Many supporters of legalizing marijuana laud the plant for being “natural” and consider themselves environmentalists. So they may be shocked to hear that pot farmers are dumping large amounts of rat poison into the forests of northern California and southern Oregon in order to protect their crops. The overuse of rodenticide has contributed to the decline of the West Coast fisher—a small brown mammal related to otters, minks, and weasels—to the point that the U.S. Fish and Wildlife Service has proposed listing them as threatened, Oregon Public Broadcasting reports. It’s not the first time the species has been threatened; in the late 1800s, the fisher was rapidly disappearing as a result of trapping and logging.