Nobody knows exactly how the gray fox first got to six of California’s eight Channel Islands, but once there, the creature evolved into its own species, becoming North America’s smallest (and most adorable) native fox. Although golden eagle predation pushed the critters to become endangered on some islands, the foxes on heavily touristed Catalina had a different set of problems. In the late 1990s, a virus killed 90 percent of them. As a result of a captive-breeding program, more foxes live on the island today than before the outbreak. More recently, though, cancer has been thinning their ranks. Nearly half of the dead Catalina Island foxes examined between 2001 and 2008 had tumors in their ears. An experimental drug administered by Catalina Island Conservancy researchers appears to be helping. It’s rare that a cancer treatment can be tested in a free-ranging endangered wildlife population, but Catalina is something of a living laboratory.