DELAYED INDUCTION OF A FILIAL PREDISPOSITION IN THE CHICK AFTER ANESTHESIA

In domestic chicks, Gallus gallus domesticus, early filial preferences are formed as the result of at least two processes: learning by expos ure to conspicuous objects (filial imprinting) and a developing predis position to approach some stimuli rather than others. The predispositi on may be measured in visually naive chicks, e.g. as a preference for a rotating stuffed jungle fowl hen rather than for a rotating red box. Non-specific experience, such as handling or being placed in a runnin g wheel in darkness, for a short time, is sufficient to induce the pre disposition. In Experiment 1, the existence of a sensitive period for the induction of the predisposition, between approximately 14 and 42 h after hatching, was confirmed. The putative effect of anaesthesia on the induction of the predisposition was investigated in Experiment 2. Soon after hatching dark-reared chicks received injections of the anae sthetic equithesin (0.12 ml, IP), or saline, or they did not receive i njections (controls). The chicks were subsequently placed in running w heels for a total of 2 h at either 24 h or 48 h after hatching. The fo llowing day the chicks' preferences were tested. In the 24 h-chicks, t he saline and control groups showed a significant mean preference for the stuffed fowl, whilst the equithesin group did not. In contrast, in the 48 h-groups of chicks, only the equithesin group showed a signifi cant mean preference for the stuffed fowl. These results suggest that the anaesthetic equithesin affects a developing filial predisposition in the domestic chick, and does so by delaying the onset of a sensitiv e period for the induction of the predisposition. (C) 1997 Elsevier Sc ience Inc.