Despite a firm hierarchical social order headed by alpha males, troops of olive baboons will sometimes follow a "majority rules" decision on where the group should move next, researchers have found.
Using GPS to track groups of the baboons in a nature center in Kenya, scientists found that any individual baboon can play a part in determining a troop's collective movement.
"Despite their social status, it's not necessarily the biggest alpha males that influence where groups go," says Margaret Crofoot, a researcher at the Smithsonian Tropical Research Institute. "Our observations suggest that many or all group members can have a voice, even in highly stratified societies."
Using GPS collars on 25 baboons, the researchers studied their locations in relation to each other over 14 days as they moved, ate, played and mated.
While activities like feeding or mating were strongly controlled by dominant individuals, the same was not true when it came to a troop's movement from one place to another, in which case neither a baboon's rank nor their sex conferred leadership ability, says Crofoot, the study leader who is also a professor of anthropology at the University of California, Davis.
Instead, the researchers say, troops movements resemble patterns predicted by theoretical models based on similar group movements seen in flocks of birds, schools of fish and swarms of insects.
When it comes to travel, decision making in baboon troops is a mostly shared process, the researcher found, as individual animals vote with the feet by choosing to either be leaders of their troop mates or followers.
The scientists determined simple behavioral rules at the level of pairs of baboons. If one individual baboon began to move away from the troop, there was a potential "pull" that could draw another baboon toward it. It that second individual baboon chose not to follow, then the first baboon would return to the troop, "anchored" by the decision of the second not to follow.
Scaled up to overall troop level, such rules had a cumulative effect; if the movement of one baboon was not challenged but followed, that behavior could spread to subgroups and eventually to the troop as a whole, the researchers explained.
What happens it two individual baboons begin to move in opposite directions? The troops' response was simple; they followed the mover who had managed to "pull" the largest subgroup, creating a movement decision most suited to the majority of the group.
Other experts applauded the study, noting its suggestion that even in highly hierarchical or stratified societies, there is evidently an evolutionary advantage to settling questions or disputes with group agreement rather than potentially violent confrontations.
"This phenomenon is very important to understand, because we do it in human societies and we don't really know how it works," says Duke University behavioral ecologist Susan Alberts, who was not involved in the study.
