Is there social transmission of feather pecking in groups of laying hen chicks?

Feather pecking is an abnormal behaviour where laying hens peck the feather s of conspecifics, damaging the plumage or even injuring the skin. If it oc curs in a flock, more and more birds show it within a short period of time. A possible mechanism is social transmission. Several studies have shown th at laying hen chicks, Gallus gallus domesticus, are able to modify their ow n behaviour when observing the behaviour of other chicks, for example, when feeding and foraging. As there is good experimental evidence that feather pecking originates from foraging behaviour, we hypothesized that feather pe cking could also be socially transmitted. To test this, we reared 16 groups of 30 chicks. After week 4, the birds were regrouped into 16 groups of 20 chicks into each of which we introduced either five chicks that showed high frequencies of feather pecking or, as controls, five chicks that had not d eveloped feather pecking. We then determined the feather-pecking rate and t he frequency of ft,raging, dustbathing, feeding, drinking, preening, moving , standing and resting of all birds in a group. Data from the introduced bi rds were analysed separately and excluded from the group data. Chicks in gr oups with introduced feather-pecking chicks had a significantly higher feat her-pecking sate than chicks in the control groups. In addition, birds in g roups with introduced feather peckers showed significantly lower foraging f requencies than those in the control groups, although the housing condition s were identical and there were no differences in either the number or the quality of the stimuli relevant to foraging behaviour. The study therefore suggests that feather pecking is socially transmitted in groups of laying h en chicks. (C) 2000 The Association for the Study of Animal Behaviour.