Nesting behaviour of hens: Effects of experience on motivation

There is some controversy as to whether animals can be deprived of resources that they have never experienced. Will domestic hens (Gallus gallus domesticus), for example, that have been housed in conventional wire cages, be as motivated to use well-defined, littered nests as hens with prior experience of nests? This was tested by varying the quality of nesting cues (trials with and without an enclosed nest box) and measuring the performance of and demand for exploratory behaviour in 16 hens with and 16 hens without prior experience of such a nest site. Each hen was tested once in a two-pen arena. The ‘home’ pen contained food, water and a perch in all trials, whereas the ‘nest’ pen had an enclosed nest box attached in only half the trials. The demand for searching behaviour was assessed by varying the width of the doorway between the two pens (widths of 160, 140, 120 and 100 mm were used, compared with a mean hen width of 122 ± 11 mm). Steps, inspections and passages between the two pens were recorded in the 3 hours prior to oviposition. All hens with the nest box laid in it, and all hens without the nest box scraped out a hollow in a corner of the arena and laid there. All hens entered the nest pen prior to oviposition and there were fewer visits with narrower gaps (38 ± 6, 22 ± 9, 12 ± 3 and 4 ± 1 visits with gaps of 160 mm, 140 mm, 120 mm and 100 mm, respectively, for hens with the nest; 133 ± 32, 107 ± 17, 73 ± 20 and 49 ± 15 for hens with no nest box; p < 0.01 for both), but no other effect on searching or nesting activities. Hens with the nest box performed less exploratory behaviour (71 ± 5 inspections and 159 ± 21 steps) and made fewer passages (20 ± 5 visits) than hens without the nest box (188 ± 18 inspections, 349 ± 44 steps and 74 ± 9 visits; all p < 0.001). There was no difference in exploratory or nesting behaviour between nest-naive and nest-experienced hens, and no difference in their response to gap width. It may therefore be possible to assess deprivation by quantifying the motivation to persevere with appetitive activities in the absence of consummatory stimuli. In this experiment demand for, and expression of, nest-seeking behaviour were independent of prior experience of nesting cues and the enclosed nest box acted as a consummatory stimulus for nest-seeking behaviour.