Big brains aren’t required to form complex communities, finds a new study of vulturine guineafowls in Kenya.

The prevailing consensus up to now was that only animals with large brains such as humans, primates, elephants, porpoises, and giraffes, can form complex, multilevel societies. However, new research shows that this isn’t the case. The study reports that vulturine guineafowl (Acryllium vulturinum), a relatively small-brained bird, can keep track of the social standing of hundreds of other individuals.

Birds of a feather

“To our knowledge, this is the first time a social structure like this has been described for birds,” says Danai Papageorgiou, lead author on the paper and a PhD student at the Max Planck Institute of Animal Behavior.

“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.”

The team explains that multilevel societies form when social units (pairs of animals or human families) coalesce into groups with stable memberships, which in turn associate preferentially with specific other groups. In humans, this can take the shape of different socio-economic groups, religious groups, political currents, and so on.

Such societies, we assumed, required animals with large brains to run — it’s not easy keeping track of hundreds or thousands of individuals and their social role throughout several groups. Since birds tend not to have very large brains (due to biological constraints related to their ability to fly), it was assumed that they can’t form such communities. Data in the field seemed to support this view: many bird species live in groups, but these tend to be open, lacking long-term stability, or highly territorial, which means they lack associations with other groups.

The vulturine guineafowl, the new paper reports, overturns these assumptions. The birds are part of an ancient lineage that’s more akin to dinosaurs than birds. The authors explain that the vulturine gunineafowl behave in a highly cohesive manner without the intergroup aggression that’s common among other social birds. All of this with a small brain, 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 Papageorgiou.

The study was the first effort to track the social life of this species. The team monitored over 400 adult birds at a site in Kenya, tracking their social relationships over several seasons.

All in all, the team found no fewer than 18 distinct social groups (with 13 to 65 individuals each). These groups remained stable throughout the study period, despite regularly overlapping with one or more other groups both during the day and at night-time roosts, which the team found surprising.

In order to check whether these groups associated with one another preferentially, rather than accidentally, the team placed GPS tags on a sample of the individuals in each group. This allowed them to track every single group continuously, giving them an idea of how they were interacting. Overall, the team says they found clear signs that the groups are associating based on preference rather than random encounters and that intergroup associations were more likely to take place during specific seasons and around particular points of interest in the landscape.

“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” says Dr Damien Farine, senior author on the paper and a Principal Investigator at the Max Planck Institute of Animal Behavior.

The paper “The multilevel society of a small-brained bird” has been published in the journal Current Biology.