Otters are carnivorous aquatic mammals found across various environments worldwide, excluding Australia and Antarctica. These agile creatures possess a high metabolic rate, necessitating a substantial daily food intake to maintain body temperature and energy. River otters may consume 15% to 20% of their body weight daily, while sea otters require up to 25% to 30%. This need for sustenance drives their hunting behaviors and shapes their diverse diets, primarily consisting of aquatic prey.
Common Fish Species Consumed
Fish form a significant portion of an otter’s diet, particularly for river otters. Otters are opportunistic hunters, targeting what is readily available and easiest to catch. They often target slower-moving, non-game fish species, which are less energetically costly to pursue than fast-swimming game fish like trout or pike. However, during spawning seasons, even faster fish become more vulnerable and may be consumed.
Freshwater fish commonly found in river otter diets include suckers, carp, minnows, shiners, daces, bullheads, and various catfish. Perch, sunfish, darters, mudminnows, and sculpins are also frequent prey. Eels are particularly favored by some otter populations, especially during warmer months. Generally, otters prefer fish 15 to 17 centimeters, as these sizes offer a good caloric return for the effort.
Environmental Influences on Diet
An otter’s habitat significantly determines the types of fish available. Freshwater otters primarily feed on species in their rivers, lakes, and streams. Their diet can shift regionally based on the dominant fish populations in a given waterway. For example, a river otter in one region might frequently encounter carp and suckers, while another in a different watershed might more often prey on perch or minnows.
Coastal otters, such as sea otters, inhabit marine environments and encounter different aquatic life. While fish are a component of their diet, marine invertebrates often constitute a primary food source for these species. This dietary distinction highlights how the specific ecosystem directly influences the types of prey an otter can access and, thus, its overall dietary composition.
Beyond a Fish-Only Diet
While fish are a staple, otters also supplement their diet with other prey. When fish are scarce, or other food sources are abundant, otters will readily consume crustaceans, such as crayfish and crabs. Amphibians like frogs and salamanders are also eaten.
Otters also prey on mollusks, including clams, mussels, and snails. For sea otters, marine invertebrates like sea urchins and abalones are important. Their diet can also include small mammals like rodents, rabbits, and voles, as well as birds and their eggs. Reptiles such as turtles and snakes, along with various insects, round out their diverse diet, demonstrating their adaptability.