The Giant otter, living in South America, and the largest of the otters in its total length, is the cousin of the sea and river otters in North America, Europe and Africa. Known throughout much of their range as 'river wolf', they are amongst South America's top carnivores. Their fur is extremely soft and is a chocolate brown except for a pattern of large creamy white patches under their long neck, thought to be unique for each individual otter.
This species is a native of South America (except for Chile), east of the Andes. Currently, there are almost none in Argentina and Uruguay, and they are very rare in Paraguay. They are seen within the Amazon, Orinoco and La Plata River systems and are found in slow-moving streams and rivers, lakes, swamps, and marshes, as well as flooded forest during the rainy season. Giant otters prefer habitats with non-floodable banks that have vegetation cover and where there is easy access to hunting places in relatively shallow waters.
This species is diurnal and lives together in family groups numbering 5-8 individuals. A family has a home range of 12 sq. km. A family consists of a mated pair and their offspring of several generation. The family members clear an area beside a stream for their living quarters, of up to 50 sq meters, usually near feeding sites. Sizeable burrows are then built under fallen logs. One to five latrines for communal use are placed along the perimeter of the site. The established territory is then marked by scent from the animals' anal glands. If intruders invade the family's territory, the parents will defend it and their family members. Despite maintaining separate territories, Giant otters are highly social mammals. Social activities include hunting, grooming, resting and communicating.
This species is monogamous, and pairs stay together for life. Reproductive behavior has largely been documented by observations of captive animals. Although some breeding occurs throughout the year, the peak of the breeding season is from late spring to early summer. Gestation lasts 65-70 days and the altricial young are born in late August until early October. There are 1-5 pups in a litter (usually 2-3) and they stay in the family den until they are 2-3 weeks old. They can open their eyes after 1 month and start to regularly follow their parents out of the den. Young are weaned at the age of 3-4 months. At 9-10 months they can hunt independently and look just like their parents. Reproductive maturity is reached when they are 2 years old.
Habitat fragmentation and loss, as well as pollution are the current major threats to the Giant otter, as the areas where they live are degraded and destroyed by logging, mining and damming. This species was excessively hunted up until the late 1970s for its valuable fur. Illegal killing still occurs, often at the hands of fishermen, who see Giant otters as competition for fish. Some pups in the wild are taken for pets, and usually die because of the inexperience of caretakers.
The IUCN Red List has no current estimate for the total Giant otter population. There are estimates for the populations of a few areas: 2,000-5,000 individuals in the Brazilian Pantanal; 180-400 individuals in Madre de Dios, southeastern Peru; 31 individuals in Cantao State Park, Brazil; 75 individuals in Amana, Brazil; at least 130 individuals in Balbina Lake, Brazil; 54 individuals in Araguaia, above Bananal Island; 32 individuals in Yasuni National Park, Ecuador; and at least 35 individuals in Rewa Head, Guyana. Estimates have been provided for the following countries: 60 animals in Bolivia in the northwest in the Madre de Dios-Beni sub-basin; 50 individuals in 118,031 km² of the Pantanal (Paraguay river sub-basin), and 600 animals in the in 186,460 km² of the northeast (Itenez sub-basin), totaling an estimated 700 individuals; less than 250 animals in Ecuador; at least 200 animals in French Guiana; and 24-32 animals in Paraguay. Overall, currently Giant otters are classified as Endangered (EN) and theirs numbers today are decreasing.