Effects of chronic social defeat on social interaction and partner preference in mandarin voles

Different types of stress produce different effects on social relationships between partners. Chronic social defeat has been found to alter the emotional and social behaviours, whether it affects partner preference remains unclear. Using monogamous mandarin voles (Microtus mandarinus), the present study found that 14 days of social defeat to male vole could increase social avoidance in sociality test, and reduced attacking, intimate, sniffing and exploratory behaviours, but increased avoidance defensive, immobile behaviours in social interaction test. In addition, this treatment significantly reduced side-by-side contact with partner throughout cohabitation period, and reduced the attacking behaviour to strangers after 11 days’ cohabitation. Furthermore, in mandarin vole with chronic social defeat, partner preference was abolished on 5 and 7 days’ cohabitation indicating that pair bonding stability was impaired by chronic social defeat. Moreover, although mandarin voles spent longer time rescuing partner than stranger in both groups, chronic social defeat did not affect rescuing significantly. Impairment of pair bonding may be due to abnormalities in social interaction induced by chronic social defeat. This finding provides some insights into mechanisms underlying effects of prolong social stress on social relationships between partners.