Handlers of a popular polar bear, brought to mate with a female in a zoo in northern Japan, found their breeding plan was doomed when they noticed that he, in fact, was a she.

　　Tsuyoshi, a four-year-old, 200 kg (441 lb) cream-colored polar bear, had been living in harmony with a female polar bear since June, the two often playing together, Masako Inoue, a zookeeper at the Kushiro Municipal Zoo, said on Wednesday.

　　"We thought he was a male, so we never had any doubts as we took care of him," she said.

　　"But one day we realized that the two bears urinate in the same way, and we thought, is that how males do it? And once we started to look at things that way, we weren't quite so sure."

　　After two DNA examinations of Tsuyoshi's hair and a manual exam, the Kushiro Municipal Zoo found Tsuyoshi to be a female.