It was previously thought that complex, multi-level societies comprising many different hierarchical positions of power were unique to humans and a select group of other large-brained mammals.
Now, researches from the Max Planck Institute in Germany has found that vulturine guineafowl – large, bald-headed birds found in forests across Central Africa - also display evidence of forming multi-level societies despite having tiny brains.
“To our knowledge, this is the first time a social structure like this has been described for birds,” said research lead Danai Papageorgiou. “It is remarkable to observe hundreds of birds coming out of a roost and splitting up perfectly into completely stable groups every single day. How do they do that? It's obviously not just about being smart.”
Multi-level societies occur when animals making up a larger group form separate smaller groups that interact differently with specific other groups – by communicating, mating and fighting, for example.
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Because this requires the animals to keep track of the 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 do live in large groups, these lack long-term stability, or are highly territorial, and so lack meaningful associations with other groups.
For the study, the researchers tracked 400 adult birds over multiple seasons in a field in Kenya. They found that the birds were split into 18 distinct social groups each made up of between 13 to 65 individuals. For the duration of the whole study, the groups remained stable and associated with each other based on clear preferences, rather than random encounters.
“This discovery raises a lot of questions about the mechanisms underlying complex societies and has opened up exciting possibilities of exploring what is it about this bird that has made them evolve a social system that is in many ways more comparable to a primate than to other birds,” said senior researcher Dr Damien Farine.