Dr. Nielsen is active with The Wildlife Society as the Past President of both the North Central Section and Illinois State Chapters. He is a Certified Wildlife Biologist® and the advisor of the SIUC Student Chapter of The Wildlife Society and Zoology Club. Dr. Nielsen is a member of the IUCN Species Survival Commission Cat Specialist Group and a Research Associate with the Northern Rockies Conservation Cooperative. In addition to having published >120 scholarly works and having given >300 guest lectures and presentations at professional meetings, his research has been showcased by major media outlets such as TIME magazine, the BBC, National Geographic magazine, NPR, the History Channel, and the Discovery Channel.