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18 Otter Facts From the Playful to Slightly Bizarre

Otters are cute marine mammals that are at risk of extinction. Otters, a member of the weasel family, are easily recognizable with their streamlined bodies, short noses and ears, long tails, and thick fur. There are 13 known species of otters around the world. Most otters live in freshwater and river areas, while sea otters and marine otters live in the Pacific Ocean. 

This article explores 18 interesting and funny otter facts and explores their playful nature that people love to watch. We also examine the differences between the sea otter and the river otter and discuss their breeding and dietary behaviors.

Related: Check out some of the other animals that start with O for more from the animal kingdom, and our ocean facts explore the sea otter home in more detail.

18 Interesting Facts About Otters

Otters on the shore
Photo by Mark Stoop on Unsplash.

1. River otters are not sea otters.

We often confuse river otters with sea otters. However, they belong to two separate animal genera. The river otter belongs to the genus Lontra, while the sea otter belongs to Enhydra. River otters primarily live in freshwater habitats but sometimes hunt in the sea. 

Some multiple features and behaviors differentiate a river otter from a sea otter. River otters are smaller than sea otters. Also, they both maintain different diets. 

A river otter has a long, stream-lined body, short legs, and webbed feet. A river otter has an average weight of 20 pounds and is 4 feet long, while a sea otter weighs 70-80 pounds and is 6 feet long. Also, river otters have longer tails than their counterparts9.

River otters prefer to spend most of their lives outside the water. You’ll find them in water if they hunt or migrate to another location. Sea otters are pretty different. They prefer to spend all their time in the ocean.

2. Some otters hold hands while sleeping.

Sea otters spend most of their life in the sea. They hunt, eat, mate, and sleep in seawater. Intriguingly, they hold hands for various reasons, most often to prevent themselves from drifting away with the water currents while asleep. The current can quickly sweep them away, so sea otters entangle themselves in kelp forests to provide an anchor. 

However, we can also find sea otters holding hands when there isn’t kelp to hand to stay together with their families, especially mother otters and their pups. Male otters also hold their mate’s hand to prevent them from being stolen by other male otters. Another reason otters hold hands is to protect themselves from predators and hunters4.

3. Otters have multiple nicknames. 

People call male otters dogs or boars, while they refer to female otters as bitches or sows. Baby otters are called pups or cubs. Also, people have come up with many names for otter groups. They call a group of otters bevy, family, lodge, romp, and raft. The name raft describes a group of resting otters in water, while the romp describes their playful nature11.

4. Giant river otters are the longest otter species. 

The longest otter in the world, also known as the giant otter, is found in South America, specifically in the Amazon, Orinoco, and La Plata rivers. A giant male river otter can grow up to 1.7 m long, while female giant otters are 1.5 m long. Their tail alone is about 70 cm long. 

Female giant otters weigh between 22 and 26 kg, while their male counterparts weigh between 26 and 32 kg. The density of the giant river otter’s fur is another distinct feature that distinguishes it from other otter species. It is the shortest (but thick) fur among other otters12.

5. Sea otters have the densest fur. 

Sea otters have the thickest fur out of all mammals in the animal kingdom, containing about 600,000 to 1,000,000 hairs per square inch. Sea otters depend on their dense fur for insulation because, unlike most other marine mammals, they do not have blubbers. Their fur is so thick that water cannot reach their skin. 

Their fur keeps them warm in the ocean by trapping a thick layer of air close to their skin10. For this reason, otters take great care in grooming themselves. They keep their fur spiky and tangled, so the trapped air bubbles can’t escape.

6. Otters are heavy eaters. 

Otters are carnivorous mammals that enjoy their food. Sea and river otters eat between 20% to 33% of their body weight in food daily. They spend about 5 hours daily hunting for food, even using stones to crack shells open. 

The otter diet comprises fish, sea urchins, shellfish, eels, crayfish, frogs, clams, and other crustaceans. Otters also feed on small mammals and birds13.

7. Otters are excellent hunters.    

Otters can eat voraciously because they are adept at hunting their prey. Their strong and extremely sharp claws enable them to catch their desired prey. Their forepaws are pretty strong. They can rub, twist, and pull with incredible strength. Also, the tough pads on their palms help them grip objects firmly.

