THE INTERACTION BETWEEN PRELAYING BEHAVIOR AND FEEDING IN HENS - IMPLICATIONS FOR MOTIVATION

While considerable research has been undertaken on the hormonal basis of pre-laying behaviour of domestic hens (Gallus gallus domesticus), l ess is known about how the behaviour is initiated and about how change s in this behaviour occur. Two experiments were conducted to investiga te aspects of the interaction of pre-laying behaviour with feeding mot ivation Experiment 1 examined the effect of the absence of food. Pre-l aying behaviour was observed in 20 laying hens either with or without food available. The duration of pre-laying behaviour was longer when d eprived of food for short or long periods of time than for hens with a ccess to food. The time of oviposition, however, appeared unchanged su ggesting that motivation for pre-laying behaviour is initially increas ing and that it competes with feeding behaviour for expression when fo od is available. Experiment 2 examined the effect of food in the absen ce of deprivation. The food of 17 hens was topped up at various interv als before oviposition. Contrary to expectation the delay in ovipositi on was greater (24 minutes) if food was presented closer to the expect ed oviposition (2 minutes) than if it was earlier (12 minutes before o viposition, which caused a delay of 12 minutes). When interrupted clos e to oviposition, most birds repeated part of the searching phase of p re-laying behaviour (7 minutes of searching as opposed to 3 minutes). It is concluded that a hypothesis based on competition between motivat ional systems offers a good predictor for the start of prelaying behav iour, but not for the duration of interruption later in the pre-laying behaviour sequence.