Baboons at the Leading Edge of a Pack, Eat First, Take the Most Risks

An adult male baboon and an adult female with clinging infant forage for food. Adult male baboons are larger than females and have impressive weaponry (i.e. larger teeth). This means that they are not only socially dominant but also less vulnerable to predators, influencing the costs and benefits of being on the edge of the group versus the center.
Photo by Margaret Crofoot

Using high-resolution GPS tracking, UC Davis Assistant Professor Margaret Crofoot and her team of researchers continuously monitored the movements of nearly an entire baboon troop in central Kenya to discover how interactions among group-mates influenced where in the troop individuals tended to be found.

“How animals position themselves within their social group can have life or death consequences,” explained Crofoot, an anthropologist. “Individuals at the front of their group may get the first crack at any food their group encounters, but they are also more vulnerable to being picked off by predators.”

Interestingly, the team’s work suggests that very simple behavioral rules may explain baboons’ apparent preferences for particular spatial positions. “Animals who pay attention to more of their group-mates when deciding where to move will inevitably end up at the center of their group,” said Crofoot. Differences in social sensitivity may therefore explain why younger baboons end up in the safest positions at the center of their troop, while adult males find themselves exposed on the leading edge.

Researchers have long noted that spatial positioning has important fitness implications, but where an animal is positioned in its group depends not only on its own behavior, but also on the behavior of its group-mates. “How natural selection shapes such emergent properties is fundamental to understanding the evolutionary dynamics of social organisms,” Crofoot said.

The findings were published in April in the journal Proceedings of the Royal Society.

The study was funded by the National Science Foundation, Office of Naval Research, Army Research Office and Human Frontiers Science Program.