The development of feather pecking and cannibalism in chicks

Abstract

Feather pecking and cannibalism are both frequently found in hens kept under intensive farming conditions. Until recently investigations into their cause, or causes, have involved manipulating the environment and then measuring the amount of feather damage that followed. Little work so far has involved observations on the actual feather pecking behaviour itself. The experiments reported here were aimed at rectifying this. Observations on small groups of chicks showed that not all birds gave or received pecks to the same extent, and that there were three possible “types” of bird; peckers, pecked and neutral. It was found that if birds were identified early in life as peckers or pecked they maintained these characteristics when reared in groups of similarly classified birds. This difference was found to last until at least point of lay, twenty-one weeks. Birds which were peckers also differed from pecked birds physically in that they were smaller; behaviourally in that they pecked more at cagemates and less at the environment and reproductively in that they came into lay later. It was suggested that differences in hormone levels might account for the difference in pecking behaviour since the peckers had several characteristics of high testosterone birds. An explanation of this type would account for the differences between batches of birds from the same strain, and within batches too, since hormone levels vary during development. It would appear that feather pecking does not develop gradually over time but is apparent early in life and although it may be responsive to changes in the external environment it is not dependent on the environment for its appearance.