By Kakae Saiteu, Guide - Greystoke Mahale.
When first the M-community chimpanzees were habituated and even for the subsequent three decades of their habituation, the chimpanzees did not go beyond or as high as 1500 meters from the sea level. They stayed in the lower part of the Kasoje forest and consumed fruits of several plants species.
It is in the 1990s when for the first time chimpanzees were noticed going up in the high altitude for considerable numbers of days. It is then; the Japanese proposed the development of new trekking trails for instance route 7 to follow the chimpanzees. Otherwise the research without route 7 (skyway) was completely impossible.
When exploring why the Chimpanzees are moving to higher ground a number of factors were disclosed. To the scope of this blog only one is described, which is the increase in number of yellow baboon from two troops in 1970s to five in 1990s within the territory of the habituated chimpanzees. An increased yellow baboon population led to more competition between them and chimpanzees, a factor that render yellow baboon to learn to eat fruits which they have never eaten before, like Saba Florida, Pseudopondia microcarpa etc. Also unlike chimpanzees, yellow baboons eat fruit before they are ripe. Therefore Granite garcinia, Cordia milleni, Mango and Harungana madagascariensis fruits, which chimpanzees love eating werent available to the same degree as before. In that case, chimpanzees found they cant compete equally with yellow baboon.
To alleviate that interspecies competition, chimpanzees have expanded their territory to higher altitude where yellow baboon cant explore as they prefer to hang about in the edge of forest and also to have more foraging areas to meet their daily needs.
