Zoos experiment with antidotes for pacing polar bears

CHICAGO — Every day, the polar bear's routine was exactly the same: the same number of paces, same plodding path, same contorted head turn.

There were days when Lee, Lincoln Park Zoo's 4-year-old male polar bear, spent almost one-third of his time in repetitive motion, a maddening circle born of stress, boredom or — some think — instinct.

It has taken the Chicago zoo more than two years of research and $1 million in renovations to change Lee's behavior, slashing the time he spends pacing in half. The idea, zoo officials say, is to improve Lee's quality of life, part of a nationwide movement to prevent zoo animals from becoming bored.

Over the past several years, zoos have spent millions of dollars improving their exhibits, hoping to make the animals' habitats more closely resemble nature. While other animals have benefited from the changes, a growing number of zoos are paying particular attention to polar bears — massive, intelligent animals that, for reasons still unclear, are more inclined to repetitive pacing.

"From what I've seen of polar bears in captivity, they survive fairly well, but there appears to be some level of stress," said Andrew Derocher, a professor of biological sciences and a polar-bear expert at the University of Alberta in Edmonton. "Enrichment activities go a long way to help."

And so zoos have added swimming pools, delivered meals frozen in ice and given their polar bears brightly colored toys.

Whirlpool installed

At the Central Park Zoo in New York, zookeepers installed a whirlpool machine in the polar-bear pool, hoping the bubbles will provide 925-pound Gus with an alternative to his incessant lap swimming. In Toledo, Ohio, the zoo spent more than $11 million on its Arctic Encounter exhibit, adding a glass wall so Marty, a frequent pacer, could watch the seals swimming next door.

Nationwide, 22 facilities are participating in a study to learn why polar bears pace and what can be done to prevent it.

"It's not one single thing that you can do and it will eliminate it. It's a multitude of things," said Robert Buchanan, president of Polar Bears International, a nonprofit that is funding the nationwide study in collaboration with the American Zoo and Aquarium Association. "Exhibits are getting a lot more sophisticated. We're learning a lot and putting a lot of that into exhibits so the bears have a much higher quality of life in captivity."

Polar bears are not alone in their pacing. Lions, tigers, cheetahs and other large carnivores exhibit similar tendencies. Elephants in captivity sometimes sway back and forth, which scientists consider part of the same phenomenon, called stereotypic behavior.

Theories abound on why captive animals pace. A recent study by Ros Clubb and Georgia Mason at Oxford University in England found that carnivores with large roaming territories in the wild tend to have poorer health, more breeding difficulties and more stereotypic behavior than other animals in zoos. The study, published in the journal Nature, showed that polar bears, in particular, are prone to pacing because their territories are vast.

Lee arrived at Lincoln Park Zoo in February 2001 with his sister, Anana, from the Seneca Park Zoo in Rochester, N.Y.

The bears were an immediate hit. But it also was immediately apparent that something was amiss with Lee.

The polar bear began pacing so frequently that the zoo started studying ways to alleviate it.

"We didn't want to just throw a toy at him and see if it works," Ross said. "We wanted to do a scientific study."

The zoo spent eight weeks observing Lee, recording his every move. Lee wasn't just walking the same route for hours, he was placing his big white paws in the exact same spots. As he turned around, the polar bear would duck his head, twist it slightly then push it upward in an exaggerated turn, a move that is common among captive polar bears exhibiting stereotypic behavior.

At the time, Lee was pacing for 32 percent of his day — enough that zoo visitors started asking questions, prompting the zoo to post a sign outside the exhibit explaining that officials were aware the polar bear was pacing and were working on it.

Giving them a choice

After studying what other zoos have done to decrease their bears' pacing, Lincoln Park officials decided to leave the doors to Lee and Anana's holding area open during the day. Just giving the polar bears the ability to choose whether to go into the previously closed area made a profound impact, Ross said. Although Lee only went back there briefly each day, his pacing decreased significantly.

The zoo's next move was not as successful. Because polar bears spend much of their time in the wild hunting, killing and eating, other zoos had reduced pacing by freezing the polar bears' food in ice or packing it inside containers, making the animals work for their meals. Lee seemed to enjoy the challenge, but it didn't reduce his pacing.

The next major move did. Basing the design largely on natural polar-bear behaviors, the zoo spent $1 million renovating Lee and Anana's area, adding under-water rocks where the bears could play and foraging pits filled with bark and mulch. Officials also changed the visitors' underwater viewing area.

The renovations were completed last winter. The results have been dramatic. Lee now spends part of his day rooting through the pits, part playing underwater and part swimming menacingly toward the visitors behind the glass, one of his favorite activities.

The polar bear's pacing is down to 16 percent of his day — half what it used to be, but still higher than Ross would like.

The zoo this winter will take more data, trying to determine if any of the decrease is due to seasonal changes. In the spring, Ross and his colleagues will try a yet undetermined new phase, hoping to further reduce Lee's pacing.