Three female lions at Tokyo's Tama Zoological Park have died from suspected heatstroke as temperatures in Japan have soared, with some areas reaching 40°C (104°F).
Since mid-July, ten of the sixteen lions at the zoo have exhibited symptoms including appetite loss and decreased activity. One lion passed away on Tuesday, another on Friday, and a third on Sunday. The zoo stated that veterinarians suspect heatstroke as the cause of death, citing observed dehydration and multiple organ failure.
"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," a spokeswoman said. "Heat here comes with high humidity – that is different from heat with dry air in Africa."
Mugi, a three-year-old lioness, showed a loss of appetite on July 19 and was unable to stand the following day. Despite receiving ventilation, water, subcutaneous fluids, liver tonics, and vitamins, she died on July 28. Ichigo, aged 11, died on July 31, and the 15-year-old Luena died on Sunday.
Autopsies revealed systemic dehydration and multiple organ failure in all three lions, further suggesting heat stress as a contributing factor. The zoo noted that definitive causes of death will be confirmed after test results are finalized. Currently, three other lions – two males and one female – remain unwell and unable to stand, and staff are administering fluids and medication.
Professor Samantha Ward, an expert in zoo animal welfare at Nottingham Trent University, told the Daily Mail that factors beyond just temperature, such as humidity, enclosure conditions, and the speed of the heatwave, likely played a role in the lions' deaths. She noted that lions do not sweat effectively and rely on panting and behavioral strategies like shade-seeking to cool down. High humidity reduces the effectiveness of evaporative cooling.
Ward cautioned that animals in UK zoos could face similar risks as extreme heat events become more frequent due to climate change. "I do not think UK zoos should assume that traditionally 'warm-climate' species will automatically cope with British heatwaves," she stated. She highlighted that many UK zoo facilities were designed with colder climates in mind, with less emphasis on preventing heat stress.
Species potentially most vulnerable include older animals, large carnivores, those adapted to cooler climates, and individuals with pre-existing health conditions. Ward recommended that zoos implement measures such as increased shaded areas, climate-controlled indoor refuges, misting systems, improved ventilation, and comprehensive heatwave action plans. Close monitoring of animal behavior can also provide early warnings of heat stress.
Dr. Paul Rose from Exeter University suggested that while healthy adult lions in the UK might be less susceptible, cubs and older individuals could be at risk. He added that zoos are generally prepared for hot weather scenarios and work to keep animals comfortable.
Human-induced climate change is linked to the increasing frequency and intensity of extreme heat events globally. In Japan, record temperatures have been registered, and a significant number of people have required hospitalization for heatstroke during recent heatwaves.