Vocal discrimination of kin and non-kin agemates among lambs

Playback experiments were conducted with 4 week old Ile-de-France lambs (Ovis aries) to assess the role of auditory cues in social discrimination. After being habituated to the test enclosure, lambs were individually exposed to bleats from two stimulus individuals. Twin lambs were tested with recorded bleats of their sibling versus an unfamiliar agemate and single lambs with bleats of a familiar agemate versus an unfamiliar lamb. Lambs responded more frequently to the bleats of their sibling (for twin lambs) or of a familiar agemate (for single lambs) than to those of an unfamiliar lamb. Such discriminative responses to the bleats of familiar twins and non-kin lambs suggest that vocalizations may be a Sufficient basis for social recognition. Acoustic analyses of the playback bleats revealed significant differences between the signals from the different stimulus lambs and suggest that fundamental frequency may be an important parameter of lambs' individual vocal signatures.