When an otter can’t crack the shell of its prey with its jaws or claws, it uses the stone it stores to crack it open6

8. Otters have a loose skin section they use as storage. 

Here’s an interesting otter fact you like didn’t know! - Otters have little pouches under each forearm to store food gathered after long hunting hours. They also use the pouch to store stones as hunting tools.

9. Sea otters are excellent swimmers. 

Sea otters are fast swimmers, leaving behind most land mammals in the water. They can travel underwater for a quarter mile without coming up for air and dive up to 50 feet deep. 

Sea otters can stay submerged for up to 8 minutes by voluntarily closing their ears and nose. While a sea otter is underwater, its pulse rate lowers, and its blood and oxygen circulation slows down, allowing it to stay submerged without coming up for breath8.

10. Most otter species are on the endangered species list. 

Otters on the shore
Photo by Kieren Ridley.

One of the most disturbing facts about otters is their status on the endangered species act list. Many species of river and sea otters are vulnerable to extinction, which include:

  • Sea otter
  • Eurasian otter
  • Otter civet
  • Giant otter
  • Marine otter
  • African clawless otter
  • Southern sea otters 
  • Southern river otter

Many factors contribute to the decline in otter populations, including habitat destruction, hunting, and a decline in what they like to eat across the food chain. 

There was a major decline in the population of sea otters in the early 18th century because humans hunted millions of otters for their fur. Sea otters have the densest fur among all animals, making them high-value pelts in the fur trade. Russians mostly found otter fur valuable and would kill millions of otters2.

The sea otters along the coasts of Mexico and California were also victims of the hunt. Eventually, Russia, Japan, Canada, and the United States signed the Treaty for the Preservation and Protection of Fur Seals in 1911, which put a stop to the harvesting of sea otters. However, significantly fewer otters remained in the wild even after the treaty was enacted.

Another factor involved in the endangerment of otters is habitat loss5. Otters are losing their homes because of the chronic pollution of waterways, climate change, oil spills, water diversions, construction projects, and human activities around marine coastlines.

Additionally, human activity resulting in water pollution kills marine animals that serve as food for otters. So they, sadly, end up dying of hunger. 

11. Otters are social animals.

Group of sea otters in the ocean
Photo by Yajun Dong.

All otters are social animals, but each species follows different social structures. Sea and river otters often live in groups. 

A group of otters, called a raft, includes the otter's mother, baby otters, and her juvenile pup. Male otters often spend their time alone or with a group of other males. 

Male sea otters live separately from female sea otters unless it's the mating season. Research to understand the levels of otters’ sociality showed that female otters are more social than their male counterparts7.

River and sea otters play a lot. You’ll catch them sliding down water hills, rolling around together in the water, and playing catch. This playful nature has led to them becoming popular attractions in zoos and wildlife parks where they are kept in captivity. 

12. Otters are a keystone species.  

A keystone species is an animal with an astounding environmental impact based on its abundance. Keystone species maintain the ecological balance of the environment, and their absence would damage other organisms across biodiverse ecosystems.

The sea otter and river otter are keystone species because of their role as natural predators1

Sea urchins are the otter's favorite meal. By preying on sea urchins, they protect the kelp forests. Sea urchins are high consumers of kelp. River otters help kelp thrive by controlling their population. Fewer sea urchins, in turn, means more kelp which helps protect shorelines from erosion.

Kelp also helps reduce the ocean’s acidification caused by absorbing excess carbon dioxide released into the atmosphere. So when we remove otters, the protectors of kelp, we are putting the marine environment in harm's way.

13. Sea otters are polygynous.  

Next on our list of otter facts is the male sea otter’s practice of polygyny; in other words, the male sea otter has multiple female partners. 

Male sea otters are territorial. So, they mate with the females in the area they are defending. Once an otter finishes mating with a female, he moves on to his next conquest without bothering to look after his pup. Even less discerningly, male sea otters are also known to attack and try their luck with baby seals. 

14. The Asian small-clawed otter is the smallest river otter species.

Asian small-clawed otter cuddling
Asian small-clawed otter cuddling. Photo: iStock.

The Asian small-clawed otter, also known as an oriental small-clawed otter, is the smallest of all 13 species of otter. They're easily recognizable with their dark brown top fur and undercoat of a lighter color. They usually have white, gray, and cream-colored markings on their face and throat. 

These little otters weigh a maximum of 4.5 kg and are at most 2 feet long. You'll find them in southeast Asia, southern India, southern China, Indonesia, and the Philippines. The small-clawed otters’ preferred habitat is in small rivers, streams, marshes, and mangroves.

