As its name suggests, this is the biggest member of the weasel family in terms of size, but it has the shortest fur of any otter.
Highly social by nature, giant otters live in extended family groups, with a dominant pair at the top of the social hierarchy. Much of their time is spent on land, where they maintain a series of dens, scent-marking their territory. They are active during the day and hunt mainly by sight. When tackling large and dangerous quarry such as anacondas, the group will launch a concerted attack. They keep in touch with each other by a series of calls.
The giant otter is the largest mustelid in the world, although it is not as heavy as the sea otter. This semi-aquatic mammal inhabits the tropical river basins of South America. It lives in groups of about six, each communicating with chirping sounds. Generally, the group comprises an adult pair and their offspring of various litters. Each group controls its own stretch of stream, preferring those areas with plenty of cover.
The giant otter's fur has a velvety appearance, more like the pelt of a seal than an otter. Its feet are large and have thick webbing, and the tail is flattened into a flipper-like shape.
The giant otter swims at high speed by waving its tail and body up and down, using its webbed feet to steer. On land it is far less agile, and is often seen sitting grooming itself. Giant otters are diurnal - only active during the day. They catch prey in their mouths and hold it in their forepaws to eat it on the shore. During the dry season, the otter groups are restricted to small areas of water, but when the rains come to flood the forest, the otters can roam over larger areas. Little is known about the mating habits of giant otters, other than that the young stay with their parents for a few years before reaching adulthood.
Distribution: Occurs throughout northern and central parts of South America in the major river systems, but has now declined dramatically and may even be extinct in some areas.
Habitat: Slow-moving rivers and creeks in forests and swamps.
Weight: 22 - 15 kg (49 - 99 lb); males are heavier.
Length: 122 - 244 cm (48 - 96 in) overall; tail measures up to 107 cm (42 in).
Maturity: 2 years.
Gestation Period: 65 - 70 days.
Breeding: 1 - 5, but averages 2; weaning occurs at 36 weeks.
Food: Piscivorous, feeding on catfish, perch, cichlids and characins; also hunts crabs, snakes and young caimans.
Lifespan: 5 - 8 years in the wild; up to 17 in captivity.
The fur is normally chocolate-brown, but it can vary from fawn to red. It appears much darker when wet.
The muzzle is short and compact, giving the head a round appearance.
Much larger giant otters probably existed in the past, with body lengths up to 240 cm (94 in).
The large feet have webbing between the toes to assist the otter's swimming ability.
These otters hunt at the surface, looking for shoals of fish in the water beneath, and then dive after them.
Giant otters call to each other to keep in touch.