Abstract

The role of the male in wild flocks of fowl, is to supervise the flock and guard it against predators, probably thereby lowering aggression and fearfulness among the members of the flock. The aim of this thesis was to study the influence of males on female behaviour in commercial farm situations by comparing all-female to sex-mixed groups of laying hens in large flocks. It was shown that males had a reducing effect on female aggression in large of laying hens (Gallus gallus domesticus) housed in groups of approx. 500 birds at a sex ratio of 1male: 24 females in a high density aviary system. However, no effect on aggression was found in flocks (ranging in size from 250 to 5000 birds) in two different loose housing systems on 25 commercial farms, probably due to the low number of males in the flocks (~ 1:350). Experiments showed that female birds in mixed flocks roosting closely together were less aggressive towards each other than birds roosting far apart. This indicates recognition of roosting partners as well as an effect of the males. Irrespective of sex composition, females in large groups were highly constant in their use of space if they were marked roosting in the ends of the compartments. Also fear reactions in females were reduced by the presence of males, as studied in large groups of 1200 birds with a sex ratio of 1:100. The vigilance behaviour and duration of tonic immobility were used as indicators, as these behaviours are considered to be protective behaviours in relation to predators. In a study of groups of 1750 birds at a sex ratio of 1:190, a positive correlation between male rank order and area covered was found. Most males, though, used more than half of the available area. However no female attachment to specific males was observed. In conclusion, males reduce female aggression and fearfulness also in large flocks and their influence on aggression is probably mainly through direct social dominance. Further, for subgroup formation in large flocks to occur, environmental features that facilitate localisation may be important.