Hunting and Feeding in the Giant Otter

The information below comes from Duplaix (1980), Chanin (1985), Harris (1968), Otternet, and Frankfurt Zoological Society Giant Otter Project.

Giant Otters are mainly fish eaters, especially of slow-moving bottom-feeding fish such as catfish and characins. If fish is scarce, they will also eat freshwater crabs, snakes, young caiman, water birds and the occasional mammal - anything they can get their paws on! Duplaix (1980) records one male that went ashore, collected tapir dung, and brought it back to the water to eat it! In the dry season, groups of otters charge about catching fish among the lily pads in very shallow water. In the rainy season, they follow the seasonal movement of the fish into the flooded forest.

Giant Otters are diurnal predators (though there is one account in Duplaix (1980) of a group travelling across the Venezuelan savannah by night), and are typically active between 06:30 and 18:30. They fish in groups, and also alone, depending on where they are hunting. In shallow water, along creeks, in swamps, along sandbars and round boulders, the otters are more successful if they hunt alone - never out of sight or sound of the rest of the group. In deeper water, the whole group hunts together, swimming side-by-side, diving and surfacing at regular intervals, in close proximity. Bright (2000) considers that they cooperate to blow bubble nets to coral fish; he may be following Hershkovitz (referenced by Duplaix). Duplaix herself sees little evidence of such behaviour. A group of otters thrashing about hunting would probably concentrate fish against any natural barrier such as the bank, and a fish pursued by one otter might be intercepted and eaten by another, but this may be accidental opportunism rather than concerted chase and intercept behaviour.

Underwater chases are very fast and turbulent. The prey is grasped in the jaws, the otter surfaces and the prey is eaten immediately - apart from mothers feeding their young, it is not shared. Smaller prey is held in the paws, and larger fish are dragged to the shore and eaten. The otter likes to rest its elbows on the bottom, grasp the prey and eat it headfirst, bones and all. While Giant Otters will manipulate things to some extent with their paws, they do not avert their gaze, or juggle, like more paw-oriented otter species.

Digestion is rapid, with food passing through completely in 40 - 60 minutes. Each adult needs about 4kg per day (6-9lb, about 20% of their bodyweight, or eight times a human's daily calorie needs), which means that during hunting periods, they catch something around every 15 minutes. Hunting sessions are initiated and terminated by the alpha female.

Giant Otter