River Otters: Characteristics,types habitats and more

We invite you to learn about the different types of  River Otters that exist in the world. If you want to become a true expert in marine species this is your best opportunitty.

Otters in general are carnivorous mammals that are members of the Mustelidae family, to which a big number of species belong. According to the mammal species of the world scientific publication, this family is made up by three subfamilies with 22 genera and has 57 living species. The Otters’ scientific name is Lutrinae and in this article we will focus on the river otters among which we find four very important species such as the river wolves, the north American River Otter, the eurasian otters and finally the extinct Japanese otter.

Neotropical River Otters or River Wolves. (Lontra longicaudis)

These otters have an elongated and robust cylindrical body, similar to the rest of otters. Their fur is dense and short, with brown hues in the dorsal area and lighter ones on the sides and ventral area. Their head is round and flattened with small ears, and their eyes are small and round. River Wolves have a Small rounded snout covered with thick whiskers.  They have also a black alopécic rhinarium that is variable among the three existing subspecies.  Their neck is thick, small and wide as well as their head. Their tail is thick, conical and muscular from the base to its end. Their legs have five fingers with an interdigital membrane, and the anterior legs are smaller than the back ones, allowing them to swim better. Female Neotropical River Otters  have  4 nipples in their lower abdomen.  The males ‘ body length varies from 138 – 162 cm and that of females goes from 109 – 127 cm.  Their weight ranges from  5 to 15 kgm.

Habitat and Distribution

Neotropical Otters  live  in lakes, rivers, swamps and lagoons located both in dry and humid forests. They are solitary and diurnal animal, whose burrows are usually natural caves located at the edge of the rivers, with a water inlet. Such Burrows can also be tunnels that they dig by themselves or nests covered with dense vegetation. Their geographic distribution ranges from northwestern Mexico to South America, especially Uruguay, Paraguay, Bolivia, Brazil and northern Argentina. They are located from the lowlands up to 3,000 m above the sea level.

Threats

The river wolves’ natural predators are the jaguars, alligators, raptors and some dogs, even the human beings due to their activities of deforestation and fragmentation of their habitat.

Conservation Status

The river wolves are considered as an endangered species. They are found in Appendix I of CITES (Convention on International Trade in Endangered Species of Silvestre Fauna and Flora); and Category 2 of the IUCN Red List of Threatened species.

What do Neotropical River Otters Feed On?

Their diet is based on fish, crustaceans, amphibians, reptiles, small mammals and also birds and insects.  They are strictly carnivorous, and occasionally they can eat vegetable fiber but it is not common when they do so.. When they are going to ingest a small prey they devour it in water, but if it is a large one they move to land to eat it.

What about their behavior

These river otters are essentially diurnal, although they sometimes have activity in the afternoon and when it gets dark, but it’s not common. They are characterized by being lonely animals, which communicate with each other employing a very acute shrieking River otters are excellent swimmers and divers, and they move around doing a sort of trot in which they shrink their backs.

How River Wolves Breed?

The reproduction of this species occurs mainly during  spring in all regions except in Venezuela, where it occurs throughout the whole year. The gestation period lasts approximately 60 days and the litters are mostly 2 or 3 offspring. However, a female can give birth to five offspring during a gestation period. The male shares with the female one day, and if she has puppies he also shares with them during this phase.

let’s watch them

Northern River Otters

They are also known as Common otters, North American River Otters or Canadian Otters, and their scientific name is. These river otters are also a carnivorous mammal belonging to the Mustelidae family, and were first described in 1777 by the German naturalist Johann Christian Daniel von Schreber.

Main Characteristics

The Northern River Otters are physically adapted for aquatic life. They have an aerodynamic profile to move in the water, but they are not very agile on the ground. In this section we will study each one of their most important characteristics.

Anatomy

Northern River Otters are sturdy animals which  from 5 to 14 kilograms. Their neck is strong and longer than their head and their body is elongated. Males of this species are larger than females. An adult male has an average weight of 11.3 kilograms while the average female weighs only 8.3 kilograms.Their length varies from 66 to 107 centimeters, and their tail possesses one third of their total length and is long and sharp.

