Animal
Giant otter
The giant otter is the biggest otter of all. It lives in rivers in South America with its family and catches fish.
The giant otter is the longest otter in the world, up to about 1.8 meters from nose to tail. It lives in the rivers and lakes of South America in noisy family groups that hunt fish together by day. It is endangered, and people are working to protect it.
Pteronura brasiliensis, the giant otter or 'river wolf', is the largest otter, a highly social piscivore of South America's Amazon, Orinoco and La Plata river systems. Families led by a monogamous pair defend river territories. The IUCN lists it as Endangered with a decreasing population.
Photo: Rdavout (uploader), CC BY-SA 2.5, via Wikimedia Commons
Meet the giant otter
The giant otter is the biggest otter in the world.
It has brown fur, webbed feet and a long flat tail. It lives with its family in rivers.
The giant otter is the biggest of all the otters. From the tip of its nose to the end of its tail it can be 1.5 to 1.8 meters long, about as long as a grown-up is tall.
It has brown fur, webbed feet and a long, flat tail. In the Amazon it is sometimes called the 'river wolf', because of its large, sharp teeth and strong, muscular body. It lives, hunts and rests with its family.
Pteronura brasiliensis is the longest of the otters: San Diego Zoo Wildlife Alliance gives adults a length of 1.5 to 1.8 meters, although the sea otter is heavier. Typical adult weights are about 29 kilograms for males and 24 for females. It has also been called the Guiana flat-tailed, winged-tailed and margin-tailed otter, names that refer to its broad, flattened tail.
Chester Zoo explains its nickname, 'river wolf', by its large, sharp teeth and muscular body. Giant otters hunt by day, and they live in close family groups.
Quick facts
- Group
- Mammal
- Length
- 1.5 to 1.8 m
- Weight
- 24 to 29 kg
- Lifespan in the wild
- 10 to 13 years
Where it lives
Giant otters live in South America.
They live in slow rivers, lakes and creeks in the rainforest. They dig dens in the riverbank.
Giant otters live only in South America, in the huge river systems of the Amazon, the Orinoco and the La Plata. They like slow-moving rivers, lakes and creeks with gently sloping banks and plants hanging over the water.
A family clears a patch of riverbank to use as a campsite. The otters trample the plants flat and dig dens under fallen logs. They mark the edges of their home with their scent to tell other otter families, "This place is taken."
The species is endemic to South America. The IUCN's global assessment lists it as extant in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname and Venezuela, with its presence in Argentina and Uruguay uncertain; it lives below about 1,000 meters.
It prefers slow freshwater rivers, lakes, oxbows and creeks with gently sloping banks and overhanging vegetation. Families maintain home ranges of about 12 square kilometers and clear campsites of up to 50 square meters near feeding areas, trampling vegetation, digging burrows beneath fallen logs and placing communal latrines around the edge. The territory is scent-marked and defended against intruders.
Continent
Its habitats
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Lives here naturally · Countries and seas named by a scientific source
Slow rivers, lakes and creeks of the Amazon, Orinoco and La Plata river systems in South America. Giant otters live in only part of each country shown.
Places: Bolivia, Brazil, Colombia, Ecuador, Guyana, Paraguay, Peru, Suriname and 1 more places.
Source: iucn-red-list · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Brazil, Peru, Ecuador, Colombia, Guyana, Suriname, Bolivia, Venezuela and 5 more places.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
Fishing as a family
Giant otters eat fish, like catfish and piranhas.
They hunt in the daytime. Sometimes the whole family fishes together. They eat small fish while floating on their backs!
Giant otters are fish eaters. They catch catfish, perch, piranhas and many other fish, and an adult can eat about 3 to 4 kilograms of food a day. When fish are hard to find, they also eat crabs, small snakes and even small caimans.
They hunt in the daytime, mostly by sight. An otter may fish alone in shallow water, but in deeper water the whole family can dive together and push fish against the shore. Big fish are carried to land; small ones are eaten while the otter floats on its back.
The giant otter is a piscivore, preferring catfish, perch and characins (the family that includes piranhas); Chester Zoo also lists crabs, snakes and even small caimans and anacondas. The Animal Diversity Web estimates daily intake at about 6 to 9 pounds (roughly 2.7 to 4 kilograms).
