The vocal expression of feeding motivation and frustration in the domesticlaying hen, Gallus gallus domesticus

Thwarting of feeding behaviour in the laying hen results in an increase in stereotyped pacing, displacement preening, and the gakel-call. These behavi ours therefore reflect the frustration arousal caused by the thwarting of f eeding behaviour. This raises the question whether the level of frustration also varies with the intensity of the motivation to perform the thwarted b ehaviour. This study investigated the relationship between the intensity of the motivation and level of frustration on the one hand and the gakel-call on the other hand. In Experiment 1, the strength of the motivation to feed was varied by thwarting hens in their feeding behaviour in an operant proc edure after different durations of food deprivation (0, 8, 23 and 47 h). Tr end analysis showed that with increasing hunger state, an increasing number of gakel-calls was given. No effect of treatments on temporal characterist ics of the,gakel-call was found. In Experiment, the level of frustration wa s varied by reducing or increasing the duration of access to food for food- deprived hens compared to the duration of access during training. It was as sumed that a shorter duration of access to food compared to training would elicit frustration, which in turn would affect the performance of behaviour s indicative of thwarting. However, we found neither a relation between the number of gakel-calls nor the temporal features of the gakel-call and the duration of access to food. Possibly, the differences between treatments we re not large enough to induce differences in frustration level. Also, other factors that might have influenced the motivation are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.