They have a broad snout, a flat head, and their ears are round and sometimes difficult to distinguish. Their whiskers are long and thick and are very useful to improve their sensory perception under water and earth. Their legs are short but strong and have fingers totally webbed.  As for their fur it is short, and abundant.  Its color varies from light brown to black through gray. In their throat and chin the tonality is grayer than the rest of the body and their lips also present such tonality. When the Northern River Otters age, their fur’s color becomes quite white and in some cases may seem albino.

river otters : lontra canandensis

Other Features

These otters have a life expectancy of 21 years when they are in captivity, although there are cases where they have reached the age of 25 years. In the wild they live for approximately 8 to 9 years. Northern River Otters are short-sighted since their eyes are adapted for underwater view. They have transparent nictitating membranes that protect them under water.

Their right lung is smaller than the left one, and possesses sharp fangs and butcher molars.  They have a total of 36 teeth and some specimens have additional premolars.

Let’s watch them

Where do Northern River Otters Inhabit?

The North River Otters live in all the coastal regions of the U.S. and Canada. Their habitats are mainly the Pacific´s forested regions and they are also present in some areas of Alaska. Despite their names, these creatures inhabit a wide variety of aquatic habitats, both freshwater and seawater, as lakes, rivers, coastal coastlines, and can be adapted to different temperatures and elevations.

What do the Northern River Otters Feed On?

These otters are characterized by ambushing their prey and then kill them with a rapid thrust. They feed on fish, crabs (int) marine insects, reptiles, amphibians, birds, small mammals and even fruits. These otters are not scavengers; they avoid consuming this type of food.

Behavior and Communication

The northern river otters are characterized by being active throughout the year. Their peak of activity occurs during the night and during the twilight.  In summer, spring and autumns they are more nocturnal, but in winter their activity is mainly diurnal. These mammals are more social than most mustelids, and they are commonly found living in families.   They establish enduring social groups even when the females are in heat, existing also social groups where the specimens are not related in blood.

One of the most known characteristic of their behavior relies on their characteristic game, which consists in fighting with their fellows without hurting them. The communication between them is mainly developed by olfactory and auditory signals being the first indispensable for intergroup communication. Their marks come from feces, urine, since when they frightened or angry produce a particular smell. They produce different beeps to communicate, a grunt when they are disturbed, and a sharp whistle when they are sore. When they play or move they make a low growl, and their danger alarm is a kind of explosive snort, which they make by expelling air through their nostrils.

Reproduction

The Northern River otters are polygamous, and the female’s reproductive cycle begins from the two years of age, although it has been known of females that give birth with only one year of age but it is not very common. As for males, they reach sexual maturity at two years of age. Copulation lasts from 16 to 73 minutes and occurs in both water and ground, being very vigorous.  The female usually howls during or after mating, and her heat period lasts around a month. Moreover, she can delay the implantation for eight months.  There is an interval between the mating and the birth that can reach twelve months. In early spring the females begin to look for a cave to give birth, commonly using those made by other animals such as beavers. Gestation lasts from 61 to 63 days and the delivery lasts from three to eight hours.

Offspring

The litter can be of up to five specimens, but mostly goes from one to three individuals. At birth they have an approximate weight of five ounces and possess all their fur. The offspring are born without teeth and open their eyes for the first time after 30 or 38 days of age. They eat solid foods after 9 or 10 weeks of life. It is rare for the male to help to breed the puppies.

When the puppies are two months of age, their skin layer grows and the mother introduces them to the water.  These mammals are natural swimmers and with the help of their mother they learn quickly

Main Threats

The northern river otters’ natural predators of are orcas , sharks and the American crocodile in the case of the aquatic environment. In their terrestrial life we can mention the coyotes, the wildcat, the puma among others. As it happens with many species of animals, their main threat is given by human factors as they are: their illegal capture to commercialize their skins, automobile accidents, and even the fishing nets in which they frequently get entangled.

Conservation Status

This species is currently classified by CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) as not threatened with extinction, but its trade is tightly controlled.

In the IUCN red list, the northern river otter is listed as a species of least concern, due to improvements in water quality through the drinking water regulation that has been applied in its various habitats.

