Lemurs who live in large groups are better at stealing food, according to a new study from Duke University. This behavior suggests that members of lemur species who exist in larger groups have a higher social intelligence than those that have fewer companions.
Duke University undergraduates studied individuals from six different breeds of lemurs housed at the Duke Lemur Center. What they hoped to find was whether lemurs were more or less likely to steal food when a human was watching. To test the theory, the students invited lemurs into a room where people were sitting at a table with a pair of plates.
There were thee different tests conducted by the researchers. One of the tests consisted of a lemur coming into a room where one person watched one of the plates and the animal, while the other faced away from both. In the second test, both researchers either faced toward or away from the plate. The third test had students facing the food and test subject, while they wore black bands across their eyes or mouths.
Lemurs who were members of species with large social groups, for instance the ring-tailed lemur, were more aware of the person watching, and less likely to steal food. Animals from smaller groups, like the mongoose lemur, did not seem to read the social clues in the situation, stealing equally from both watched and unwatched plates. The black bands had little effect on the animals, who did not seem to understand their significance.
This research, sponsored by the National Science Foundation, is the first published study of the effect of group size on social behavior performed across several species of animal. The researchers believe that living in large social groups drove an evolutionary trend in this animal toward being more aware of social situations. This research may lend credence to the "social intelligence hypothesis" which states that living in groups favors higher social skills in the quest for food and mates.
The study also found that brain size does not affect either group size or social intelligence. This could have effects in the study of primates, as intelligence is usually based on the size of the species' brain. With social intelligence, at least, this does not seem to be the case.
Results of the study are published in the June 27 online journal PLOS ONE.