By Dan Klepal
The Cincinnati Enquirer

Ulaq plays in the water of the polar bear exhibit at the Cincinnati Zoo in this Dec. 10, 2002, photo. He was found dead Thursday. Enquirer file

Ulaq, one of the Cincinnati Zoo & Botanical Garden's three polar bears, was found dead in the zoo's Lord of the Arctic exhibit Thursday morning.

Zoo officials said they thought the bear, 5, was in excellent health and the post-death examination, or necropsy, did not reveal a definitive cause.

Terri Roth, vice president of animal sciences and director of the zoo's Center for Conservation and Research of Endangered Wildlife (CREW), said it is not unusual for animals to die suddenly.

"It does happen," Roth said. "What's challenging about wildlife, it's not in their nature to show weakness in the wild. So they often won't show any signs of illness. That makes it tough for us to get in there and treat them right away."

Animals, like humans, can die suddenly of heart attack or stroke. But Roth said either one of those causes would have shown up in the necropsy. Tissue samples from each of the bear's major organs will be examined at laboratories. Those test results could take several days or even weeks to get back.

Officials also are examining daily records kept by the zoo's veterinarians and animal keepers.

Polar bears are not endangered, and usually live in captivity until their mid-20s.

E-mail dklepal@enquirer.com