Development of species identification in ducklings: XV. Individual auditory recognition

The present experiments examined the ability of domestic mallard ducklings (Anas platyrhynchos) to learn individual mallard maternal calls by either repetition-rate differences or spectral (Hz) differences, both of which are present in such calls recorded in nature. The ducklings could learn both kinds of differences within the first 24 hr after hatching, corresponding to the period prior to the exodus from the nest in nature. The hatchlings were able to learn these differences based upon only 12 min of exposure to the maternal calls during the first day after hatching. They were also able to retain (remember) the familiar call for an additional day after exposure. Embryos, on the other hand, could learn the spectral differences after either 12 or 24 min of exposure but could not retain the information under either exposure condition. An additional difference between the auditory learning competence of hatchlings and embryos was that the hatchlings were capable of learning the spectral features of a maternal call even if it was pulsed at different repetition rates during exposure (familiarization) and the subsequent test for recognition. The evolutionary significance of the results was discussed in terms of the general importance of familiarization as a basic behavioral mechanism underlying not only parental attachment but dietary and habitat preferences and the like.