Classification and Range
Otters belong to the Mustelid family which includes weasels, skunks, badgers and wolverines. The otter subfamily Lutrinae has 13 species in six genera. The Aonyx genus includes three clawless or small-clawed species. The Asian small-clawed otter is also known as the Oriental or Malaysian small-clawed otter, Asian clawless otter or short-clawed otter.
The range of the Asian small-clawed otter encompasses southern and southeastern Asia, including areas of India, Indonesian islands, Malaysia, Southeast Asia, Taiwan, southern China and Palawan in the Philippines.
The Asian small-clawed otter uses a wide variety of watery habitats which provide shallows or pools for hunting, denning areas along banks, and sheltering vegetation. While most inhabit tropical or subtropical regions, others live in sub-montane streams in the Himalayan foothills. They use natural habitats of ponds and lakes, rivers and streams, coastal tide pools and estuaries, freshwater and mangrove swamps, and also human habitats, especially rice fields.
All otters share characteristics adapted for an aquatic lifestyle. Their bodies are long, streamlined and short legged. Their long undulating, muscular tails (except sea otters), webbed paws and powerful hind limbs propel them through water. Otters have very dexterous front paws with opposable “thumbs” for grasping. The small, rounded ears have a valve structure enabling closure underwater when their nostrils also close. Vibrissae, stiff hairs on the snout and elbows, sense water turbulence and aid in locating prey. Otters have duo-layered coats. The underfur is extremely dense for warmth and the outer guard hairs provide water-proofing.
The three Aonyx genus species have partial webbing and blunt or no claws on some toes. Their common names reflect this: Asian small-clawed (A. cinerea), African clawless (A. capensis), and Congo clawless (A. congicus). While their fingers are stubby, their paws are still agile and dexterous. Their hunting technique is more hand-oriented, as opposed to the mouth-oriented hunting of more web-footed otter species. In size, the Asian small-clawed is the smallest otter with the giant otter the longest and the sea otter the heaviest. The North American river otter is twice the size of the Asian small-clawed otter.
Length from head to tail: 2 – 3 feet (0.6 – 0.9 m); tail 8 – 12 inches (0.2 – 0.3 m)
Weight: 2.2 – 11 pounds (1 – 5 kg)
In the wild up to 10 years; around 11 years in captivity.
Carnivorous. Invertebrates such as crabs, mollusks and snails comprise major food sources along with small fish and amphibians. Diet includes insects, birds and bird eggs, rodents, snakes and worms.
Reproduction - Big bonded family
Otters reach sexual maturity at 2 to 3 years old but may not reproduce until 5 to 7 years. Males of most species have little to no role after breeding; however, Asian small-clawed otters form large bonded families. Together the monogamous pair digs a den along a bank or uses another animal’s empty den. They mate in the water but occasionally on land. Gestation lasts 60 to 64 days and typically results in two or three young, but can be up to six young. Both parents care for the tiny pups which are born toothless and with eyes closed. Males provide food for nursing females. By 40 days, the pups’ eyes open and by 60 days they actively swim. The pair usually produces two litters each year. They remain together for life with the female as dominant partner. Older offspring help raise the young and stay until one parent dies when the extended family disbands. Groups usually contain eight to 12 individuals, but can include as few as four or as many as 30.
Life in a lodge
A group of otters comprise a lodge. With large families, Asian small-clawed otters are more social than most otter species. They are also more vocal with at least 12 different vocalizations. Each whistle, buzz, twitter, chirp or staccato chuckle has a distinct meaning, such as alarm, distress, greeting or mating calls. Otters, like other mustelids, communicate with scent. With the exception of sea otters, otters have paired scent glands at the base of their tails which emit heavy, musky odors. Scent markings pass information such as sexual readiness. Scented feces deposits and small mounds of gravel, sand, mud and vegetation indicate territorial boundaries.
Otters live a high energy life style. Very high metabolism rates help keep their bodies warm in cold water. This requires frequent eating and multiple hunting sessions each day. Otters are fast, flexible swimmers and can remain underwater five minutes or perhaps longer. Asian small-clawed otters prefer shallow waters where they probe in mud and under rocks for prey. Their long, sensitive whiskers and short but nimble fingers detect prey. Their large, broad, back teeth crush hard shells of crabs and snails. Asian small-clawed otters spend more time on land than most otters. On banks or back at the den, they dry their fur by rolling or rubbing, groom to maintain the fur’s insulation, and rest. Otters can be agile and quick on land, allowing them to flee to water for safety.
Otters play with purpose. Play activity hones hunting and fighting ability. For the very social Asian small-clawed otters, play enhances family bonds and rules of behavior. Some play may actually be for sheer enjoyment, for example river otters repeatedly sliding down snow banks.
Otters in Culture - Who is helping/harming whom?
