Maternal and peer imprinting in mallard ducklings under experimentally simulated natural social conditions

Previous studies revealed that if socially reared mallard ducklings actively follow a stuffed mallard (Anas platyrhynchos) hen, they later show a visual preference for the familiar mallard hen over an unfamiliar redhead (Aythya americana) hen. The present study determined that the experience of actively following the hen is essential to the induction of a visually controlled, species-typical, maternal preference. Domestic mallard ducklings that had not been given the opportunity to follow the mallard hen were "passively" reared in social groups consisting of a stuffed mallard hen and seven same-aged siblings for either 24, 48, or 72 hr after hatching. These birds were largely unresponsive to the hen in a later choice test, even when they were passively exposed to the mallard hen for as long as 72 hr prior to testing. The question arose as to whether passive exposure to the ducklings induced a preference for them that interfered with establishment of maternal imprinting under these simulated natural nest conditions. Results indicated that socially reared ducklings do prefer stuffed ducklings to a stuffed mallard hen in a simultaneous choice test even when the hen is present and vocalizing during social rearing. Further, even ducklings reared individually with the mallard hen were unresponsive to her in the later choice test. That there is something special about the stimulation provided by ducklings was further demonstrated by the finding that stuffed ducklings were preferred over the mallard hen (1) when the social rearing situation precluded active physical interaction with live ducklings and (2) when reared with inanimate stuffed ducklings. Thus, the ineffectiveness of the stuffed mallard hen in inducing visual imprinting under simulated nesting conditions cannot be attributed to the fact that she was not alive or reciprocally interactive. The present results suggest that mallard ducklings do not become visually imprinted to their hen until after departure from the nest, that the visual component of maternal imprinting likely involves active following subsequent to nest departure, and that early in postnatal development siblings are more visually attractive than is the hen.