Hunting is diurnal and mainly visual, though hearing, smell and touch help in murky water. Solitary hunts along vegetated shallows yield more fish per otter, while family groups hunt in deeper water with synchronized dives and sometimes herd prey against the bank. Large prey is taken ashore; small prey is eaten while floating on the back.
Built for the river
Giant otters have webbed feet for swimming.
Their long flat tail helps them zoom through the water. Each otter has a pale patch on its throat. No two patches look the same.
A giant otter's body is built for swimming. Its feet are webbed, and its long tail is flat, a bit like a paddle. When it swims slowly it paddles with all four feet, but to go fast it holds its feet still and waves its strong tail up and down.
Giant otters have cream-colored marks on the throat. Their shape is different on every otter, a bit like a fingerprint, so scientists photograph the patches to tell one otter from another.
Adaptations for aquatic hunting include a streamlined, muscular body, webbed feet and a broad, flattened tail; Chester Zoo calls the tail 'wing-like'. At slow speeds the otter paddles with all four limbs while the tail stays still; at high speed the feet are held still and the tail undulates to drive it forward. Like other otters, it has whiskers above the lips that sense changes in the water around it.
The pale throat markings are individually distinctive. Field researchers photograph them to build ID kits of each group: a survey on the Río Torno in northeastern Peru, carried out in July 2013 and published in 2014, identified eight individuals from their throat patterns, a key tool for following families over time.
Growing up in the family
Baby giant otters are called cubs.
They are born in a den. Their eyes open when they are one month old. They live with their mom, their dad and their older brothers and sisters.
A mother giant otter is pregnant for about 65 to 70 days. Then she gives birth in a den to 1 to 5 cubs, usually 2 or 3. Each newborn cub weighs only about 170 to 230 grams, less than a can of beans.
The cubs stay in the den for their first few weeks and open their eyes at about a month old. Then they start following their parents out to the river. By 9 or 10 months they can hunt by themselves and look just like the grown-ups.
Gestation lasts about 65 to 70 days, and births of altricial young are recorded mainly from late August to early October in observed populations, with a second litter possible if the first is lost. Litters range from one to five, usually two or three, each cub weighing about 170 to 230 grams.
Cubs remain in the family den for two to three weeks, open their eyes at about a month and then regularly follow their parents out. They are weaned at three to four months and are independent hunters, indistinguishable from adults, by 9 to 10 months. Sexual maturity comes at about two years, and lifespan is estimated at 10 to 13 years. Much of this is known from captive animals.
Noisy, busy families
Giant otters live in big families.
They groom each other, hunt together and rest together. They make lots of sounds to talk to each other.
Giant otters are very social. A family is made up of a mother and father that stay together and several generations of their young. Groups are often 5 to 8 otters, and sometimes many more.
Family members groom each other, hunt, rest and 'talk' together. Scientists have described nine different giant otter calls. If an intruder comes into their territory, the parents defend it and their young. They can also move quickly over land, sometimes traveling hundreds of meters from one pool to another.
Giant otters live in cohesive family groups built around a monogamous breeding pair and offspring from several litters. The Animal Diversity Web gives typical groups of 5 to 8, an IUCN Otter Specialist Group study cites 3 to 16 depending on region, habitat and season, and Chester Zoo reports groups of up to 20.
The Animal Diversity Web records nine distinct vocalizations, though what each one means is not well documented. Grooming, cooperative hunting and resting together reinforce the group. Territories are scent-marked with anal glands and defended. Adults have few predators (occasionally jaguars and pumas), but unattended cubs are vulnerable to large cats, anacondas and caimans.
Did you know?
Every giant otter has its own throat patch.
Scientists tell giant otters apart by the pale patches on their throats, which are different on every otter.
Individually distinctive throat markings allow photo-identification; one survey in Peru, published in 2014, identified eight otters this way.
Protecting the river wolf
There are not many giant otters left.
People once hunted them for their fur. Now that is not allowed. People are working to keep their rivers clean and safe.
Giant otters are endangered. In the past many were hunted for their water-resistant fur: Chester Zoo reports that 20,000 pelts were sent out of Peru alone between 1950 and 1970. The fur trade was banned in 1973.
Today's dangers include the loss of their riverbank homes to logging and farming, and rivers polluted with mercury from mining. Scientists count and follow otter families, and in one part of Peru a conservation group and a village are working together to protect the rivers where otters live.
