Aonyx cinerea - Small-clawed otter

Photo by: Shirley Ng

NameBinomial: Aonyx cinerea (Illiger, 1815)Vernacular: Small-clawed otterOther names: Asian small-clawed otter, Asian short-clawed otter, Oriental small-clawed otter

EtymologyThe species epithet refers to the rudimentary claws of the species.

Taxonavigation

Class: MammaliaOrder: Carnivora

Family: Mustelidae

Genus: AonyxSpecies: cinerea

Table of contents

DiagnosisDescriptionBiologyDistributionThreatsType informationLinks to other types of species pages

Diagnosis

Two otter species occur in Singapore. They include the larger and more common smooth-coated otter Lutrogale perspicillata and this species which is cat-sized when fully grown. Below are several diagnostic features that set them apart from other Asian species.

Smooth-coated otter (Photo by: Meryl)

Small-clawed otter (Photo by: Soon Tuck)

From Sivasothi, 1995 1

The small-clawed otter is the smallest species of otter with a body length of about 0.9m, which is only slightly more than half the size of a smooth-coated otter. Although there can be overlaps in size with the cubs of larger species of otters, a family group which consists entirely of small-sized otters is a telling sign that it is of this species.

Approximate relative size of Singapore species. A: Small-clawed otter; B: Smooth-coated otter. (from Sivasothi, 1995)

Another diagnostic feature is their paws. As its common name suggests, the small-clawed otter has incompletely webbed feet which bear reduced claws that do not extend beyond the toes unlike the other Asian species.

Forepaw of A: Small-clawed otter; B: Smooth-coated otter (ZRC Specimen: from Sivasothi,1995 1 )

Their rhinaria is usually bare with a flat dorsal margin and anterior surface protruded forward, distinctly different from the other Asian species.

Rhinariums of Asian otters. A: Small-clawed otter; B: Smooth-coated otter; C: Eurasian otter; D: Hairy-nose otter (ZRC Specimen: from Sivasothi,1995 1 )

Description

Schematic drawing of  , side view (from: Sivasothi & Nor, 1994)Aonyx cinerea 2 .

Size: Smallest otter species in the world of about 0.9m long and 5kg in weight.Head & Body (HB) Length: 406-635mm; Tail length (T): 246-351mm; Total length: 652-939mm; weight usually 2.7-5.4kg. The females are on average only

.a little smaller than the males  1 3 4   5

Feet: Narrow, webbed only to last joint of toes; claws reduced, blunt

Tail: Tapered, not unusual

Rhinarium: Pink or dusky; bare; flat dorsal margin  1

Colour: Generally very deep chocolate, almost blackish-brown, sometimes with a rufous tinge; paler below 3 4  whitish to greyish.

Biology

HabitatSmall-clawed otters are found in a variety of habitats which include freshwater swamps, meandering rivers, mangroves and tidal pools  6 7   8 . Rice fields with substantial crab abundance can also sustain otter populations  8 9 .

Feeding habitsConsists mostly of crabs and molluscs, followed by significant proportions of amphibians and fish  8 9   10   11 .Their dextrous and very sensitive hand-like front paws are used to feel for prey under boulders and logs, crevices, debris and vegetation both underwater and on the banks where their mostly invertebrate prey are hiding 12   13   14 . The dexterity of their paws can be appreciated in captivity, where juggling stones is common (see video).

Reproduction

From Lancaster, 1975 15 ; Foster-Turley & Engfer, 1988 16

Based on captive studies, small-clawed otters reach sexual maturity at 2 years. Breeding is not seasonal but based on an oestral cycle of 24-30 days, with a 3 day oestrus. Mating usually takes place in water. At the end of a 60-64 day gestation period, up to 6 pups are born.This species form monogamous pairs and mate for life, with the female being dominant. Only the alpha pair of a group (the original parents) will breed.

Social organizationA gregarious species, they are often seen in groups that range from 2 individuals up to 15 12 17 18  which communicate through spraint (otter faeces) and over 12 separate vocalizations 19

More on the species biology here.

Distribution

From Hussainet al., 2008 20

The small-clawed otter has a large distribution range, extending from India in South Asia east ward through entire Southeast Asia up to Palawan (Philippines), Taiwan and southern China in the north. In recent years, it has established itself in England after escaping from captivity  21 22 .

Distribution of the small-clawed otter (From Sivasothi, 1995)

Native to:Bangladesh; Bhutan; Brunei Darussalam; Cambodia; China; India (Arunachal Pradesh, Assam, Himachal Pradesh, Karnataka, Kerala, Tamil Nadu, West Bengal); Indonesia; Lao People's Democratic Republic; Malaysia; Myanmar; Nepal; Philippines; Singapore; Taiwan, Province of China; Thailand; Vietnam

Threats

From Melisch  , 1996et al. 9  and Hussain et al., 2008 20

Listed as 'Vulnerable' by IUCN and under Appendix II of CITES, the biggest threat to small-clawed otter populations is habitat destruction. Around Asia, wetland habitats are being reclaimed, dammed and converted to aquaculture among other things. The quality of existing habitats are reduced when waterways are canalized or dammed as bankside vegetation is reduced and high concrete walls are constructed, making it highly unfavourable for otter landings. Reduction of prey biomass and heavy metal contamination also contribute to the decline of otter populations.

