There's No Such Thing As a Free Lunch, Or Free Sex

By stealthily following a group of about 20 adult chimpanzees in Côte d’Ivoire's Taï National Park, behavioral ecologists Cristina Gomes and Christophe Boesch of Max Planck Institute for Evolutionary Anthropology in Germany carefully noted which male chimpanzees copulated with which females. The researchers found that she-chimps put out more often for males that shared food with them at least once, compared to stingy males who never offered meat.