Inter-individual distances during open-held 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 i n single sex pairs of quail of lines divergently selected for high (HSR) or low (LSR) levels of social reinstatement (SR) behaviour. Tests were carrie d 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 l ine 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-wee ks of age, IIDs in mixed line pairs were intermediate to those in HSR and L SR 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 e ffects 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 e xpressed at higher levels in HSR line birds than LSR line birds. Difference s in IIDs between HSR and LSR line birds may, therefore, be due to an inter action between environmental and genetic effects. In young HSR chicks, soci al reinstatement is the primary motivation and IIDs are short. However, as the HSR line chicks' age, IIDs reflect an interaction between social attrac tion and aggression related avoidance behaviour that tends to increase IIDs . In LSR line chicks aggression and social motivation are low at all ages a nd IIDs tend to remain stable. (C) 1999 Elsevier Science B.V. All rights re served.