#1 African Clawless Otter (Aonyx capensis)

The African clawless otter, also known as the Cape clawless otter or groot otter, is the second-largest freshwater species of otter, and the largest African otter species. They are closely related to the Congo clawless otter, which is regarded as the same species by some authorities, but the IUCN Otter Specialist Group and the IOSF view them as a separate species.

Appearance

They are chestnut in colour, and have distinctive white facial markings on the upper lips, the sides of the face, neck, throat, belly, and lower ears. Their front paws are basically hands; they are very dexterous and can be used to carry objects. The fingers are clawless and have no webbing between them. The hind paws have partial webbing and rudimentary claws.⁽¹⁾

Habitat

African clawless otters can live in a wide variety of habitats, including rivers, lakes, estuaries, mangroves, lowland forests, savannah and deserts, as long as there is enough fresh water and prey available.⁽²⁾ While they mostly occur in fresh water areas, they may also live in marine areas but require fresh water for drinking.⁽¹⁾ They can also live up to 3,000 metres (9,842 feet) above sea level. They prefer shallow waters over deep waters.⁽²⁾

Behaviour

These otters are mainly crepuscular and tend to be more nocturnal in urban areas.⁽¹⁾⁽²⁾ They are mostly solitary in fresh water areas but can form family groups.⁽¹⁾ They mainly hunt by digging with their sensitive fingers through mud.⁽²⁾ After hunting they roll in grass or sand to dry off and use a nearby latrine.⁽¹⁾

African clawless otters have a variety of vocalisations, including low pitched and high pitched whistles, grunts, squeals, moaning, mewing and snuffling noises.⁽¹⁾ Females can carry their young in their hands and walk bipedally when they do. Small objects can be held against the chest.⁽¹⁾

Pups are very playful; they like to throw pebbles into the water and try to catch them before they hit the bottom, or submerge floating objects and watch them move upwards.⁽¹⁾

Reproduction

Mating usually occurs in December and gestation is about 2 months.⁽¹⁾ There are about 2 to 5 cubs in a litter and they stay with their mother for about a year. The father may also help with taking care of the cubs.⁽²⁾

Diet

Their diet consists mostly of crabs but they also eat frogs, lobsters, insects and fish. Their diet often depends on the area and season. During the winter they especially eat more fish instead of crabs and may occasionally hunt for waterfowl.⁽²⁾

Threats

African clawless otters are sometimes killed by fishermen since they are seen as competition. They may also be hunted for fur and traditional medicine. The biggest problems are habitat destruction and pollution though.⁽²⁾

Body length: 113–163 cm / 45–64 in
Tail length: 46.5–51.5 cm / 18–20 in
Weight: 10–36 kg / 22-80 lb
Lifespan: Up to 12 years (wild), up to 15 years (captivity)
Range: South Africa to Ethiopia and across the continent to Senegal.
Conservation status: Near threatened
Subfamily: Lutrinae
Recognised subspecies⁽³⁾

References

#2 Asian Small-Clawed Otter (Aonyx cinereus)

The Asian small-clawed otter, also known as the oriental small-clawed otter, is the smallest species of otter native to southwest Asia. They are the most common species of otter found in zoos and perhaps even in the exotic pet market.

Appearance

Their fur is greyish dark brown with light grey markings on the throat, lips and cheeks. Their paws are like hands with very dexterous fingers and very little webbing and, as their name suggests, small rudimentary claws. The head is distinctly rounded and has round ears. Their legs are thin and their tails are relatively short.

Habitat

Asian small-clawed otters can live in a wide variety of fresh water environments, such as rivers, streams, lakes, mangroves, marshes, paddy fields and coasts, but they generally prefer shallow water. They can also live in mountain streams up to 2,000 metres (6,561.6 feet) above sea level.⁽¹⁾⁽²⁾

Behaviour

Asian small-clawed otters live in family groups led by the alpha female. Once one of the alpha couple dies, the other group members disperse and look for a mate to start a new family.⁽¹⁾

Reproduction

Much like wolves, the alpha couple are the only ones allowed to mate, but the whole group helps raising the pups. The mother gives birth to one to six pups after the father brings bedding into the holt. In the early stage the father feeds the mother and the pups.⁽¹⁾

Asian small-clawed otters can interbreed with smooth coated otters. A whole population of hybrids has been discovered in Singapore.⁽³⁾

Diet

They mainly eat invertebrates, especially crustaceans, such as shrimps and crabs, which they catch using their sensitive fingers, but they can also eat fish, small amphibians.⁽¹⁾⁽⁴⁾ They leave clams to dry out in the sun and open up, so they can access the inside.⁽⁵⁾

Threats

While Asian small-clawed otters have a wide distribution, they face many threats. Logging and the draining of swamps for development causes loss of suitable habitats. Agriculture and industry also pollute the environment with pesticides and heavy metals, which accumulate in the otters’ prey and poisons them.⁽²⁾

Pet otters, otter cafés, and poaching

Despite being a wild animal, the Asian small-clawed otter is highly infantilized in social media. There are many videos online of people showing off their pet Asian small-clawed otters, and while some owners seemingly have the time and resources to properly care for them, many people who are influence by these videos to purchase otters of their own likely know little to nothing about how to care for them, let alone have the means to. Otters are extremely curious and require a lot of space to explore. They can be destructive of property and even tame ones can become aggressive during mating season. Exotic pets also require specialised veterinary care, which will generally never be of the same quality that domestic pets receive, given their medical needs are not as well understood.

