Otter Ecology & Biology

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Physical Description

Otters are semi-aquatic members of the family mustelidae, there are 13 species in this family and they all share the same characteristics adapted for an aquatic lifestyle. They have long and streamlined bodies, powerful hind limbs, webbed paws and long tapering tails which aids in propulsion, enabling them to glide easily through the water. Otters have very dexterous front paws with opposable thumbs that are well adapted for catching and handling prey. The Asian small-claw otter (Aonyx cinerea ) is easily distinguished from other otters by its small size, they are the smallest of all the otter species. They have tiny claws which do not protrude beyond the ends of the fingers and the webbing on between their digits is incomplete. Asian small-claws typically have brown fur on its dorsal side with a paler ventral side. Their upper lip, throat, chin and face are greyish -white. They have stiff hairs on their snout and elbows called vibrissae which sense water turbulence, helping them to locate prey in the murky water. Their coats are duo-layered, the under layer is extremely dense protecting them from the cold, while the outer-guard hairs provide water-proofing.

 

Size and maturity

Asian small-claws weigh between 2.7 to 5.4 kg. Their combined head and body length has a range between 406 to 635 mm, with a tail length of 246 to 304 mm. They become sexually mature at two to three years old. Successful mating in captivity has usually taken place in the water and occasionally on land. Gestation period is around 60 days with up to two litters being produced in one calender year, with inter-birth interval being as short as eight months. Pups are born with their eyes closed which will remain so until the fifth week. They will usually stay within the safety of the breeding den until their first taste of the water at approximately two months of age and shortly after will begin to eat solid food.

 

Aggregation and distribution

Otters are gregarious animals with strong social bonds. They are monogamous, with both parents sharing the responsibility and care of the offspring. The elder siblings stay within the group to help care for the younger members of the family and as a result family groups can easily build up to between twelve and fifteen members. Asian small-claws have a large distribution, ranging from north-western and south-western India, through southern China and the Malay Peninsular to Sumatra, Java and Borneo in Indonesia and Palawan, Philippines. In Palawan they are known to dwell in swampy mangroves, freshwater wetlands, lazy streams and rice fields. They make their own dens in riversides but are also known to utilise the abandoned dens of other animals.

 

Feeding and Diet

The small-claw is adapted to feeding on invertebrates, they have two large upper teeth to aid in the crushing of crabs’ exoskeletons and other hard-shelled prey. They tend to favour crabs, snails, molluscs and small fish, but are also known to supplement their diets with rodents, snakes and amphibians too, depending on food availability.