The IUCN lists the giant otter as Endangered with a decreasing population (assessed 2020, amended version published 2023). Hunting for pelts took a heavy toll in the twentieth century; Chester Zoo cites 20,000 pelts exported from Peru alone between 1950 and 1970, before the 1973 trade ban. Illegal killing continues locally.
The IUCN assessment lists threats including mining, logging, farming and ranching, dams, fishing, pollution, droughts and habitat change. Chester Zoo notes that mining poisons rivers with mercury. Conservation relies on monitoring families by their throat patterns, protected areas and work with local communities, which studies in Peru show must be fitted to each local situation.
IUCN Red List
How is the giant otter doing in the wild?
- Least Concern
- Near Threatened
- Vulnerable
- Endangered (this animal)
- Critically Endangered
- Extinct in the Wild
- Extinct
Endangered
At very high risk of disappearing from the wild.
See the IUCN Red List assessment · The IUCN Red List of Threatened Species 2022.2
Amazing facts
-
Giant otters are called river wolves.
In the Amazon the giant otter is nicknamed the 'river wolf', for its large, sharp teeth and strong body.
Chester Zoo explains the nickname 'river wolf' by the giant otter's large, razor-sharp teeth and muscular build.
-
Giant otters can eat small fish while floating on their backs.
A giant otter carries big fish to the bank, but it eats small ones while floating on its back.
Large prey is taken ashore, while small prey is eaten as the otter floats on its back.
-
Every giant otter has its own throat patch.
Scientists tell giant otters apart by the pale patches on their throats, which are different on every otter.
Individually distinctive throat markings allow photo-identification; one survey in Peru, published in 2014, identified eight otters this way.
-
Giant otters make lots of different sounds.
Scientists have described nine different giant otter calls, though what each one means is still not well known.
Nine distinct vocalizations have been described, though the function of each is still poorly documented.
Words to know
- webbed feet
- feet with skin between the toes, good for swimming
- piscivore
- an animal that eats mainly fish
- territory
- an area an animal or group lives in and defends
- cub
- a baby giant otter
- endangered
- at risk of disappearing from the wild
- mercury
- a poisonous metal that can get into rivers from mining
Discovery challenge
-
What do giant otters eat most?
What is the main food of giant otters?
Which food makes up most of a giant otter's diet?
- Fish
- Leaves
- Seeds
Show the answer
Fish
Giant otters eat lots of fish, like catfish and piranhas.
They mostly eat fish, such as catfish and perch, and eat crabs and small snakes when fish are scarce.
It is a piscivore, preferring catfish, perch and characins.
-
What helps people tell one giant otter from another?
How do scientists tell individual giant otters apart?
Which feature do researchers use to identify individual giant otters?
- The pale pattern on its throat
- The color of its tail
- How loud it splashes
Show the answer
The pale pattern on its throat
Every otter has its own throat patch.
The pale throat patch has a different shape on every otter, so photos of it identify each one.
Individually distinctive throat markings are photographed to build ID kits for each group.
-
Who does a giant otter live with?
Who lives in a giant otter group?
What is the core of a giant otter social group?
- Its family
- Nobody, it lives alone
- A herd of cows
Show the answer
Its family
Giant otters live with their families.
A group is a mother and father and several generations of their young.
A monogamous breeding pair with offspring from several litters.
-
Where do giant otters live?
On which continent do giant otters live in the wild?
Which continent holds the giant otter's entire native range?
- South America
- Europe
- Australia
Show the answer
South America
Giant otters live in South America.
They live in the Amazon, Orinoco and La Plata river systems of South America.
The species is endemic to South America.
Places where you might see it
-
Watch
Country
Brazil
Brazil covers about half of South America and is the fifth-largest country in the world. It holds most of the Amazon River basin and much of the world's largest rainforest, and about 214 million people lived there in 2026, most of them near the Atlantic coast.
-
Watch
Country
Peru
Peru is a country on the Pacific coast of South America. It has a dry desert coast, the high Andes mountains and the Amazon rainforest, and about 34 million people lived there in 2025, many of them in the capital, Lima.
-
Watch
Natural wonder
Angel Falls
Angel Falls is a waterfall in Canaima National Park in Venezuela. It pours off the cliff of Auyán-tepui, a giant table-shaped mountain, and falls about 979 meters. UNESCO calls it the world's highest waterfall.
