The Role of Visual Cues in Lambs' Discrimination Between Individual Agemates

Abstract

The role of visual cues in individual agemate discrimination by lambs (Ovis aries) was assessed in two experiments. Lambs in the initial experiment were tested in pairs in a dark room, thereby eliminating access to the partners' visual phenotypes. When tested with a familiar penmate, lambs bleated less than did those paired with an unfamiliar unrelated partner, which implies that the penmates were recognized despite the absence of visual cues. In the second experiment, lambs were exposed individually to a projected life-size image of a familiar penmate (F), their (familiar) twin (T) or an unfamiliar unrelated lamb (U). The subject lambs responded in a more positive manner to the T slide than to a U image, however the F and U images did not elicit differential reactions. Visual cues thus appeared to be a sufficient basis only for twin recognition in this context. These results were compared to data from related studies concerning the roles of audition and olfaction in social discrimination by lambs.