Recognition of faces of known individuals in two lemur species (Eulemur fulvus and E. macaco)

<p>Three brown lemurs, Eulemur fulvus, and two black lemurs, Eulemur macaco, were trained to selectconsistently the photograph of the face of a known individual (KI: belonging to the same social group)when it was presented simultaneously with a photograph of the face of an unfamiliar individual(UI: belonging to another social group). After the learning phase, the subjects were presented with newpairs of photographs (KI versus UI: photographs that were not used in the learning phase), the same pairspresented in different associations, and finally pairs of photographs that were completely novel(50 different pairs). All the subjects selected the KI significantly more often than the UI under allconditions. Additional tests showed that the subjects preferentially selected photographs of a UIbelonging to their own species versus a UI belonging to the other species. No preference was observedwhen the subjects were presented with two KI or with their own photograph associated with a UI. Theseresults reveal that the face contains information allowing lemurs to discriminate familiar individualsfrom unfamiliar ones.</p>