Southern sea otters feed primarily on benthic invertebrates, such as sea urchins, abalone, crabs and snails, but they have been occasionally observed eating birds. There are documented cases of cormorants, western grebes, surf scoters, common loons, and gulls being killed and/or eaten by otters in the Monterey Bay. Most of the otters observed feeding on seabirds have been adult males. At one site, it appeared that the same individual repeatedly captured birds.
Sea otters will typically capture a bird by diving and then grabbing it from underwater as the bird rests on the surface. After capturing the bird, the otter repeatedly pulls it underwater and wrestles with it on the surface while biting it on the head and neck. Once the bird has been subdued, the otter clasps the bird with its forepaws and then strips the flesh from the breast, neck and legs. The feeding sessions last for only 10 – 15 minutes after which time the otter discards the carcass and swims away.
Although sea otter predation on birds is rare and has not been widely observed, the behavior is indicative of the sea otter’s ability to learn new foraging tactics, and is consistent with the species’ high degree of individual variation in diet. Researchers also suggest that sick otters may turn to birds for an additional source of nutrition so as to reduce the need to dive for food. Otters may also target less preferred prey items, such as birds, when other prey have been depleted.
Riedman, M. L., and Estes, J. A. 1988. Predation on seabirds by sea otters. Can. J. Zool. 66: 1396-1402.
Sea Otter Predation on Birds near Monterey, California | Author(s): Robert F. VanWagenen, Michael S. Foster, Frank Burns | Source: Journal of Mammalogy, Vol. 62, No. 2 (May, 1981), pp. 433-434