Relationship between behavioural activity and social space requirements in laying hens

Abstract

The aim of this experiment was to study the effects of spatial restriction on the frequency with which different behaviour patterns were performed. Hens (Gallus domesticus) were kept in groups of three in four different sized litter pens giving space allowances of 5630, 3000, 1200 or 600 cm2 per bird. Using overhead time-lapse photography, the mean distance between the birds in the group when all birds were performing the same activity and the mean frequency of that activity in the time budget, were determined. In the largest pen, the birds were furthest apart when they were walking (310 ± 64 mm), closer together when they were standing (234 ± 75 mm) or ground pecking (237 ± 13 mm) and closest together when they were preening (154 ± 98 mm). As pen size decreased, the frequency of walking and ground pecking decreased significantly, the frequency of preening remained unchanged and the frequency of standing increased.A comparison of time-budget changes with the average distances between birds while performing these different activities indicated that the behaviour patterns which were performed at the largest inter-bird distances decreased in frequency as pen size got smaller. This suggested that the distance between birds when they were walking or ground pecking was sufficiently important so that when the available space decreased, the birds performed these activities less often rather than performing them at inappropriate inter-bird distances. Preening was performed when birds were close to each other and the frequency of this behaviour was unaffected by the space restrictions used in the experiment. As the frequency of some behaviour patterns decreases, there must be a corresponding increase in the frequency of others. Standing appeared to be one such ‘time-filler’ behaviour pattern. The results also suggest that the technique of reducing the space available to birds may be useful in experimentally assessing the resilience of particular behaviour patterns and thus the importance birds attribute to performing them.