Giant River Otter, Pteronura Brasiliensis, Giant Otter: Facts & Pictures

The giant river otter, or giant otter, is a carnivorous mammal that inhabits the rainforests of South America. On this page, you'll find giant river otter facts, pictures, video and in-depth information, giving you the complete lowdown on this distinctive semiaquatic predator...

Giant Otter Facts At A Glance

  • Scientific name: Pteronura brasiliensis
  • Other name(s): Giant river otter, giant Brazilian otter, river wolf
  • Type of Animal: Mammal
  • Animal Family: Mustelidae (the weasel family)
  • Where Found: North-central South America
  • Body length: Male 1.5 to 1.7m (4.9 to 5.6ft); female 1.0 to 1.5m (3.3 to 4.9ft)
  • Tail length: Up to 70cm (28in)
  • Weight: Male 26 to 32kg (57 to 71lb); female 22 to 26kg (49 to 57lb)
  • Conservation Status: Endangered

Giant River Otter: Introduction

Giant River Otter Head

The giant river otter, Pteronura brasiliensis, also known as the giant otter, is the world’s longest, and second-heaviest, otter species. It is native to South America, where it is found in the Amazon, Orinoco, and La Plata river systems.

The giant river otter is also the longest, and second-heaviest member of the entire weasel family, Mustilidae. (The heaviest otter (and member of the weasel family) is the sea otter, Enhydra lutris.)

Like other otters, the giant river otter is a semiaquatic, carnivorous mammal. Although primarily found on land (source), the species has numerous adaptations for moving and hunting in water, including a streamlined body with short legs, webbed feet, and a long, muscular tail.

Predominantly found near freshwater rivers, the giant river otter lives in family groups and is territorial. The members of the group communicate to one another using a diverse range of vocalizations. (The giant river otter is one of the most social, and noisiest, of all otters.)

Giant Otter In Water

The river otter digs dens, known as "holts", which serve as resting places and safe havens for raising its young. The entrances to these dens are typically underwater, providing protection from predators.

The otter's diet is primarily fish-based, but it also consumes crustaceans and small reptiles, including snakes and even small caimans.

The International Union for Conservation of Nature (IUCN) currently lists the giant river otter as "Endangered" due to threats including habitat destruction, water pollution, and historical hunting for its fur.

Giant River Otter Family And Related Species

The giant river otter is a member of the weasel family, Mustelidae. Along with weasels and otters, this family is also home to animals such as badgers and the wolverine.

Thirteen otter species are currently recognized. Together, they make up the subfamily Lutrinae.

The giant otter is the only member of the genus Pteronura, and has two subspecies: P. b. brasilensis and P. b. paraguensis. (Source: Mammal Species of the World).

What Does The Giant Otter Look Like?

Giant river otter
Giant river otter in the peruvian Amazon jungle at Madre de Dios, Peru

The giant river otter is a robust semi-aquatic mammal, known for its impressive size. Its body is streamlined and muscular, built for agility in water, with a length that can reach up to 1.8 meters (approximately 6 feet).

The fur of a giant otter is predominantly dark brown, giving off an almost black sheen when wet, and is dense and velvety to the touch, providing insulation against the cool waters it frequents. The guard fur (the outer layer of fur) is thick and water-repellent. A shorter inner coat provides insulation.

The quality of the giant otter’s coat has led to the species being targeted by fur hunters, a contributing factor to the species' endangered status.

One of the otter's most distinctive features is the white or cream-colored patch on its throat. This patch varies in shape and size and can be used to identify individuals.

The giant river otter has short, sturdy legs equipped with webbed feet, which aid in propelling the otter efficiently through water. The tail, which is long and muscular, further enhances its swimming capabilities. Its head is broad and slightly flattened, with small, rounded ears and sharp, keen eyes that are positioned high on the skull, allowing for better visibility while swimming.

Where Is The Giant River Otter Found?

Giant River Otter In The Amazon Rainforest

The range of the giant otter covers most of north-central South America, and includes the Orinoco, Amazon, and Parana basins.

Countries in which the giant river otter is found include: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, and Venezuela.


