EFFECTS OF SOCIAL INTERACTIONS ON PRELAYING BEHAVIOR IN HENS

The aims of this study were to investigate the effects of social inter actions 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 roun d pen. Aggressive pecks, together with the identity of the individuals involved, were recorded for 8 h of the day. Behaviour in the hour pri or to oviposition was also recorded at 15 s intervals using a video ca mera 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 catego ry, for hens whose pre-laying behaviour overlapped with that of domina nt pen-mates; and (3) undisturbed category, for hens that showed pre-l aying behaviour when no other hens were showing it. Dominant hens show ed a pre-oviposition increase (median) interquartile range 13.0 (3.0-3 0.0)) 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 he ns however, received more aggressive pecks in the hour before oviposit ion (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 recei ved or given between pre and post-oviposition time periods. Subordinat e hens were also displaced more times from the nest (7.0 (4.3-12.5)) i n the 30 min prier to oviposition than undisturbed hens (1.5 (0.8-2.3) , P < 0.05), In the period 60-25 min before oviposition, subordinate h ens 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), Subordinat e 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 t he 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 sear ching phase. whereas dominant hens remained nearer the nest site. (C) 1998 Elsevier Science B.V.