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

There is increasing evidence that odorants are important in the formation of attachments by the domestic chick, Gallus gallus domesticus. We investigated whether early exposure to nonaversive odorants altered the responses of 1-day-old chicks to a number of odorants from naturalistic sources, including feathers and faeces of adult chickens, wood litter and food (chick starter mash). The odorants were delivered by dynamic olfactometry, in which air containing different concentrations of each odorant was presented separately to individually housed chicks together with a small, coloured bead at which they could peck. When tested with a faecal odorant, but not the other odorants, control chicks, incubated and reared under standard conditions, shook their heads more but their pecking responses did not vary for any of the odorants tested. Chicks that had been exposed to a moist-food odorant from embryonic day 20 to 18 h posthatching and tested with odorants from either moist or dry food pecked less than controls but shook their heads the same amount. Early exposure to the moist-food odorant did not affect responses to the odorants of feathers or faeces. Chicks apparently learn about their olfactory environment during the later part of incubation and in the early posthatching period and the memory formed alters behaviour on day 1 posthatching. Copyright 1999 The Association for the Study of Animal Behaviour.