Development of species identification in ducklings: I. Nature of perceptual deficit caused by embryonic auditory deprivation.

In simultaneous choice tests with normal and filtered maternal calls, devocal-isolated ducklings were much more likely than vocal-communal ducklings to select the mallard maternal call in which the higher frequencies were severely attenuated, thus indicating their relative insensitivity to the higher frequency components of the maternal call. On the other hand, the devocal ducklings were as adept as vocal ducklings in selecting the normal mallard maternal cal1 when it was pitted against a low-frequency attenuated mallard call. Thus, the perceptual deficiency resulting from embryonic and postnatal auditory deprivation is selective in the sense of being relegated to the higher frequency components of the maternal call. Devocalization prevents the embryo and hatchling from hearing their own vocalizations all of which happen to be in the high-frequency range (greater than or equal to 1,500 Hz).