Habitats in which the giant river otter may be found include:

  • Rivers: Especially within the Amazon, Orinoco, and La Plata river systems, giant river otters frequent clear, fast-flowing rivers, preferring habitats with minimal human disturbance. It prefers areas with a high density of fish and gently-sloped riverbanks with dense vegetation.
  • Creeks and Streams: Besides major rivers, they also thrive in smaller waterways, often with dense vegetation along the banks that provide them with shelter and concealment.
  • Lakes and Ponds: While rivers and streams are primary habitats, giant river otters can also be found in larger still waters, especially if these water bodies have abundant food sources.
  • Swamps and Marshes: In areas of flooded forests and wetlands, these otters find ample opportunity to hunt and establish dens.

The species is also occasionally spotted in agricultural canals, reservoirs of dams, and roadside drainage channels.

The ideal habitat for the giant river otter is characterized by clean water with abundant food supply, especially fish, and minimal human disturbance. As apex predators, their presence in a habitat often indicates a healthy ecosystem.

Social Behavior

The giant otter is unusually sociable for a mustelid (member of the weasel family, Mustelidae). It lives in family groups of 2 to 20 individuals (typically 3 to 8), consisting of a dominant breeding pair, their offspring from several litters, and sometimes unrelated, non-breeding adults.

Family groups are highly cooperative and members will travel, sleep, play and hunt together.

The giant otter is generally a peaceful species and will usually avoid conflict. However, giant otters are known to show aggression when defending a territory against rival groups.

Territories are marked with urine and secretions from scent glands and are typically defended by adult males.

Giant River Otter Life Cycle

Giant river otters are born in dens, known as "holts," which are dug by their parents on riverbanks. These dens have underwater entrances, providing a safe environment for the vulnerable pups. Newborn otters are altricial, meaning they are born blind, helpless, and rely entirely on their parents. Their eyes open after about a month.

After around two months, the young otters, now covered in fur and more active, start to emerge from the den. They begin learning the basics of swimming and hunting, although they will continue to nurse for several more months.

As they approach their first year, the otters become more skilled hunters and start venturing further from the family unit. However, giant river otters are known for their strong family bonds, and adolescents often stay with their natal group, aiding in the rearing of subsequent litters.

Giant river otters reach sexual maturity between two and three years of age. At this point, some may choose to leave the family group to find a mate and establish their own territories.

Once a pair forms, they usually mate for life. The female undergoes a gestation period of approximately 65-70 days, after which she gives birth to a litter, typically consisting of one to five pups, though litters of up to eight have been recorded. Both parents, along with older siblings, participate in raising the young, making the giant river otter family structure notably cooperative.

In the wild, giant river otters can live up to 8-10 years, though some may live longer under optimal conditions. Throughout their lives, they maintain social structures, usually centered around a dominant breeding pair and their offspring from multiple litters.

Giant River Otter Predators

Natural predators of the giant river otter include jaguars, caimans, and anacondas.


The giant otter is a noisy animal with a diverse range of vocalizations (vocal sounds). A total of 22 distinct sounds used by adults and 11 by the young have been reported.

The sounds range from fast 'hah' barks and explosive snorts to low growls and whistles. The various vocalizations are thought to communicate danger, aggression, reassurance and curiosity.

Giant River Otter Diet

The diet of the giant otter consists almost entirely of fish, including cichlids, characins (such as piranha) as well as catfish.

When there isn't enough fish, the giant otter will also feed on small caimans, crabs and turtles as well as anacondas and other snakes. A giant otter will consume roughly 3kg (7lb) – about 10% – of its body weight per day.

The giant otter is known to hunt alone, in pairs and in groups. It prefers to hunt in shallow water, using its keen vision to locate the prey which can be attacked either from above or below. The prey is held in the otter’s forepaws and eaten immediately.

Other species competing for food resources with the giant otter include the neotropical otter (Lontra longicaudis) and various caimans.

Is The Giant Otter Endangered?

The giant otter is rated 'Endangered' by the IUCN.

Excessive hunting for its pelts until the late 1970s caused the numbers to plummet. The species is now legally protected, but the remaining population is highly fragmented across the range and most subpopulations are small.

The behavioral patterns of the giant otter make it an easy target for humans, and its late breeding age and low cub survival make it particularly vulnerable to local extinctions.

The main threats to the giant otter include:

  • Habitat loss and fragmentation: The river habitat preferred by giant otters is also used by people for settlements, mining, logging, damming, transport and tourism.
  • Other human impacts: Humans affect the giant otters also through pollution, overfishing, illegal killing, pathogens spread by domestic animals and keeping otter cubs as pets.

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