Temperatures in Japan have gotten so extreme that zoo animals are dropping dead — though this may be as much an indictment of the conditions that the animals are made to live in as it is climate change.

On Monday, Tokyo’s Tama Zoological park announced that three of its female lions had died of what’s suspected to be heat-related illness. Their deaths occurred within five days of each other, as the country is gripped by a grueling spell of intense heat.

Per multiple reports, preliminary autopsies showed that the lions, named Mugi, Ichigo, and Ruena, had suffered from systemic dehydration and multiple organ failure before dying.

“We believe heat stress was a contributing factor,” the zoo said in a statement.

Japan experienced its first “cruelly hot day” toward the end of July, in a historic heat wave that caused multiple cities to be scorched with temperatures over 104 degrees Fahrenheit. Tokyo’s average daily temperature that month was 90 degrees Fahrenheit, which would feel like 110 degrees when accounting for humidity. 

The “cruelly hot day,” by the way, was introduced by Japan’s meteorological agency this year in anticipation of a sweltering summer. It’s no exaggeration to say that it’s now so hot in Japan that the country invented a new word for it: “kokushobi.”

On the first day to receive this official designation, at least 260 people in Tokyo were taken to the hospital, according to local reports. Between July 20 and 26, some 18,600 people across Japan were hospitalized for heatstroke, with 45 of them pronounced dead on arrival, the country’s Fire and Disaster Management Agency said.

While temperatures have temporarily fallen, the overall heat hasn’t relented, as this Wednesday Japan’s Environment Ministry issued a heatstroke alert for most of western and southern Japan, per the Associated Press.

It’s brutal for humans, and no less so for animals in captivity. According to the Tama zoo, one of the lions, the three year old Mugi, began showing signs of appetite loss in mid-July and was unable to stand the day after the symptoms appeared. 

The zoo staff tried to cool her off by spraying her with water and providing her fluids with intravenous dips, but Mugi eventually died on July 28. The 11-year-old Ichigo died three days later, and 15-year-old Ruena two days after that.

Four other lions who were ill are showing signs of recovery, the zoo said, with six others that have appeared to be in good health throughout the ordeal.

Experts say that along with the extreme temperatures, it’s the high humidity that makes it difficult for the lions to stay cool. Rather than sweating, they regulate their body temperature by panting, pushing hot moisture out of their airways.

“Lions are more used to a dry heat environment,” Aaron Whitnall, a zookeeper in England who cares for 11 lions, told the New York Times, though he said it was to early to speculate on the exact cause of the lions’ deaths.

During spells of extreme heat and humidity, zoos should give lions ample shade, deploy cooling pads, and mist them with water, Whitnall said. At his Big Cat Sanctuary in England, zookeepers gave the animals popsicles made with frozen animal blood to help them stay cool.

The Tama Zoo has suspended its lion exhibit since last month, and hasn’t announced when it’ll re-open.

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