River Otters


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Order: Carnivora
Family: Mustelidae
Life Span: 10-12 years
Population: Depending on the species, 200 individuals - over 100,000 individuals
Species Status: Extinct - Near Threatened

Fun Factoid

Did you know? The oldest Otter ever recorded lived to age 27!

Welcome to the world of River Otters! River Otters (of the scientific subfamily Lutrinae) are a super cute member of the taxonomic family Mustelidae, which includes other animals like muskrats, weasels, badgers, wolverines, and others. In total, there are 13 different species of River Otter around the world! River Otters on average weigh between 10 to 70 pounds and are between 2.5 to 5.5 feet long. River Otters are semi-aquatic rodents who normally live up to 12 years old and are very close relatives to Sea Otters, however, they tend to be much smaller than their sea-dwelling cousins. River Otters are very curious creatures who live close to the water’s edge, which means they also live very close to human populations. Unfortunately, many River Otter populations need our help due factors putting their homes and health at risk.


Fun Factoid

Fun Factoid: Did you know? The Hairy-nosed Otter is one of the rarest Otter species in the world.

River Otters live in bodies of fresh water, like rivers, lakes, and streams, all over the world except for super frigid climates. They live in mostly freshwater estuaries, ponds, lakes, wetlands, and river habitats compared to Sea Otters, whose habitat is primarily in the cold oceans around Canada, Japan, and Russia. The 13 different species of River Otter can be found throughout the continents, and are only not found in Australia, and Antarctica. Some species like the North American River Otter can be found throughout the North American continent, while some such as the Hairy-nosed Otter are only found in small pockets like the lowland wetlands of South East Asia.

What are River Otters?

River Otters are a kind of semi-aquatic rodent, meaning they live in both water and on land, however, since they are mammals, they are both warm blooded and breathe air using their lungs. River Otters all have a very sleek and long bodies, with a large tail to help navigate through the water. River Otters also have two layers of fur, the inner layer for warmth, and the outer layer for waterproofing. All River Otters have short, stubby legs to help them move faster through the water and some have short claws on their paws, except for the African Clawless Otter. Although Otters have good eyesight and hearing, they also have whiskers around their face, called vibrissae, to help catch prey under water. River Otters are relatively small mammals, with the smallest of the species growing only up to 2ft, and the largest growing up to 5 ½ ft long! Depending on the species, they can weigh anywhere from 6lbs to 70lbs!

Fun Factoid

Fun Factoid: Did you know? River Otters can hold their breath for up to 8 minutes!


River Otters usually live alone or in small social groups and love to play! If you ever observe them in the wild, they love to roll around, chase each other, and play games. River otters typically communicate with each other through yelps, whistles, and growls but also through touch, such as grooming each other. River Otters also communicate through scent marking in their territories. Although River Otters are normally friendly and love to play, male Otters can be territorial, and will sometimes fight because of it. River Otters live inside of dens that they create in fallen trees, under rocks, and even in abandoned hollows and holes on the banks of rivers and lakes. They like to line their dens with cozy moss, leaves, and grasses.

Fun Factoid

Did you know? Some River Otters can shut their nostrils to keep water out during deep dives.


Fun Factoid

Did you know? River Otters can travel up to 18 miles a day while foraging for food.

River Otters are carnivores! Meaning meat makes up their entire diet, which consists of a wide variety of foods like frogs, turtles, fish, snakes, crayfish, crabs, insects, and even some other kinds of small mammals. River Otters will usually hunt by themselves or in pairs. They will also hunt not only in the water, but also on land. Otters eat about 20% of their body weight each day! Because of this, they tend to eat their catch on the spot, instead of taking it back to their den.


River Otters will usually mate between late winter and early spring. Male and female otters do not stay together once they have mated. Female river otters have an incredible reproductive cycle that involves something called delayed implantation. This means that even when the female Otter has a fertilized egg inside of her, the eggs will stay dormant for up to one year before they begin to grow when conditions are optimal. After they begin to grow, the gestation period is about 60 – 75 days. Female River Otters typically give birth to 1 to 6 pups per litter, who are born both blind and deaf. River Otter pups remain blind and deaf for a month and after they develop their eyesight and hearing, they can start exploring at 2 months old. By four months old, they can start to swim and hunt on their own. The pups will usually stay with their mother until she has her next litter of pups about a year later.

Fun Factoid

Did you know? River Otter Pups only weigh about 5 ounces when they are born.


All species of River Otters face threats in their wild habitats. Although some populations are not labelled as endangered, or even threatened, the ecosystems they live in face constant threats such as pollution, overdevelopment, illegal hunting, toxin exposure, and loss of food sources. River Otters were hunted to near extinction in many places for their warm pelts until it was made illegal in many places in recent history. Since River Otters tend to share a lot of their habitat with humans, they are heavily affected by humans. River otters encounter a lot of litter and toxic chemicals used within lawn sprays. As the human population grows, overdevelopment of wetland and wild habitat continues to destroy the vulnerable ecosystem that River Otters live in. Many River Otter populations are dropping, even in species like the North American River Otter, who is labeled as “least concern” by the International Union for Conservation of Nature (IUCN).


Since there are 13 different species of River Otter around the world, many populations have different population statuses. Species like the Asian Small Clawed Otter are listed as “near threatened”, while other species like the Hairy-nosed Otter, also in Asia, are critically endangered. The species of the Japanese River Otter went extinct in 2012 due to loss of habitat, over-hunting, and pollution exposure. Regardless of where River Otters are located in the world, all populations are struggling with the same challenges, and if they are not assisted soon, more River Otter species could become extinct as well. Luckily, there are ways you can help!

How to Help

River Otters rely on clean and unpolluted waterways to hunt and live. By learning about ways you can reduce pollution and conserve water, you can help protect River Otter habitats. Pick up all trash you see and throw it away in an appropriate place. Avoid using weed killing sprays and toxic fertilizers, they can destroy delicate ecosystems! Help support conservation organizations and spread awareness about the importance of preserving our waterways and wetlands. By working together, we can make a huge difference for this amazing and fun group of species!

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Fun Factoid

Did you know? The Giant River Otter species, found in the Amazon, has been slowly growing its population thanks to major conservation efforts.