Otter cafés in Japan are also a controversial matter among animal rights groups. These establishments allow tourists and locals to pet and spend time with the otters. The concern is that many of these otters are stressed, live in poor conditions, and are fed an unsuitable diet.⁽⁶⁾⁽⁷⁾

Due to the increased demand for pet otters, low-welfare backyard breeding facilities have been on the rise, as well as illegal trafficking in Indonesia, Malaysia, and especially Thailand. In some villages, people regard the Asian small-clawed otter as a pest, since they will often eat their fish and ruin their paddy fields. Farmers are known shoot and kill the parents, and if the pups (baby otters) are found, they are sometimes sold into the exotic pet trade. Poachers are also reported to kill the parents because of the money selling their pups can bring.⁽⁷⁾

The Asian small-clawed otter is recognised as vulnerable by the IUCN.⁽²⁾ Poaching and illegal trafficking to feed Southeast Asia’s appetite for pet otters has not helped matters, and social media’s interest in pet otter videos continues to blind much of the public from the reality of the species’ situation.

They are not Japanese otters

Asian small-clawed otters that are kept as pets in Japan are sometimes erroneously and misleadingly called “Japanese otters” in social media. They are not even native to Japan. The true Japanese otter († Lutra nippon) was a completely different species. They were declared extinct by the country’s Ministry of the Environment in 2012.⁽⁸⁾

Body length: 65.2–94 cm / 25.7–37 in
Weight: 3–6 kg / 7–13 lb
Lifespan: Unknown (wild), up to 16 years (captivity)
Range: Mangrove swamps and freshwater wetlands in south and southeast Asia.
Conservation status: Vulnerable
Subfamily: Lutrinae
Recognised subspecies⁽⁹⁾

References

#3 Congo Clawless Otter (Aonyx congicus)

The Congo clawless otter is one of the largest African otter species.⁽¹⁾⁽²⁾ They are sometimes considered a subspecies of the closely related African clawless otter, but the IUCN Otter Specialist Group and the IOSF treat them as a separate species. They are also sometimes known as “swamp otters”, which is a bit misleading since they can also live in rivers and streams.⁽³⁾

Appearance

These otters are large and have very long tails. As their name implies, they lack claws on their front paws, which also lack webbing, though they do have rudimentary claws and partial webbing on their hind paws.⁽¹⁾⁽²⁾ There are two disconnected dark spots on the flanks of the snout and the hairs on the head and shoulders have silvery tips.⁽²⁾⁽³⁾

Habitat

They live in tropical rainforests and lowland swamp forests, and can be found in swamps, rivers and streams.^(1)(2)(3) Holts are made in holes in the riverbanks, in riverbank vegetation and under tree roots.⁽²⁾

Behaviour

These otters are less aquatic than other African otter species. They use their sensitive dexterous fingers to dig for worms in the mud and remove shells from prey. They seem to be most active at night but have also been spotted during daytime.⁽¹⁾⁽²⁾

Reproduction

They can breed throughout the year, as is typical for tropical species. The pups are white at birth and develop the adult coat pattern after 2 months. Sexual maturity is reached in about 2 years.⁽³⁾

Diet

In most areas they primarily eat worms, but they can also eat fish, snails, frogs and crabs.⁽¹⁾

Threats

The biggest threats are habitat destruction and hunting. They are hunted for bushmeat and witchcraft.⁽³⁾

Body length: 60–100 cm / 24–39 in
Tail length: 40–71 cm / 16–28 in
Weight: 14–34 kg / 31–75 lb
Lifespan: Unknown (wild), unknown (captivity)
Range: The lower Congo basin, between southeastern Nigeria and western Uganda.
Conservation status: Near threatened
Subfamily: Lutrinae
References

#4 Eurasian Otter (Lutra lutra)

The Eurasian otter, also known as the European otter, has the largest range of all otter species; spanning from Ireland and North Africa in the west to Russia and Japan in the east.⁽¹⁾

Appearance

They are medium sized otters with brown fur, the shade of which can vary a bit throughout their range. They tend to be darker in Ireland and paler in East Asia. Their size varies as well, with large otters in Russia and much smaller otters in northern Scotland, where they also have distinctly light throat patches.⁽¹⁾ Their fur looks spiky after they come out of the water.

