In the first major study of wildlife tourism around the world, researchers at the University of Oxford’s Wildlife Conservation Research Unit—the same group that had been studying Cecil the Lion before he was shot in July—found that the millions of people who visit wildlife attractions each year don’t seem to realize that places they’re visiting have ill effects on animals.

Wildlife attractions account for between 20 and 40 percent of all tourism worldwide, with 3.6 to six million people visiting these sites annually. The study found that every year two to four million tourists financially support attractions that aren’t good for animal welfare or conservation. And it found that 80 percent of reviewers didn’t recognize that certain wildlife attractions