Otters

ASIAN SMALL-CLAWED OTTER

Amblonyx (or Aonyx) cinerea

Physical Description

The Asian Small-clawed, Short-clawed, or Clawless, Otter’s name derives from its small claws, which do not protrude beyond the ends of its digital pads. This otter is also known as the Chinese Dwarf Otter and the Laughing Otter of India.

The Asian Small-clawed Otter’s feet lack fully developed webbing and look very much like human hands. Specialised structures on the Small-clawed Otter’s eyes enhance the Otter’s vision on land and in the water. The Small-clawed Otter has a dark brown to ash grey coat with lighter undersides. The Otter’s throat is pale grey to whitish.

The Asian Small-clawed Otter is the smallest of the 13 otter species. Adult Small-clawed otters weigh between 2.7 and 5.4 kilograms (six and 12 pounds). The Otter’s average length is 65 centimetres (two feet) from head to tail, and the average length of the Otter’s tapered tail is over 20 centimetres (eight inches).

Habitat

The Asian Small-clawed Otter inhabits freshwater and peat swamp forests, rice fields, lakes, streams, reservoirs, canals, mangroves, and tidal pools. The Otter avoids bare, open areas that offer little shelter. The Asian Small-clawed Otter is found in the hill ranges of southern India and Kerala, in the Himalayan foothills of northern India, Nepal, Bhutan, and Tibet, in southern China and Taiwan, in northwest India and Bangladesh, and throughout South East Asia.

Eating Habits

In the wild, the Asian Small-clawed Otter’s diet consists mainly of crabs, snails, mollusks, and other crustaceans. The Otter uses its sensitive finger pads to locate its prey in the mud beneath rocks. The Small-clawed Otter’s diet requires the otter to do more crushing than slicing, and as a result, the Otter has developed enlarged, broadened cheek teeth. The Small-clawed Otter also feeds on aquatic birds, frogs, and small fish.

Although otters in the wild rarely eat plants, otters in captivity quickly adapt to plant-based diets.

Behaviour and Reproduction

The Otter is active during the day and the night, but is mainly nocturnal. The Asian Small-clawed Otter, unlike sea otters, actually spends more time on land than in water. The Otter takes shelter in riverside shrubbery, the deserted dens of other animals, and dens it has constructed itself.

A Small-clawed Otter’s everyday activities include hunting, sleeping, sunning on rocks or stumps, and playing. Games popular with the social animal include chasing other otters and slipping and sliding on muddy or icy hills. The Asian Small-clawed Otter is one of the few species of otters that lives in social groups. Groups range in size from four to 12 otters. The otters use at least 12 distinct calls to communicate amongst themselves.

The Small-clawed Otter usually fishes or swims in quiet pools and sluggish streams. The Otter is a skillful, agile swimmer and diver. The Smallclawed Otter keeps its front legs tucked tightly under its body while swimming. The Otter kicks its hind legs to propel itself through the water and uses its lean tail for steering. The Small-clawed Otter has great endurance. On long-distance swims, the Otter swims on its back or its side.

The Small-clawed Otter is able to remain underwater for six to eight minutes.

The Small-clawed Otter can give birth to up to two litters per year. The Otter’s gestation period is 60 to 64 days. Each mother generally gives birth to two to six pups. Otters pair for life, and as such, father and mother both participate in raising the pups. Pups are small and helpless at birth, not opening their eyes for 40 days. The pups are able to swim by nine weeks of age, and begin eating solid food at about 80 days of age.

The pups reach sexual maturity by two to three years of age. Young otters usually remain with their parents even after they have reached maturity, forming the nucleus of a small social group. The life span of the Small-clawed Otter is about 11 years for otters in captivity.

Present Status

The Asian Small-clawed Otter is categorized as Lower Risk: Near Threatened in the 2003 IUCN Red List of Threatened Species and is listed in Appendix II of CITES. The Asian Small-clawed Otter is under second class protection in China and is included in Schedule IV of the Indian Wild Life (Protection) Act of 1972.

Threats to Survival

Much of the Asian Small-clawed Otter’s habitat has been destroyed by developmental activities, including the reclamation of peat swamp forests and mangroves, increased human settlements, aquaculture, and logging, which results in the siltation of small streams. Furthermore, the Otter’s prey base has been negatively impacted by overharvesting and the contamination of waterways with organochlorides and heavy metals.

