Tokyo's main zoo plans to rebuild the enclosure for Japanese monkeys to help them feel more comfortable during the scorching summer season.

The "monkey mountain" at Ueno Zoological Gardens was built in 1932. It is the oldest existing observation facility among zoos in Japan. Shaped like a rock mountain, the concrete structure enables visitors to easily see the monkeys.

The zoo plans to renew the aging facility in consideration of animal welfare, a concept widely spreading among zoos worldwide including Japan. The idea aims to help animals stay healthy without stress.

The new enclosure will be like a forest with artificial trees, which would provide more shade for the monkeys.

For ground cover, materials that do not get hot so easily are being considered.

Officials at Ueno zoo say Japanese macaques are relatively tolerant to cold weather, but are vulnerable to heat as they do not sweat much.

In summer, temperatures in the existing monkey facility sometimes exceed 40 degrees Celsius due to heat being reflected from the concrete. Currently, Ueno zoo has set up sprinklers and other cooling measures, but providing a more comfortable habitat for the monkeys in extremely hot conditions is a major challenge.

Construction of the new enclosure is scheduled to start around March next year and will be completed in about a year. Plans are for the Japanese macaques to be moved to a temporary facility in the interim period.