Most otters eat crayfish, crabs, fish, frogs and other aquatic invertebrates. The diet of otters varies, however, depends on the species, location of residence and availability of food sources. Small otters generally consume small mollusks, crayfish and crabs, while the largest species eat fish, frogs and even land mammals such as birds, rodents and rabbits.
Giant otters and other larger species consume prey such as minnows, trout, salmon and crabs in shallow waters and along coastlines. Cape clawless and small-clawed Asian otters, which are among the smallest breeds, dine primarily on soft-shell and blue crabs and supplement their intakes with lobsters, squid, clams and mussels. They occasionally snatch frogs and small insects from shorelines and may also consume eggs of birds and other land animals. Occasionally, two or more species of otters live in one location. However, the diets of species are often quite different, and only in times of scarcity do coinhabiting species compete for food. In Thailand, for instance, three species of otters share overlapping territories. Here, the smallest small-clawed otters eat crabs, while smooth otters consume larger fish, and the largest Eurasian otters eat small fish and amphibians. Regardless of what they eat, otters must feed constantly because they have high metabolic rates to generate the heat they need to stay warm.