Giant otter  (Pteronura brasiliensis)

The giant otter is classified as Endangered (EN) on the IUCN Red List (1), and listed on Appendix I of CITES (3).

The giant otter, known through much of its range as the 'river wolf', is one of South America's top carnivores and is the largest of the otter species in terms of total length. The muscular, sinuous body is covered with velvety, brown fur, which is dense and water-repellent. A patch of cream colouring is present on the throat and chin, the pattern of which is unique to each individual from birth. The giant otter has short legs and large webbed feet which, along with the wing-like tail, allow the otter to move quickly through the water. The movement of prey is detected by the large eyes and sensitive whiskers (2) (4).

This species is endemic to South America (except Chile), east of the Andes mountain chain. Currently, it is almost or completely absent from Argentina and Uruguay (4), and very rare in Paraguay. The giant otter is seen within the Orinoco, Amazon and La Plata River systems (5).

The giant otter is found in slow-moving rivers and streams, lakes, swamps, and marshes, and, during the rainy season, flooded forest (2) (6).

Key factors influencing giant otter habitat preference are the presence of non-floodable banks with vegetation cover and easy access to hunting areas with an abundance of vulnerable prey in relatively shallow waters (2).

The giant otter generally lives in family groups of three to ten individuals, composed of a monogamous, breeding pair and their offspring born during previous years (2) (6). These groups rest, play, travel, fish and sleep together. Members of the group use communal latrines where they rub their faeces and urine into the earth with their paws, in order to advertise the group's residency (2) (6).

Breeding can take place throughout the year, although most young are born during the dry season. Litter size varies from one to six cubs, following a 64 to 72 day gestation (7). The new cubs are cared for by both the adults and older siblings. At two to three weeks the cubs are put in the water by the female, and at three to four months the cubs begin hunting and travelling with the family. The young are weaned at six months, and are efficient hunters by the age of ten months, although they remain with the family group for at least another year; sexual maturity is attained at age 2.5 years, after which many young adults disperse (2) (5) (6).

The giant otter is diurnal. Although highly adapted to its amphibious lifestyle, and despite its clumsy appearance on land, giant otters may travel several hundreds of metres between areas of water (2) (6). The diet is composed almost exclusively of fish, but it is also known to eat caimans, anacondas, other snakes and even the occasional turtle (2) (6).

Up until the late 1970s the giant otter was excessively hunted for its valuable fur (2) (5) (8), with its naturally curious disposition making it a particularly easy target. The fur trade is less of a threat today thanks to protective legislation, but illegal killing does still occur, often due to perceived conflict with fishermen. Some cubs are taken from the wild to be kept as pets (4), and usually die in the hands of inexperienced caretakers. Habitat loss and fragmentation, and pollution are currently the major threats to the survival of the giant otter, with the areas in which they live being destroyed and degraded by mining, logging, and damming (2) (6) (8).

The giant otter is protected through much of its range and is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which effectively bans international trade (3).

 In 1990, the IUCN developed an action plan for the conservation of otter species. It recommended a number of conservation measures for the giant otter, including continuing studies on the ecology and requirements of this remarkable species, improving the management of existing protected areas in which it occurs, and stricter regulations to prevent the escape of toxic waste from factories, human settlements and agriculture into the surrounding rivers and wetlands. Education campaigns are also required to raise awareness of the plight of this fascinating species (8).

The charismatic giant otter also plays an important role in nature tourism that may provide some financial incentives for protection measures (6).

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

To help conserve this species by working in the field with Earthwatch, click here.

Learn more about the giant otter and its conservation:

• Giant Otter Research:
  http://www.giantotterresearch.com/
• IUCN Otter Specialist Group:
  http://www.otterspecialistgroup.org/
• Giant Otter Corner:
  http://www.facebook.com/giantotter.corner
• BBC Wildlife Finder:
  http://www.bbc.co.uk/nature/species/Giant_Otter