A new early behavioural indicator of underlying sociality and fearfulness in Japanese quail

Abstract

One challenge faced by ethologists in poultry welfare is to help birds to form functionally successful groups over time through the expression of their social behaviours. Searching for phenotypic variability, we developed a test, the density-related permanence (DRP) that enables us to classify young birds (while in groups) according to their individual permanence in proximity to either a high or low density of conspecifics (HD or LD, respectively). The present study addressed the question of whether contrasting DRP quail behaviours reflect underlying differences in sociality and/or fearfulness. The classification apparatus consisted of 2 boxes interconnected by a central region delimited by 2 sliding doors. Each box contained at its distal end either 12 or 3 conspecifics confined behind a glass. At 11 days of age and every 1h, the sliding doors were closed and experimental birds (36) were identified and released back in the central region of the device. According to where they were found (box containing high-density, low-density or in the central region) each bird received a 1, -1 or a 0 score, respectively. The procedure was repeated 9 times and the scores summed. A total of 271 and 330 birds with final values ≥3 or ≤-3 were respectively categorized as HD or LD. After 1 to 4 weeks, categorized birds underwent one of the following tests: home-cage and resident/intruder behaviour, open field (OF), tonic immobility (TI) or plasma corticosterone (CORT) response to potential stressors. One-way ANOVAs showed that LD vs. HD groups of 6 birds of the same category presented higher levels of agonistic interactions among cagemates (P≤0.05) and towards individual intruders (P≤0.05). Two-way ANOVA showed that birds introduced 5-min inLD groups presented higher (P≤0.01) CORT levels than undisturbed controls, whereas intruders in HD groups did not. ANOVAs also showed that HD compared to LD quail walked more, faster and a greater distance in the OF (P≤0.05, ≤0.01 and ≤0.01, respectively), presented lower CORT levels after 10-min restraint (P≤0.05), and required more inductions and developed shorter TI responses (P≤0.01 and 0.05, respectively). The bird´s response to the DRP test could be considered a consequence of their differential capacity to interact with conspecifics and their environment suggesting HD and LD underlying differences in sociality and fearfulness.