Social specificity: interaction with own species is necessary to foster species-specific maternal preference in ducklings.
Previous studies have shown that if domestic mallard ducklings are allowed social interaction with broodmates after their initial exposure to a stuffed mallard (Anas platyrhynchos) hen, they later show a visual preference for the familiar mallard over an unfamiliar redhead (Aythya americana) hen. Birds kept in social isolation do not make this difficult discrimination. In the present study, we examined whether this social enhancement of imprintability to a natural maternal model is merely the result of social stimulation in its most general sense, or if its effects are specific to social interaction for 30 min (training). This experience resulted in visual preference for the familiar mallard hen over the unfamiliar redhead hen in simultaneous choices tests at 48 hr and 72 hr after hatching only if the birds were allowed social experience with a group of same-age undomesticated mallard hatchings. No visual preference for the familiar mallard hen was found if the ducklings were permitted social experience with a group of same-age chick (Gallus domesticus) hatchlings or muscovy (Cairina moschata) ducklings. Thus, it appears that for ducklings to show a visually imprinted preference for a natural maternal model, they must be allowed social interaction with broodmates of their own species. Social rearing with other precocial bird hatchlings, even other ducklings, is without apparent effect. These results provide further evidence of the importance of nonobvious experimental factors in the development of species-typical behavior. They also suggest that in the evolution of the species-specific learning underlying early species identification, natural selection has operated on the entire (organism-environment) developmental manifold and not merely on genetic, organic, or organismic aspects of that system.