Majority rules: Baboons take travel decisions democratically

The roots of democracy may be traced to our primate cousins. Researchers have found that despite their hierarchical social order, olive baboon troops decide where to move democratically - by voting with their feet.

Following a group of baboons with high-resolution GPS trackers at the Mpala Research Centre in Kenya, the researchers found that any individual baboon can contribute to a troop's collective movement.

"Despite their social status, it is not necessarily that the biggest alpha males influence where group go," said Margaret Crofoot, assistant professor of anthropology at the University of California, Davis in the US.

"Our observations suggest that many or all group members can have a voice, even in highly stratified societies."

Wild olive baboons live in strongly hierarchical troops. Dominant individuals displace subordinates when feeding or mating.

However, analysing the second-by-second GPS trajectories of each individual in a single troop revealed that neither a baboon's rank nor their sex conferred leadership ability.

For the study, the researchers trapped and fitted 25 members of a wild baboon troop with custom-designed GPS collars to record each individual's location once per second for 14 days.

The researchers found that each individual's movement away from the group could potentially 'pull' another one toward it.

If the second individual did not follow, the movement initiator would return, 'anchored' by the decision of its neighbour.

These simple behavioural rules have cumulative effects. If an individual's movement decisions are unchallenged, it is likely to eventually be followed by a subgroup of other baboons, and eventually the whole troop.

Voting comes in if there is conflict about where to go, but this is also determined democratically.

If multiple individuals initiate movements in similar directions, the baboons' solution to the resulting conflict is surprisingly simple: they follow the majority, the study said.

This majority rule means that they are more likely to follow the subgroup containing the greatest number of initiators, and as a result make a decision that suits the majority of the troop.

The results appeared in the journal Science.