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Alaska’s Admiralty Island is home to an estimated 1800 brown bears, the largest concentration of bears in the world. Nearly 100 miles long and 20 miles wide, it is half the size of Yellowstone National Park, yet it sustains four times more grizzlies. The native Tlingít people call this island “Kootznoowoo,” meaning “Fortress of the Bears.” It is a place where bears depend on fish, fish depend on trees, and the trees depend on fish-eating bears to spread the nitrogen rich bodies of salmon throughout the forest. Everything depends on the annual salmon run. But a change in the weather can keep the salmon from arriving, and affect the entire ecosystem. Nature enters this world shaped by bears, trees and salmon to explore the delicate balance of their interconnected lives. Fortress of the Bears premieres Wednesday, January 25 at 7 p.m. on WTVP-HD. Chris Morgan narrates. After broadcast, the episode will stream online at pbs.org/nature.

It is spring. A young bear mother and her three cubs graze in the open, a naïve and dangerous move in a place where the cubs might be killed by adult males nearby. In bear society, it is best to avoid other bears, especially larger bears. The bigger, more powerful bears dominate all others in matters of feeding and mating. When the mother sees a large male enter the clearing, she quickly gathers her family and retreats to the forest, realizing her mistake.

As they wait for the salmon run to begin, the bears hunt and scavenge for anything they can find to supplement their unsatisfying diet of grass. The receding tide offers unique opportunities, and one young bear demonstrates a remarkable talent for clamming. Using her jaws to crack open her finds, she delicately removes the clam meat from the shells with her dexterous four-inch claws. But the feast is short-lived. A few hours later, the tidal flats become ocean again.

By mid-summer, humpback whales arrive from Hawaii to feast on enormous shoals of herring. But the salmon have yet to appear. A La Niña winter has cooled the water to two degrees below normal, keeping the salmon out of the streams and delaying the run. It’s the worst salmon season in the last 40 years. The bears have little or nothing to eat and become ever more gaunt and desperate. The young mother loses two cubs to hunger, or to another bear. But as the summer begins to wane, the tide finally turns for the salmon and for the bears. Two months late, the waters warm and the streams fill with spawning salmon. Ravenous bears that have survived the devastating summer of want can finally eat their fill. The much-needed salmon has saved the young mother and her one remaining cub. When she appears once more in the meadow, it is clear she has gained both weight and wisdom. Now she is cautious and sniffs for other bears before leaving the safety of the trees. She has managed to protect the cub through the most difficult season in memory and together they face an uncertain future. What is certain is that the cycle of life will begin anew next year as it has always done in this fortress of the bears.

NATURE is a production of THIRTEEN in association with WNET for PBS. Fred Kaufman is executive producer. Fortress of the Bears is a production of Moore & Moore Films and THIRTEEN in association with National Geographic Channel and WNET.

NATURE pioneered a television genre that is now widely emulated in the broadcast industry. Throughout its history, NATURE has brought the natural world to millions of viewers. The series has been consistently among the most-watched primetime series on public television.

NATURE has won more than 600 honors from the television industry, the international wildlife film communities, and environmental organizations including 10 Emmys, three Peabodys and the first award given to a television program by the Sierra Club. The series received two of wildlife film industry’s highest honors: the Christopher Parsons Outstanding Achievement Award given by the Wildscreen Festival and the Grand Teton Award given by the Jackson Hole Wildlife Film Festival. Recently, Fred Kaufman was named the recipient of the Lifetime Achievement Award for Media by the 2012 International Wildlife Film Festival.

PBS.org/nature is the award-winning web companion to NATURE featuring streaming episodes, filmmaker interviews, teacher’s guides, and more.

Major corporate support for NATURE is provided by Canon U.S.A., Inc. Additional support is provided by the Lillian Goldman Charitable Trust, Filomen M. D’Agostino Foundation, the Corporation for Public Broadcasting, and the nation’s public television stations.

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