Habitat

Eurasian otters require areas with clean fresh water and can be found in fresh water habitats, such as rivers, lakes, marshes and canals, but some live along the coast and swim in the sea, which is especially common in Scotland. Even then they always need fresh water to clean their fur.⁽¹⁾

Behaviour

Most Eurasian otters are active during the night, but in coastal areas they can also be seen during daytime. In general, Eurasian otters are territorial with males having larger territories than females. Considered the least social species of otter, the male and female usually only come together for mating, but while males are usually thought to leave after mating, family groups with up to nine members have also been observed on the Scottish isles.⁽¹⁾

Reproduction

Mating can happen any time of the year. They play with each other in the water before they mate. Gestation is about 63-65 days.⁽²⁾ The female gives birth to two or three pups in a hidden holt, which is usually only accessible through an entrance under water. The pups stay inside with their mother until they are big enough to learn to swim at the age of 3-4 months. At first they don’t like the water but at the age of 5-6 months they learn to catch prey of their own.⁽¹⁾

Diet

Their favourite food is fish, especially eel and trout. During the winter and in colder areas they have to rely more on amphibians, particularly frogs,⁽¹⁾⁽³⁾ but they also aren’t afraid to enter a hole in the ice to catch subglacial fish. They may also eat insects, birds and small mammals.⁽¹⁾ Crabs are a more important food source in Sri Lanka.⁽²⁾

Threats

The biggest threats Eurasian otters face are pollution, habitat destruction and roads. Otters are very sensitive to water quality, so before the most toxic pollutants were banned in Europe, the otter populations declined drastically and went locally extinct in the Netherlands, Belgium and Switzerland. Even with the ban on some of the pollutants, such as organochlorines and PCBs, the effects of other chemicals are still a potential risk and must be monitored.⁽¹⁾⁽⁴⁾

Reintroduction to the Netherlands

Right after the last recorded Dutch otter roadkill in 1989, plans were made to clean up the Dutch waterways and make the Dutch wetlands liveable again. This involved cleaning the water from pollutants, restoring bankside vegetation and placing otter tunnels underneath roads such that otters can safely get to the other side.⁽⁵⁾⁽⁶⁾

In 2002 otters were released into the Weerribben and the Wieden in the province Overijssel. Since then the population has continuously increased and has surpassed the viable population threshold of 400 in the winter of 2019/2020. They have spread to other provinces and have even been spotted east of Amsterdam. Traffic casualities remain a problem in many areas though, so more otter tunnels are needed.⁽⁵⁾⁽⁶⁾

Because of the success of the reintroduction as well as to bring awareness to the remaining problems, 2021 has been designated the Year of the Otter by CaLutra, the beaver and otter board of the Dutch Mammal Society.⁽⁵⁾

Body length: 60–90 cm / 24–35 in (males), 59–70 cm / 22–28 in (females)
Weight: 7–12 kg / 15–26 lb (males), 3–8 kg / 7–17 lb (females)
Range: The waterways and coasts of Europe, many parts of Asia, and parts of northern Africa.
Lifespan: Up to 4 years (wild), up to 22 years (captivity)
Conservation status: Near threatened
Subfamily: Lutrinae
Recognised subspecies⁽⁷⁾

References

#5 Giant Otter (Pteronura brasiliensis)

The giant otter, also known as the giant river otter, or misleadingly called a river wolf, is native to the inland areas of northern South America.

Appearance

As their name implies, they are huge! These human-sized otters are not only the longest otters, but also the longest mustelids. With their huge size they are top predators of the Amazon, even capable of killing caimans; though with difficulty.

Giant otters are some of the oddest looking otters, having unusually flat tails that are almost wing-like in shape. Like hairy-nosed otters, giant otters have noses that are almost entirely covered with hair. They also have some of the most well developed webbing between their digits, which makes them excellent swimmers. One of their most striking features is their throat spots, which form a unique pattern in each individual like a finger print and can be used to recognise each other.⁽¹⁾

Habitat

They live in the Amazon, primarily in slow moving rivers, streams and lakes with lush bankside vegetation, especially oxbow lakes with large fish populations.⁽¹⁾⁽²⁾ They may also occasionally occur in agricultural canals, drainage channels and reservoirs of dams.⁽²⁾

Behaviour

Giant otters live in large family groups of up to about 10 individuals. When the older otters go hunting, the younger adults take care of the pups. Pups learn to hunt when they are weaned at the age of 9 months. They take about 2 years to mature.

