Otters are semi-aquatic mammals known for their sleek bodies, dense fur, and playful demeanor. They thrive in diverse environments, from freshwater rivers to the cold, open ocean. Understanding their diet reveals the precise balance of energy needed to sustain their highly active lifestyles. This requires a closer look at their metabolic demands and feeding strategies.
The Carnivorous Core of the Diet
Otters are obligate carnivores, meaning their survival depends almost entirely on nutrients derived from animal sources. This requirement is driven by an exceptionally high metabolic rate necessary for thermoregulation in cold water. To maintain body temperature, otters consume a substantial amount of food daily, often eating between 15% and 30% of their total body weight every 24 hours.
The bulk of this intake consists of high-protein, high-fat prey. Fish, such as trout, carp, and non-game species, are typically the primary food source for most river otter species. Their diet also incorporates other aquatic life, including crustaceans like crayfish and crabs, amphibians, and mollusks.
When Otters Consume Vegetation
While their diet is overwhelmingly composed of meat, otters occasionally consume plant material. This consumption is usually accidental, occurring when an otter swallows aquatic weeds or roots attached to a fish or other prey item. The primary goal is always animal protein.
Sea otters are sometimes observed consuming parts of kelp, often pieces that have detached and are floating. This behavior may provide roughage or occur when preferred invertebrate prey is scarce. Plants do not supply a meaningful amount of the daily calories otters need to survive.
Acquiring Food: Hunting Techniques
Otters employ physical and sensory adaptations to successfully capture their prey.
Physical Adaptations
Their streamlined bodies and webbed feet allow for speed and agility in the water, enabling them to chase down fish and other aquatic animals. They can hold their breath for several minutes and dive to considerable depths to pursue a meal.
Sensory Adaptations and Tool Use
A keen sense of touch is crucial, especially in murky water where vision is limited. Otters use their long, sensitive facial whiskers, known as vibrissae, to detect subtle water movements caused by prey. These vibrissae allow them to pinpoint the location of a fish or crustacean. Sea otters also demonstrate tool use by selecting rocks to crack open the hard shells of clams, crabs, and sea urchins, showcasing dexterity in their foraging.
How Habitat Influences What Otters Eat
The composition of an otter’s diet varies significantly based on its geographic location and whether it inhabits a freshwater or marine environment.
River otters (Lontra) exhibit a flexible diet that shifts with the seasons and local availability. Their meals may include a higher proportion of crayfish and amphibians in one season, switching to small birds or reptiles in another, depending on what is easily captured.
In contrast, the Sea Otter (Enhydra lutris) lives almost entirely in coastal ocean waters and relies heavily on slow-moving marine invertebrates. Their preferred foods are hard-shelled organisms like sea urchins, clams, abalone, and mussels, which they retrieve from the ocean floor.