Sea otters are marine mammals that spend most of their lives in coastal waters, primarily along the Pacific Coast. Their existence is intricately linked to their diet, which not only sustains them but also plays an important part in the health of their marine environment. These adaptable animals consume a variety of prey, and their feeding habits have broader ecological consequences. Understanding what and how sea otters eat provides insight into their role within the complex marine ecosystem.
Primary Food Sources
Sea otters are carnivores with a diet consisting mainly of marine invertebrates. Their prey includes a range of shelled creatures such as sea urchins, clams, mussels, abalone, crabs, and snails. The specific composition of a sea otter’s diet can vary depending on its geographic location and prey availability.
Sea urchins are a well-known part of the sea otter’s diet, and their consumption directly influences kelp forest ecosystems. Beyond urchins, sea otters also consume bivalves like clams and mussels. Crabs are another frequent food source, which sea otters handle with their dexterous forepaws. Although primarily focused on invertebrates, sea otters may occasionally eat small fish, octopus, or squid.
Foraging and Feeding Habits
Sea otters display distinct behaviors to obtain and consume their food. They dive to the ocean floor to retrieve prey, using their sensitive whiskers to locate items in crevices and their strong forepaws to dig for buried creatures. Dives last one to two minutes, though they can hold their breath for over five minutes. They forage in shallow waters, less than 30 meters deep. Upon surfacing, a sea otter rolls onto its back, using its chest as a makeshift dining table.
A notable aspect of their feeding behavior is tool use. Sea otters are among the few animals known to use rocks to break open the hard shells of their prey, such as clams and abalone. They may place a rock on their chest and repeatedly strike the prey against it, or they might use a rock as a hammer to dislodge abalone from surfaces. This behavior not only allows them to access difficult-to-reach food but also helps reduce tooth damage. Sea otters have a high metabolic rate to maintain their body temperature in cold waters, requiring them to consume a large amount of food daily, between 25% to 30% of their body weight.
Ecological Impact of Their Diet
The diet of sea otters has significant consequences for marine ecosystems, particularly due to their role as a keystone species—one that has a disproportionately large effect on its environment relative to its abundance. Sea otters are especially effective at controlling populations of sea urchins, which are marine grazers that feed on kelp. By consuming urchins, sea otters prevent them from overgrazing kelp forests, which otherwise can lead to the formation of “urchin barrens” where kelp is scarce.
Healthy kelp forests are important marine habitats, providing shelter and food for a wide array of marine life, including various fish, invertebrates, and other mammals. These underwater forests also contribute to carbon sequestration by absorbing carbon dioxide from the atmosphere, thus playing a part in mitigating climate change. The presence of sea otters helps maintain the structure and biodiversity of these ecosystems, demonstrating how their feeding habits contribute to the health and resilience of coastal environments.