--- title: "Largest Otter Species: Giant Otter vs Sea Otter" url: https://thesea.org/largest-otter/ date: 2026-11-13 modified: 2026-11-13 lang: en author: "Blane Perun" description: "TheSea.Org▸Marine Mammals▸Sea Otter▸Largest Otter Largest Otter Species — Giant Otter vs Sea Otter Sea Otter Q&A By Blane Perun November 13, 2026 8 min read What is the largest otter..." categories: - "Sea Otter Q&A" word_count: 1958 --- # Largest Otter Species: Giant Otter vs Sea Otter [TheSea.Org](/)▸[Marine Mammals](/marine-mammals/)▸[Sea Otter](/sea-otter/)▸Largest Otter # Largest Otter Species — Giant Otter vs Sea Otter Sea Otter Q&A By [Blane Perun](/about-blane-perun/) November 13, 2026 8 min read What is the largest otter in the world? It depends on how you measure. The **giant otter** (*Pteronura brasiliensis*) of South America is the **longest**, reaching about **1.8 m (6 ft)** from nose to tail tip. The **sea otter** (*Enhydra lutris*) of the North Pacific is the **heaviest**, with large males weighing up to about **45 kg (100 lb)**, against roughly 32 kg for the biggest giant otters. One is built long, the other heavy. Quick facts Longest otter**Giant otter**, up to ~1.8 m with tail Heaviest otter**Sea otter**, males 22–45 kg Giant otter weight~22–32 kg Sea otter length~1.0–1.5 m Smallest otterAsian small-clawed otter, under ~5 kg Otter species13 living species Giant otter statusEndangered (IUCN) Sea otter statusEndangered (IUCN) Ask “what is the largest otter?” and you will get two different answers depending on who you ask, and both are right. South America’s giant otter is the longest member of the otter family, a sleek, six-foot predator of rivers and oxbow lakes. The sea otter is shorter but far bulkier, and holds the title of heaviest otter and heaviest member of the whole weasel family. This page compares the two, ranks the other big otters, and looks at the extinct giants that dwarfed them both. The giant otter: the longest otter The giant otter can reach about 1.5–1.8 m (5–6 ft) including its tail, which makes it the “6 foot otter” people search for. Males are the larger sex, usually around 26–32 kg, with females at roughly 22–26 kg. Much of the length is tail: thick at the base and flattened into a paddle, it can make up close to a third of the total. The body is long and muscular, the fur short and velvety chocolate brown, and each animal has a pale, cream-coloured patch on the throat with a pattern unique to that individual. Researchers use those throat patches to recognise otters in the field, much as whale biologists use tail flukes. Giant otters live in the Amazon, Orinoco and La Plata river systems and the Pantanal wetlands. They are social in a way few otters are: family groups of usually three to ten animals, built around a breeding pair and their offspring from several years, which hunt, rest and defend territory together. Locally they are called *lobo de río*, the river wolf. They are loud, too. Studies of their calls have described more than twenty distinct vocalisations, from screams and snorts to soft hums used inside the group. Fish make up most of the diet, especially characins and catfish, and an adult can eat several kilograms a day. A group working together can mob and drive off caimans and even jaguars. The species was hunted heavily for its pelt until the 1970s, and today habitat loss, mining pollution and conflict with fishermen keep it on the IUCN list as Endangered. The sea otter: the heaviest otter Male sea otters usually weigh 22–45 kg and measure 1.2–1.5 m; females weigh 14–33 kg. Exceptional males have been recorded at over 50 kg. The sea otter is built for cold water, and in cold water bulk helps. A heavier body has less surface area for its volume, so it loses heat more slowly. Even so, the sea otter has almost no blubber; it keeps warm with the densest fur of any animal and a metabolism that burns food at two to three times the rate of a land mammal of its size. We cover that in detail in [sea otter adaptations](/sea-otter-adaptations/), and you can see full measurements in [how big are sea otters](/how-big-are-sea-otters/). The tail is the giveaway when you compare the two. A sea otter’s tail is short, only about a quarter to a third of its body length, while the giant otter’s long tail stretches its total length. Put a large sea otter and a large giant otter side by side on a scale and the sea otter wins; put them nose to tail on a tape measure and the giant otter wins. | Species | Total length | Weight | Habitat | | ------- | ------------ | ------ | ------- | | Giant otter | Up to ~1.8 m | ~22–32 kg | South American rivers | | Sea otter | ~1.0–1.5 m | ~14–45 kg | North Pacific coasts | | African clawless otter | Up to ~1.6 m | ~10–21 kg | Sub-Saharan Africa | | Eurasian otter | Up to ~1.3 m | ~5–12 kg | Europe, Asia, North Africa | | North American river otter | Up to ~1.3 m | ~5–14 kg | North America | | Marine otter | Up to ~1.15 m | ~3–6 kg | Pacific coast of Peru and Chile | | Asian small-clawed otter | ~0.7–1.0 m | Under ~5 kg | South and Southeast Asia | Figures are typical published ranges; individual animals vary, and captive otters are often heavier than wild ones. Other big otters After the two record-holders, the next largest is the **African clawless otter** (*Aonyx capensis*), a heavy-set otter of rivers, lakes and some coastlines south of the Sahara. As its name suggests, its fingers are mostly clawless and very dexterous, and it feeds heavily on crabs, which it handles almost like a sea otter handles shellfish. Big individuals can top 20 kg. The **Eurasian otter** and the **North American river otter** are similar in build and size, long and lean, rarely over 12–14 kg. Both can live along sea coasts as well as rivers. In Scotland and Norway, for example, “sea otters” seen along the shore are usually Eurasian otters feeding in salt water, not true sea otters. If you are trying to sort out which otter you are looking at, our page on [sea otters vs river otters](/can-sea-otters-live-in-fresh-water/) covers the field marks. Giant otter vs neotropical otter: telling them apart In much of South America the