What is “periscoping”?

Standing up in the water to look around

What is a giant otter latrine?

A shared toilet that works as a smell signpost

Giant otter

Pteronura brasiliensis

The giant otter (Pteronura brasiliensis) is the longest otter in the world, reaching 1.5–1.8 m including its flat, paddle-like tail. It lives in noisy family groups in the rivers, lakes and swamps of tropical South America, is active by day and eats mainly fish. Hunted for its fur until the 1970s, it is now Endangered because of habitat loss, mercury pollution from gold mining and conflict with fishers.

Also known as River wolf, Giant river otter, Giant Brazilian otter

Giant otter abilities

294 otters identified in one park
Every giant otter has its own pattern of cream marks on the throat and chest. Scientists use it like a fingerprint to follow each otter through its life.
- The marks are there from birth and range from a tiny spot under the chin to a big bib across the chest.
- Over 16 years in Manu National Park, Peru, researchers identified 294 otters this way, including 177 cubs. Only 3 had no mark.
- Curious otters often swim towards boats and stretch up out of the water, so researchers can film each throat and check it against a catalogue.
Sources [1, 3, 11, 15]
22 call types in adults
One of the noisiest otters. A study of wild and zoo families sorted adult calls into 22 types, from soft contact hums to loud screams.
- Hums keep the family together while they swim and travel; snorts and “hah” calls warn of danger; youngsters scream when they beg for fish.
- Newborn cubs babble: researchers heard 11 different call types in their babbling.
- A study in Brazil’s Pantanal counted 15 sound types. The total depends on how scientists split up similar calls.
Giant otter call types found by each study
Adults (Mumm & Knörnschild 2014)22
Adults, Pantanal (Leuchtenberger et al. 2014)15
Babbling newborn cubs11
First study, Suriname (Duplaix 1980)9
Studies split similar calls in different ways, so the totals differ.
Sources [1, 6, 16]
45–65 cm flat, paddle-like tail
Pteronura means “winged tail”. The thick, flattened tail is the giant otter’s high-speed paddle.
- Swimming slowly, it paddles with all four webbed feet. For speed, it holds its feet still and waves its tail instead.
- The tail can be nearly half as long as the head and body.
- All five toes on each foot have thick webbing.
Total length 1.45–1.8 m
Tail: 45–65 cm
Head and body 96–123 cm, tail 45–65 cm.
Sources [1, 11, 17]
20–30 m closest people should get
To check out something new, a giant otter stands up in the water and stretches its head and neck high, often snorting a warning.
- Most families in Manu reacted to researchers’ canoes by swimming closer and periscoping again and again.
- Periscoping shows off the throat patch, which helps scientists recognise each otter.
- Experts advise never getting closer than 20–30 m and never chasing a family. Otters that have been hunted flee from people even 100 m away.
Sources [1, 3, 6]
2 of 2 family stand-offs that sent a jaguar away
A family is a match for big predators. Groups have been seen mobbing a jaguar on the riverbank until it left.
- Jaguars do sometimes catch giant otters. The first confirmed case, in 2015, was a lone otter resting on the bank, not a family.
- When predators or strange otters appear, the whole family screams together. Each family’s chorus sounds slightly different.
- Families also defend their stretch of river against other otter groups with scent marks and loud calls.
Sources [7, 15, 18, 19]
62% of marks made by the breeding male
Families keep shared toilets, called latrines, on the riverbank. The smell tells other otters that this stretch of river is taken.
- They trample droppings, urine and smelly mucus into campsites, logs and rocks.
- In a Pantanal study, families spent 4.3–44.7 minutes scent-marking. The breeding male made 62% of the marks and often marked over the others’.
- Latrines smell so strong that researchers find them easily, and collect droppings there to learn what otters eat.
Sources [1, 10, 15, 20]
3–4 kg of fish a day
An adult eats about 3–4 kg of fish a day, and a meal passes through its body in about 3 hours.
- In zoos, adults eat about 10% of their body weight every day. A sea otter needs about 25%.
- Favourite prey include trahiras, cichlids, characins and catfish, mostly 7–30 cm long and caught near the bank.
- Cubs live almost only on milk until about 3 months, when their parents start bringing them small fish to practise on.
Food eaten each day
Giant otter (zoo adults)≈10%
Sea otter≈25%
Sources [1, 3, 5, 20, 21]
8 vs 5 bigger groups catch more fishStill debated
Do giant otters hunt as a team? Families fish side by side, but scientists still argue about how much they really work together.
- Groups of about 8 spent less time getting food and caught fish faster than groups of about 5.
- Yet each otter usually catches and eats its own fish. True cooperative fishing seems uncommon, though not absent.
- In a zoo test, pairs of giant otters pulled the two ends of a rope together to get food, but struggled when the timing got harder.
Sources [1, 3, 6, 22]

