His research program focuses on various aspects of mammalian ecology, especially urban systems, and dynamics of wildlife disease, and human-carnivore conflicts. He is principal investigator of a 15-year study of coyotes in the Chicago area, which has involved the capture and monitoring of over 900 individuals. Other research includes coyote and deer ecology in Cleveland, Ohio, and a collaborative project on coyotes in Cape Breton Highlands National Park, Nova Scotia. His research has been featured in numerous print, radio, and television outlets, including PBS, ABC Nightline, NBC Nightly News, National Geographic, and History Channel.