Video: Researchers are finding that any macaque in a group can persuade the others to move to a new location.
Ants and bees are well known for their collective decision-making. Now the first evidence is rolling in to back up the theoretical models that mammals such as monkeys and deer can also reach decisions in a democratic way.
of the National Centre of Scientific Research in Strasbourg, France, studied Tonkean macaques native to Indonesia. For four months, she filmed two groups of 10 and 22 animals in an enclosed park.
Petit noticed that a group’s motivation to move always began with a single animal. It would advance 1 to 5 metres, glance back, and wait. Other animals then followed, eventually drawing in the whole group. Rarely, two monkeys might try to pull the group in opposing directions – one aiming for food, and the other for rest, for example. The remaining macaques then started to line up behind their chosen leader. To avoid splitting the troop, the group always ended up following the majority vote, Petit told last month’s European Conference on Behavioural Biology in Dijon, France.
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Whether or not the individual monkeys were successful in getting the rest of the group to follow them didn’t seem to relate to their age, sex or status. “Even the children can get the group moving,” says Cédric Sueur, a graduate student who worked on the study with Petit.
The style of decision-making most frequently documented in the animal kingdom is dictatorial. In mountain gorillas, for example, the obedient tribe will follow the dominant male silverback. Horses, mongooses and wolves also follow despotic leaders. But theories are emerging which suggest that mammals who make democratic decisions may have an evolutionary edge because they can pool the experience of each group member. Larissa Conradt of the University of Sussex, UK, welcomes Petit’s work. “Empirical research is badly lagging behind,” she says.
