The Intentional and Unintentional Human Food Subsidy Landscape for a Large Carnivore

Humans have transformed ecosystems and resource availability. Many species exploit these novel resources, which can increase conflict between humans and wildlife. This is particularly true for large carnivores that readily consume human foods, which can lead to conflict. However, disentangling the different forms of human food subsidies, their drivers across a landscape, and potential consequences for conflict has not been explored. American black bears (Ursus americanus) consume large quantities of unintentional (e.g., refuse, crops) and intentional human food (e.g., hunting bait). Up to 40% of a wild bear's diet can be from human food subsidies. This consumption has been associated with increasing numbers and more conflict. The state of Wisconsin, USA, has a liberal bear baiting policy and high densities of bears compared to neighboring states and has the potential for high consumption of human foods and conflict. We estimated the proportional diets of black bears using stable isotope analysis (δ¹³C and δ¹⁵N) from a statewide sampling in Wisconsin. We modeled the response of diets to landscape variables likely to influence the consumption of either natural food items and two sources of human food subsidies: intentional and unintentional. We then predicted a human subsidy landscape that explored the spatial variation between intentional and unintentional sources and modeled the relationship between human food subsidies and conflict. We found substantial consumption of intentional (7%; 95% CI [0%, 25%]) and unintentional (32%; 95% CI [27%, 38%]) subsidies. The consumption of intentional subsidies increased in areas with public lands and higher hunter activity, while the consumption of unintentional subsidies increased with corn production and less natural land cover. We found the number of reported complaints increased with the consumption of unintentional human subsidies. Our predicted map of human subsidy consumption disentangled the form of the human food subsidy and showed that the consumption of unintentional human food subsidies along their expanding range can lead to greater conflict with people and property. Our mapped subsidy landscape can be used by managers to target management actions to reduce the availability of human subsidies and to predict areas of human-wildlife interactions.