Tokyo: Green polar bears are drawing questions from puzzled visitors at a Japanese zoo.

Three normally white polar bears at Higashiyama Zoo and Botanical Gardens in central Japan changed their colour in July after swimming in a pond with an overgrowth of algae.

The sight of the green polar bears has prompted many questions from visitors concerned about whether the animals are sick or carrying mould, zoo official Masami Kurobe said.

"Visitors seem to be shocked by the colour, and we are asked every day why they are so green," he said.

High temperatures in July and August and less-frequent water changes because of the zoo’s conservation efforts caused an algae growth in the bear pond and safety moat, Kurobe said.

Algae that enters hollow spaces in the bears’ fur is hard to rinse off, he said.

The bears are expected to return to their natural colour when the algae growth subsides in November, Kurobe said. — AP