Changes in olfactory responsiveness by the domestic chick after early exposure to odorants

There is increasing evidence that odorants are important in the formation o f attachments by the domestic chick, Gallus gallus domesticus. We investiga ted whether early exposure to nonaversive odorants altered the responses of 1-day-old chicks to a number of odorants from naturalistic sources, includ ing feathers and faeces of adult chickens, wood litter and food (chick star ter mash). The odorants were delivered by dynamic olfactometry, in which ai r containing different concentrations of each odorant was presented separat ely to individually housed chicks together with a small, coloured bead at w hich they could peck. When tested with a faecal odorant, but not the other odorants, control chicks, incubated and reared under standard conditions, s hook their heads more but their pecking responses did not vary for any of t he odorants tested. Chicks that had been exposed to a moist-food odorant fr om embryonic day 20 to 18 h posthatching and tested with odorants from eith er moist or dry food pecked less than controls but shook their heads the sa me amount. Early exposure to the moist-food odorant did not affect response s to the odorants of feathers or faeces. Chicks apparently learn about thei r olfactory environment during the later part of incubation and in the earl y posthatching period and the memory formed alters behaviour on day 1 posth atching. (C) 1999 The Association for the Study of Animal Behaviour.