Tap a pin on the model or a part below.

3 of 294 otters had no mark
- Cream or white marks on the lips, chin, throat and chest. Every otter’s pattern is different.
- It can be a tiny spot under the chin or a big bib across the chest, and it is there from birth.
- In Manu National Park, Peru, only 3 of the 294 otters studied had no throat mark at all.
Sources [1, 2, 3]
- Giant otters hunt mainly by sight, so they prefer clear-water and black-water rivers, lakes and creeks.
- They are active by day, which makes them one of the easier South American carnivores to watch.
- Cubs are born with their eyes closed. In zoos the eyes open at about 4–6 weeks.
Sources [1, 4, 5]
22 adult call types to hear
- Very small, round and furry.
- They pick up a big vocabulary: scientists have described 22 call types in adults.
- Each family’s group chorus sounds a little different, so neighbours may be able to tell who is calling.
Sources [1, 6, 7]
- Stiff whiskers circle the muzzle, with more above the eyes and on the sides of the lower lips.
- In Eurasian otters, the whisker nerves have about 4 times as many fibres as a polecat’s, a sign that whiskers matter in water.
- Nobody has yet tested what giant otters feel with theirs. They seem to rely mostly on their eyes when hunting.
Sources [1, 8]
- Even the nose pad is covered in short fur.
- Their DNA shows that many smell-receptor genes have stopped working, as in other water mammals.
- Smell still matters: families leave scent messages at shared latrines along the bank.
Sources [1, 9, 10]
3–4 kg of fish a day
- Zoo cubs only a few days old already had their canine teeth.
- Most prey fish are 7–30 cm long, but giant otters have been seen catching fish up to about 100 cm.
- At about 3 months, cubs start grabbing fish with their mouth and front paws.
Sources [1, 3, 5]
4 km+ walked overland to a lake
- All five toes on each foot are joined by thick webbing.
- On land a giant otter can travel 4 km or more to reach a lake, and climb almost vertical banks 4 m high.
- Families trample and rub scent into the ground with their paws when they mark their territory.
Sources [1, 10]
45–65 cm long
- Thick at the base and strongly flattened towards the tip, like a paddle.
- It gives the giant otter its scientific name: Pteronura means “winged tail”.
- The tail can be nearly half as long as the head and body.
Sources [1, 2, 11]
- Very short, smooth, dark brown fur that looks chocolate-coloured when wet.
- In the late 1960s one giant otter skin sold for about US$440, more than twice the price of a neotropical otter’s.
- An estimated 386,000 giant otters were killed for their skins in the central-western Brazilian Amazon between 1904 and 1969.
Sources [1, 2, 12, 13]
≈3 h from meal to latrine
- Food passes through in about 3 hours, a sign of a fast metabolism.
- In zoos, adults eat about 10% of their body weight in fish every day.
- Mercury builds up in fish-eaters at the top of the food chain: Pantanal otters had 7.15 µg/g in their fur on average.
Sources [1, 5, 14]

Real giant otters

Photos from Wikimedia Commons. Three of them can repaint the 3D model.

