Food Ecology of Otters in Natal, South Africa

Abstract

Food habits of otters Aonyx capensis (Schinz) and Lutra maculicollis Lichtenstein were studied in trout and non-trout areas by collecting and examining faeces. In both habitats Aonyx lived almost entirely on freshwater crabs and frogs, and principal items in Lutra's diet were crab, fish, and frog. Seasonal variations were observed in both otters' diets, with most crabs taken during summer and the incidence of fish being highest during winter. These variations were explained in terms of crabs retreating into inaccessible places during winter, and fishes' efficiency of locomotion being reduced in cold water. Both otter species took more small fish that larger specimens. It was concluded that small fish (< 200 mm) were easier to capture than larger ones, and were more abundant. Food ecology of otters was compared with that of the water mongoose Atilax paludinosus (G. Cuvier) which lived chiefly on crabs, small mammals, birds, and frogs. Although there was from 58-66% food overlap between Atilax and the otters, Atilax utilises a wider range of habitats than do otters, and does not exploit certain habitats which are exclusive to lutrines. The otters occupy restricted niches, whereas Atilax occupies a wide niche.