Social dispersal by domestic chicks in a novel environment: reassuring properties of a familiar odourant

It may be possible to exploit olfactory attachments shown by chickens, Gallus gallus domesticus, to improve their welfare. In the present study, chicks were housed in groups of 15 in wooden boxes from 1 day of age. Experiment 1 compared fear responses in pairs of 8–10-day-old chicks with no previous experience of vanillin when they were exposed to an unfamiliar open field containing a dish of food in either the presence or absence of this odourant. The vanillin had no detectable effects. Chicks were housed similarly in experiment 2 but this time dishes containing vanillin were placed underneath the wire floor. We then asked if its presence would increase social dispersal and reduce fear when pairs of chicks were tested in the open field. At 8–10 days of age, two cagemates were placed close together in an open field in the presence of either the familiar odourant or a colour-matched solution of odourless food dyes (control). When the open field contained vanillin the chicks moved apart significantly sooner (minimum criterion=20 cm) and also tended to pace, preen and peck at the environment more often, although not significantly so; the proportions of pairs that moved apart and that fed were significantly greater. Novelty elicits fear and frightened chicks would be expected to move apart and to feed only when their fear levels had dissipated sufficiently. Our results confirm the existence of olfactory memories in domestic chicks, they suggest that behavioural modification reflected the familiarity of vanillin rather than any anxiolytic properties of this odourant per se, and they support our hypothesis that familiar odourants can act as reassuring agents in otherwise unfamiliar situations. These findings may have important implications for poultry welfare and productivity.