AdultDark chocolate fur with a big cream throat patch that runs down the chest in two long streaks.1.5–1.8 m and 20–35 kg · one of the breeding pairPeriscoping in the Pantanal: note the cream throat print. Photo: Charles J. Sharp, CC BY-SA 4.0
JuvenileSmaller and a little paler than the adults, with a blotchy cream bib it has had since birth.6 months to 1.5 years old · still fed by the familyA juvenile on the Cuiabá River, Pantanal. Photo: Charles J. Sharp, CC BY-SA 4.0
Lunch time: an adult eats 3–4 kg of fish a dayPhoto: Giles Laurent, CC BY-SA 4.0
Family members resting on a log in the PantanalPhoto: Charles J. Sharp, CC BY-SA 4.0
Swimming in Encontro das Águas State Park, BrazilPhoto: Giles Laurent, CC BY-SA 4.0
A family heads ashore in Cantão State Park, BrazilPhoto: Araguaia.org (Rio Cicica), CC BY 3.0
A noisy giant otter calls as it swims towards a boatPhoto: Alastair Rae, CC BY-SA 2.0
A family group on the Cuiabá River, PantanalPhoto: Bernard Dupont, CC BY-SA 2.0
Adult with cubAn adult carrying a small cub in its mouth. Cubs are born furred, with closed eyes and their throat marks already showing.Cubs leave the den at about 2 monthsA young giant otter. Photo: Warren Garst, CC BY-SA 4.0
A giant otter family stands up to a jaguar in the PantanalPhoto: Thomas Fuhrmann, CC BY-SA 4.0

Giant otter by the numbers

Measured by scientists in the wild and in zoos, with comparisons you can picture.

Length: 1.5–1.8 m; from nose to tail tip; Giant otter (max)1.8 mAverage US man1.75 m; About as long as a grown-up is tall⁠[3, 1, 24]
Weight: 20–35 kg; males 23–32 kg and females 20–29 kg in one review; Giant otter (male)32 kgBig male sea otter45 kg; Longer than a sea otter, but lighter⁠[3, 11, 2, 21]
Tail: 45–65 cm; flat and paddle-like; ≈ a third of its total length⁠[11]
Family: 2–16; otters per group; 6 on average in Manu, Peru; Groups of up to 20 have been reported⁠[3, 15]
Food: 3–4 kg; of fish a day for an adult; ≈ 10% of its body weight⁠[3, 1, 5]
Digestion: ≈3 h; for a meal to pass through⁠[1, 5]
Calls: 22; adult call types, plus 11 in babbling cubs⁠[6]
Litter: 1–5; cubs per litter seen in the wild, most often 2⁠[3]
Newborn: 150–265 g; in zoos; born furred with eyes closed; Grows to 20–35 kg⁠[5, 1]
Oldest: 15.5 yrs; in the wild (Manu, Peru); 20 years in a zoo⁠[3, 1]

Giant otter myths and facts

Tap Myth or Fact for each claim, then check the answer.

0 of 8 answered

“The giant otter is the biggest otter, so it must be the heaviest too.”
“You can tell giant otters apart by the cream marks on their throats.”
“Giant otters hunt as a team, like a wolf pack.”
“Giant otters can grow to 2.4 m long.”
“Every grown-up in a giant otter family has cubs.”
“Nothing hunts a giant otter.”
“Giant otters empty rivers of the fish people need.”
“Giant otters only eat fish.”

Giant otter records

Superlatives and record holders, each checked against its source.

