Sea otters are a keystone species within marine ecosystems, maintaining healthy coastal environments by consuming invertebrates like sea urchins, which prevents overgrazing of kelp forests. Despite their important ecological position, sea otters are prey for other animals, highlighting their role in the ocean’s food web.
Apex Marine Predators
Orcas, particularly transient populations, prey on sea otters. These intelligent marine mammals adapt their diets based on prey availability. When populations of their typical prey, such as seals and sea lions, decline, some orcas may begin to target sea otters. This shift has been observed in areas like the Aleutian Islands, where a decrease in larger marine mammals coincided with increased orca predation on sea otters. Orcas employ various hunting strategies, which can involve coordinating attacks to separate and subdue their prey.
Great White Sharks also contribute to sea otter mortality, though otters are not a primary food source. Many shark bites on sea otters are investigatory, meaning sharks bite to identify the object rather than to consume it. Despite being exploratory, these bites often prove fatal due to severe injuries. This interaction has become a notable cause of death for southern sea otters, particularly in areas where their populations were attempting to recover.
Other Opportunistic Predators
Bald Eagles are opportunistic predators, targeting vulnerable sea otter pups. Young otters, especially those separated from their mothers or in shallow waters, are susceptible to aerial attacks. A decline in sea otter populations can shift the eagle’s diet, indicating adaptive foraging. Eagles primarily snatch pups from the water’s surface, as adult otters are typically too large and agile to be captured.
Brown and black bears can pose a threat to sea otters, primarily when otters come ashore. In coastal areas, such as tidal flats or estuaries, bears may encounter otters that have hauled out to rest or forage. While not typical prey, bears are generalist predators that take advantage of available food sources. Observations in places like Katmai National Park have documented brown bears hunting sea otters in these terrestrial and nearshore environments.
Steller Sea Lions have been observed preying on sea otters, though such instances are rare. These large pinnipeds typically consume fish and other marine life. While not a regular part of their diet, isolated cases of large male Steller sea lions attacking and consuming otters, including pups, have been documented. These events usually occur under specific, localized conditions, not representing a consistent predatory relationship.