Sea Otter (Enhydra lutris)

The Sea Otter inhabits the Pacific Ocean from Alaska to Mexico, having adapted to the cold with their dense fur coat, the thickest of any animal. In the past, northern and southern sea otters lived along the Oregon coast. However, the latter eventually moved to the Central Coast of California.

Unlike other marine mammals that rely on blubber to keep warm, sea otters use their fur to survive in their coastal habitats. They have about 600,000 to 1,000,000 hairs per square inch, giving them the thickest fur of all animals.

In comparison to river otters, sea otters float on their back. They are typically bigger, with males reaching up to 100 pounds and almost 5 feet. 

Moreover, they give birth to baby otters in the water, unlike river otters that go ashore to build dens. Lastly, their tails are flat and muscular, serving as efficient rudders in their marine environment.

Sea urchins, when unchecked, can overgraze and destroy kelp forests. Because of their sea urchin-rich diet, they are considered keystone species for maintaining the balance of their ecosystems1. Hence, there is a need to conserve sea otter populations, which, unfortunately, are considered endangered species.

Giant Otter (Pteronura brasiliensis)

The Giant Otters or Giant River Otters are the largest otter species in the world, standing tall at 5.5 feet, including the tail, and weighing 70 pounds. 

These social creatures live in the rivers and streams of South America. These diurnal carnivores mainly eat fish, but they also eat crabs, snakes, and small caimans. 

Additionally, the Giant Otter is the most vocal among otter species. A study discovered 22 unique vocalizations among adults and 11 in baby otters3.

North American River Otter (Lontra canadensis)

The North American River Otter can survive in various habitats ranging from the icy rivers of Alaska to the humid marshlands of Florida. 

These mustelids have a streamlined body, weighing 25 pounds and standing up to 3.5 feet. They also have a broad, flattened head and thick fur, insulating them against the cold of their watery habitats.

These otters have a varied diet, with fish being their main staple. In addition to fish, they also eat amphibians, crustaceans, small mammals, and birds. 

Interestingly, North American River Otters perform a poop dance and use designated "latrine sites" for their waste deposits.

Marine Otter (Lontra felina)

The Marine Otter is a small species of otter found primarily along the rocky coastlines and kelp forests of Chile and Peru. It stands tall at 3.7 feet, weighing up to 11 pounds. You can differentiate them by their dark brown bodies, yellowish-brown throat, and underside.

Its diet includes crustaceans, mollusks, and fish, occasionally indulging in birds and small mammals.

Southern River Otter (Lontrhttps://upload.wikimedia.org/wikipedia/commons/thumb/f/fd/Southern_River_Otter.jpg/440px-Southern_River_Otter.jpga provocax)

The Southern River Otter inhabits the rivers, lakes, and coastal marine habitats in Chile and Argentina. They have an elongated body reaching up to 3.8 feet and 22 pounds. 

Their diet is varied, from fish to crustaceans and mollusks. However, they also prey on small birds and mammals when the opportunity arises.

Neotropical River Otter (Lontra longicaudis)

The Neotropical River Otter lives in the freshwater bodies and coastal areas of Central and South America. It has a sleek, elongated body and dense fur ranging from brown to grayish-brown. Moreover, it has a long tail and white or cream-colored underbelly and throat. 

It feeds on fish, crustaceans, small mammals, birds, insects, and reptiles. Furthermore, local fishermen confirmed these animals attack their fishing nets on rocky coasts to eat the remaining stuck fish2, which affects their productivity.

Eurasian Otter (Lutra lutra)

Eurasian otters live in various habitats, such as freshwater rivers, serene lakes, bustling marshes, and coastal areas. They are the most widespread among the otter species, living not only in Europe but also in Asia and North Africa.

They have dense brown fur coats, cream bellies, and longer tails than the previous type. On average, male otters are 4.6 feet, including tails, and can weigh up to 26 pounds. 

Regarding diet, these nocturnals hunt fish, amphibians, crustaceans, and occasionally small birds or mammals.

Hairy-Nosed Otter (Lutra sumatrana)

The Hairy-Nosed Otter is a semi-aquatic mammal living in peat swamp forests, coastal mangroves, and rice fields across Thailand, Cambodia, and Vietnam. It can grow up to 4.3 feet and weigh up to 18 pounds.

Moreover, its dark brown coat, slightly lighter on the underbelly, shines in its freshwater habitats. It has a unique fur-covered nose that distinguishes it from other otters.

Spotted-necked otter (Hydrictis maculicollis)

The Spotted-Necked Otter, also called the Speckle-throated Otter, is a unique species inhabiting various parts of Africa. It has a dark brown body and a distinctive pattern of white spots on its neck and chest. 

They live in rivers, streams, and lakes, hunting for fish, crabs, frogs, and insects. Meanwhile, they have predators like crocodiles and eagles.

Smooth-Coated Otter (Lutrogale perspicillata)

The Smooth-Coated Otter resides in the waterways of South and Southeast Asia. It can grow up to 3.5 feet long, including its tail. Moreover, it sports smooth and short, glossy brown coats that inspired its name. Its upper parts are dark but lighter brown on its underside.

Interestingly,  Smooth-Coated Otters can quickly adapt to human-altered landscapes such as rice fields and canals. Some otter populations are even surviving and being protected by authorities in Singapore.

Their hunting tactics involve groups forming a semi-circle in the water to drive fish toward the shore, making them easier to catch. Besides hunting, they also engage in friendly activities such as sliding down muddy banks, wrestling, and chasing their tails.

Asian Small-Clawed Otter (Aonyx cinerea)

The Asian Small-Clawed Otter is the world's smallest otter species, reaching only 2 feet and 12 pounds. You can find one in Southeast Asia, from India's mangroves to Indonesia's rice fields, where they feed on crustaceans, mollusks, and small fish. 

To distinguish Asian Small-Clawed Otters from the others, their cheeks, chin, throat, and sides of the neck are whitish, transitioning to dark fur at the back and light brown at the underside.

African Clawless Otter (Aonyx capensis)

The African Clawless Otter that lives in sub-Saharan Africa is also known as the Cape Clawless Otter or Groot Otter. As the third largest mustelid, it can be  5.3 feet long and 79 pounds heavy. Unlike its relatives, it has claw-less paws except for the three digits on its hind feet.

Moreover, African Clawless Otters can survive in various habitats, from semi-arid regions to dense forests, as long as a body of water is nearby. Their diet primarily consists of crustaceans, especially crabs, but they also eat amphibians, small mammals, and birds.