Three lionesses have died from suspected heatstroke at Tama Zoological Park on the western outskirts of Tokyo, with several more lions under treatment, as Japan endures another summer of record-breaking heat. The zoo confirmed that ten of its sixteen lions had displayed symptoms including loss of appetite and reduced activity since mid-July. A veterinarian found evidence of dehydration and multiple organ failure in the three animals that died — a three-year-old named Mugi, an eleven-year-old named Ichigo, and a fifteen-year-old named Luena. The lion enclosure, where visitors can normally tour the habitat aboard zebra-patterned safari buses, has been closed to the public until further notice.

Although lions are widely considered heat-tolerant animals, their African habitat is characterised by dry air, which allows body heat to dissipate efficiently. Japan's summer heat is fundamentally different: oppressive humidity hampers the ability to regulate body temperature, even for animals adapted to hot climates. Compounding the problem this year, the heat arrived abruptly once the rainy season ended in late July, leaving little time for adaptation. The zoo has responded by sprinkling water across enclosures, improving ventilation, and installing spot air conditioners, while the remaining sick lions are being housed in a separate facility equipped with coolers and fans.

The crisis at Tama Zoo reflects broader thermal extremes gripping Japan and the wider region. Parts of Japan have recently recorded temperatures reaching 40C, a threshold that now officially qualifies as a "cruelly hot day" under a new national designation. Between 20 and 26 July alone, nearly 18,600 people were hospitalised for heatstroke, with 45 pronounced dead on arrival. Japan already records around 1,300 heat-related human deaths each year and has set a target of halving that figure by 2030. Neighbouring South Korea is simultaneously battling a heatwave linked to at least 16 deaths.

Animal rights group PETA used the deaths to renew its criticism of captive facilities, arguing that the three lionesses "were born, lived, and died in confinement" and that zoos prioritise display over animal welfare. The zoo has not commented on those claims but has acknowledged that keepers have been intensifying heat-management measures over several years as Japanese summers have grown progressively more severe.

Scientists attribute the increasing frequency and intensity of such extreme heat events to human-induced climate change. Japan's all-time temperature record of 41.8C was set as recently as August 2025 in Isesaki, north of Tokyo. The deaths at Tama Zoo serve as a stark illustration of how rising temperatures are no longer an abstract threat — they are already reshaping daily life, public health, and the survival of animals both in the wild and in captivity across Asia.