Adult giant otters living in family groups have no known serious natural predators, however there are some accounts of black caimans in Peru and yacare caimans in the Pantanal preying on giant otters.
In addition, solitary animals and young may be vulnerable to attacks by the jaguar, cougar, and anaconda, but this is based on historical reports, not direct observation.
Pups are more vulnerable, and may be taken by caiman and other large predators, although adults are constantly mindful of stray young, and will harass and fight off possible predators.
When in the water, the giant otter faces danger from animals not strictly preying upon it: the electric eel and stingray are potentially deadly if stumbled upon, and piranha may be capable of at least taking bites out of a giant otter, as evidenced by scarring on individuals.

Even if without direct predation, the giant otter must still compete with other predators for food resources.
Duplaix documented interaction with the neotropical otter.
While the two species are sympatric (with overlapping ranges) during certain seasons, there appeared to be no serious conflict.
The smaller neotropical otter is far more shy, less noisy, and less social; at about a third the weight of the giant otter, it is more vulnerable to predation, hence, a lack of conspicuousness is to its advantage.
The neotropical otter is active during twilight and darkness, reducing the likelihood of conflict with the diurnal giant otter.
Its smaller prey, different denning habits, and different preferred water types also reduce interaction.

Other species that prey upon similar food resources include the caimans and large fish that are themselves piscivores.
Gymnotids, such as the electric eel, and the large silurid catfish are among aquatic competitors.
Two river dolphins, the tucuxi and boto, might potentially compete with the giant otter, but different spatial use and dietary preferences suggest minimal overlap.
Furthermore, Defler observed associations between giant otters and the Amazon river dolphins, and suggested that dolphins may benefit by fish fleeing from the otters.
The spectacled caiman is another potential competitor, but Duplaix found no conflict with the species in Suriname.
Adult giant otters living in family groups have no known serious natural predators, however there are some accounts of black caimans in Peru and yacare caimans in the Pantanal preying on giant otters. In addition, solitary animals and young may be vulnerable to attacks by the jaguar, cougar, and anaconda, but this is based on historical reports, not direct observation. Pups are more vulnerable, and may be taken by caiman and other large predators, although adults are constantly mindful of stray young, and will harass and fight off possible predators. When in the water, the giant otter faces danger from animals not strictly preying upon it: the electric eel and stingray are potentially deadly if stumbled upon, and piranha may be capable of at least taking bites out of a giant otter, as evidenced by scarring on individuals.
Even if without direct predation, the giant otter must still compete with other predators for food resources. Duplaix documented interaction with the neotropical otter. While the two species are sympatric (with overlapping ranges) during certain seasons, there appeared to be no serious conflict. The smaller neotropical otter is far more shy, less noisy, and less social; at about a third the weight of the giant otter, it is more vulnerable to predation, hence, a lack of conspicuousness is to its advantage. The neotropical otter is active during twilight and darkness, reducing the likelihood of conflict with the diurnal giant otter. Its smaller prey, different denning habits, and different preferred water types also reduce interaction.
Other species that prey upon similar food resources include the caimans and large fish that are themselves piscivores. Gymnotids, such as the electric eel, and the large silurid catfish are among aquatic competitors. Two river dolphins, the tucuxi and boto, might potentially compete with the giant otter, but different spatial use and dietary preferences suggest minimal overlap. Furthermore, Defler observed associations between giant otters and the Amazon river dolphins, and suggested that dolphins may benefit by fish fleeing from the otters. The spectacled caiman is another potential competitor, but Duplaix found no conflict with the species in Suriname.
Giant otter