The fur of river otters is so dense that water never reaches their skin, even when they're swimming. Giant otter guard hairs trap air and keep the dense inner fur dry. Their coat is mainly brown or gray and is usually darker on the back and lighter on the chest. Lips, chin, throat, and upper chest exhibit white blotches - which may merge into a single white ‘bib’.
Giant river otters are social, typically forming groups of 4-8 individuals. Cubs are reared in a central den area (1.2-1.8 m wide) that connects to an adjacent waterway via a tunnel or series of tunnels. Its life span is approximately 14 years.
The giant river otter has become rare or nonexistent over most of its range. This decline is largely due to habitat loss and commercial fur hunting. Though the fur trade is currently prohibited, hunting does continue. It is listed as endangered by IUCN.