A team of researchers has for the first time begun to quantify the economic and social impact of bringing back large carnivores. Using cougars and their value in reducing deer-vehicle collisions as a case study, the researchers found that within 30 years of cougars recolonizing the Eastern U.S., large cats could thin deer populations and reduce vehicle collisions by 22 percent — each year preventing five human fatalities, 680 injuries and avoiding costs of $50 million.