The female lions died within five days of each other despite zookeepers’ efforts to shelter them from Japan’s blistering summer temperatures. Three female lions have died at a zoo in Japan after suffering heat-related illnesses, staff at the facility said. The country is grappling with a blast of extreme heat that has led zoos to rethink how to protect their animals. The lions, named Mugi, Ichigo and Ruena, died within five days of one another at Tokyo's Tama Zoological Park, according to a statement from the facility released on Monday. The zoo said it was too soon to determine the animals’ exact cause of deaths, but that initial postmortem findings indicated that all three had suffered from systemic dehydration and multiple organ failure. “We believe heat stress was a contributing factor,” the zoo said in the statement.