They are the most social and noisiest of all otter species. They are capable of producing many different sounds.⁽¹⁾

Reproduction

There is one dominant mating pair in a group and they typically produce one litter a year. Gestation is about 64 to 77 days. The litter consists of one to six pups, though rarely more than four, and stays inside the holt for two to three months after birth.⁽¹⁾⁽²⁾

Diet

Their favourite prey is fish, particularly catfish and characins, such as piranhas, but they can also eat crabs, birds, mammals and reptiles, even large ones such as anacondas and young caimans.⁽¹⁾⁽²⁾

Threats

The giant otter population has been devastated by the fur trade from the 1940s to the 1970s and has dropped by 80%. Hunting started being banned in the 1970s but poaching still goes on. Pollution and habitat destruction are also problematic. Pollution has been caused by gold mining with the use of mercury.⁽¹⁾⁽²⁾

Rediscovery in Argentina

In May of 2021, a lone giant otter was discovered in Bermejo River in Impenetrable national park, in north-east Argentina’s Chaco province. The species had not been seen in the country since the 1980s.⁽³⁾⁽⁴⁾

Body length: 1.5–1.8 m / 5–6 ft (males), 1.5–1.7 m / 5–5.5 ft (females)
Weight: 23–32 kg / 51–70 lb (males), 20–29 kg / 44–64 lb (females)
Lifespan: Up to 8 years (wild), up to 17 years (captivity)
Range: Northern inland areas of South America.
Conservation status: Endangered
Subfamily: Lutrinae
Recognised subspecies⁽⁵⁾

References

#6 Hairy-Nosed Otter (Lutra sumatrana)

The hairy-nosed otter is the rarest of all otter species. They were once thought to be extinct until a living otter was spotted again in 2000, and they remain elusive and mysterious.⁽¹⁾

Appearance

Whereas most other mammals have a furless rhinarium that is typically black and moist, hairy-nosed otters have, as their name suggests, noses that are almost entirely covered with hair. Their fur is dark brown with lighter markings on their chin and throat. They are long and slender and have very long tails, giving them a rather snake-like appearance. Their paws have claws and webbing.⁽¹⁾

Habitat

They live in a variety of aquatic environments, such as flooded forests, forest streams and swamps. They can be found especially in Melaleuca swamp forests.⁽¹⁾⁽²⁾

Behaviour

Hairy-nosed otters can live alone or in groups of up to six individuals. They can be active both day and night but seem to be the most active during the evening. Apparently because of the tidal fluctuations, they do not have fixed latrines.⁽¹⁾ They often climb trees to leave spraints.

Reproduction

Breeding periods vary by region. In Vietnam it is mainly in November and December and in Cambodia it can vary from November to March. Gestation is thought to be about 9 weeks.⁽¹⁾

Diet

Their primary food is fish but they also eat crustaceans, water snakes, lizards, birds and amphibians.⁽¹⁾⁽²⁾

Threats

They are threatened by hunting and habitat destruction. Fishermen often do not like the otters since they can take fish out of their nets. Hairy-nosed otters are very sensitive to water quality which makes it a challenge to keep them in captivity.⁽¹⁾

Body length: 57.5–82.6 cm / 22.6–32.5 in
Tail length: 35–50.9 cm / 13.8–20 in
Weight: 5–8 kg / 11–18 lb
Lifespan: Unknown (wild), unknown (captivity)
Range: Southeast Asia.
Conservation status: Endangered
Subfamily: Lutrinae
References

#7 Marine Otter (Lontra felina)

The marine otter is one of the smallest otter species and the smallest of all marine mammals. This small size enables them to hunt between the boulders on the sea floor.⁽¹⁾ In Chile they are known by the name “chungungo”, and another common Spanish name is “gato marino” meaning “sea cat”.

Appearance

They have dark brown fur with long sturdy guard hairs that stand almost erect, giving them a spikey appearance. Their underside is a bit paler. Their spikey guard hairs protect them well from the cold sea water and the heavy weather. Unlike most other otter species, they do not have to seek fresh water to wash the salt off. They do frequently have to groom their fur however. Their paws are fully webbed and the pads are covered in fur as protection against the rough rocky surface.⁽²⁾

Habitat

Marine otters are found in littoral zones; their territories cover long expanses of shoreline (up to four kilometres), but they rarely go more than 100 metres (328 feet) from the land.⁽³⁾ Caves and crevices in rocks are used as holts for resting.⁽²⁾

Behaviour

Marine otters are the least aquatic of all otter species, and spend on average 81% of their time on land, mostly resting. They are seemingly diurnal, but have been extensively observed out at night as well. They are mostly solitary, but they have been found in groups of three. It is unknown whether they are territorial; males have been observed fighting, but such fighting has been observed among mating pairs as well.⁽³⁾

Reproduction

Marine otters can be monogamous or polygamous, and breed in December and January. Gestation lasts from 60 to 70 days, and they produce anywhere from two to five pups.⁽³⁾ The pups stay with their mother for about 10 months, during which they learn everything they need to know in order to survive on their own.⁽²⁾

Diet

Their prey include crustaceans, mollusks and fish.⁽⁴⁾ A study on Chiloé Island suggests their favourite prey is the kelp crab.⁽²⁾ They may also eat fruit, such as chupones.⁽⁴⁾

