Effects of social interactions on pre-laying behaviour in hens

Abstract

The aims of this study were to investigate the effects of social interactions on access to the nest site and pre-laying behaviour of hens in small groups. Nine groups of four hens were placed in a littered round pen. Aggressive pecks, together with the identity of the individuals involved, were recorded for 8 h of the day. Behaviour in the hour prior to oviposition was also recorded at 15 s intervals using a video camera and VCR. Records of pre-laying behaviour were divided into three categories: (1) dominant category, for hens whose pre-laying behaviour overlapped with that of subordinate pen-mates; (2) subordinate category, for hens whose pre-laying behaviour overlapped with that of dominant pen-mates; and (3) undisturbed category, for hens that showed pre-laying behaviour when no other hens were showing it. Dominant hens showed a pre-oviposition increase (median) interquartile range 13.0 (3.0–30.0)) in the number of pecks given in the hour before oviposition when compared to the hour after (1.0 (0.0–10.0), P < 0.05). Subordinate hens however, received more aggressive pecks in the hour before oviposition (21.5 (10.0–37.0)) than in the hour after (0.0 (0.0–5.0), P < 0.05). Undisturbed hens showed no changes in aggressive pecks either received or given between pre and post-oviposition time periods. Subordinate hens were also displaced more times from the nest (7.0 (4.3–12.5)) in the 30 min prior to oviposition than undisturbed hens (1.5 (0.8-2.3), P < 0.05). In the period 60-25 min before oviposition, subordinate hens walked more (163.5 (112.5–174.7) steps) than dominant (85.0 (43.0–221.5)) and undisturbed hens (59.0 (18.5–74.5)), P < 0.05). Subordinate hens also walked more (113.5 (50.3–281.2) steps) than dominant (14.0 (9.0–15.0)) and undisturbed hens (43.0 (20.0–59.5), P < 0.05) in the last 25 min before oviposition. For this time period, differences in the time spent sitting were also observed (subordinate 10.0 (4.1–14.6), dominant 19.3 (12.6–20.9) and undisturbed 13.8 (10.5–18.9) min, P < 0.05). Results suggested that hens compete for access to the nest site. Variations in pre-laying behaviour owing to social interactions were observed in both directions: subordinate hens showed an increased searching phase, whereas dominant hens remained nearer the nest site.