vietnam and Japan; 35 of them were bound for sale in Japan.
Conservation
The Asian small-clawed otter was listed on CITES Appendix II
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
and is protected in almost all range countries prohibiting its killing. Since August 2019, it is included in CITES Appendix I
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of intern ...
, thus strengthening its protection in regards to international trade.
In captivity
The Association of Zoos and Aquariums
The Association of Zoos and Aquariums (AZA), originally the American Association of Zoological Parks and Aquariums, is an American 501(c)(3)
nonprofit organization founded in 1924 and dedicated to the advancement of zoos and public aquariums in ...
established a Species Survival Plan
The American Species Survival Plan or SSP program was developed in 1981 by the (American) Association of Zoos and Aquariums to help ensure the survival of selected species in zoos and aquariums, most of which are threatened or endangered in the ...
for the Asian small-clawed otter in 1983 to encourage research on captive breeding.
In Europe, Zoo Basel
Zoo Basel is a non-profit zoo in the city of Basel, Switzerland. Its official name is ''Zoologischer Garten Basel'' — or in English: Basel Zoological Garden. Basel residents affectionately call it ''Zolli''. keeps Asian small-clawed otters together with Indian rhinoceros
}
The Indian rhinoceros (''Rhinoceros unicornis''), also called the Indian rhino, greater one-horned rhinoceros or great Indian rhinoceros, is a rhinoceros species native to the Indian subcontinent. It is listed as Vulnerable on the IUCN Red Li ...
.
Asian small-clawed otters suffering from osteoporosis display resorption of hyperactive bone and cartilage by osteoclast
An osteoclast () is a type of bone cell that breaks down bone tissue. This function is critical in the maintenance, repair, and remodeling of bones of the vertebral skeleton. The osteoclast disassembles and digests the composite of hydrated pro ...
s in many bone sites, which causes pockmarks on all the bones.
References
External links
*
*
*
*
{{Taxonbar, from=Q244277
Asian small-clawed otter
Mammals of Bangladesh
Mammals of China
Mammals of India
Carnivorans of Malaysia
Mammals of Nepal
Mammals of Singapore
Mammals of Southeast Asia
Fauna of South China
Asian small-clawed otter
Taxa named by Johann Karl Wilhelm Illiger
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