ABSTRACT
When I first set foot in the Kakamega Forest in western Kenya, 34 years ago, I had never seen a wild monkey before. Armed with new binoculars and gumboots, I followed Thelma Rowell down a muddy trail. Thelma, my doctoral supervisor, was here to introduce me to the forest she had chosen as a promising study site. It became clear immediately that sensitive ears were essential for studying monkeys here: The first sign of my subjects was their alarm chirps, which I initially mistook for bird calls. Eventually we located the source, and I was able to pick out the two species of guenons that are common in the forest—blue monkeys and redtail monkeys. Only a few individuals were visible, and they were widely scattered: They stared at us from the top of the canopy, bobbing their heads and chirping. By midday, I wondered if I would be able to collect enough data to answer my research question, which focused on the adaptive value of mixed-species associations of these two guenons. Would I see enough monkeys? Would I see them do something other than make alarm calls? Only later in the afternoon did we see more than a few of them at a time: In fact, it seemed that suddenly there were blue monkeys in all directions, challenging my expectation that they lived in small groups of 10 to 20, as had been reported before. Thelma suggested, “Maybe they don’t live in groups at all.” She was prone to provocative statements, but in this case, it seemed a surprisingly reasonable proposal: We observers could not detect a group center or edge, much less a direction of movement. As I planned to follow particular groups, studying their movements and feeding patterns and relations with groups of redtails, my inability to distinguish a group was a problem.