Charismatic, small and acrobatic, otters find themselves part of the pet trade in some range countries, especially in SE Asia. Fishermen have trained Asian small-clawed otters to drive fish into their nets. In rice fields, otters help by consuming crawfish, crab and snail considered agricultural pests. However, when otters forage and accidentally uproot rice plants, they are considered pests. They are also killed as pests around aquaculture facilities for farming shrimp and prawns. People poach otters for their soft pelts, meat, and body parts used in some traditional Asian medicines. Due to habitat loss, now more otters live closer to human communities. In the wild, otters have few natural predators; however, domestic dogs both kill otters and spread canine diseases into otter populations.
Location at the Zoo
Asian small-clawed otters are featured in the Bamboo Forest Reserve exhibit complex, open May 2013. Bamboo Forest Reserve also includes a tropical aviary and will feature new homes for sloth bears and Malayan tigers when Phase Two of fundraising and construction is complete.
Bamboo Forest Reserve is part of the Tropical Asia biome at the zoo, which also houses exhibits for elephants, orangutans, siamangs, lion-tailed macaques, Indian python, Malayan tapirs and Visayan warty pigs. Looking for the North American river otter? That species can be seen in the Northern Trail biome.
With rapidly declining habitat, range and population, the Asian small-clawed otter moved from Near Threatened status in 2004 to the more serious Vulnerable category in 2008. The population in the wild is unknown, with some estimates at 5,000 and others at far fewer. Once common, Asian small-clawed otters are locally extinct in Hong Kong, Singapore and in India’s Sunderbans and East Calcutta. While all otter species have “Protected Status” under Convention on International Trade in Endangered Species (CITES) and killing is prohibited in most range countries, enforcement remains very limited.
Habitat loss presents otters the gravest threat. As southern and southeastern Asian populations grow rapidly, human activities expand into otter habitat. Deforestation, drainage of wetlands and growth of plantations drastically reduce suitable habitat. Housing areas with accompanying sewage and trash, agriculture and aquaculture, plus industry and mining all introduce pollutants. Pesticides, heavy metals and wide-spread use of PCBs (an organic compound) seriously impact otter health. The otters’ prey base also suffers and declines. Other otter species (smooth-coated, Eurasian and hairy-nosed) share ranges with Asian small-clawed otters, as well as many other endangered species including Malayan and Sumatran tigers, elephants, orangutans and tapirs.
Otters need help. National parks and preserves exist in some range countries and some healthy populations of otters exist. However, environmental disturbances outside of these areas still impact them. Little is known about Asian otters in the wild. IUCN Otter Specialist Group coordinates efforts in field surveys, census studies, expansion of protected areas, and awareness building.
Institutions accredited by the Association of Zoos & Aquariums are participating in a Species Survival Plan (SSP) for the Asian small-clawed otter, a cooperative captive breeding and conservation program designed to maintain genetic diversity in species populations. The Asian small-clawed otter SSP serves as a model for other endangered otter species captive management programs.
Sources and Suggested Reading
Otter Specialist Group website. http://www.otterspecialistgroup.org/
Otter World website. http://www.otter-world.com
“Action Plan for Asian Otters” http://data.iucn.org/dbtw/html/otter/11.html
“Aonyx cinerea” http://www.IUCNredlist.org/apps/redlist/details/44166/0
“Appendix 1: Cites Otter Identification Sheets” http://data.iucn.org/dbtw-wpd/html/otter/Appendix%201.html
“Asian Small-clawed Otter” http://www.brookfieldzoo.org/czs/Brookfield/Exhibit-and-Animal-Guide/Tropic-World/Asian-Small-clawed-Otter
“Asian small-clawed otter” http://www.montereybayaquarium.org/animals/AnimalDetails.aspx?enc=VsGX+Lst7QZGKQu2utONtw
“Asian small-clawed otter” http://www.seaworld.org/animal-info/animal-bytes/animalla/eumetazoa/coelomates/deuterostomes/
“Asian Small-Clawed Otter (Aonyx cinerea)” http://www.nagonline.net/Fact%20Sheet%20pdf/AZA%20-%20Asaian%20Small-clawed%20Otter%20species
Gonzalez, Jeric Bocol. “Distribution, Exploitation and Trade Dynamics of Asian Small-clawed Otter Amblonyx cinereus Illiger 1815 in Mainland Palawan, Philippines” April 2010. http://www.otterspecialistgroup.org/Library/Papers/Distribution_Exploitation_and_Trade_Dynamics_of
“Mammals: Otter” http://www.sandiegozoo.org/animalbytes/+-otter.html
“Oriental Short-clawed Otter” http://www.sch.im/wip/pages/short-clawed%20otter%202.htm
“Otters” and “The Weasel Family.” Macdonald, David ed., The Encyclopedia of Mammals. An Andromeda Book. Spain, 1999. pp.108-109, 124.
“Short-Clawed Otter (Aonyx cinerea)” http://www.indonesianfauna.com/shortclawedotter.php