Mugi is pictured on May 28, 2025. Tama Zoological Park

Three lions at a Tokyo zoo have died from suspected heatstroke and others are under treatment, a spokeswoman said on Tuesday, with the big cats struggling with high humidity.

Japan sweltered through its hottest summer on record last year and parts of the country have hit 40 degrees Celsius in recent weeks, qualifying for the new designation "cruelly hot day," with thousands of people hospitalized.

Ten of the 16 lions in Tama Zoological Park have suffered symptoms such as "loss of appetite and decreased activity" since mid-July, and three lionesses died, the zoo said in a statement.

One 3-year-old female named Mugi died on Tuesday. Three days later, an 11-year-old female named Ichigo died and on Sunday, a 15-year-old female named Luena died.

The Tama Zoological Park said the lion enclosure, where visitors can normally be driven around in zebra-pattern "safari" buses, was closed to the public until further notice.

"According to our veterinarian, the cause of the deaths is suspected to be heatstroke" because dehydration and multiple organ failure were observed, a spokeswoman told AFP.

"Even though lions are thought to be resistant to heat, zookeepers have been strengthening countermeasures to cope with Japan's summer heat in recent years. Heat here comes with high humidity; that is different from heat with dry air in Africa," she said.

The spokeswoman said the heat "arrived suddenly" this summer after the rainy season ended in late July. The zoo said it used water sprays and industrial fans, and delivered intravenous fluids and medication to the affected lions.

"We are strengthening measures against the heat (further), sprinkling water, improving ventilation and installing spot air conditioners," she said.

Several lions are still being treated, she added.

"Born, lived, and died in confinement"
Animal rights group PETA said the lions "were born, lived, and died in confinement, deprived of everything that makes life worth living for a wild animal."

"Zoos are not rescues or sanctuaries; they exist to display animals for profit, not to put animals' needs first," PETA said in a statement.

Close to 18,600 people were taken to hospitals for heatstroke between July 20 and 26, with 45 of them pronounced dead on arrival, according to the fire and disaster management agency.

A woman in her 70s died of suspected heatstroke as she sheltered in her car, officials said Monday, public broadcaster NHK reported, and the temperature in Kumamoto City hit a record 40.3 degrees Celsius.

According to the Japan Meteorological Agency, 34 locations nationwide have hit temperatures of 40 degrees Celsius or higher this summer, the Asahi Shimbun reported, breaking the record set last year. Average temperatures in western Japan during mid-to-late July were also the highest since recordkeeping began in 1946, the newspaper reported.

Japan experiences about 1,300 heat-related deaths annually and is aiming to halve that number by 2030.

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