Asian Otter
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The Asian small-clawed otter (''Aonyx cinereus''), also known as the oriental small-clawed otter and the small-clawed otter, is an
otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the Mustelidae family, which also includes wea ...
species native to
South South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...
and Southeast Asia. It has short claws 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 Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
wetlands and mangrove
swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s. It feeds on
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is esti ...
s,
crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
s and other small aquatic animals. It lives in pairs, but was also observed in family groups with up to 12 individuals. It is listed as
Vulnerable Vulnerable may refer to: General * Vulnerability * Vulnerability (computing) * Vulnerable adult * Vulnerable species Music Albums * ''Vulnerable'' (Marvin Gaye album), 1997 * ''Vulnerable'' (Tricky album), 2003 * ''Vulnerable'' (The Used album) ...
on the IUCN Red List, and is threatened by habitat loss, pollution, and in some areas also by
hunting Hunting is the human activity, 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 (skin), hide, ...
.


Taxonomy

''Lutra cinerea'' was the
scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
proposed by Johann Karl Wilhelm Illiger 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 specimens were described: *''Lutra concolor'' proposed by
Constantine Samuel Rafinesque Constantine Samuel Rafinesque-Schmaltz (; October 22, 1783September 18, 1840) was a French 19th-century polymath born near Constantinople in the Ottoman Empire and self-educated in France. He traveled as a young man in the United States, ultimat ...
in 1832 was a uniform coloured otter from Assam. Rafinesque also proposed ''Amblonyx'' as name for a subgenus for otters with short, obtuse claws. *''Lutra leptonyx'' proposed by Thomas Horsfield in 1824 were two adult small-clawed otters collected in Java. It was subordinated to the genus '' Aonyx'' by John Edward Gray in 1843. *''Amblonyx cinerea nirnai'' proposed by
Reginald Innes Pocock Reginald Innes Pocock F.R.S. (4 March 1863 – 9 August 1947) was a British zoologist. Pocock was born in Clifton, Bristol, the fourth son of Rev. Nicholas Pocock and Edith Prichard. He began showing interest in natural history at St. Edward ...
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 abbreviatio ...
in South India.


Phylogeny

Results of a mitochondrial cytochrome B 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 of '' Lutrogale'', lending support to retaining the genus ''Amblonyx'' or expanding ''Aonyx'' to make it
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
. 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 (''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''. Hybridisation of Asian small-clawed otter females with smooth-coated otter males occurred in Singapore. 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

The Asian small-clawed otter has deep brown fur 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 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 paws 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 claws are short, almost erect, and in some individuals even absent. Females have four
mammary glands A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in prima ...
. 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 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 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 Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...
, Java, Borneo and Palawan. It lives in freshwater wetlands such as
swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s, meandering rivers, irrigated rice fields as well as estuaries, coastal lagoons and tidal pools. It occurs in West Bengal, Assam and Arunachal Pradesh, and in coastal regions of Odisha. In Karnataka, Nilgiri and Palni hills in Tamil Nadu, it lives in shallow mountain creeks up to an elevation of . In West Java, it inhabits areas along slow-flowing irrigation channels, pond areas and rice fields surrounded by vegetation that offers shelter. It also occurs in mangroves. In the 1980s, a few Asian small-clawed otters escaped from captivity in England and established a population in the wild.


Behaviour and ecology

The Asian small-clawed otter is mostly active after dark. It lives in groups of up to 15 individuals. In the Bangladesh Sundarbans, 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 at latrine 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 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
crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
s,
mudskipper Mudskippers are any of the 23 extant species of amphibious fish from the subfamily Oxudercinae of the goby family Oxudercidae. They are known for their unusual body shapes, preferences for semiaquatic habitats, limited terrestrial locomotion and ...
s and '' Trichogaster'' fish. Its diet varies seasonally. When and where available, it also catches snakes, frogs, insects, rats and ricefield fish like catfish, '' Anabas testudineus'' and '' Channa striata''. The size of crabs found in spraints in Huai Kha Khaeng Wildlife Sanctuary ranged in
carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...
width from . Captive Asian small-clawed otters were observed to leave
shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater envir ...
in the sun, so that the heat causes them to open. That way, they consume the crustaceans without having to crush the shells.


Reproduction

Information about the Asian small-clawed otter's mating and breeding behaviour has been studied in captive environments. Captive pairs are
monogamous Monogamy ( ) is a form of Dyad (sociology), dyadic Intimate relationship, relationship in which an individual has only one Significant other, partner during their lifetime. Alternately, only one partner at any one time (Monogamy#Serial monogamy, ...
. The estrous cycle of females lasts 28 to 30 days with estrus lasting between one and 13 days. Usually, mating takes place in the water.
Gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
lasts 62 to 86 days. Interval between births is at least eight months. About two weeks before parturition, 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. 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 for its fur, loss and
destruction of habitats 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 ...
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
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...
s. It is the most sought after otter species for the illegal pet trade 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 Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
; 35 of them were bound for sale in Japan.


Conservation

The Asian small-clawed otter was listed on CITES Appendix II and is protected in almost all range countries prohibiting its killing. Since August 2019, it is included in CITES Appendix I, thus strengthening its protection in regards to international trade.


In captivity

The Association of Zoos and Aquariums established a Species Survival Plan for the Asian small-clawed otter in 1983 to encourage research on captive breeding. In Europe, Zoo Basel keeps Asian small-clawed otters together with Indian rhinoceros. Asian small-clawed otters suffering from
osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone ...
display resorption of hyperactive bone and cartilage by osteoclasts in many bone sites, which causes pockmarks on all the bones.


References


External links

* * * * {{Taxonbar, from=Q244277
Asian small-clawed otter 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. It has short claws that do not extend beyond the pads of its web ...
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 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. It has short claws that do not extend beyond the pads of its web ...
Taxa named by Johann Karl Wilhelm Illiger Articles containing video clips