What Do Sea Otters Typically Eat?

Sea otters live in the Pacific Ocean and are found in Russia, Alaska, Washington state and California. These furry marine mammals are one of only a few marine animals known to use tools to obtain their food.

A Sea Otter's Diet

Sea otters eat a wide variety of prey, including marine invertebrates such as echinoderms (sea stars and sea urchins), crustaceans (e.g., crabs), cephalopods (e.g., squid), bivalves (clams, mussels, abalone), gastropods (snails), and chitons.

How Do Sea Otters Eat?

Sea otters obtain their food by diving. Using their webbed feet, which are well adapted for swimming, sea otters can dive more than 200 feet and stay underwater for up to 5 minutes. Sea otters can sense prey using their whiskers. They also use their agile front paws to find and grasp their prey.

Sea otters are one of the only mammals that are been known to use tools to obtain and eat their prey. They can use a rock to dislodge mollusks and urchins from the rocks where they are attached. Once at the surface, they often eat by placing the food on their stomachs, and then placing a rock on their stomachs and then smashing the prey on the rock to open it and get at the flesh inside.

Prey Preferences

Individual otters in an area seem to have different prey preferences. A study in California found that among an otter population, different otters specialized in diving at different depths to find different prey items. There are deep-diving otters that eat benthic organisms such as urchins, crabs, and abalone, medium-diving otters that forage for clams and worms and others that feed at the surface on organisms such as snails.

These dietary preferences may also make certain otters susceptible to disease. For example, sea otters eating snails in Monterey Bay appear more likely to contract Toxoplama gondii, a parasite found in cat feces.

Storage Compartments

Sea otters have loose skin and baggy "pockets" underneath their forelimbs. They can store extra food, and rocks used as tools, in these pockets.

Impacts on the Ecosystem

Sea otters have a high metabolic rate (that is, they use a high amount of energy) that is 2-3 times that of other mammals their size. Sea otters eat about 20-30% of their body weight each day. Otters weigh 35-90 pounds (males weigh more than females). So, a 50-pound otter would need to eat about 10-15 pounds of food per day.

The food sea otters eat can impact the entire ecosystem in which they live. Sea otters have been found to play a pivotal role in the habitat and marine life that inhabit a kelp forest. In a kelp forest, sea urchins can graze on the kelp and eat their holdfasts, resulting in deforesting the kelp from an area. But if sea otters are abundant, they eat sea urchins and keep the urchin population in check, which allows kelp to flourish. This, in turn, provides shelter for sea otter pups and a variety of other marine life, including fish. This allows other marine, and even terrestrial animals, to have abundant amounts of prey.

Sources:

• Estes, J.A., Smith, N.S., and J.F. Palmisano. 1978. Sea otter predation and community organization in the Western Aleutian Islands, Alaska. Ecology 59(4):822-833.
• Johnson, C.K., Tinker, M.T., Estes, J.A., Conrad, P.A., Staedler, M., Miller, M.A., Jessup, D.A. and Mazet, J.A.K. 2009. Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system. Proceedings of the National Academy of Sciences 106(7):2242-2247
• Laustsen, Paul. 2008. Alaska's Sea-Otter Decline Affects Health of Kelp Forests and Diet of Eagles. USGS.
• Newsome, S.D., M.T. Tinker, D.H. Monson, O.T. Oftedal, K. Ralls, M. Staedler, M.L. Fogel, and J.A. Estes. 2009. Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis) Ecology 90: 961-974.
• Righthand, J. 2011. Otters: The Picky Eaters of the Pacific. Smithsonian Magazine.
• Sea Otters. Vancouver Aquarium.
• The Marine Mammal Center. Animal Classification: Sea Otter.