Longest otter
1.5–1.8 m
Giant otter
the longest member of the weasel family, tail included⁠[29, 3, 11]
Heaviest otter
36–45 kg+
Sea otter (big males)
shorter than a giant otter, but heavier⁠[21]
Biggest otter vocabulary
22 call types
Giant otter
the most vocal and most social otter studied so far⁠[6]
Only otter with helpers
1 of 13 species
Giant otter
the only otter known to breed cooperatively, with older offspring helping to raise the cubs⁠[23, 3]
Oldest wild giant otters
15.5 and 13.5+ yrs
A male and a female in Manu, Peru
their ages when last seen: the oldest recorded in the wild⁠[3]
Oldest in a zoo
20 yrs
A male at Brazil’s National Institute of Amazonian Research
another male at Dortmund Zoo, Germany, lived to 19 years 8 months⁠[1]
Most cubs from one pair
25 cubs
A breeding pair in Manu, Peru
raised to at least 6 months old while they led their family⁠[3]
Biggest known stronghold
≈3,950 otters
Brazilian Pantanal
estimated along 7,350 km of rivers⁠[2]

Life of a giant otter cub

From a furry newborn in a riverbank den to a parent with its own territory.

Day 1
Born in a den
After a pregnancy of 64–77 days, cubs are born in a den dug into the bank. They have fur and closed eyes and, in zoos, weigh 150–265 g.⁠[3, 1, 5]
≈2 weeks
First dip
Wild parents carry cubs out of the den in their mouths and dip them in the water at the entrance, even before their eyes open.⁠[5]
4–6 weeks
Eyes open
In zoos the eyes open at 4–6 weeks. In the wild, cubs are following their parents out of the den by about 6 weeks.⁠[5]
≈2 months
Out with the family
Cubs leave the den behind and start joining the family on fishing trips.⁠[3, 6]
≈3 months
First fish
Until now cubs live almost only on milk. Parents bring them small fish to grab with their mouth and front paws.⁠[5]
6–10 months
Growing up
Cubs are weaned at about 6 months. By about 10 months they hunt as well as their parents and look like adults.⁠[3, 5]
≈1.5 years
Family helper
Young otters still get fish from the family until about 1.5 years old, and help look after the next litters.⁠[3, 23]
2.5–3 years
Leaving home
On average, females leave at about 2.5 years and males at about 3, to find a mate and a territory of their own.⁠[3]
3–5 years
First cubs
The youngest parents recorded were 3 years old. On average, females had their first litter at about 4.4 years.⁠[3]
15+ years
A long life
The oldest wild giant otters known were 15.5 (a male) and at least 13.5 (a female). In zoos they have lived to 20.⁠[3, 1]

Giant otter family life

Dens, campsites and smelly latrines: how a giant otter family shares its stretch of river.

2–16
otters in a family
A breeding pair and their young from several years. Groups of up to 20 have been reported; in Manu the average was 6.⁠[3, 15]
1 pair
has the cubs
Only the dominant female and male breed. Older brothers and sisters babysit, share food and teach the cubs to fish.⁠[3, 23]
182 dens
and 193 campsites in one reserve
Families dig dens into the bank and clear campsites to rest and groom, almost always less than 2 m from the water.⁠[30, 1]
62%
of scent marks by the breeding male
Families trample droppings, urine and scent into shared latrines. Groups spent 4.3–44.7 minutes marking during a Pantanal study.⁠[10]
4–59×
bigger home range in the wet season
When the rivers flood, families follow the fish into flooded forest, grassland and swamps, leaving their usual campsites and dens for a while.⁠[31, 4]
11 of 43
begs answered
When an old breeding female named Cacao could no longer catch big fish, her grown-up young shared food with her: she begged 43 times and was given food 11 times.⁠[23]

Are giant otters endangered?

Yes. Giant otters bounced back in some protected rivers after the fur trade ended, but new threats now crowd the riverbanks they depend on.

IUCN Red List

Endangered (EN)

Population decreasing

Gone from Uruguay and probably Argentina, and patchy across much of its range. Experts think numbers fell by more than half over the last 25 years (about three otter generations) and could halve again in the next 25 if current trends continue.⁠[32, 2, 33]

IUCN Red List, 2023 assessment (Groenendijk et al.).

