Otters are perhaps one of the most charismatic of mammals. They possess cleverness and playfulness in equal quantities, and an abundance of cute. But don't let the adorable face distract you from all the many other fascinating qualities of otters. We have 15 interesting facts (and yes, ridiculously cute photos) about otters that will keep you fascinated!

Why sea otters hold hands when sleeping

Sea otters sometimes hold hands while they're sleeping to keep from floating away from each other. Often a mother and pup will hold on to each other while they are resting so that they don't drift off from each other or the rest of their group, which is called a raft.

Sea otters holding hands isn't that common in the wild, according to the Seattle Aquarium. Instead, large rafts are more likely to keep track of each other by keeping an eye on one another, listening and keeping in touch through occasional tail and flipper contact. "Paw holding is most likely a learned behavior specific to certain individual sea otters, who may find it comforting!" according to the aquarium.

In this video, two sea otters at the Vancouver Aquarium hold paws while they float:

In addition to holding hands, sea otters also often sleep on their backs, wrapped in long strands of kelp which grow from the sea floor all the way up to the surface of the water. They use the kelp as an anchor while sleeping so they can nap without worry of floating out to open ocean.

Did you just call me a sea otter?

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It's really common to watch someone point at a river otter and say, "Look at the sea otter!" especially when that river otter is anywhere near the coast. It happened a lot to Sutro Sam, a famous San Francsico river otter that lived in a fresh water pond directly next to the ocean's crashing waves. However, river otters and sea otters are different creatures. River otters live primarily in fresh water, though they can also swim and hunt in sea water, and sea otters live exclusively in the ocean along on the coastline. Sea otters are also WAY bigger than most species of river otter, and are the heaviest of all otter species. So size and location are easy give-aways for telling these two commonly confused species apart.

Species found around the world

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Otters live on every continent except Australia and Antarctica. Most people know of sea otters and river otters — but that's not the only classification. There are actually 13 different species of otter found around the world. These range from the tiny Asian small-clawed otter which is only 2-3 feet in length, to the giant otter which can reach 5-5.5 feet in length.

According to the IUCN, 12 of the 13 otter species are listed as vulnerable, threatened or endangered and are experiencing population declines. The North American river otter is the only species not threatened, thanks to existing recovery efforts that are successfully protecting river otters from pollution and other factors.

On an upswing, however, is the California sea otter. Reported in 2016, the California sea otter population reach 3,272 otters, the highest number since 1982 and an 11% increase since 2013. Conservationists credit a surplus population of sea urchins in helping the otters recover, but they caution that there is still a lot of work to be done to help the California sea otter off the endangered species list, including fuller ecological recovery.

Family names

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Baby animals have all sorts of different names depending on the species. Any guesses on what a baby otter is called?

Baby otters are called pups. Though they can also be called kits or kittens. Either way, they are definitely called adorable.

So many names!

Photo: F. JIMENEZ MECA/Shutterstock

A group of otters has a range of names, including a bevy, family, lodge or, as their energy level and antics might suggest, a romp. When in the water, a group of otters is called a raft.

Even otter dens have a special name (or two). Their resting spots are called a hover or a couch, which are usually little more than a bed of reeds. But otters also use what's called a holt. Holts are small underground dens where otters can escape danger, take shelter, and where females raise their young.

The rarest otter of them all

So, if nearly all of the otter species are vulnerable to extinction, you may be wondering which is the most threatened. Nope, it isn't the sea otter. It is the hairy-nosed otter. This small species found in Asia is so rare that it was actually thought to be extinct up until 1998. It was only then that small populations were discovered, including one population found in Malaysia in 2010, using remote camera traps. It was thought to be gone from that region for the last century. The species still exists, but barely. Only around 86 or so hairy-nosed otters are thought to still live in southeast Asia.

Sea otters have the world's thickest fur

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Sea otters don't just have the densest fur of all otters — they have the densest fur of all animals! They have as many as 1 million hairs per square inch on the densest parts of their body. They need every last hair because they are the only marine mammal to not have a layer of blubber as insulation against the freezing ocean water. Their fur protects them from the cold and keeps them waterproof.

So much hair requires a lot of grooming. Sea otters spend their time either eating, sleeping or grooming. When they're awake and not eating, they're grooming all that fur to keep as dry and warm as possible. There are just a few places on a sea otter's body that doesn't have such dense fur, and that includes their paws. This is one reason why they hold their paws up when resting — they need to keep them out of the water and conserve body heat.

The giants of river otters

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The giant otter is a species found in South America, living primarily along the Amazon river and the Pantanal. This species is the longest of the otter species, though the sea otter beats it for heaviest otter species. The giant otter can grow to as long as 6 feet and weigh as much as 75 pounds (sea otters can weigh nearly 100 pounds). They have a serious appetite to match their size and activity — they can eat between six and nine pounds of food every day!

