 More than 40 different populations of wild chimpanzees have been studied across Africa, between which many species-specific, as well as population-specific, behaviors have been observed.The researching scientists found 65 different categories of behaviors among these various groups of chimpanzees, including the use of leaves, sticks, branches, and stones for communication, play, food gathering or eating, and comfort.Each of the groups used the tools slightly differently, and this usage was passed from chimpanzee to chimpanzee within the group through a complex mix of imitation and social learning.