Effects of selection for divergent levels of social motivation on behavioral repertoire and synchronization in Japanese quail (Coturnix japonica)

Behavioral synchronization occurs when individuals perform the same behavior simultaneously and in close proximity. It is widely recognized as a key mechanism that fosters social cohesion, coordination, and cooperation within groups, providing substantial adaptive benefits. However, since individuals within a group often exhibit inter-individual differences in social tendencies, these variations may influence group organization and the extent to which synchronization occurs. Here, we investigated how genetic selection for social motivation (i.e., an individual’s internal drive to seek contact, approach and remain close to a group of conspecifics) in Japanese quail (Coturnix japonica) impacts their behavioral repertoire and their behavioral synchronization, by comparing 10 trios (groups of three) constituted of individuals selected for high social motivation (S+) and 10 trios constituted of individuals selected for low social motivation (S-). For this purpose, trios were placed for 24 consecutive hours in an arena filled with wood shavings and providing ad libitum access to feed and water. Birds’ behaviors were recorded and analyzed during four one-hour time windows (hour 1: 8:30–9:30 am, hour 2: 11:00–12:00 am, hour 3: 1:30–2:30 pm and hour 4: 4:00–5:00 pm). Results revealed that S- quail exhibited more locomotion behaviors, while S+ quail displayed more inactivity behaviors and particularly "sit relaxed" behaviors. Also, S+ individuals had a longer total synchronization duration than S- individuals. Specifically, S+ quail performed more synchronized "sit relaxed" behaviors, spent more time in this state and remained synchronized longer during a "sit relaxed" bout compared to S- quail. The S+ group also exhibited a significantly higher overall Kappa coefficient, as well as a higher Kappa coefficient for the behavior "Sit relaxed", both of which significantly differed from 0, indicating a structured pattern of behavioral synchronization consistent with coordinated group dynamics. Notably, during synchronization bouts of the behavior "Sit relaxed", birds reduced inter-individual distances, indicating an active preference for staying closer together during this activity. Overall, these findings suggest that individuals with higher social motivation are more likely to engage in synchronized behaviors, particularly during resting behaviors, which may promote close proximity and strengthen social bonds. Such synchronization may foster social cohesion and lead to more harmonious and stable group dynamics. Further studies will be necessary to better elucidate these effects and confirm these different hypotheses. This research highlights the critical role of individual differences in social motivation in shaping collective behavior. These insights enhance our understanding of animal social dynamics and could contribute to more effective management strategies in animal husbandry.