-
Watch
Natural wonder
Pantanal
The Pantanal is one of the world's largest freshwater wetlands, mostly in Brazil and reaching into Bolivia and Paraguay. Each rainy season its rivers overflow and flood the lowlands, making shallow lakes and marshes; in the dry season the water slowly drains away. This rhythm feeds an amazing number of animals, from jaguars and giant otters to about 600 kinds of birds.
-
Watch
Natural wonder
Amazon River
The Amazon River flows from tiny streams in the Andes Mountains of Peru across Colombia and Brazil to the Atlantic Ocean. NASA calls it the largest river in the world: about 219,000 cubic meters of water pour into the ocean every second, nearly a fifth of all the water that rivers carry to the oceans.
Explore next
-
Watch
Country
Brazil
Brazil covers about half of South America and is the fifth-largest country in the world. It holds most of the Amazon River basin and much of the world's largest rainforest, and about 214 million people lived there in 2026, most of them near the Atlantic coast.
-
Watch
Country
Peru
Peru is a country on the Pacific coast of South America. It has a dry desert coast, the high Andes mountains and the Amazon rainforest, and about 34 million people lived there in 2025, many of them in the capital, Lima.
-
Watch
Animal
Amazon river dolphin
The Amazon river dolphin, or boto, is the largest river dolphin. Many adults are pink. It lives only in fresh water, in the Amazon and Orinoco river basins of South America, and its bendy neck and big flippers let it twist between tree trunks in flooded forests as it hunts fish using sound.
-
Watch
Animal
Sea otter
The sea otter is a marine mammal of the North Pacific coast that spends almost its whole life in the water. It has the thickest fur of any animal, floats on its back to eat, and even uses rocks as tools. By eating sea urchins, sea otters help kelp forests stay healthy.
-
Watch
Animal
Red-bellied piranha
The red-bellied piranha is a silver fish with a red belly that lives in rivers, creeks and floodplain ponds of South America. It has a famous reputation, but experts say the danger to people is greatly exaggerated: piranhas mostly eat fish, insects, snails and plants.
-
Watch
Natural wonder
Angel Falls
Angel Falls is a waterfall in Canaima National Park in Venezuela. It pours off the cliff of Auyán-tepui, a giant table-shaped mountain, and falls about 979 meters. UNESCO calls it the world's highest waterfall.
-
Watch
Natural wonder
Pantanal
The Pantanal is one of the world's largest freshwater wetlands, mostly in Brazil and reaching into Bolivia and Paraguay. Each rainy season its rivers overflow and flood the lowlands, making shallow lakes and marshes; in the dry season the water slowly drains away. This rhythm feeds an amazing number of animals, from jaguars and giant otters to about 600 kinds of birds.
-
Watch
Natural wonder
Amazon River
The Amazon River flows from tiny streams in the Andes Mountains of Peru across Colombia and Brazil to the Atlantic Ocean. NASA calls it the largest river in the world: about 219,000 cubic meters of water pour into the ocean every second, nearly a fifth of all the water that rivers carry to the oceans.
For parents & teachers
What children will learn
- Describe how the giant otter's body is adapted to swimming and hunting fish.
- Explain how giant otter families live, hunt and defend territories together.
- Understand how scientists identify individual otters by their throat patterns.
- Explain why the giant otter is endangered and how people are helping.
Recommended ages: 3 to 17 · About 12 minutes
Talk about it
- Why might hunting as a family help giant otters catch fish in deep water?
- How could pollution in one part of a river affect animals far downstream?
- Why is it useful for scientists to recognize individual animals?
Try at home or in class
- Measure 1.8 meters with a tape measure and lie down next to it to compare your length with a giant otter's.
- Draw five different throat-patch shapes, mix them up and ask a friend to match each one to its 'otter'.
Key vocabulary: webbed feet, piscivore, territory, cub, endangered, mercury
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Pteronura brasiliensis (giant otter) , Animal Diversity Web, University of Michigan Museum of Zoology
- Otter , San Diego Zoo Wildlife Alliance
- Giant otter , Chester Zoo
- Presence of Giant Otters (Pteronura brasiliensis) in the Río Torno in Northern Peru (Tramm 2014) , IUCN Otter Specialist Group Bulletin
- Pteronura brasiliensis (Giant Otter), global assessment (amended version of 2022 assessment, published 2023) , IUCN Red List of Threatened Species
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 24, 2026. Spotted a mistake? Tell us.