Japanese River Otters

The Japanese river otter (Lutra lutra whiteleyi)  was a semi-aquatic carnivore  otter that used to inhabit the rivers of Japan, and was distributed in Hokkaido, Honshu, Shikoku and Kyushu until the 1920s. However, due to the excessive hunting of their skins and fluvial environmental changes associated with the economic development in the postwar period, the otter population in Japan gradually decreased. Since 1979, when a specimen of these otters was last reported in Shikoku, no evidence of them has been reported again. In 2012, the Ministry of the Environment declared the Japanese otter extinct.

Main Characteristics:

An adult specimen used to measure between 65 and 80 cm long, and its tail 45 to 50 cm long. Moreover, they had a thick fur with dark brown skin. Their legs were short with webbed fingers. They were last seen in 1979 in the rivers of Shikoku, a city located in the center of Japan. They used to eat fish and lived in many areas of Japan before World War II. By that time the Japanese river otters were a very precious target for hunters because of the value of their skins.

Habitat and distribution

They were distributed throughout Japan. However, from 1930 their population was reduced suddenly and there were specimens only in the inner sea of ​​Seto and in the Uwa sea.The last living specimen was seen in Kochi prefecture in 1979 and was photographed at the Shinjo River in Shikoku. Their habitat, as in the case of most otters, was burrows that were commonly located near water bodies.

Alimentation Habits

They used to feed on fish, crabs, shrimp, eels, watermelons and potatoes. They were not very demanding when it came to selecting their food, and they used to eat to eat of everything that their habitat offered them. Japanese Otters used to consume about 15% to 25% of their body weight, and were known to be the main carnivores of the aquatic food chain.

Common Habits Of the Japanese Otters

They were characterized for being nocturnal creatures, time of day in which they used to leave from their burrows to look for food. Their territory was about ten kilometers in diameter and they usually marked their areas with feces. They used to make three or four nests under the rocks or in the bushes. These otters were considered adults after the first year of life, and were solitary; they only joined together during mating. The males and females didn’t use to live together, except for the young males that used to live with their mother during the first three years of life until they were mature.

river otters Japanese River Otters

Reproduction

Japanese otters used to reach sexual maturity after two or three years of age. The males used to look for the females during their heat period making a characteristic call. The females had to give their consent for the mating, and if this didn´t happen the male had to look for another female. The acceptance of the female was to roll around the male.

These otters used to used to have from one to six pups per reproductive period, which couldn’t open their eyes until 30 days of age. The female Japanese otter was an excellent mother, which used to breastfeed her puppies for eight hours a day, and taught them valuable survival lessons. After four months of age, the mother used to provide her puppies solid food while taught them how to hunt.

Causes of the Japanese Otters Extinction

The Japanese otters were distributed throughout Japan, but due to their indiscriminate hunting to market their skins; their population dwindled until it disappeared. Other factors such as the contamination of their habitats and the human settlements in them also had negative effects on this species since they exhausted their food sources.

Scientific Studies

In the year 1990 some scientists made several attempts to locate surviving Japanese otters. In December 1991, Japan’s environmental agency, associating with Kochi Prefecture, gathered a research team and began its search.  A year later, hairs and excrement were found in the aforementioned prefecture, which is believed to have come from this otter. Traces and ten additional samples of excrement were found also, which after being analyzed it was concluded that they belonged to such otters.

The last study which was conducted in 1996, and was carried out by a group of zoo officers, municipal government officers and animal lovers from all over Japan, was not successful in seeking new findings in the same area where evidence was found of such otters in 1991 (coastal area in Sukaki, along the Niyod River.) Finally in August 2012, the species was declared extinct by the Japanese Ministry of the Environment

Unfortunately we wont’s see them anymore

 

Eurasian Otters or European Otters

Also known as Otter Palaearctics, although name their scientific  Lutra Lutra. These otters are arnivorous mammal l that belong to the mustelidae family that lives in the aquatic environment, specifically in the fresh waters of the European continent as their name implies.

The species is distributed mainly in the European continent, although they can also be found in fresh waters of  Asia continent and some areas of Africa, and if you want to learn everything about them, we suggest you to read our article Eurasian Otters

 

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