NOVEMBER 4, 2019
Multilevel societies have, until now, only been known to exist among large-brained mammals including humans, other primates, elephants, giraffes and dolphins. Now, scientists from the Max Planck Institute of Animal Behavior and the University of Konstanz report the existence of a multilevel society in a small-brained bird, the vulturine guineafowl (Acryllium vulturinum). The study, published in Current Biology, suggests that the birds can keep track of social associations with hundreds of other individuals—challenging the notion that large brains are a requirement for complex societies, and providing a clue as to how these societies evolved.
Multilevel societies occur when social units, such as pairs, of animals form groups that have stable membership, and these groups then associate preferentially with specific other groups. Because this requires the animals to keep track of individuals in both their own and other groups, the assumption has long been that multilevel societies should only exist in species with the intelligence to cope with this complexity. While many bird species live in groups, these are either open, lacking long-term stability, or highly territorial, lacking associations with other groups.
Vulturine guineafowl, however, present a striking exception: The researchers observed these birds, which are from an ancient lineage resembling dinosaurs, behaving highly cohesively without exhibiting the signature intergroup aggression that is common in other group-living birds. And they manage this despite having relatively small brains, even relative to other birds. "They seemed to have the right elements to form complex social structures, and yet nothing was known about them," says Danai Papageorgiou, lead author on the paper and a Ph.D. student at the Max Planck Institute of Animal Behavior.