Giant otters build dens, which are holes dug into riverbanks, usually with multiple entrances and multiple chambers inside.
They give birth within these dens during the dry season.
 In Cantão State Park, otters dig their reproductive dens on the shores of oxbow lakes starting around July, when waters are already quite low.
They give birth between August and September, and the young pups emerge for the first time in October and November, which are the months of lowest water and fish concentrations in the dwindling lakes and channels are at their peak.
This makes it easier for the adults to catch enough fish for the growing young, and for the pups to learn how to catch fish.
The entire group, including nonreproductive adults, which are usually older siblings to that year's pups, collaborates to catch enough fish for the young.

Details of giant otter reproduction and life cycle are scarce, and captive animals have provided much of the information.
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.
Study of captive specimens has found only males initiate copulation.
At Tierpark Hagenbeck in Germany, long-term pair bonding and individualized mate selection were seen, with copulation most frequently taking place in water.
Females have a gestation period of 65 to 70 days, giving birth to one to five pups, with an average of two.
Research over five years on a breeding pair at the Cali Zoo in Colombia found the average interval between litters was six to seven months, but as short as 77 days when the previous litter did not survive.
Other sources have found greater intervals, with as long as 21 to 33 months suggested for otters in the wild.

Mothers give birth to furred and blind cubs in an underground den near the river shore and fishing sites.
Males actively participate in rearing cubs and family cohesion is strong; older, juvenile siblings also participate in rearing, although in the weeks immediately after birth, they may temporarily leave the group.
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.
They are weaned by nine months and begin hunting successfully soon after.
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.
They then search for new territory to begin a family of their own.

The giant otter is very sensitive to human activity when rearing its young.
No institution, for example, has successfully raised giant otter cubs unless parents were provided sufficient privacy measures; the stress caused by human visual and acoustic interference can lead to neglect, abuse and infanticide, as well as decreased lactation.
In the wild, it has been suggested, although not systematically confirmed, that tourists cause similar stresses: disrupted lactation and denning, reduced hunting, and habitat abandonment are all risks.
This sensitivity is matched by a strong protectiveness towards the young.
All group members may aggressively charge intruders, including boats with humans in them.

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.
The animal is susceptible to a variety of diseases, including canine parvovirus.
Parasites, such as the larvae of flies and a variety of intestinal worms, also afflict the giant otter.
Other causes of death include accidents, gastroenteritis, infanticide, and epileptic seizures.
Giant otters build dens, which are holes dug into riverbanks, usually with multiple entrances and multiple chambers inside. They give birth within these dens during the dry season.  In Cantão State Park, otters dig their reproductive dens on the shores of oxbow lakes starting around July, when waters are already quite low. They give birth between August and September, and the young pups emerge for the first time in October and November, which are the months of lowest water and fish concentrations in the dwindling lakes and channels are at their peak. This makes it easier for the adults to catch enough fish for the growing young, and for the pups to learn how to catch fish. The entire group, including nonreproductive adults, which are usually older siblings to that year's pups, collaborates to catch enough fish for the young.
Details of giant otter reproduction and life cycle are scarce, and captive animals have provided much of the information. 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. Study of captive specimens has found only males initiate copulation. At Tierpark Hagenbeck in Germany, long-term pair bonding and individualized mate selection were seen, with copulation most frequently taking place in water. Females have a gestation period of 65 to 70 days, giving birth to one to five pups, with an average of two. Research over five years on a breeding pair at the Cali Zoo in Colombia found the average interval between litters was six to seven months, but as short as 77 days when the previous litter did not survive. Other sources have found greater intervals, with as long as 21 to 33 months suggested for otters in the wild.
Mothers give birth to furred and blind cubs in an underground den near the river shore and fishing sites. Males actively participate in rearing cubs and family cohesion is strong; older, juvenile siblings also participate in rearing, although in the weeks immediately after birth, they may temporarily leave the group. 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. They are weaned by nine months and begin hunting successfully soon after. 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. They then search for new territory to begin a family of their own.
The giant otter is very sensitive to human activity when rearing its young. No institution, for example, has successfully raised giant otter cubs unless parents were provided sufficient privacy measures; the stress caused by human visual and acoustic interference can lead to neglect, abuse and infanticide, as well as decreased lactation. In the wild, it has been suggested, although not systematically confirmed, that tourists cause similar stresses: disrupted lactation and denning, reduced hunting, and habitat abandonment are all risks. This sensitivity is matched by a strong protectiveness towards the young. All group members may aggressively charge intruders, including boats with humans in them.
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. The animal is susceptible to a variety of diseases, including canine parvovirus. Parasites, such as the larvae of flies and a variety of intestinal worms, also afflict the giant otter. Other causes of death include accidents, gastroenteritis, infanticide, and epileptic seizures.
Giant otter