Frustration-induced aggression in the domestic hen: The effect of thwarting access to food and water on aggressive responses and subsequent approach tendencies

Frustration-induced aggression (FIA) is one of a number of behavioural responses that are elicited in animals by thwarting access to a needed resource. FIA is a potential cause of injury and reduced welfare in group-housed domestic hens and the factors that give rise to this type of aggression need to be understood. The expression of frustration-induced aggression was examined in an experiment in which dominant:subdominant pairs of birds were tested under either food or water deprivation. The dominant bird was trained to run down a runway to a test arena to find the food or water reward. The subdominant bird was secured in this test arena by means of a light harness. There was one 10 min trial/day, with access to the reward being thwarted by means of a perspex cover on the reward dish once every fourth trial, with three non-thwarting trials intervening. It was shown that the total rate of aggressive interactions, unsignalled running attacks and non-aggressive pecks was higher on the thwarting days than on the intervening days (all p < 0.001). There was also an increase in pacing, walking and time spent out of the test arena (all p < 0.001). The birds were slower to approach the test arena on the two post-thwarting days (p < 0.05), indicating that the experience of thwarting was aversive, and additionally that this information may be coded cognitively. Additionally, the repetition of the thwarting experience did not reduce the occurrence of the more vigorous forms of aggression shown (p < 0.05). The results also indicate that an increase in FIA and active behaviours may be a general response to thwarting as there was no difference between the response to the thwarting of access to food or water (p < 0.05). The results suggests that a potentially serious consequence of thwarting in a group-housing situation would be a greater number of damaging interactions, with the welfare of both the attacked bird and the thwarted bird being compromised.