Threats

These otters used to be hunted, which drastically reduced their numbers, removing them from most of Argentina and the Falkland Islands. They are now protected in Chile, Peru and Argentina. Poaching, habitat loss and pollution remain problems, as does competition with fishermen.⁽²⁾⁽⁴⁾

Body length: 87–115 cm / 34–45 in
Tail length: 30–36 cm / 12–14 in
Weight: 3–6 kg / 6.6–13 lb
Range: From the coast along southwestern South America to southern Argentina.
Lifespan: Unknown (wild), not unknown (captivity)
Conservation status: Endangered
Subfamily: Lutrinae
References

#8 Neotropical Otter (Lontra longicaudis)

The neotropical otter has the widest range of all South American otter species, ranging from northwest Mexico to central Argentina.⁽¹⁾⁽²⁾ Relative to body size they have the longest tails of all otter species, which is why they are also known as “long-tailed otters”.

Appearance

Their tails are long and cylindrical in shape and take up more than one third of their total length.⁽³⁾ Their fur is dark greyish brown and is lighter on the underside. They have small paws with fully webbed digits.⁽¹⁾

Habitat

Neotropical otters are the most versatile species of otter and can adapt to a wide variety of habitats,⁽²⁾ from cold, glacial lakes to warm rainforests, from natural rivers and streams to rice fields and drainage ditches, from coastal swamps to mountain streams up to 3,000 metres (9,842.5 feet) above sea level.⁽¹⁾⁽²⁾ They tend to prefer deep water and require lush vegetation on riverbanks.⁽²⁾

Behaviour

These otters are thought to be solitary animals but have also been observed in small groups in Uruguay.⁽¹⁾ They are usually active during the day, in particular mid to late afternoon, but may be more nocturnal in areas with a lot of human activity.⁽¹⁾⁽²⁾

Reproduction

In temperate areas they breed mostly in the spring, but they can breed throughout the year in tropical areas.⁽¹⁾⁽²⁾ Gestation is about 56 days⁽²⁾ and the females give birth to one to five cubs at a time, but most cubs do not survive into adulthood.⁽¹⁾ The mother raises her cubs alone without help from the father.⁽²⁾

Diet

Neotropical otters are mostly fish eaters, but they also feed on crustaceans and occasionally molluscs.⁽¹⁾ Their diet varies between different habitats and seasons.⁽¹⁾ They eat more frogs in the dry season, when fish and crustaceans are less available and frogs are easier prey due to their mating season.⁽⁴⁾ Crustaceans are a more important food source in coastal areas.⁽²⁾⁽⁴⁾

In the Biological Reserve of Tirimbina in Costa Rica, it was observed that otters ate a lot of shrimp, but on the Río Yaqui in Mexico, they preyed more on aquatic birds.⁽¹⁾ Neotropical otters may also prey on small mammals, reptiles and insects.⁽¹⁾⁽²⁾

Threats

Hunting used to be common, especially in the 1970s, but these otters are now fully protected, however forest destruction and water pollution are now their main threats.⁽¹⁾

Body length: 50–79 cm / 20–31 in
Tail length: 37–57 cm / 15–22 in
Weight: 5–15 kg / 11–33 lb
Lifespan: Up to 11 years (wild), up to 15 years (captivity)
Range: Central America, South America and the island of Trinidad.
Conservation status: Near threatened
Subfamily: Lutrinae
Recognised subspecies⁽⁵⁾

References

#9 North American River Otter (Lontra canadensis)

The North American river otter, also known as the northern river otter or the common otter, is native throughout the inland waterways and coastal areas of North America.

Appearance

North American river otters are relatively large otters and have large noses, long thick necks and thick tails.⁽¹⁾ Some older otters develop black spots on their muzzles, but this is far from universal.⁽²⁾

Habitat

They can live in a wide variety of environments, such as rivers, lakes, marshes, swamps, estuaries and coasts. They can deal with the extreme heat of the Mojave Desert, but the frigid winters of Yellowstone are no problem for them either.⁽¹⁾

Behaviour

North American river otters can live alone but also in groups.⁽¹⁾ Strength in numbers can especially be useful in areas with a lot of enemies such as coyotes, since a lone otter is a relatively easy target, but a group is quite capable of fending off predators.⁽³⁾ Adult male otters often form groups of independent hunters without any specific dominant individual.⁽¹⁾⁽²⁾

Reproduction

Mating season is from the end of winter to the beginning of spring. The mother is ready to mate again after her cubs are born, but due to delayed implantation, she will not give birth again until her current litter is a year old and ready to become independent.⁽¹⁾⁽³⁾

Diet

They prefer to eat fish, especially perch, suckers and catfish, but they also consume small mammals, birds, amphibians, reptiles and crustaceans, especially crayfish.⁽¹⁾⁽⁴⁾ One time an otter was even observed to eat a python.⁽¹⁾

Body length: 66–107 cm / 26–42 in
Tail length: 30–45 cm / 12–51 in
Weight: 5–14 kg / 11–31 lb (males), 8.3 kg / 18 lb (females)
Lifespan: Up to 9 years (wild), up to 21 years (captivity)
Range: Throughout North America
Conservation status: Least concern
Subfamily: Lutrinae
Recognised subspecies⁽⁵⁾

References

#10 Sea Otter (Enhydra lutris)

The sea otter is found along the coastal waters of east Russia, Alaska, British Columbia, Washington, and California. They are the heaviest and considered the most evolutionarily divergent species of all Mustelidae.

