The giant otter lives in the rivers of the Amazonian rainforest, and adults may grow to nearly 1.5 m (5 feet) long. It has a powerful aquatic predator and has few natural enemies other than anacondas and jaguars. The giant otter has become endangered through increased human activity, and is especially threatened by water pollution and hunting for its short, thick fur. The Giant Otter is a species from the Pteronura genus. The giant otter ranges across north-central South America; it lives mostly in and along the Amazon River and in the Pantanal.
Giant otter muzzles are long and sloping. The ears are small and rounded. The nose is completely covered in fur, with only the two slit-like nostrils visible. The giant otter's highly sensitive whiskers allow the animal to track changes in water pressure and currents, which aids in detecting prey. The legs are short and stubby and end in large webbed feet tipped with sharp claws. Well suited for an aquatic life, it can close its ears and nose while underwater.
Although generally peaceful, the species is territorial, and aggression has been observed between groups. The giant otter is diurnal, being active exclusively during daylight hours. It is the noisiest otter species, and distinct vocalizations have been documented that indicate alarm, aggressiveness, and reassurance.
It feeds mainly on fish, including cichlids, characins, and catfish.
Females appear to give birth year round, although in the wild, births may peak during the dry season. The estrous cycle is 21 days, with females receptive to sexual advances between three and 10 days. Mothers give birth to furred and blind cubs in an underground den near the river shore and fishing sites. Pups open their eyes in their fourth week, begin walking in their fifth, and are able to swim confidently between 12 and 14 weeks old. The animal reaches sexual maturity at about two years of age and both male and female pups leave the group permanently after two to three years. The longest documented giant otter lifespan in the wild is eight years. In captivity, this may increase to 17, with an unconfirmed record of 19.