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Chimpanzees of the Mahali Mountains, Tanzania, were recorded to chew barks of 21 species of trees and wood vines. They mainly utilize the barks of savanna-living deciduous trees during the mid-rainy season of the year when few fruits are available. The degree of their dependence on bark for food varies drastically year by year. The bark seems to occupy an important role as emergency food in a lean year in the survival of chimpanzees, as well as in that of some other higher primates.
Toshisada Nishida (Thu,) studied this question.