Foraging success rates of North American River Otters, Lutra canadensis, hunting alone and hunting in pairs

Abstract

The foraging behavior of North American River Otters, Lutra canadensis, living near the Tomahawk River in northcentral Wisconsin was observed during winter and early spring, 1977. I compared percent successful dives, duration of dives, and duration of eating (an index of prey size) by otters hunting alone and those hunting in pairs to determine whether hunting in pairs affected individual foraging success. Otters preyed primarily on fish (7.5-20 cm long) and I observed no food sharing or fighting over food. Animals hunting together usually remained within a few meters of each other, but did not dive together or coordinate their hunting efforts. Otters hunting alone had significantly higher success rates than animals hunting in pairs, but otters hunting together tended to spend longer times consuming their prey.