15. River otters have a pooping ritual.  

Researchers claim otters' poop has a fishy, pungent smell. The North American river otter poops similarly to humans because they have a specific spot where they like to do their business. Like humans have an area designated as our toilets, river otters have a particular spot near the water they poop on. 

An even more curious otter fact is that North American river otters perform a poop dance. They lift their tails up while stomping their hind feet on the ground. They also eject a substance scientists refer to as anal jelly3. It's different from their poop, with the researchers concluding it could be the bits of an otter's intestinal lining.

16. Only otter mothers raise the offspring.

Otter fathers are absent fathers; they do not take part in the upbringing of their offspring. Instead, otter mothers do the job of raising the pups during the first eight months. Pups can't survive without their mother for the first eight months and are born with their eyes closed shut. So, they can't swim within the first month of their birth once they can see where they are going. 

Their mother grooms them and blows air into the otter pup's fur to stay afloat as it's too dense for them to swim at first. She also spends about 14 hours of the day hunting for food. While out hunting, she often wraps her pup in kelp as an anchor to keep them together. This experience stresses female otters, who often fall ill.

17. River otters live in other animals’ homes.

River otters live in streams, rivers, lakes, freshwater, and saltwater marshes. They typically prefer water areas with rocky banks and pools. They don't construct a home or den of their own. Instead, they take over the dens made by beavers, muskrats, and woodchucks.

18. Some otters do not have claws.

Not all species of otters have claws. These species of otters are the African clawless otter and Congo clawless otter. They don't have claws on their webbed feet except on their hind legs. However, the claws on their hind paw are short.

1

Rasher DB, Steneck RS, Halfar J, Kroeker KJ, Ries JB, Tinker MT, Chan PTW, Fietzke J, Kamenos NA, Konar BH, Lefcheck JS, Norley CJD, Weitzman BP, Westfield IT, Estes JA. Keystone predators govern the pathway and pace of climate impacts in a subarctic marine ecosystem. Science. 2020 Sep 11;369(6509):1351-1354.

2

Gibson, J.R.. (2011). Feeding the Russian fur trade: Provisionment of the Okhotsk seaboard and the Kamchatka Peninsula, 1639-1856. 1-337.

3

HÁJKOVÁ, P., ZEMANOVÁ, B., BRYJA, J., HÁJEK, B., ROCHE, K., TKADLEC, E. and ZIMA, J. (2006), Factors affecting success of PCR amplification of microsatellite loci from otter faeces. Molecular Ecology Notes, 6: 559-562. 

4

Jeanette . (2015, March 20). Sea Otters Holding Hands. Sea Otters Holding Hands - North York Central Library Blog. Retrieved January 26, 2023

5

Boyle . (2006, September 2). North American River Otter (Lontra canadensis): A Technical Conservation Assessment (pdf).

6

Fujii, J. A., Ralls, K., & Tinker, M. T. (2015). Ecological drivers of variation in tool-use frequency across sea otter populationsBehavioral Ecology26(2), 519-526.

7

Gail M. Blundell, Merav Ben-David, R. Terry Bowyer, Sociality in river otters: cooperative foraging or reproductive strategies?Behavioral Ecology, Volume 13, Issue 1, January 2002, Pages 134–141.

8

Williams, T. M. (1989). Swimming by sea otters: adaptations for low energetic cost locomotion (pdf). Journal of Comparative Physiology A164, 815-824.

9

Link. (2004, May). Living With Wildlife in the Pacific Northwest. River Otters (pdf). Retrieved January 26, 2023

10

Morrison, P., Rosenmann, M., & Estes, J. A. (1974). Metabolism and thermoregulation in the sea otterPhysiological zoology47(4), 218-229.

11

Kruuk, H. (2006). Otters: ecology, behaviour and conservation (book). Oxford University Press.

12

Boitani, L., Bartoli, S., & Anderson, S. (1983). Simon and Schuster's guide to mammals. Simon & Schuster.

13

J.L. Bodkin, Sea Otters, Editor(s): John H. Steele, Encyclopedia of Ocean Sciences (Second Edition), Academic Press, 2001, Pages 194-201, ISBN 9780123744739

By Jennifer Okafor, BSc.

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Photo by Kedar Gadge on Unsplash
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