Although protected by CITES, the small-clawed otter still faces the threat of being hunted for their pelt, killed as a pest and illegally traded in Indonesia where wildlife law enforcement is lacking.

Otters are fully protected under Singapore law 2 . However they are still at risk amid ongoing development. Reclamation work, damming and canalization of rivers, conversion of wetland habitats to urban areas, pollution and high coastal activity continue to threaten otter survival.

Status in Singapore

Small-clawed otter sighting in Singapore (Photo by: Norman Lim)

From Sivasothi & Nor, 1994 2

Two species of otters, the small-clawed otter and smooth-coated otter Lutrogale perspicillatahave been recorded in Singapore. Old records suggest that this was a common and abundant species in Singapore prior to the 1950s. However, from Harrison's (1966) 22  time, they appeared to be visitors rather than residents. In 1989, there was possibly a resident population in Pulau Tekong Besar (an island northeast of mainland).

From Sivasothi, 1994 23

Based on several sightings between 1994 and 1995, it was concluded that a family group of at least one adult and four cubs was resident in Pulau Tekong Besar - the first recent records of resident small-clawed otters in Singapore.

From Vertebrate Study Group of the Nature Society (Singapore) and Raffles Museum of Biodiversity records,Recent records (post-1998) of small-clawed otters are far and few between. The records were mostly between 2004 to 2006 and concentrated to the northeastern islands of Singapore (Pulau Tekong and Pulau Ubin).

Taxonomy

Being such a well-known species, it is surprising to find out that their taxonomy has always been problematical.

From Sivasothi, 1995 1

Taxonomic problems mainly concern its generic status. According to Harris 4 the species was first described as   by Illiger (1815). Lutra cinereaSubsequently, it was considered   Amblonyx Rafinesque, 1832, a subgenus of Aonyx Lesson, 1827, followed by many mammal listings; though some use A

 as a full genus. This classification was based on the assumption that rudimentary-clawed otters were closer related compared to the clawed ones. mblonyxWhen Van Zyll de Jong 24  subjected quantitative and qualitative characters of extant species of otters to morphometric and cladistic analyses respectively, the results indicated that   are divergent taxa.Amblonyx and Aonyx

During the rest of the 19th century, the species was renamed frequently, becoming amongst other things: Lutra leptonyx Horsfield, 1824; Thomas, 1889, Aonyx leptonyx Cantor, 1846, Aonyx horsfieldii Gray, 1837, Lutra barang Blyth, 1863, Micraonyx cinerea J. A. Allen, 1922; G. M. Allen, 1938. The specific epithet assignment of   or   was also a point of contention, where supporters of the latter argued that it should be accordance with the cinerea cinereusgender of the genus 24 . 

Eventually, the names  ,   and   were used.Aonyx cinerea Aonyx cinereus Amblonyx cinereus

From Koepfliet al., 2008 25

A recent publication based on molecular taxonomy made it clear that this was the latest Asian otter species to arise and that surprisingly, was more closely related to the smooth-coated otter   rather than the African clawless otter  .Lutrogale perspicillata Aonyx capensis

Phylogeny of extant otter species

Type information

The holotype and original description for any species is always crucial for its documentation. It is especially so for the case of Aonyx cinerea, which was initially known under many names until the realization that they all referred to the same species. The holotype for this species was designated long after the original descriptor, Illiger, 1815.

From Becking, 1989: 51 26

The holotype is located in the Rijksmuseum van Natuurlijke Historie (National Museum of Natural History) in Leiden, The Netherlands under the epithet “Amblonyx cinerea wurmbi Sody, 1933”.

Additional holotype information,Holotype: RMNH 33855 (coll. Sody No. Bras III No. 1), adult femaleType Locality: Indonesia, E. Java, Besuki, Watangan Mts, near Puger, 50m.Collected by J. H. F. Bras, 8 November 1929Annals and Magazine of Natural History, London, Ser. 10, 12:411.

Literature and References

1 Sivasothi, N., 1995. A review of otters (Carnivora: Mustelidae: Lutrinae) in Singapore and Malaysia, and the diet of the Smooth Otter (Lutrogale  Unpublished MSc thesis, National University of Singapore. [ ]perspicillata) in Penang, West Malaysia. a b c d e f

2 Sivasothi, N. & B. H. M. Nor, 1994. A review of otters (Carnivora: Mustelidae: Lutrinae) in Malaysia and Singapore.  ,  : 151-170. [ Hydrobiologia 285 a b c]

3 Pocock, R. I., 1941.  . London: Taylor & Francis. Pp 265-317. [ ]The fauna of British India including Ceylon and Burma, Mammilia II a b

4 Harris, C. J., 1968.  . Weidenfeld & Nicolson, Lond., 397 pp. [ ]Otters: A Study of the Recent Lutrinae a b c

5 CITES, 1983. CITES otter identification sheets. (Appendix 1). In Foster- Turley et al., op. cit.: 90-113.

6 Osman, B. & S. Shariff, 1988. A preliminary survey on the status and distribution of otters in Peninsular Malaysia. IUCN/SSC Asian Otter Specialist : 11.Group Newsletter,1

7 Nor, B. H. M., 1989. Preliminary study on food preference of   and   in Tanjung Piandang, Perak.  : Lutra perspicillata Aonyx cinerea J. Wildl. Natl Parks,847-51.

