Hairy-nosed otter  (Lutra sumatrana)

Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (4).

Perhaps the world’s rarest otter, the hairy-nosed otter is a little-known, enigmatic species endemic to Southeast Asia. The most distinctive feature of this otter is its hairy rhinarium (surface around the nostrils), which is covered in short, dark fur, apart from the upper-edge of the nostrils, which is bare (3) (5). The fur on the upperside of the body is typically a silky dark brown, occasionally tinged with red, fading to a lighter colour on the underside, and yellowish-white on the throat, chin and upper lip (2) (3) (5). The long, sinuous, streamlined body and fully-webbed feet are superbly adapted for aquatic life, while the well-developed claws, make this otter equally at home on land (2) (5). The skull of this species is flattened and elongate, and equipped with numerous sensitive whiskers used for detecting prey underwater (2) (5). The hairy-nosed otter may also be distinguished by the rounded base of its long, tapering tail and the lack of extensive lightened fur down the sides of the body, a common feature on other Asian otters (5).  

Due to elusive habits, and a lack of species-specific surveys, the distribution of the hairy-nosed otter is poorly understood. Endemic to Southeast Asia, historically it may have been widespread in this region; however, due to rapid trade-driven declines and habitat destruction, it is now likely restricted to isolated populations (6). Currently, the species is known from Sumatra (Indonesia), southern Thailand, Peninsular Malaysia, Sabah (Malaysia), Southwest Cambodia, Tonle Sap lake in Cambodia, and southern Vietnam (5) (7) (8) (9) (10) (11) (12) (13). There are also historical records from Brunei, Sarawak (Malaysia) and northern Myanmar (1) (6).

The hairy-nosed otter has been found in lowland peat swamp forests, freshwater wetlands, Melaleuca forests, evergreen swamp forest and coastal areas, including mangroves (1) (3) (5) (6). Historical records also suggest that this otter may have previously been found at higher altitudes, occupying freshwater streams up to 1,800 metres (5).

As there have been so few observations of the hairy-nosed otter in the wild, very little is known of its biology. However, this elusive species has been photographed early in the morning and late in the afternoon, and also been observed to be active at night (5). Fish and water snakes are the preferred prey of this otter, although it may supplement this diet with a variety of frogs, lizards, turtles, crabs, small mammals and insects (1). The most commonly employed hunting method is believed to be a quick lunge at speed that startles its prey and traps it in the roots of a semi-submerged tree, although this stealthy predator is also known to steal from fishing nets (5). In the water, the hairy-nosed otter has few natural predators, aside from pythons, and the Siamese crocodile (Crocodylus siamensis) in Tonle Sap Lake. On land, however, it may fall prey to feral dogs, and its cubs in particular may be taken by large birds of prey, such as the grey-headed fish eagle (Ichthyopaga ichthyaetus) (5). 

Although many otters are highly social animals and often live in small family groups, the hairy-nosed otter is thought to be a largely solitary species, like its cousin the Eurasian otter (Lutra lutra). However, groups of up to six otters have been seen, and it is possible that small family units of parents with their cubs form after the breeding season. The timing of this is not fully understood, but is thought that cubs are born from December through to February after a two month gestation period (1) (5).

Scent marking with faeces, urine and scent glands is an extremely important form of communication amongst otters. Fishy, musky smelling spraints are typically placed on exposed logs or branches in the water to inform other otters of the boundaries of foraging sites (2) (12). Various vocalisations are also used to communicate, with the most commonly heard sound of the hairy-nosed otter being a single syllabic chirp, while chatters are also used by mothers to their cubs (5).

The most significant threat to the survival of the hairy-nosed otter is the illegal wildlife trade (5). A single otter pelt may fetch up to $200, an attractive reward to many hunters who often live in economically poor areas, and the hairy-nosed otter may also be hunted for its meat, with hunting still particularly rampant in Tonle Sap Lake and the Mekong Delta (5) (10). As a result of this hunting, otter populations across Southeast Asia have undergone substantial declines (1) (14).

The hairy-nosed otter is further threatened by the loss of its habitat. Tropical peat swamps are under immense pressure from unnatural fires, palm oil plantations, encroaching agriculture, logging and, in Vietnam, fish farming (1) (5). This is most severe in the Mekong Delta, where the majority of the area has been converted to rice paddies, and in Indonesia, where the coverage of peat swamps has been halved in the last 20 years (1). Furthermore, much of the remaining habitat has already been selectively logged and is further threatened by pollution and development (1) (5).   

Overharvesting of water snakes and fish in the Mekong Delta is also likely to be having a detrimental effect on some of the hairy-nosed otter’s key food resources, and this represents a significant threat to this otter, as well other otter species found within the region (15).

Its limited distribution, and the rarity of sightings make the hairy-nosed otter a good candidate for ex-situ conservation (3). Unfortunately, however, maintaining this species in captivity has proved challenging, with previous animals succumbing to disease and other illnesses, and at present there are no captive animals (16).

The hairy-nosed otter is protected by law in all of its range states, and is also listed on Appendix II of the Convention on the International Trade in Endangered Species (CITES), which should ensure that international trade is monitored (1) (4). Its habitat is also protected in some areas by the RAMSAR Convention and the Convention on Biological Diversity, and it is found in a number of protected areas (1) (10). In reality, however, this species has received little protection, mainly because of a lack of law enforcement at the local level, and hunting and habitat loss has continued to threaten this Endangered species (3) (10). In addition to improved law enforcement, this species would also benefit from further studies into its ecology, and further surveys in areas which could potentially support populations, such as the Irrawaddy Delta, as information on its distribution is limited, while there is no such information on its population (3) (6).   

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on the conservation of otters, see:

• The IUCN Otter Specialist Group:
  http://www.otterspecialistgroup.org/
• The International Otter Survival Fund:
  http://www.otter.org/
• Furget-Me-Not:
  http://www.furgetmenot.org.uk/