This thesis investigates the motivation behind the feather pecking behaviour common in the laying hen industry. The severe version of this pecking is a welfare concern, since feather removal is painful for the pecked bird and current solutions to this problem, such as beak-trimming and housing in wire cages to limit contact with conspecifics, are also detrimental to well-being. It has been hypothesized that feather pecking stems from frustrated motivation to forage or to dustbathe. However, the evidence to date is not conclusive, since foraging and dustbathing share similarities; it has thus not always been clear which motivation is being fulfilled when birds are interacting with a substrate. The objectives of this thesis were to (1) determine whether early experience or current environment had a greater influence on feather pecking; (2) determine the diurnal rhythm of feather pecking and compare this to dustbathing and foraging; (3) determine the effects of different types of enrichment on feather pecking; (4) validate a new method of studying abnormal (stereotypic) behaviour patterns; and (5) apply this to uncover the underlying motivation behind feather pecking. In addition, (6) the methods used here, and in previous research on similar problems, were surveyed to analyse how future work should best test hypotheses about the motivational bases of abnormal behaviour. Results showed that current environment was most influential on the levels of feather pecking shown (P0.05) and this over-rode any potential positive effects of early substrate access (P>0.05). Feather pecking was evenly distributed throughout the light hours, as was foraging (P>0.05 for both), whereas dustbathing peaked around four to seven hours after lights on (P0.05). The provision of any of the enrichments used decreased the amount of feather pecking, but foraging substrates decreased it the most (P0.05). A novel method of studying abnormal behaviour using Fixed Action Patterns was validated, with the motivation behind a behaviour pattern influencing the motor patterns involved. The motor patterns (head angles, durations of movements and fixation) involved in foraging and dustbathing pecks proved to be different (P0.05), and severe feather pecks were found to be similar to foraging pecks (P>0.05) but different from dustbathing pecks (P0.05). Overall, it appears that severe feather pecking stems from frustrated foraging behaviour and the design of industry-useable forages should be encouraged.
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