Officials at Chicago's Brookfield Zoo say they have already taken steps to find a new companion for their lone elephant, Christy.

Officials at the Cranbrook Institute of Science in suburban Detroit said the world's oldest known bat in captivity celebrated his 23rd birthday Friday. Rob Mies, director of the Bloomfield Hills, Mich., institute's Organization for Bat Conservation, said the 23-year-old winged mammal, Tanner, is a rare

n Erie, Pa. Officials at the Erie Zoo say one of their new Amur tigers is too shy to explore a new $500,000 exhibit. Nikki, a 370-pound male tiger, has refused to come out of his den into the public exhibit since it opened two months ago.

By LINDSEY TANNER By Lindsey Tanner The Associated Press CHICAGO Gorillas on Weight Watchers? Polar bears slurping sugar-free Jell- O shots? Giraffes nibbling alfalfa biscuits? The days of letting visitors throw marshmallows to the animals are mostly history at zoos around the country, replaced by a growing focus on diet and nutrition that parallels the fitness craze in humans.

Veterinarian Kathryn Gamble sat next to a table in Chicago's Lincoln Park Zoo Hospital the other day polishing the big, sharp teeth of an anesthetized black leopard with bubble-gum flavored toothpaste.