A polar bear in the wild can hunt artic prey and roam ice flows in a home range that may extend 31,000 square miles.
At the Henry Vilas Zoo, 702 S. Randall Ave., polar bears Nanuq and Mishka inhabit a significantly smaller exhibit and pass their time by eating, lounging and playing with toys zookeepers offer for stimulation.
It is a life animal rights activists consider exploitative, but zookeepers contend the animals live well and offer the public an opportunity to view beautiful creatures they would otherwise only find on television.
However, according to a report released Thursday in the journal Nature, polar bears and other wide-ranging carnivores do so poorly in captivity that zoos should either improve their habitats or stop housing the animals altogether.
According to the study, which was conducted by biologists from Oxford University, zoo animals with large natural habitats display poor health, high infant mortality rates and a tendency for repetitive behavior.
The repetitive behavior is known as stereotypy, and in zoos it is most commonly seen in animals pacing around their cages, according to the report.
\They're not behaviors that you typically see in wild animals in their natural state, and therefore they are an indication that something is wrong. The animal's bored; they're lonely; they're frustrated, whatever,"" said Lisa Wathney, captive exotic animals specialist for People for the Ethical Treatment of Animals.
Rick Bilkey, educational coordinator at Henry Vilas Zoo, criticized the researchers' reliance on stereotypical behavior as an indication of an animal's distress. He said excessive pacing is a bad sign but noted that wild animals patrol their territory and viewed minimal pacing as a way for animals to get exercise.
Jeff Stafford, supervisor of Henry Vilas Zoo, said stereotypic behavior is detrimental only if it causes harm to the animal, such as pacing that wears at an animal's feet.
""That happens with just about every species,"" Stafford said of stereotypic behavior. ""People do it all the time. People bite their fingernails; you see them twirling their hair in class. That's stereotypical behavior.""
The study said zoo habitats that prevent animals' natural behavior patterns can give rise to animal stress and frustration and impair creatures' brain development.
Stafford said the zoo tries to counteract mental stagnation by giving animals stimulating toys. For example, Nanuq and Mishka get balls to play with as well as ""polar bear popsicles,"" fruit, fish or blood frozen in blocks of ice.