As a result, fewer prey are available for the otters to eat, and otters that eat contaminated prey may become ill and die or fail to reproduce successfully. The Asian Small-clawed Otter is also mercilessly hunted for its pelt, which is used to trim garments.

References

Columbus Zoo, Asian small-clawed otter, http://columbuszoo.com/animalareas/islands/otter.html, Aug 2004.

Hussain, S.A., 2000: Amblonyx cinereus. In: IUCN, 2003: 2003 IUCN Red List of Threatened Species, http://www.redlist.org. See also: http:/

/www.wii.gov.in/envis/envisdec99/smallclawedotter.htm, Aug 2004.

International Otter Survival Fund, Species – Asian Short Clawed Otter, http://www.otter.org/Small%20clawed.html, Aug 2004.

Lincoln Park Zoo, Asian Small-clawed Otter, http://www.lpzoo.com/tour/factsheets/mammals/s_c_otter.html, Aug 2004.

 

EURASIAN RIVER OTTER

Lutra lutra

Physical Description
There are about eleven subspecies of the Eurasian River Otter, which is also known as the European, Common, or Old World Otter. One of these subspecies definitely occurs in Tibet, and at least four others occur in nearby regions. The range of Lutra lutra kutab extends from Kashmir to Tibet, L. lutra monticola and L. lutra aurobrunnea are found in the Himalayas, L. lutra lutra ranges across northern Asia and Siberia, and L. lutra chinensis occurs in China and Taiwan.
The Eurasian River Otter’s coat is grayish brown to reddish or dark brown, with a lighter belly. The Otter’s lips, cheeks, and throat are spotted yellow, grey, or white. The Eurasian River Otter’s fur is dual-layered. The coarse, glossy guard hairs that compose the outer layer of the Otter’s fur measure about 17 to 18 millimetres long and are waterproof. The Eurasian River Otter’s soft, dense underfur measures about 8 to 9 millimetres long and provides insulation.
Like other mustelids, the Eurasian River Otter has a long body with short legs and a thick, round tail that tapers and flattens from the base to the tip. The Otter’s body, including its tail, is muscular; the Otter lacks the insulating layer of body fat found in other aquatic mammals, relying entirely on its fur to keep it warm. The Eurasian River Otter has small, round ears set low on its head, small, round, and wide-set eyes, a short, broad, round muzzle, a trapezoid-shaped nose, thick whiskers, powerful jaws, and a short, thick neck.
The Eurasian River Otter has developed several adaptations for aquatic life. In addition to having waterproof guard hairs, the Otter has webbed paws, with five toes each and strong claws. The Eurasian River Otter uses its webbed paws in combination with its powerful tail to propel itself in the water. The Otter’s front legs are shorter than its back legs, which makes the Otter a more efficient swimmer. The Eurasian River Otter can also close its ears and nostrils to prevent water from entering during dives underwater. The Otter is able to remain underwater for up to two minutes.
The Eurasian River Otter is medium-sized in comparison to other otters. The Otter’s body length is 55 to 95 centimetres (22 to 38 inches) and the Otter’s tail length is 30 to 55 centimetres (12 to 22 inches). The Eurasian River Otter stands about 30 centimetres (12 inches) tall at the shoulder, and weighs from five to 12 kilograms (11 to 26 pounds).

Habitat

The Eurasian River Otter inhabits many different types of shallow freshwater ecosystems, including rivers, lakes, streams, marshes, swamp forests, rice fields, sewer systems, estuaries, caves, and terrestrial habitats adjacent to waterways. The Otter is found at elevations from below sea level (in the Netherlands) to above 4,120 metres, or 13,500 feet (in Tibet).
The Eurasian River Otter builds dens for itself called holts, by lining, with grass and dry leaves, holes in the river bank or hollows among tree roots, piles of rock, wood, or debris. Entrances to the holts are generally located underwater. The living chambers, located above ground, include ventilation shafts. The Otter rarely strays more than 100 metres (330 feet) away from water.
The Eurasian River Otter is distributed more widely than any other otter species. The Otter is found throughout Europe and Asia, south of the Arctic Circle, and even occurs in a portion of northern Africa.
Eating Habits
The Eurasian Otter hunts and feeds several times in a day, consuming about one kilogram of food per day. The bulk of the Eurasian Otter’s diet (sometimes over 80%) consists of fish. The Otter also eats crustaceans, clams, small mammals including rabbits and voles, amphibians, water birds, eggs, insects, worms, and some vegetation. The Eurasian Otter uses its whiskers to sense the movements of prey underwater. The Otter uses its mouth, rather than its hands, to catch its prey.
Behaviour and Reproduction

Eurasian River otters are most active at dusk and during the night. Except in coastal areas, the otters usually spend the days resting under cover or sunning themselves. Eurasian River otters occasionally form groups of up to six animals, but for the most part, otters are solitary, with the exception of mothers accompanied by their young and mates paired temporarily. On the other hand, otters do like to play with each other.
Young and old otters alike have been observed sliding down slopes covered with mud or snow on their bellies and chasing each other in the water. Eurasian River otters communicate with each other vocally, using over 12 specific calls.

