Competes with Jaguars for prey
The Giant Otter, Pteronura brasiliensis, (also known as the river wolf) is the longest of the world's otters, as well as the largest mustelid. It can only be found in South America.
They have a long body with a strong tail, which can act as a rudder, and short legs with webbed feet.
Weighing in at around 26kg (female) to 34kg (male), it can reach up to 1.8m in length
Giant Otter fur is extremely soft. It is uniformly chocolate brown with the exception of large creamy white patches on the underside of the otter's long necks. The pattern found in this area is thought to be unique to each individual otter.
As one of the largest predators in the region, the giant otter can choose from a wide variety of animals to feed on. This mainly consists of fish (including piranha), but also crabs, small caiman alligators and small anacondas.
Due to their size and swimming speed they compete successfully for fish with Jaguars and Black Caimans.
An amazing thing about their whiskers, which are called vibrissae, is that they can use them to detect changes in currents and water pressure. This helps when they are searching for fish and other prey because they can detect the prey's movement.
They are also the only mustelid that is monogamous (ie they only have one mate and therefore form couples).
Your chances of seeing one in the wild
Once found throughout lowland tropical rainforests of northern South America, Giant Otter populations had decreased dramatically by the 1970's due largely to a demand for their pelts.
However they can still be found fairly easily in the wild, and many tourist companies in the region offer trips to go and see them.
It is listed as Appendix I by CITES and as Endangered by IUCN- Red List.