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Glacier Bay hot real estate for sea otters
by Ned Rozell


April 05, 2005

Sea otters have had a rough time since Vitus Bering's journey to Alaska: They were hunted almost to extinction in the 1700s and 1800s, made a comeback in the 1900s, then declined again in the last few decades. Though sea otter numbers are dropping in the Aleutians and elsewhere in Alaska, the animals are increasing in Glacier Bay.

About five sea otters lived in Glacier Bay in 1995, but today more than 1,800 live there. Jim Bodkin and his colleagues at the USGS Alaska Science Center in Alaska have studied the sea otter's recent emergence in Glacier Bay. A biologist, Bodkin started the study in 1993, two years before otters showed up in the bay. He and other researchers knew otters were nearby at the time and would probably soon move in. Glacier Bay National Park, located in Southeast Alaska, has been in existence for about 250 years, when huge glaciers at the mouth of the bay began retreating.

jpg otters

A sea otter in Glacier Bay, one of the few places in Alaska
with a growing sea otter population.
Photo by Jim Bodkin

The Russians and later the Americans almost wiped out Alaska's sea otters because the otter's fur is among the thickest in the animal world, with more hairs per square centimeter than the total on any person's head, according to Males can be nearly five feet long and can weigh more than 100 pounds. They dive to the sea floor to hunt and eat while floating on their backs, using their forepaws to eat sea urchins, clams, mussels, crabs, and octopus.

Starting in 1965, the Alaska Department of Fish and Game captured otters on Amchitka Island in the Aleutians and some in Prince William Sound, releasing 412 off the coast of Southeast Alaska, a few of those off Cape Spencer near Glacier Bay. In the mid-1990s, some otters found their way into Glacier Bay.
Bodkin and his coworkers counted five otters during an aircraft survey of Glacier Bay in 1995. They counted 39 in 1996 and 21 in 1997, but since then the yearly counts have showed more and more otters. From 2000 to 2001, sea otter numbers more than doubled, from 554 to 1,238.

At the same time, sea otters in the Aleutians and other areas of Alaska have been decreasing. Some scientists think the population crash is due to killer whales eating more sea otters in the Aleutians, possibly because traditional killer whale prey, such as large whales and sea lions, have also dwindled in the Aleutians. Terrie Williams of the University of California and Jim Estes of USGS authored a recent study in the journal Ecology showing that male sea otters contained almost 62,000 calories when eaten whole, a decent percentage of the 243,000 calories an average male killer whale needs to survive each day.

Killer whales also hunt in Glacier Bay, but they don't seem to be slowing down the otters. People have seen killer whales eat otters in Southeast Alaska, but other marine mammals that killer whales eat are not as rare in Southeast as they are in the Aleutians and that perhaps takes the pressure off the otters, Bodkin said.

While the possible otter/killer whale connection in the Aleutians is intriguing, Bodkin and his colleagues are more interested in looking at the sea otter as a predator and how its sudden emergence in Glacier Bay will affect other living things. Clams in Glacier Bay might be fewer and smaller after a few years, and the distribution of sea birds, fish and some other mammals could change there with the sea otter feasting on local crabs, sea urchins and other shellfish.

Because scientists began the study before otters were in Glacier Bay and sea otters haven't yet occupied the entire bay, the researchers have been able to document the plants and animals of the bay before otters. While other scientists study the otters in the Aleutians as victims of changes that began with the 1741 passage of Bering's ship, the St. Peter, Bodkin will look at Glacier Bay otters as agents of change in a young ecosystem.


This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell ( ) is a science writer at the institute.


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