Assessment of pre-laying motivation in the domestic hen using social interaction

While much is known about the hormonal basis of pre-laying behaviour of domestic hens, Gallus gallus domesticuslittle is known about how the behaviour is initiated or how changes in this behaviour occur. An experiment was conducted in which hens had to overcome an aversive task, during the course of pre-laying behaviour, in order to reach a nest site. Twelve hens were tested in four treatments presented as a Latin square design. The test arena was arranged such that hens could approach the nestbox only along one corridor, and return to the home pen by another. The four treatments consisted of leaving the corridor leading to the nestbox empty, or placing a hen that was dominant, subordinate or unfamiliar to the test-bird in it. Hens took longer to enter the corridor leading to the nestbox when there was a dominant or unfamiliar stimulus-bird than with a subordinate or an empty corridor. They also made more attempts to find alternative routes to the nestbox during the searching phase of pre-laying behaviour when there was a dominant or unfamiliar stimulus-bird, than with a subordinate stimulus-bird or empty pen and made fewer entries into the corridor with an unfamiliar stimulus-bird, but not a dominant or subordinate stimulus-bird or an empty pen. We suggest that hens are weakly motivated to reach the nest site during the searching phase. However, the motivation to gain access to a nest site increases near the start of the sitting phase of pre-laying behaviour.