Three lions from a Tokyo zoo have died from suspected heatstroke and others are undergoing treatment, a spokesperson said on Tuesday, as the big cats struggle in Japan’s high levels of humidity. The cause of the deaths is suspected to be heatstroke, as dehydration and multiple organ failure were observed by a veterinarian, the zoo said. “Even though lions are thought to be resistant to heat, zoo keepers have been strengthening countermeasures to cope with Japan’s summer heat in recent years. “But this summer, heat arrived suddenly after the rainy season was over” in late July, they added. View image in fullscreen The exterior of Tama Zoological Park.