It is now well-known that illicit cannabis cultivation impacts many species of forest wildlife, either by direct mortality or indirectly through sublethal exposure to pesticides, water theft, and habitat manipulation. Given the rampant spread of illegal cultivation in northwestern California over the past two decades and our lack of knowledge about how these activities impact mountain lions (Puma concolor) and the species they rely on for food, we studied the risks to mountain lions from illegal cannabis cultivation and the pesticides associated with this activity. For the first phase of this project, our objectives were to: 1) analyze prey selection and spatial foraging patterns of lions in northwestern California; 2) visit kill sites to determine diet and exposure of prey to anticoagulant rodenticides and other toxicants found at trespass cannabis grow sites; and 3) analyze lion movement and home ranges in relation to the distribution of both public land cannabis cultivation sites and private land, unlicensed sites on the National Forests and private lands adjacent to the Hoopa Valley Reservation in northwestern California.