Human activity can change how and what predators eat. Niche partitioning – the way that animals divvy up resources like food and habitat spaces – allows different predator species to coexist while avoiding conflict. But as humans expand into new environments, these carefully balanced scales can tip and force animals into competing with each other instead of living in harmony. 

Researchers from the University of Wisconsin-Madison investigated how human activity impacted the feeding behaviors of predators within the Great Lakes region of the United States. They examined the diets of seven species (wolves, coyotes, bobcats, red foxes, gray foxes, fishers, and American martens) living in areas impacted by varying levels of human disturbances, ranging from protected areas to urban landscapes.

They discovered that human activity caused predators to alter their diets and feeding behaviors. As human activity increased, the predators' diets more frequently overlapped. They also ate crops and preyed on domestic animals more often.

Predators reacted to human activity differently depending on their dietary preferences: Flexible species with generalist diets, like foxes and coyotes, took advantage of readily available crops and domestic animals. Specialized species with restricted diets, like bobcats, were unable to alter their behavior, so their diets more frequently overlapped with other predators. Small predators (like martens) completely shifted their diets to avoid competition with larger species. 

Human disturbances that simultaneously change food and habitat availability force species to compete over limited resources. As animals incorporate humans' food resources into their diets, they increase the likelihood of human-wildlife conflicts. The researchers warn that by altering predator behaviors, human activities could unhinge the established order and function of entire ecosystems.