Keystone Otter
Sea otter. Photo by Dr. Lloyd Glenn Ingles © California Academy of Sciences.
JB: This is Earth and Sky, on sea otters. These playful creatures are an important part of the food webs in undersea kelp forests.
DB: Otters feed on porcupine-like sea urchins. The urchins in turn feed on the tangled forests of kelp. Like a forest on land, kelp forests provide habitat and food for many animals – like snails, crabs and fish. Otters help reduce the sea urchin populations – which helps the kelp forest to thrive.
JB: We spoke with James Estes, a research scientist with the U.S. Geological Survey in Santa Cruz, California. He studies sea otters in the Aleutian Islands of Alaska, an area that’s shown a dramatic decline of otter populations in the past decade.
James Estes: So when the otters are taken out of the system, the urchin populations become vastly more abundant, and the urchins themselves are important consumers of the kelp. And so you have this interaction among three species… the otters, the herbivores, and the kelp… And the fact that the otters have such a strong impact across all those trophic levels makes them what people have called a keystone species.
DB: And when a keystone species disappears, a whole ecosystem changes. More on sea otters from Dr. Estes – tomorrow. Thanks to the U.S. Forest Service and to the National Fish and Wildlife Foundation – supporting the conservation of native fish, wildlife, plants and their habitats. We’re Block and Byrd for Earth and Sky.
The following individual was interviewed for today’s show. Our thanks to:
James A. Estes, Ph.D.
Research Biologist
Western Ecological Research Center
U.S. Geological Survey
Santa Cruz, CA USA
Additional Teacher Resources
U.S. Geological Survey, Biology: Sea Otters in the North Pacific Ocean
This site provides a natural history of the sea otter in the north Pacific Ocean. From central Baja California, north and west along the Pacific Rim to the Kamchatika Peninsula in Russia, and south to the Kuril Islands of northern Japan. The primary area of focus is the recovery of the otter population from mass depletion due to hunting and its effect of the ecosystems of the north Pacific Ocean.
U.S. Geological Survey, Western Ecological Research Center: Sea Otter Research at WERC
Sea otters are keystone predators in the nearshore environment of the eastern Pacific Ocean, in a food web composed of sea otter, sea urchin, and kelp forest. Without sea otters, the kelp forest can be overgrazed by sea urchins, which in turn can affect other species that depend on this ecosystem. This report explains the role of the keystone species in this ecosystem.
Defenders of Wildlife, Sea Otters: Conserving Sea Otter Populations Worldwide
This site is a great resource for finding introductory information about sea otter species, their population status, distribution, and importance in the ecosystems in which they inhabit. The site also provides a variety of links on sea otter species, fact sheets, and conservation organizations.
Science News for Kids: Sea Otters, Kelp, and Killer Whales
This article discusses the sea otters’ role as a keystone species within its ecosystem, and how it came to be that killer whales began to eat them. The article then deals with how the National Oceanic and Atmospheric Administration is working to find out what new threats otters face. The research is hoped to shape a new plan to help otter populations thrive.
