Inter-individual distances during open-field tests in Japanese quail (Coturnix japonica) selected for high or low levels of social reinstatement behaviour

Inter-individual distances (IIDs), during open-field tests, were measured in single sex pairs of quail of lines divergently selected for high (HSR) or low (LSR) levels of social reinstatement (SR) behaviour. Tests were carried out when the chicks were 1-, 3- and 6-weeks of age. IIDs were established within 1 min and remained stable thereafter. In HSR and mixed line pairs, but not LSR line pairs, IIDs increased with age. IIDs were shorter in HSR line pairs than in LSR or mixed line pairs at 1- and 3-weeks of age but not at 6-weeks of age when IIDs were similar in all pair-types. At 1- and 3-weeks of age, IIDs in mixed line pairs were intermediate to those in HSR and LSR line pairs. The sex of the pair-members did not influence IIDs. Previous studies have shown that selection for SR behaviour, in quail chicks, has effects that persist into later life and influence characters not present in the birds' behavioural repertoire at the time of testing for the purposes of selection. Such behaviour patterns include aggression, sexual behaviour and socio-sexual proximity behaviour. All of these behaviour patterns are expressed at higher levels in HSR line birds than LSR line birds. Differences in IIDs between HSR and LSR line birds may, therefore, be due to an interaction between environmental and genetic effects. In young HSR chicks, social reinstatement is the primary motivation and IIDs are short. However, as the HSR line chicks' age, IIDs reflect an interaction between social attraction and aggression related avoidance behaviour that tends to increase IIDs. In LSR line chicks aggression and social motivation are low at all ages and IIDs tend to remain stable.