Eurasian River otters are territorial, using scent marking to delineate the boundaries of their home ranges and displaying aggression towards intruders of the same sex. Home ranges measure about seven to 15 kilometres (four to nine miles) for straight-line territory. Males have larger territories than females. The most dominant males within a hierarchy occupy the most favorable areas. Male territories may overlap the territories of several females, but not the territories of other males. Similarly, female territories do not overlap each other.
The Eurasian River Otter reaches sexual maturity at two to three years of age. The Otter is able to breed throughout the year. When the peak in mating occurs depends on climatic conditions. Mating occurs both on land and in the water. The Eurasian River Otter’s gestation period is 61 to 65 days. Females give birth in their holts. Litter sizes range from one to five cubs and average two or three cubs. Cubs weigh 99 to 122 grams (3.5 to 4.3 ounces) and are covered in soft dark or grey fur at birth.

Cubs begin to crawl at two to three weeks of age and begin to swim at eight weeks of age. Cubs do not open their eyes until about four to five weeks after birth. Cubs are weaned at about three to four months of age, and generally leave their mothers at eight to twelve months of age. Occasionally, cubs stay with their mothers until they are 14 months old.
The Eurasian River Otter’s life span, for otters in the wild, is about ten to fifteen years. In captivity, the Otter may live for as many as 22 years. The Eurasian River Otter’s natural predators include wolves, lynx, and birds of prey.
Present Status

The Eurasian River Otter is categorized as Vulnerable in the 2003 IUCN Red List of Threatened Species and is included in Appendix I of CITES. The Otter is under second class protection in China and is listed under Schedule IV of the Indian Wild Life (Protection) Act of 1972. The Eurasian River Otter has become extinct throughout much of its range, and its populations have decreased significantly in other areas.

Far more is known about the status of the otters inhabiting Europe than those inhabiting Asia.
Threats to Survival

The most severe threat to the Eurasian River Otter’s survival is the loss and degradation of the Otter’s fragile aquatic habitat as a result of several developmental activities. These include the canalization of rivers, the construction of dams, the removal of bank side vegetation, wetlands draining, and aquaculture. Furthermore, industrial waste, untreated sewage, and agricultural runoff have polluted waterways the Otter depends upon.

The Eurasian River Otter is also threatened by hunting, especially in the Asian region, where the trade in endangered animal products continues to flourish despite legislation efforts. In Tibet, otter pelts are used to line and trim traditional garments. The Eurasian River Otter may additionally be killed in traps or nets set for other animals. In areas where the Otter lives in close vicinity to roads, otters are vulnerable to being accidentally run over.
References

BBC, BBC – Science & Nature – Wildfacts – Eurasian river otter, European otter, common otter…, http://www.bbc.co.uk/nature/wildfacts/
factfiles/196.shtml, Oct 2004.
Kennedy, S., 2003: Lutra lutra, Animal Diversity Web, http://animaldiversity.ummz.umich.edu/site/accounts/information/
Lutra_lutra.html, Oct 2004.
Otternet, OTTERNET.COM Species Profiles- Eurasian Otter, http://www.otternet.com/species/otter.htm, Oct 2004.
Postanowicz, Rebecca, Lioncrusher’s Domain — Eurasian River Otter (Lutra lutra) facts and pictures, http://www.lioncrusher.com/
animal.asp?animal=179, Oct 2004.
Reuther, C., 1999: Lutra lutra, In: IUCN 2003, 2003 IUCN Red List of Threatened Species, http://www.redlist.org, Oct 2004.
Hussain, S.A., Mustelids, Viverrids and Herpestids of India: Species Profile and Conservation Status, www.wii.gov.in/envis/envisdec99/
eurasianotter.htm, Oct 2004.

By: Environment and Development Desk, DIIR, CTA.