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

Area of Science:

• Ecology
• Wildlife Management
• Conservation Biology

Background:

• Human activities transform ecosystems, creating novel food resources (subsidies) exploited by wildlife.
• This exploitation, especially by large carnivores like American black bears (Ursus americanus), can escalate human-wildlife conflict.
• Disentangling the drivers and consequences of different human food subsidy types remains underexplored.

Purpose of the Study:

• To estimate the proportional diets of American black bears in Wisconsin, USA, focusing on human food subsidies.
• To model the influence of landscape variables on the consumption of intentional (e.g., bait) and unintentional (e.g., refuse, crops) human food subsidies.
• To predict the spatial variation of human subsidy consumption and its relationship with human-wildlife conflict.

Main Methods:

• Stable isotope analysis (δ13C and δ15N) of bear tissues to determine diet composition.
• Statistical modeling to link diet proportions to landscape variables (e.g., land cover, human activity).
• Spatial prediction mapping of human subsidy consumption and conflict risk.

Main Results:

• American black bears consumed substantial amounts of unintentional (32%) and intentional (7%) human food subsidies.
• Intentional subsidy consumption correlated with public lands and hunter activity; unintentional subsidy consumption increased with corn production and reduced natural land cover.
• Reported human-wildlife conflict incidents rose with increased consumption of unintentional human food subsidies.

Conclusions:

• Human food subsidies, particularly unintentional ones, significantly alter American black bear diets and are linked to increased human-wildlife conflict.
• A landscape-level understanding of subsidy consumption patterns is crucial for targeted wildlife management.
• Management strategies should focus on reducing the availability of human food subsidies to mitigate conflict.