Appearance

Sea otters are heavy set animals with short skulls and tails compared to other otters. Their bodies are dark, and they have light coloured heads. Their back legs have evolved into flippers and are not terribly useful for walking on land.

Habitat

Sea otters live off the northern Pacific coasts, ranging from Hokkaido through eastern islands of Russia to the west coast of North America. Being fully adapted to a marine lifestyle, they can live their entire lives in the sea and only come on land whenever they feel like it.⁽¹⁾

Behaviour

While most marine mammals keep themselves warm with a layer of blubber, sea otters instead have thick fur, which is the densest fur of the entire animal kingdom. They frequently groom their fur and blow air into it in order to maintain its insulating properties.⁽¹⁾

A unique characteristic of the sea otter is their ability to use tools. They can use stones to smash shellfish. An anvil stone is laid on the stomach and the shellfish is held in the paws and smashed against the stone until it cracks. Stones can be stored in special pouches in the arm pits. Most sea otters have a favourite stone that they keep until it is worn out or broken. Abalones that are attached to rock walls may also be removed by smashing them with a sharp stone.

Another important part of their toolbox is kelp, which they use as an anchor. They wrap themselves and their pups in kelp in order not to drift off. They can even store live prey by wrapping it in kelp.

Reproduction

Due to delayed implantation gestation may vary in length but it’s usually around 5 to 7 months. In California, mating typically occurs from July to October and pups are born mostly from January to March. In Alaska on the other hand, mating occurs in September and October and births take place in May and June.⁽¹⁾⁽²⁾

Males can be quite rough during mating—often biting the nose of the female, which can leave scars.⁽²⁾

Addressing reports of forced copulation with harbour seals

Male southern sea otters (Enhydra lutris nereis) without a territory tend to live in male groups and may have trouble finding a female to mate with. Males have been observed in Monterey Bay, California to forcefully copulate with juvenile (not necessarily baby) Pacific harbor seals (Phoca vitulina richardsi). These encounters are usually fatal for the seal. Similar behaviour has also been observed in other marine mammals.

One explanation for why this occurs with the southern sea otter is that males typically create a dominance hierarchy based on age, size, and relative fitness. Subdominant males will have less access to receptive females, and those seeking a female could result in interspecific sexual encounters. This aggressive copulatory behaviour is perhaps the outcome of a recent demographic shift in the population, which has resulted in a more male-biased sex ratio inside Monterey Bay, resulting in misdirected sexual activity in the lack of accessible female conspecifics.⁽³⁾

Unfortunately, rather than focus more on providing sensible reasons for why male southern sea otters may behave as they do, there are articles attempting to demonise them.⁽⁴⁾⁽⁵⁾ These articles criticise the “moral compass” of male sea otters while simultaneously demonising the species as a whole. This anthropomorphising of sea otter behaviour has made its way to social media, where people are not always specific about (or simply do not know) what species of otter is being referred to. Needless to say, this has lead many to falsely assume these minority behaviours are traits of all otter species.

Some articles begin with statements such as, “I thought otters were cute and cuddly” or, “Otters are not cute, they are sick depraved jerks” and so on. Therein lies the problem—we sometimes romanticise and infantilise wildlife to a point where we have idyllic and, frankly, childlike expectations. They are being unfairly chastised for failing to meet the standards we have ascribed onto them. It bears mentioning that the reproductive habits of seals are not always “chivalrous” either, as there have been reports of some seals engaging in forced copulation with seals of a different species, and even penguins.^(6)(7)(8) Given the latter fact, one may assume those who generalise otters as “evil”, “rapists”, or “murderers” probably care about seals as much as they do otters.

We must remember that wildlife is neither concerned with nor reasonably capable of living up to the moral standards of humans. That is, if we are genuinely interested in learning the reasons why they may behave as they do. A more in-depth read regarding this subject for the sea otter.

Diet

Sea otters eat various marine invertebrates, but also fish and may even occasionally catch a bird. They are especially good at controlling sea urchin populations, which has earned them the title “keystone species”. Areas where sea otters were hunted to extinction experienced a dramatic rise in sea urchin populations which in turn meant a dramatic decrease in kelp. On the other hand, areas where sea otters thrive have intact kelp forests, which provide shelter for various fish species.

