It was previously demonstrated that the domestic mallard duck embryo must be exposed to its embryonic contact-contentment call at a repetition rate of four notes per second in order for the neonate to manifest the species-typical preference for the species maternal call at its normal rate (3.7 notes/sec) after hatching. The present study examined whether the exposure to the contact call must occur in the late embryonic period in order to be effective. It was found that exposure for as little as 5 min/hr for 24 hr was sufficient for normal perceptual development and that such stimulation could occur either before or after hatching, provided that a 48-hr "consolidation" period intervened between the end of stimulation and testing.
Age Factors Animals