Are Otters Generalists or do they prefer Larger, Slower Prey? Feeding Flexibility of the Neotropical Otter Lontra longicaudis in the Atlantic Forest

Despite there being several studies focusing on feeding habits of Lontra longicaudis, few studies aimed to evaluate its prey selectivity and none of them considered prey mobility. In this study, we report both its feeding flexibility and specialist feeding behaviour between two parts of Mambucaba River, Southeastern Brazil. We observed that they fed mainly on fish, crabs and crayfish. We did not observe seasonality either in diet or prey community availability. However, using ANOVA, we found differences between stretches for diet composition and in the availability of prey. Monotonic Multi-Dimensional Scaling ordination showed that the otter diet in mangroves was dominated by Brachyura and the prey availability by Brachyura, Caridea, Ariidae, Mugilidae, Gerreidae, Centropomidae and Cichlidae, while the diet in the river stretch was dominated by Cichlidae, Caridea and Heptapteridae, and the prey availability by Characidae, Erythrinidae and Heptapteridae. According to Ivlev Electivity Index, along the river few preys were consumed according to their abundance, the majority being selected. Otters preferred slower prey, no matter their size. We observed variation in the level of preference of the same prey in different stretches, with flexibility in otter diet. Otter ate few preys according to their abundance, but showed specialist feeding behaviour, eating the slowest prey of the stretch.