8 Foster-Turly, P. 1992. Conservation as aspects if the ecology of Asian small-clawed and smooth otters on the Malay Peninsula. IUCN Otter Specialist ,  : 26-29. [ ]Group Bulletin 7 a b c

9 Melisch, R., L. Kusumawardhami, P. B. Asmoro & I. R. Lubis, 1996. The otters of West Java: A survey of their distribution and habitat use and a strategy towards a species conservation programme.  . [ ]PHPA/Wetlands International – Indonesia Programme, Bogor a b c

10 Lekagul, B. & J. A. McNeely, 1988.   Darnsutha Press, Thailand, 758 pp.Mammals of Thailand. Second edition.

11 Kruuk, H., B. Kanchanasaka, S. O’Sullivan & S. Wanghongsa, 1994. Niche separation in three sympatric otters  and Lutra perspicillata, L. lutra Aonyx  in Huai Kha Khaeng, Thailand.  ,  : 115-120.cinerea Biological Conservation 69

12 Wayre, P., 1976.  . Souvenir Press, Lond., 187 pp. [ ]The River People a b

13 Foster-Turley, P., 1991. The status of otters in Asia. In: Reuther, C.: Rochert, R. (eds.), Proceedings of the Vith International Otter Colloqium, Hanskensbuttel.  ,  : 21-25.Habitat 6

14 Kruuk, H., 2006. . Oxford Biology, 256pp.Otters: ecology, behaviour and conservation

15 Lancaster, W. E., 1975. Exhibiting and breeding the Asian small-clawed otter, Amblonyx cinerea, at the Adelaide Zoo.  ,  :International Zoo Yearbook 1563-65.

16 Foster-Turley, P. & S. Engfer, 1988. The species survival plan for the Asian small-clawed otter Aonyx cinerea.  ,  : 79-84.International Zoo Yearbook 27

17 Furuyu,Y., 1977. Otters in Padas Bay, Sabah, Malaysia.  ,  : 39-43.J. Mammal. Soc. Jpn. 7

18 Mason, C. F. & S. M. Macdonald, 1986.  . Cambridge: Cambridge University Press, Cambridge, 236pp.Otters – ecology and conservation

19 Timmis, W. H. 1971. Observations on breeding the oriental short-clawed otter Amblonyx cinerea at Chester Zoo.  ,  :109–International Zoo Yearbook 11111.

20 Hussain, S.A., P.K. de Silva. & M. M. Feeroz , 2008.  . IUCN Red List of Threatened Species, Version 2010.3. Lutrogale perspicillata http://www.. Accessed on 11 November 2011. [ ]iucnredlist.org/apps/redlist/details/12427/0/ a b

21 Jefferies D. J., 1990. The Asian short-clawed otter Amblonyx cinerea (Illiger) living wild in Britain.  ,  (3): 21-25J Otter Trust 2

22 Jefferies D. J., 1991. Another record of an Asian short-clawed otter living free in the Oxford area of England, with notes on its implication. J Otter Trust,  (5): 9-12. [ ]2 a b

23 Sivasothi, 1994. A family group of the small-clawed otter, Amblonyx cinereus (Illiger, 1815) (Carnivora: Mustelidae: Lutrinae, on Pulau Tekong Besar, the second resident wild carnivore in Singapore.  ,  : 23-31.The Pangolin 7

24 Van Zyll de Jong, C. G., 1987. A phylogenetic study of the Lutrinae (Carnivora: Mustelidae) using morphological data.  ,  : 2536-2544. [ Can. J. Zool. 65 a ]b

25 Koepfli, K-P., B. Kanchanasaka, H. Sasaki, H. Jacques, K. D. Y. Louie, T. Hoai, N. X. Dang, E. Geffen, A. Gutleb, S. Han, T. M. Heggberget, L. LaFontaine, H. Lee, R. Melisch, J. Ruiz-Olmo, M. Santos-Reis, V. E. Sidorovich, M. Stubbe & R. K. Wayne, 2008. Establishing the foundation for applied molecular taxonomy of otters in Southeast Asia.  ,  : 1589-1604.Conserv. Genet. 9

26 Becking, J. H., 1989.  . Brill Archive, 272 pp.Henri Jacob Victor Sody (1829-1959): his life and work: a biographical and bibliographical study

Links to other types of species pageshttp://www.otterspecialistgroup.org/Species/Aonyx_cinereus.htmlhttp://data.iucn.org/dbtw-wpd/html/Otter/Appendix%201f61.html

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This page was authored by   Meryl ThengLast curated on 2011