Poaching for their velvet-like fur caused a significant population decline and is one of the main reasons why this species is highly endangered. Threats also include habitat degradation, pesticides, pollution from mining, and even conflicts with fishermen who consider the species a competitor. Experts estimate that only between 1,000-5,000 giant otters still exist, though pinning down a more exact number is hard. Otters are one of the most difficult mammals to census. Only extended conservation efforts protecting the species and, importantly, large stretches of riparian habitat, can keep the giant otter from disappearing.

Otters eat A LOT of food

Photo: Kjersti Joergensen/Shutterstock

So we mentioned that giant otters eat a whole lot of food. A hefty appetite isn't unique to that species. Otters in general need to eat a whole lot to satisfy speedy metabolisms. They eat between 15-25% of their body weight in food every day. To get enough to eat, they may spend as much as 5 hours a day foraging for food.

According to Defenders of Wildlife, "River otters primarily eat fish. They are also known to eat whatever is easiest to find, like crustaceans, mollusks, insects, birds, oysters, shellfish, crabs, crayfish, frogs, rodents, turtles and aquatic invertebrates."

Sea otters play a key role in the coastal ocean ecosystem. Sea otters eat a diversity of fish and crustaceans, but importantly, they eat the urchins that feed on kelp. This means sea otters are an important species in keeping kelp forests healthy. Without the sea otters, urchin populations boom and kelp disappears — and along with the kelp goes a myriad of other species that depend on the kelp forests. So a hefty appetite is a welcome attribute in a sea otter!

Otters act as ecological early warning systems

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Just as sea otters are linked to the health of a kelp forest, so too are river otters linked to the health of riparian habitats. River otters need clean water and an abundance of prey, and so they are sensitive to disruptions in river systems.

The River Otter Ecology Project puts it like this: "Because they are top predators [at the pinnacle their food chain], and utilize both water, and land environments, otters are ideal environmental indicators — canaries in the mine, so-to-speak. Any contaminants that enter their food web become more concentrated with each step, resulting in the highest concentration at the top. They are among the first species to disappear from a polluted watershed. This applies to every species of otter, in every nation."

It may be an increase in pollutants, or a loss of prey due to habitat destruction, or habitat fragmentation along waterways, but one thing is for sure: when otters disappear, we know right away that something is off kilter in the ecosystem.

A mother's love is groomy

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We mentioned that sea otters spend a lot of time grooming themselves. Well for mother sea otters, that job is twice as difficult since she has to groom both herself and her very fluffy pup.

A pup can't groom itself and if the fur gets matted with oils or pollutants, it won't keep the pup's skin dry and warm, and also buoyant. Such a problem as poorly groomed fur is lethal for pups. So, a sea otter mother will spend several hours a day simply on grooming.

It is no easy task, as humans caring for orphaned sea otters have found out. At the Shedd Aquarium, caregivers would go through one and sometimes two wash loads of towels every day for one of their otter pups. These folks know just how hard a mother sea otter works to keep her pup fluffy and clean.

The otter squatter

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When an otter doesn't feel like finding its own home, it will take up residence in abandoned beaver lodges or muskrat dens. In fact, the homes of other animals are pretty attractive and sometimes otters will move in even when beavers are still living in the lodge, taking up residence in areas that the beavers aren't utilizing.

Otters will also take over the dens of foxes, badgers and rabbits as long as the holes are dug near enough to river banks.

Speedy swimmers

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It should be no surprise that otters are great swimmers. But how great are they?

Otters have a powerful, somewhat flattened tail perfect for propelling themselves through the water. They have webbing between their toes as well. They can close their nostrils and ears to keep out water, and have sensitive whiskers to feel out prey even in the murkiest water. Otters can hold their breath for 3-4 minutes at a time while they swim, and can swim at speeds of 6.8 miles per hour.

When river otters are born, they actually don't know how to swim. Despite being born in the water, they still need to be taught to swim by mom.

Look, Ma, no claws!

Photo: Targn Pleiades/Shutterstock

Most otters have sharp claws at the end of each toe, which help them to grab prey. However, there are three species of otter that have blunt or no claws. Their common species names are give-aways: The Asian small-clawed otter, the African clawless otter and the Congo clawless otter.

These species also have less webbing between their digits. This along with the shorter claws allow them to have greater dexterity in using their paws to feed on smaller prey.

Saving otters around the world

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We see videos and photos of otters all the time, so it can be hard to remember that these species are under many severe threats. Otters are in decline around the world, and these charismatic animals need our help to survive. If you'd like to help otters, please check out the following organizations: