Postnatal Consequences of Prenatal Sound Stimulation in the Sheep

Two experiments were carried out to test the hypothesis that prenatal sound stimulation has postnatal effects in sheep. In the first, a group of domesticated ewes was stimulated with an alien sound and their lambs' response to the same sound was compared with that of lambs born to unstimulated mothers. In the second experiment a group of Soay ewes was stimulated with an alien sound and a comparable group stimulated with a series of bleats. Lambs born to these ewes were tested with both sound stimuli. Lambs tested with sound patterns which they had not heard before birth showed more heart rate acceleration during or after stimulation than did lambs tested with sounds which could already have been familiar. This difference was much greater in the response to alien than to species sounds, and it was less consistent on the first than on subsequent trials. There was also a tendency for a marked change in the respiratory pattern, evidenced as a sigh, to occur in response to familiar sound.