Threats

The fur trade (past)≈386,000
An estimated 386,000 giant otters were killed for their skins in the central-western Brazilian Amazon in 1904–1969, and Peru officially exported at least 23,162 pelts from the mid-1940s to 1973. Noisy, curious families active by day were easy targets.⁠[13, 3, 1]
Gold mining and mercury7.15 µg/g
Mercury used to mine gold builds up in fish and then in otters. Pantanal otters averaged 7.15 µg/g of mercury in their fur, above the 1–5 µg/g of otters living away from pollution, even about 475 km from mining.⁠[14, 3, 1]
Lost and burned habitat
Dams, deforestation, roads and settlements crowd the riverbanks otters need. After fires burned 3.9 million ha of the Pantanal in 2020, giant otters showed the steepest drop of 35 species in one camera study.⁠[1, 2, 34]
Conflict with fishers
Some fishers blame otters for empty nets and kill them. Studies in Brazil and Colombia found that otters and people mostly take different fish.⁠[26, 25, 35]
Diseases from dogs5 of 10
Five of 10 wild giant otters tested in Brazil had antibodies to canine distemper virus, a disease spread by dogs.⁠[36, 1]
Pushy tourism
In three lakes heavily visited by tourists, families raised about a third fewer young than expected. Mothers with small cubs are especially sensitive.⁠[1]

What’s helping

Hunting bans and CITES0 → 41
Peru banned commercial hunting in 1973, and from 1975 the CITES treaty stopped the international skin trade. On Peru’s Yavarí-Mirín and Yavarí rivers, surveys found no otters in 1992–93 but 41 in 2003–04.⁠[3, 13, 37]
Protected lakes and calm tourism7 → 12
In Manu National Park, the number of family groups grew from 7 to 12 between 1991 and 2005. Viewing towers, boat limits and minimum distances let otters and visitors share lakes.⁠[3, 1]
Back to Argentina
Two pairs of zoo-bred giant otters were released in Argentina’s Iberá wetlands between 2019 and 2022, where the species was thought to be extinct. Zoos on four continents now breed giant otters together.⁠[2, 38]
New global protection2026
In 2026 the Convention on Migratory Species added the giant otter to both of its appendices, from 27 June 2026, to help countries protect it across borders.⁠[39, 2]

Other otters

Sea otterEndangered
Heavier than the giant otter, with the densest fur of any mammal: 500,000 hairs per cm². The fur trade nearly wiped it out too.⁠[40, 41]
Eurasian otterNear Threatened
A smaller, mostly solitary otter that has made a comeback in the British Isles since the 1980s.⁠[42, 43]
Neotropical otterNear Threatened
Shares many rivers with the giant otter. In the 1950s–1970s, more than 30,000 were killed for their skins every year.⁠[44, 45]

Giant otter vs sea otter vs Eurasian otter

Three very different otters: the longest, the heaviest and one of the most widespread.

Giant otter vs sea otter vs Eurasian otter
	Giant otter	Sea otter	Eurasian otter
Scientific name⁠[11, 40, 42]	Pteronura brasiliensis	Enhydra lutris	Lutra lutra
Lives in⁠[1, 40, 42]	Rivers, lakes and swamps of tropical South America	North Pacific coasts, such as Alaska	Fresh water and coasts from Ireland to China and South-East Asia
Total length⁠[3, 21, 42]	1.5–1.8 m	up to ≈1.5 m	1.0–1.4 m
Weight⁠[3, 11, 21, 42]	20–35 kg	males 36–45 kg or more; females 23–32 kg	4–11 kg
Tail⁠[11, 40, 42]	45–65 cm, flat like a paddle	12–33 cm	35–40 cm
Social life⁠[3, 40, 42]	Family groups of 2–16	Groups of males or of females	Mostly alone; mothers with young
Main food⁠[1, 40, 42]	Fish	Clams, crabs and sea urchins	Fish, crustaceans and amphibians
IUCN status⁠[32, 41, 43]	Endangered	Endangered	Near Threatened

The giant otter is the longest otter; big male sea otters are the heaviest.

