Space and density effects on group size preferences in laying hens.

1. T-maze preference tests were used to study group size and space preferences in laying hens kept on deep litter. The first experiment revealed a non-significant tendency to prefer a larger group (120 hens) in a large space (9 m2) over a smaller group (5 hens) in a small space (1 m3), but when the space was constant and large, a strong preference for the smaller group in a large space emerged. 2. In experiment 2, 5 different group size/space options were tested using a T-maze and test hens were non-randomly selected, choosing more aggressive "peckers' and more subordinate "receivers'. Chi-squared tests showed preferences for (1) a larger group (70 over 4 or 0 hens), (2) a larger space (9 m2 over 1 m2) and (3) 4 hens rather than an empty space. Although both peckers and receivers preferred the same size companion hen groups, receivers were more consistent in their choice than peckers. 3. The results have important implications for hens in all group size and suggest that while smaller group sizes may be important, they need to be combined with sufficient space. Furthermore, the "ideal group size' may differ depending on the individual hen's dominance status.