A chimpanzee feeds on a piece of frozen watermelon to cool off from summer heat waves at Chongqing Zoo in southwest China's Chongqing, July 13, 2018. (Xinhua/Tang Yi)

A staff member feeds frozen food to giant pandas as a relief from summer heat waves at Chongqing Zoo in southwest China's Chongqing, July 13, 2018. (Xinhua/Tang Yi)

A staff member feeds frozen food to giant pandas as a relief from summer heat waves at Chongqing Zoo in southwest China's Chongqing, July 13, 2018. (Xinhua/Tang Yi)

A staff member feeds frozen food to giant pandas as a relief from summer heat waves at Chongqing Zoo in southwest China's Chongqing, July 13, 2018. (Xinhua/Tang Yi)

Giant pandas feed on frozen food to cool off from summer heat waves at Chongqing Zoo in southwest China's Chongqing, July 13, 2018. (Xinhua/Tang Yi)

Two monkeys cool off in a pond in Hongshan Forest Park in Nanjing, east China's Jiangsu Province, July 13, 2018. Zoo authorities have taken measures to keep the animals cool in the summer around China. (Xinhua/Su Yang)

A giant panda cools off in a room equipped with air-conditioner in Hongshan Forest Park in Nanjing, east China's Jiangsu Province, July 13, 2018. Zoo authorities have taken measures to keep the animals cool in the summer around China. (Xinhua/Su Yang)

Two parrots take a shower to cool off at a zoo in Zhuquan Village of Linyi City, east China's Shandong Province, July 13, 2018. Zoo authorities have taken measures to keep the animals cool in the summer around China. (Xinhua/Wang Yanbing)

A bear takes a shower to cool off at a zoo in Zhuquan Village of Linyi City, east China's Shandong Province, July 13, 2018. Zoo authorities have taken measures to keep the animals cool in the summer around China. (Xinhua/Wang Yanbing)

A hippo cools off in a pond in Hongshan Forest Park in Nanjing, east China's Jiangsu Province, July 13, 2018. Zoo authorities have taken measures to keep the animals cool in the summer around China. (Xinhua/Su Yang)

A monkey eats watermelon to cool off at a zoo in Zhuquan Village of Linyi City, east China's Shandong Province, July 13, 2018. Zoo authorities have taken measures to keep the animals cool in the summer around China. (Xinhua/Wang Yanbing)