The (Simian) Social Network
Barbary macaques, Macaca sylvanus, have rich social lives. Witnessing them interact in their home environment, says Julia Fischer, a professor of cognitive ethology at the German Primate Center and the University of Göttingen, in Germany, "is like watching Dallas or Dynasty."
"There are all these shenanigans, and they have friendships, and there are things that look like revenge," explains Fischer. Endangered in the wild, the macaques live under harsh, cold conditions high in the mountains of Morocco and Algeria, in groups of about 35. Members of individual clans coexist peacefully, with little more than the occasional scuffle, Fischer says, since knowing their neighbors means knowing they won’t do anything more threatening than "reach over the garden fence once in a while."
But Barbary macaques are much more aggressive toward strangers, whose behaviors may not be so predictable. Being able to quickly identify friends and enemies, in other words, helps macaques defend themselves. The question was how the monkeys manage to keep the many players in their various soap operas straight.
Fischer and colleagues working at a wildlife park in Rocamadour, France, where three especially large groups of the monkeys live, carry booklets with photos to help them identify each macaque. Noticing that their subjects seemed interested in the pictures, they designed an experiment to test whether monkeys from two of the groups could recognize images of their group-mates. Using handfuls of food, the researchers enticed the free-roaming macaques to look at a series of photos and then filmed their reactions. The adult monkeys spent about twice as long staring at photos of unfamiliar monkeys as they did at those of primates they knew, suggesting that they could tell which was which. That meant they had memorized a lot of faces -- one monkey group had 46 members, the other 57. What’s more, the ability seemed to require a lot of practice: Juvenile macaques were much more excited about the pictures than adults -- touching, sniffing, and smacking their lips at the faces -- but they spent an equal amount of time reacting to each face, suggesting they hadn’t yet learned to tell them apart.
The results of the study, published online in the February edition of Animal Cognition, add to a growing collection of animal-recognition data indicating that creatures from crayfish to cattle can tell the difference between individual members of their species. In the case of the macaques, Fischer was surprised to find that they could remember so many faces, and that they could draw connections between the photos and the real-life animals depicted. As the world of primate cognition turns, it’s a plot twist that makes the questions her lab is pursuing -- "Just how much do monkeys know about their group-mates? And how much do they know about others?" -- that much more intriguing.
