Sea otters are marine mammals often associated with kelp forests, leading some to wonder if these creatures consume algae. While their habitat is closely linked to these underwater forests, sea otters do not eat algae. Their diet consists of a wide range of marine invertebrates, reflecting their role as predators in coastal ecosystems.
The Sea Otter Diet
Sea otters are carnivores, relying on a diverse diet of marine invertebrates. Their diet includes sea urchins, clams, mussels, crabs, and snails. Northern sea otters also include fish. To access the meat within hard-shelled prey, sea otters dive to the ocean floor, using their forepaws and whiskers to locate prey in crevices. Once found, they bring their catch to the surface, often using their chest as a makeshift table while floating on their backs.
They also use tools, employing rocks to break open shells. This behavior is uncommon among mammals. Sea otters possess a high metabolic rate, about three times higher than most similarly sized mammals. To sustain this metabolism and maintain their body temperature in cold ocean waters, they must consume a significant amount of food daily, often 25% to 30% of their body weight. Their digestive systems are adapted for high-calorie, protein-rich invertebrates, not plant matter like algae.
Ecological Impact of Sea Otter Feeding
The feeding habits of sea otters significantly impact the marine environments they inhabit, particularly kelp forests. Sea otters are considered a keystone species, meaning their presence has a disproportionately large effect on their ecosystem. Their consumption of sea urchins plays a significant role in maintaining kelp forest health. Sea urchins are voracious kelp grazers, and without sea otters to control their populations, urchins can overgraze, leading to the destruction of kelp beds and the creation of “urchin barrens.”
Healthy kelp forests provide many benefits to the marine ecosystem. They serve as habitats, offering shelter and food for diverse marine life, including fish and other invertebrates. Kelp forests also act as carbon sinks, absorbing carbon dioxide from the atmosphere and storing it, which contributes to mitigating climate change. By consuming urchins, sea otters indirectly support the growth of these underwater forests, fostering biodiversity and contributing to the health and resilience of coastal ecosystems.