giant otter shares its rivers with a smaller cousin, the neotropical otter (*Lontra longicaudis*), and the two are easy to confuse at a distance. The neotropical otter is roughly a third of the weight, usually around 5–15 kg, and it lives mostly alone or in pairs rather than in loud family groups. Its tail is long but tapered and round rather than flattened like a paddle, and it lacks the giant otter’s bold cream throat blotch. Behaviour is often the quickest clue: if you see several otters porpoising together, periscoping with their heads high out of the water and snorting at the boat, you are almost certainly looking at giant otters. The same caution applies on the Pacific coast of South America, where the little marine otter (*Lontra felina*) lives along rocky shores of Peru and Chile. It is the smallest marine mammal of all, at only a few kilograms, and its name causes endless confusion with the sea otter. The two have never overlapped: the sea otter lives only in the North Pacific. How size changes through an otter’s life Size also varies within each species. A newborn sea otter weighs only about 1.4–2.3 kg and depends on its mother for six months or more; it takes several years to reach full adult weight, and males keep filling out after females have stopped growing. Giant otter cubs are born blind in a riverbank den and do not swim well for their first couple of months. In both species, the biggest animals tend to be prime-age males in places with abundant food. Older animals with worn teeth often lose condition, which is one reason record weights come from animals in their prime rather than the oldest individuals. Why are these two otters so big? The giant otter and the sea otter got big for different reasons. The sea otter lives in cold water, where a larger body loses heat more slowly, and it feeds on hard-shelled prey that rewards a strong, heavy body and broad crushing teeth. The giant otter lives in warm water, so heat is not the issue. Its size likely reflects its prey and its rivals: it hunts large fish in open water and shares its rivers with caimans, jaguars and big predatory fish. A long, powerful body and a group of relatives make it one of the top predators of its habitat. I find this kind of comparison useful because it shows how “largest” depends on what an animal needs. In my reef tanks the fastest-growing corals were not always the biggest; they were the ones best matched to the light and flow I gave them. Otters are the same: each species is the size that suits its water. Extinct otters were bigger still The living record-holders are small compared with some fossil otters. In 2017, researchers described *Siamogale melilutra*, a wolf-sized otter from about six million years ago in Yunnan, China, estimated at around 50 kg. In 2022, a team studying fossils from Ethiopia’s Omo Valley described *Enhydriodon omoensis*, an otter-relative estimated at around 200 kg, roughly the weight of a lion. Its teeth and bone chemistry suggested it may have spent much of its time on land rather than in water. Weight estimates from fossils carry wide error bars, but they show that the otter family once produced animals far larger than anything alive today. Where to see the largest otters If I were planning a trip to see a giant otter, I would look at the Pantanal in Brazil or the oxbow lakes of Manu and Tambopata in Peru, ideally in the dry season when water levels drop and the family groups are easier to find. For sea otters, Monterey Bay and Morro Bay in California, or Kachemak Bay, Prince William Sound and Kenai Fjords in Alaska, are reliable; the details are in [where sea otters live](/where-do-sea-otters-live/). In both cases, keep your distance. Giant otter families are sensitive to disturbance at their dens, and in the United States the Marine Mammal Protection Act makes it illegal to harass sea otters. “Put a sea otter and a giant otter on a scale and the sea otter wins. Lay them out nose to tail and the giant otter wins. ‘Largest’ depends on the question.” — Blane Perun, TheSea.Org Frequently asked questions What is the largest otter in the world? The giant otter is the longest, up to about 1.8 m (6 ft) including the tail. The sea otter is the heaviest, with males up to about 45 kg. Are there 6 foot otters? Yes. Large giant otters of South America can reach about 6 ft (1.8 m) from nose to tail tip. Is a sea otter bigger than a river otter? Yes. A sea otter is typically two to four times heavier than a North American river otter, although river otters can be almost as long thanks to their longer tails. How much does a giant otter weigh? About 22–32 kg, with males heavier than females. What is the smallest otter? The Asian small-clawed otter, which usually weighs under 5 kg. What was the biggest otter ever? The extinct *Enhydriodon omoensis* of Ethiopia, described in 2022, was estimated at around 200 kg. Sources & further reading - IUCN Red List: *Pteronura brasiliensis* (Endangered) and *Enhydra lutris* (Endangered), IUCN Otter Specialist Group. - Leuchtenberger, C. et al. (2014). The giant otter’s vocal repertoire. *Behaviour* 151. - Wang, X. et al. (2017). A new otter of giant size, *Siamogale melilutra*, from the Late Miocene of Yunnan, China. *Journal of Systematic Palaeontology*. - Grohé, C. et al. (2022). Giant otter-like *Enhydriodon* from the Omo Valley, Ethiopia. *Comptes Rendus Palevol*. - Smithsonian’s National Zoo: giant otter and Asian small-clawed otter fact sheets. Continue reading More about sea otters [Sea Otter Q&AHow Big Are Sea Otters?Length, weight and size comparison. ](/how-big-are-sea-otters/) [Sea Otter Q&ASea Otters vs River OttersCan sea otters live in fresh water? ](/can-sea-otters-live-in-fresh-water/) [Marine MammalsSea Otter — main guideEverything about the heaviest otter. ](/sea-otter/) BP Last updated November 13, 2026 Written by Blane Perun Blane Perun has been exploring Earth’s oceans and marine life for over 25 years. Founder of TheSea.Org in 1999, underwater photographer, coral aquaculture pioneer, and explorer of 80+ countries. [About Blane Perun →](/about-blane-perun/) [More on sea otters →](/sea-otter/)