Social isolation-induced effects on male-specific courtship behaviours and dendritic architecture in associative forebrain areas in Zebra finches (Taeniopygia guttata)

Zebra finches (Taeniopygia guttata) are highly monogamous birds that maintain lifelong pair-bonds. Females make the mate choice based on the quality of males who initiate pair-bond formation by courting the female. A mate separation-reunion paradigm can help to evaluate the adaptive value of social affiliation of male finches and their affinity to new females in absence of mated females which can manifest at a neuronal level by dendritic measures. The aim of this study was to examine behavioural and neuronal changes as a result of social isolation following pair-bonding in male zebra finches. Towards this, male zebra finches from a pair-bonded group were isolated for a period of ten days and then exposed to either the mate or a new female. Four main courtship behaviours: clumping, allopreening, nest box occupancy and directed singing were recorded and analysed. Brains were processed by a modified Golgi technique to detect changes in dendritic arborizations using the Sholl analysis. Baseline behavioural results showed an increase in clumping and nest box activity by day 10. Isolated males re-introduced with their pair-bonded females demonstrated increased nest box activity. Alternatively, isolated males exposed to new females demonstrated increased directed singing when compared to their pair-bonded state, but lower than when exposed to same female. Neuro-morphological changes assessed through quantification of dendritic intersections and branch points were observed in pallial brain areas known to be implicated in the development of social/sexual preferences, with the pair-bonded group demonstrating more branching and longer dendrites when compared to the socially-isolated group. Thus social isolation impacts both courtship behaviour and neuronal morphologies with differential responses to the pair-bonded female versus a new female.