Imanishi's methods to identify and name individual chimpanzees, following them over a long period of time in order to understand relationships within the community. The Mahale scientists habituated themselves to the chimpanzees through food provisioning: first with sugar cane, and later with bananas. Nishida developed a "mobile provisioning" technique in which a random site was chosen to distribute food, then scientists would announce their presence by imitating the chimpanzees' hooting calls, allowing the apes to approach and obtain food. As the scientists never used a fixed feeding site, the chimpanzees normal roaming patterns remained intact. Since the 1960s, the Mahale field site has been important to chimpanzee research. There, scientists have learned that chimpanzees medicate themselves with plants, that they have complex tool skills that differ from group to group, they hunt and eat meat, they raid neighbouring territories, and that males engage in power politics while competing over status and females. In 1982, at the same time that Frans de Waal wrote Chimpanzee Politics on apes in captivity, Nishida and his students were documenting very similar power struggles among wild chimpanzees, including one by a male named Kalunde. Kalunde played a game that Nishida called "allegiance-fickleness", which allows elderly males to maintain a key position in the group by regularly switching sides in alliances with younger males. Cultural differences in chimpanzees Nishida collaborated frequently with Western scientists. In 1975, he invited William McGrew and Caroline Tutin, primatologists familiar with the chimpanzees at Gombe National Park, to Mahale. They had no reason to expect major behavioural differences in the same subspecies of chimpanzee with the same ecology; however, McGrew and Tutin observed the Mahale chimpanzees frequently engaging in handclasp grooming, a behavior that had not been observed in the Gombe chimpanzees. Based on their visit, McGrew and Tutin were the first to seriously question the assumption of "typical" chimpanzee behaviour, an important step towards culture studies on the great apes. Zoopharcognosy While at the Mahale site in the early 1970s, Nishida observed wild chimpanzees consuming Aspilia leaves, which have no nutritional value and are not digested. He noticed the chimpanzees consuming them very slowly in the morning, swallowing the leaves without chewing. Nishida, along with primatologist Richard Wrangham, published their observations of the potentially medicinal use of plants by wild chimpanzees in 1971. De Waal believes that this paper, along with later studies conducted on self-medication among animals, became the