Crabs, which eat animals like sea hares, are consumed by sea otters. Algae that grows on seagrass is eaten by sea hares. Seagrasses are suffocated and killed by excessive algae. By encouraging more algae-eating sea hares the sea otter’s crucial function in controlling crab populations in the seagrass environment benefits the health of the overall ecosystem.⁽⁹⁾

Predators

Their primary predator is the great white shark in California. Orcas are also reported to consume sea otters in Alaska, possibly due to the decline of seals and sea lions in that region. Natural disturbances to the ecosystem and overfishing may be another cause. On land, sea otters may also fall prey to stellar sea lions, coyotes, bears, and eagles.⁽¹⁰⁾

Threats

During the 18th and 19th centuries sea otters were almost hunted to extinction for their luxurious fur. Their original population of about 150 to 300 thousand had been reduced to less than 1 percent of its original size by the time the first hunting ban was introduced in 1911.⁽¹⁾⁽²⁾

Modern threats include pollution from butyltin, organochlorine pesticides and PCBs, but also parasites from flushed cat litter.⁽¹⁾

Conflicts with fisheries

After sea otters rebounded, southern Californian shellfish fishermen were concerned for their competition, so otter-free zones were implemented and sea otters were moved out to a nature reserve on San Nicholas Island. Unfortunately for the fisheries, the otters swam back and it turns out otter-free zones don’t work.⁽¹⁾

Overfishing has also led sharks and orcas to hunt sea otters due to insufficient amounts of other prey.⁽¹⁾

Body length: 119–149 cm / 3.9–4.9 ft (males), 101–140 cm / 3.3–4.6 ft (females)
Weight: 23–45 kg / 51–99 lb (males), 14–27 kg / 30–60 lb (females)
Lifespan: Up to 23 years (wild), up to 27 years (captivity)
Range: Coastal waters of east Russia, Alaska, British Columbia, Washington, and California. Some reports of recolonization in Mexico and Japan.
Conservation status: Endangered
Subfamily: Lutrinae
Recognised subspecies⁽¹¹⁾

References

#11 Smooth-Coated Otter (Lutrogale perspicillata)

The smooth-coated otter is found in most of the Indian subcontinent and Southeast Asia. They are closely related to Asian small-clawed otters and can interbreed with them, though this seldom occurs.⁽¹⁾ A hybrid population has been observed in Singapore.

Appearance

Unlike their smaller relatives, smooth-coated otters have large paws.⁽¹⁾⁽²⁾ The tracks are often more than 8 cm (3 in) wide.⁽¹⁾ The webbing between their digits are well developed, making them excellent swimmers. They have flattened tails⁽¹⁾ and, as their name suggests, they have smooth velvety fur.⁽²⁾

Habitat

They can be found in a wide variety of habitats such as mangrove swamps, rivers, estuaries and rice fields. They may venture into salt water but need fresh water to clean their fur. In India and Nepal they prefer rocky banks, where they can make their holts.⁽¹⁾⁽²⁾

Behaviour

Smooth-coated otters are primarily diurnal and can live in groups of up to 11 individuals, although most of them live alone or in pairs.⁽¹⁾ Loud screaming wails are used to warn their group members of predators such as crocodiles and tigers.⁽¹⁾⁽²⁾

Reproduction

Mating may occur throughout the year but in India and Nepal it mostly occurs from October to February. Gestation is about 60 to 63 days and up to five pups may be born.⁽¹⁾⁽²⁾ At three to five weeks of age the eyes start to open and weaning occurs in about 19 weeks. They reach adult size in about a year and take a few more years to reach sexual maturity.⁽²⁾

Diet

Their favourite food is fish, in particular riverine catfish and false four-eyed fish,⁽²⁾ but they also like to eat crabs, frogs, rats, insects and snakes.⁽¹⁾⁽²⁾

Use by fishermen

There is a tradition in East Asia in which fishermen use otters to catch fish.⁽²⁾ This practise is in decline and now mostly restricted to Bangladesh. Three otters are typically used: two adults and one young otter in training. During the day the young otter is trained by encouraging it to chase a fish. The real fishing is done by night time. The otters chase fish into nets and also have the opportunity to catch their own fish.⁽²⁾

Singapore’s urban population

The Bishan otter family is a family of smooth-coated otters in Singapore that gained local and international fame. They were first spotted in the Bishan-Ang Mo Kio Park in 2014 and in 2015 they moved to Marina Bay where they chased out the Marina otter family that had been living there.

