Otters are highly dexterous aquatic mammals known for their varied diet and ability to manipulate objects. Their foraging habits often involve consuming tough-shelled invertebrates, leading to curiosity about whether they eat starfish. The answer is yes, but this behavior is primarily limited to the Sea Otter. This specific species has the necessary adaptations and habitat overlap to consume this prey.
Otter Species That Prey on Starfish
The consumption of starfish, or sea stars, is overwhelmingly a behavior of the marine-dwelling Sea Otter. These otters inhabit the nearshore coastal waters of the North Pacific, diving to the seabed to forage on a diverse array of invertebrates. Their diet includes common species like the Ochre Sea Star, though starfish are not a primary food source. They are consumed opportunistically as part of a varied diet of over 100 different prey species.
In contrast, the North American River Otter and other freshwater species rarely consume starfish. River otters primarily hunt fish, crayfish, frogs, and aquatic insects found in rivers and lakes. Even when river otters inhabit coastal marine environments, their diet remains focused on fish and crustaceans. They lack the specialized foraging adaptations required for handling large, spiny sea stars.
Tools and Techniques Used for Starfish Consumption
Sea otters have developed unique adaptations to consume hard-bodied prey, including sea stars. After procuring a sea star from the seafloor, the otter brings the prey to the surface and floats on its back, using its chest as a feeding table. For hard-shelled mollusks like clams, otters often use a rock as an anvil, striking the prey against the stone to break the shell. This tool-use behavior is rare among marine mammals.
Starfish present a different challenge than bivalves, as they have a tough, spiny upper surface but no true shell to crack. The otter does not use a tool to smash the organism; instead, it uses its powerful jaws and teeth to access the soft tissue inside. The otter carefully peels or bites through the central disc or the underside of the sea star, where the spines are less dense. This method allows the otter to bypass the tough external skeleton and consume the nutrient-rich soft parts.
Ecological Role of Otter Predation
The Sea Otter’s diet, including sea stars, influences the nearshore marine environment. Sea otters are recognized as a keystone species, meaning their presence has a disproportionately large effect on maintaining ecosystem structure. Their primary role is controlling populations of sea urchins, which are voracious grazers of kelp. By preying on urchins, otters prevent the formation of “urchin barrens” and allow kelp forests to thrive, providing habitat for numerous other species.
The consumption of sea stars also contributes to this ecological balance. For example, a severe sea star wasting event decimated populations of the Ochre Sea Star, a prominent predator of mussels. The resulting explosion in mussel populations created a temporary “prey surplus” that sea otters exploited, shifting their diet to include more mussels. This demonstrates keystone interdependence, where the collapse of the sea star predator directly altered the foraging habits of the sea otter predator.