Development of species identification in ducklings: VI. Specific embryonic experience required to maintain...

Earlier results showed that highly specific responsiveness to the mallard maternal call at the species-typical repetition rate (around 4 notes/sec) develops in the embryo in advance of auditory experience. If the embryo continues to be deprived of normally occurring auditory experience (exposure to its own and/or sib vocalizations), the repetition-rate specificity is lost after hatching. The present results show that the embryo must be exposed to the embryonic contact-contentment call at the normal rate of 4 notes/sec in order to maintain the specific responsiveness to the maternal call at 4 notes/sec after hatching. Exposure to other rates of the embryonic call neither maintains nor modifies the 4 notes/sec specififity. Thus, the maintenance of seemingly innate postnatal behavioral development is dependent upon a highly specific, normally occurring prior experience; it will not be maintained if only rath er general (nonspecific) sensory-stimulative conditions prevail during ontogeny, as has been assumed in the past.