Threats to koi fish

While many Singaporeans are reported to hold otters in high esteem, the growing population of smooth-coated otters in the city in particular has been a concern for residents who raise pet koi in private ponds. They have been blamed for the deaths of many of these expensive fish.⁽³⁾

Threats

Like all Asian otter species they are vulnerable to poaching, but particularly to habitat destruction and loss of prey due to overfishing and pollution from agriculture and industry. The populations in the wild seem to have declined more than 30% in 30 years.⁽²⁾⁽⁴⁾

Body length: 59–64 cm / 23–25 in
Tail length: 37–43 cm / 15–17 in
Weight: 7–11 kg / 15–24 lb
Range: Most of the Indian subcontinent and Southeast Asia, with a disjunct population in Iraq.
Lifespan: Up to 10 years (wild), up to 20 years (captivity)
Conservation status: Vulnerable
Subfamily: Lutrinae
Recognised subspecies⁽⁵⁾

References

#12 Southern River Otter (Lontra provocax)

The southern river otter has the most restricted range of all otter species, ranging from Chile to the southern part of Argentina. They are locally known by the name “huillín”.

Appearance

They are medium sized otters with prominent whiskers and well developed claws and webbing. They have dark brown fur and are lighter on the underside, with grey spots on the throat.⁽¹⁾

Habitat

These otters can live in both fresh water and marine habitats. They require vegetation on riverbanks for shelter and cannot live in areas without crustaceans, therefore they generally do not live in altitudes above 300 metres (984 feet).⁽¹⁾

In coastal areas their range overlaps with the marine otter. An isolated population exists on Isla de los Estados. Unlike marine otters though, coastal southern river otters tend to avoid windy wave-exposed areas and prefer abundant cover of vegetation.⁽²⁾

Behaviour

Southern river otters are nocturnal and solitary. They make their holts under tree roots and in rock crevices within usually about 50 metres (164 feet) distance from water.⁽¹⁾

Reproduction

Southern river otters tend to mate in the winter months of July and August. Due to delayed implantation the cubs are born a year later. The litter consists of one to four cubs, usually two, and they stay with their mother for about a year.⁽¹⁾

Diet

The greatest part of their diet consists of crustaceans, in particular crabs and crayfish, though they tend to eat more fish in coastal areas. They may also prey on mollusks, birds and amphibians.⁽¹⁾

Threats

Southern river otters are vulnerable to habitat destruction and poaching. The draining of wetlands and canalisation causes a loss of suitable habitats. Coastal otters also suffer from competition from Chilean fisheries. It’s also been thought that the introduced North American mink may compete over food and thereby put pressure on the otter population, but research suggests that it is actually the otters who keep the mink population under control.⁽¹⁾⁽²⁾

Body length: 65–71 cm / 25.5–28 in
Tail length: 35–45 cm / 14–18 in
Weight: 5–9 kg / 11–20 lb
Range: Chile and Argentina.
Lifespan: Up to 10 years (wild), unknown (captivity)
Conservation status: Endangered
Subfamily: Lutrinae
References

#13 Spotted-Necked Otter (Hydrictis maculicollis)

The spotted-necked otter, also known as the speckle-throated otter, is the smallest otter of Africa.⁽¹⁾ They are locally known as “water hyenas”.⁽¹⁾ Like giant otters, they have unique patterns of spots on their necks, which allows one to distinguish individuals.⁽¹⁾

Appearance

They are slender otters with chestnut to dark brown fur. As their name implies they typically have light spots on their throat, lips and chest. They also have well developed webbing and claws, suitable for their aquatic lifestyle.⁽¹⁾

Habitat

Spotted-necked otters primarily live in clear rivers and lakes and require dense bankside vegetation. They prefer deeper bodies of water than other African otter species.⁽¹⁾⁽²⁾ They can also live in mountain streams as high as 2,500 metres (8,202 feet).⁽¹⁾

Behaviour

They are primarily diurnal animals and hunt for fish by sight.⁽²⁾ They are particularly active during mornings and late afternoons,⁽²⁾ but tend to be more nocturnal in South Africa.⁽¹⁾ Spotted necked otters are more aquatic than other African otter species⁽²⁾ and never stray far from the water. They are not territorial and often form same-sex groups of up to 10 individuals.⁽¹⁾⁽³⁾

Reproduction

Spotted-necked otters can mate any time of the year. The females give birth to usually two or three cubs who stay with her for at least a year.⁽¹⁾ Gestation is about 60-63 days.⁽²⁾

Diet

They are primarily fish eaters, but also eat frogs, crustaceans, snails and insect larvae. They may also occasionally catch birds.⁽²⁾ They eat more fish in the winter when crabs are less available.⁽¹⁾

Threats

While the fur trade has been regulated since 1977, spotted-necked otters continue to be hunted for bushmeat and traditional medicine. The main threats however are pollution and removal of bankside vegetation, which cause degradation of suitable habitats. Overfishing may also be a problem.⁽²⁾⁽⁴⁾

Body length: 71–76 cm / 28–30 in (males), 57–61 cm / 22–24 in (females)
Tail length: 39–44 cm / 15–17 in
Weight: 5.7–6.5 kg / 13–14 lb (males), 3–4.7 kg / 6.6–10.4 lb (females)
Range: Sub-Saharan Africa.
Lifespan: Up to 8 years (wild), up to 14 years (captivity)
Conservation status: Near Threatened
Subfamily: Lutrinae
References

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