Ethological study of manual laterality in naturalistic housed chimpanzees (Pan troglodytes) from the Mona Foundation Sanctuary (Girona, Spain).

During recent years, handedness of nonhuman primates has been the subject of several studies, especially focused on our closest relatives: the chimpanzees. These studies have dealt with both wild and captive chimpanzees, and they seem to point to divergent conclusions, which have been interpreted as a by-product of the human influence in the captive samples. Here we present the results of a study of 10 chimpanzees (Pan troglodytes). In the past, they were trained in circus and marketing tasks (humanised behaviours), until they were confiscated and accepted into the Mona Foundation (in northeast Spain) in 2000, where they live in a semi-naturalistic environment. This study has been performed through observational bouts without systematic human influence, recording the actions carried out by chimpanzees when performing spontaneous activities. Our results indicate that chimpanzees that were under strong human influence in the past show the same trend in handedness as those living in freedom: few significant lateralities were observed among either individuals or tasks. So, laterality may not be influenced by humanisation. However, this conclusion must be taken as preliminary because very few individuals were studied.