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Species Profile: Giant Otter    
Pteronura brasiliensis    

        The Giant Otter is the most recognizable otter. It is, as its name says, giant. From head to tail, it reaches an astounding six feet, the longest of any otter. Although the Sea Otter can weigh more, the Giant Otter is clearly the longest. It has such distinct characteristics, there is some question as to whether it is truly a direct member of the otter family.

The endangered Giant Otter lives in the tropical rainforest in South America in social groups of up to 10 individuals, who hunt, sleep and play together. They are referred to as "river wolves" locally.

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       The Giant Otter is the largest otter. From its head to its body, it is 960 to 1230mm long. Its tail is 450 to 650mm long. In total it is 1450 to 1800mm long. Males are usually longer than females. The male Giant Otter weighs between 26 and 32kg, females weigh between 22 and 26kg. The Giant Otter has a round head with small ears set low on the head. The eyes are large and superb for hunting. The legs are short and thick. The tail of the Giant Otter is flattened and flanged.

        There are strong claws on the large webbed feet of the Giant Otter.

        The hair, like most otters, is fine and velvety in texture. Their guardhair is short in size, 8mm long. Their underfur is 4 to 4.5mm long. Some say there is no underfur, seeing that it is so short, and so close in size to the guardhairs.

        Very dark burnt umber above, with a unique white mark on the throat.


        The nose is covered in fur and all you can see is the two slit like nostrils.

        The giant otter lives in large rivers in the tropical rainforest of South America.

Distribution and Population
        The Giant Otter lives in the tropical rainforest of South America in the countries around Brazil and Brazil. It lives in freshwater rivers, creeks, lakes, and sometimes they are spotted in reservoirs of small dams and agricultural canals. The Giant Otter population once was widespread from Venezuela to northern Argentina. Today only isolated pockets of otters are left due to fur hunting and habitat destruction.

        The Frankfurt Zoological Society in 1990 initiated a significant research project on Giant Otters in Peru which continues currently. This research has helped to better understand these unique otters and help us protect them into the future.

        The Giant Otter likes to eat fish, preferably perch, catfish, and members of the characin family, but when it can not find any good fish, it can feed on small caiman, crustaceans, and small snakes. When hunting, The Giant Otter uses mostly its eyesight, but it also uses its hearing and smell when possible in the water. Fish are hunted in groups or alone. In groups they normally hunt in deeper water that is normally around the middle of the river. Alone, a Giant Otter usually hunts in shallow water. There, fish try to hide in the foilage. In a day, the Giant Otter can eat 6-9 pounds of seafood. The Giant Otter is at the top of the brazilian rain forest food chain, being able to kill a cayman or an Anaconda.

Life Cycle
        The gestation period for the Giant Otter is 65 to 72 days. They give birth in the dry season which is May through September. Only one female (the dominant female) giving birth lives in each holt, but the whole holt helps take care of the young. In the first two months of a Giant Otter's life, it stays in the den. When there is a need to change dens, adults carry the young by the fur of the neck. When the group goes out to hunt, the pups are taken care of by their older brothers and sisters.

When they are two or three months old, they start to travel out of the den and sometimes participate in group hunts. The young otters eat fish as they start hunting, but are still dependent on their mother's milk until they are 5 months old. The Otters reach sexual maturity after two or three years, where they leave the group and wander about in search of vacant territory or a mate, both of which are hard to find. Some "singles" return back to their group. Others find a vacant territory and a mate and start a new group.

        There are many threats to the Giant Otter, which is surprising for an animal at the top of its food chain. We humans are the real problem. We cut down large amounts of rainforests, the Giant Otter's habitat, for farming and development. This is very bad because the rainforest soil is rich and developed over centuries. A farm may do well for a little while, but then the owner will have to go elsewhere, for the nutrients in the soil will be gone.

       We also over-fish by depleting the fish population in certain areas through constant fishing or use of nets to fish in rivers. Over-fishing can only be done in the tropical rainforest for a few consecutive years. After that, it has disturbed the ecological balace and the ecosystem gets out of wack, with the entire food chain damaged. Because of this, the otter's main food source is depleted.

       Water pollution is also a very bad thing. In some places, mercury is used to extract gold from river sediment. In the final part of separating, the mercury-gold compund is heated until the mercury turns into a gas and evaporates. Two grams of mercury are needed to gain one gram of gold! Tons of mercury is released into the environment each year this way. Fish that were examined from different parts of South America, from the Manu Preserve to the fish marked of Puerto Maldonado, for mercury contamination found concentrations that were far beyond the legal limits for selling fish in the U.S. and Germany. Even more surprisingly, the fish in the Manu Preserve, far away from the mining area, were highly contaminated due to fish migration and mercury evaporation.

       A very direct threat to otters is poaching. Giant Otters are protected by right and law, but still they are getting killed. Usually, the first otter to be killed is the dominant female, for she usually approaches the canoe first. This means that there is a large disturbance of the group's social structure AND the death of the female's litter. In the early days, Giant Otters were killed and eaten, despite their horrid taste, because there was nothing to eat. They are also viewed as competitors for fish, especially in over-fished areas near towns. Currently they are primarily killed for their dense fur.

       Giant otters are very sensitive to human disturbance. Disturbances within the surroundings of the den may have fatal consequences for the young. The Manu National Park and the indian settlement of Tyakome are visited by humans. The largest six lakes are the home for more than seventy-five percent of the otters of Manu National Park, and are regularly frequented by visitors. Canoeing is a serious menace to the otters of Manu, especially in the breeding season. Tourisim is a large threat for otters, too, unless its well planned and well organized. The otters get scared by human presence and the reproductive rate is lessened.

       Otters could also die of a disease called parvovirosis, a disease common to dogs and cats. When close to human settlement, Otters may catch the disease. The disease can kill large numbers of Otters. A pet disease also killed hundreds of black footed ferrets in North America.

        Giant Otters live in groups called holts. Each holt has a territory, and different holts territories do not overlap. Giant Otters are very social animals living in family groups, including male and female parents and their young. Olders siblings even "babysit" young cubs while the rest of the family is hunting.

Other Names

Brasilian Otter
Spanish: Lobo del Rio, Lobito de Cola Ancha, Arirai, Lobo 
French: Loutre geante du Bresil 
Dutch: Riesen Otter 
Italian: Lontra gigante del Brasile 
Puerto Rican: Ariranha 

Other scientific name: Lutra Brasiliensis

Quick Links
Friends of the Sea Otter, Monterey Bay Aquarium's Otter Research and Conservation Center, Marine Mammal Center Sea Otter writeup, Jimmy's Sea Otter page, Canada WWF Sea Otter
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