The giant otter is a highly social animal and lives in extended family groups.
Group sizes are anywhere from two to 20 members, but likely average between four and eight. (
Larger figures may reflect two or three family groups temporarily feeding together.)
The groups are strongly cohesive: the otters sleep, play, travel, and feed together.

Group members share roles, structured around the dominant breeding pair.
The species is territorial, with groups marking their ranges with latrines, gland secretions, and vocalizations.
At least one case of a change in alpha relationship has been reported, with a new male taking over the role; the mechanics of the transition were not determined.
Duplaix suggests a division between "residents", who are established within groups and territories, and nomadic and solitary "transients"; the categories do not seem rigid, and both may be a normal part of the giant otter life cycle.
One tentative theory for the development of sociality in mustelids is that locally abundant, but unpredictably dispersed, and prey causes groups to form.

Aggression within the species ("intraspecific" conflict) has been documented.
Defence against intruding animals appears to be cooperative: while adult males typically lead in aggressive encounters, cases of alpha females guarding groups have been reported.
One fight was directly observed in the Brazilian Pantanal in which three animals violently engaged a single individual near a range boundary.
In another instance in Brazil, a carcass was found with clear indications of violent assault by other otters, including bites to the snout and genitals, an attack pattern similar to that exhibited by captive animals.
While not rare among large predators in general, intraspecific aggression is uncommon among otter species; Ribas and Mourão suggest a correlation to the animal's sociability, which is also rare among other otters.

A capacity for aggressive behavior should not be overstated with the giant otter.
Researchers emphasize that even between groups, conflict avoidance is generally adopted.
Within groups, the animals are extremely peaceful and cooperative.
Group hierarchies are not rigid and the animals easily share roles.
The giant otter is a highly social animal and lives in extended family groups. Group sizes are anywhere from two to 20 members, but likely average between four and eight. (Larger figures may reflect two or three family groups temporarily feeding together.) The groups are strongly cohesive: the otters sleep, play, travel, and feed together.
Group members share roles, structured around the dominant breeding pair. The species is territorial, with groups marking their ranges with latrines, gland secretions, and vocalizations. At least one case of a change in alpha relationship has been reported, with a new male taking over the role; the mechanics of the transition were not determined. Duplaix suggests a division between "residents", who are established within groups and territories, and nomadic and solitary "transients"; the categories do not seem rigid, and both may be a normal part of the giant otter life cycle. One tentative theory for the development of sociality in mustelids is that locally abundant, but unpredictably dispersed, and prey causes groups to form.
Aggression within the species ("intraspecific" conflict) has been documented. Defence against intruding animals appears to be cooperative: while adult males typically lead in aggressive encounters, cases of alpha females guarding groups have been reported. One fight was directly observed in the Brazilian Pantanal in which three animals violently engaged a single individual near a range boundary. In another instance in Brazil, a carcass was found with clear indications of violent assault by other otters, including bites to the snout and genitals, an attack pattern similar to that exhibited by captive animals. While not rare among large predators in general, intraspecific aggression is uncommon among otter species; Ribas and Mourão suggest a correlation to the animal's sociability, which is also rare among other otters.
A capacity for aggressive behavior should not be overstated with the giant otter. Researchers emphasize that even between groups, conflict avoidance is generally adopted. Within groups, the animals are extremely peaceful and cooperative. Group hierarchies are not rigid and the animals easily share roles.
Giant otter