Giant otter quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What makes each giant otter look different from the others?

Giant otter field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

Giant otters are expert fish hunters. Now and then they also eat crabs, snakes, turtles and young caimans.

Primary Foods

Fish
Foraging Method: Pursuit

Ecological connections

JaguarRare predator
Jaguars rarely catch giant otters. The first confirmed case, in 2015, was a lone otter resting on a riverbank.
Yacare CaimanOccasional prey
Giant otters now and then catch young caimans, such as the yacare caiman in the Pantanal.
Peacock BassHunts
Giant otters often catch cichlids, the fish family that includes peacock bass.
Spotted CatfishHunts
Catfish are a common food source for giant otters.

Safety

Danger 2/5 · Low

Giant otters are wild predators with strong teeth. Watch only from a boat or a viewing tower, stay at least 20–30 m away, and never chase, feed or touch them. If you see one up close, tell an adult.

Traits

Collections

Mammals

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Genus: Pteronura

Also known as

River wolf · Giant river otter · Giant Brazilian otter · Lobo de río (Spanish) · Ariranha (Portuguese) · Perro de agua (Spanish)

Sources for these giant otter facts

46 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Giant otter?

Compare ears, muzzle, tail, feet and coat markings. Size is hard to judge without something nearby for scale, and young mammals may not have adult coloring yet. Mammal Identifier: upload a photo and compare the visible details.

How long is Giant otter?

150-180 cm

How much does Giant otter weigh?

20-35 kg

How long does Giant otter live?

8-20 years

What does Giant otter eat?

Giant otters are expert fish hunters. Now and then they also eat crabs, snakes, turtles and young caimans.

Where is Giant otter usually found?

Wetlands

How does Giant otter hunt?

Pursuit

How many babies does Giant otter usually have?

1-5

How big is a giant otter?

Adults measure 1.5–1.8 m from nose to tail tip, about as long as a grown-up is tall, and weigh about 20–35 kg. The tail alone is 45–65 cm. Males and females are almost the same size.

Is the giant otter the biggest otter?

It is the longest otter and the longest member of the weasel family. But the sea otter is heavier: big males weigh 36–45 kg or more, while giant otters weigh about 20–35 kg.

Why is the giant otter called the river wolf?

Lobo de río (“river wolf”) is one of its Spanish names. Like a wolf pack, a giant otter family lives, travels and defends its territory together, and scientists compare its breeding system with that of African wild dogs.

What do giant otters eat?

Mostly fish such as trahiras, cichlids, characins and catfish: fish turned up in every dropping in two diet studies. An adult eats about 3–4 kg a day. Now and then they also take crabs, snakes, turtles and young caimans.

Are giant otters dangerous to people?

They are wild predators with strong teeth, and families defend their cubs and territory. Watch them only from a boat or a viewing tower, stay at least 20–30 m away, and never chase, feed or try to touch them. If you see one up close, tell an adult.

Why are giant otters endangered?

Hunting for their skins wiped them out from large areas until the 1970s. Today the main threats are habitat loss, dams, mercury pollution from gold mining, fires and droughts, diseases from dogs and conflict with fishers. Families have few cubs, so numbers recover slowly.

How many giant otters are left?

Nobody knows the world total. Surveys suggest about 4,700 in Brazil (about 3,950 of them in the Pantanal) and about 1,000 in Bolivia, with far fewer elsewhere. The species is gone from Uruguay and probably Argentina, where zoo-bred otters are now being released.

How do scientists tell giant otters apart?

By the cream marks on their throats. Each pattern is different and present from birth, so researchers film otters as they periscope and match each throat to a catalogue, sometimes for the otter’s whole life.