The relationship between humans and mountain lions has always been uneasy. A century ago, mountain lions were vilified as a threat to livestock and hunted to the verge of extinction. In recent years, this keystone predator has made a remarkable comeback with the help of enlightened wildlife management policies and protection under the Endangered Species Act. But its recovery has led to an unexpected conundrum: Do more mountain lions mean they’re a threat to humans and domestic animals? Or, are mountain lions still in need of our help and protection as their habitat dwindles and they’re...