The survival advantage of group living remains poorly understood. Here, this was investigated by using several physiological and neurobehavioral traits in Indian house crows (Corvus splendens) in the face of a temporally disrupted day-night environment. Crows were housed singly or with two other conspecifics and subjected to daily 12-h light and 12-h periods of complete (0 lx) or dimly lighted (∼6 lx) dark nights. Nocturnal melatonin and sleep levels were measured as indices of the direct and circadian effects, while mood (feeding, preening, and self-mutilation) and cognition (innovative problem-solving task) performances were considered reflecting the higher-order brain function effects. Under 6-lx dim light at night (dLAN) condition, group housing alleviated the depressive-like responses and enhanced cognitive performance but had no effect on the midnight melatonin levels and nocturnal sleep consolidation. Concurrently, there were increased nr4a2 and decreased tnfr1 gene expressions in hippocampus, increased dcx and darpp-32 gene expressions in the nidopallium caudolaterale, and th expression in midbrain. We interpret that an increased conspecific interaction improved mood and cognitive performance without affecting the melatonin secretion and sleep in communally roosting house crows. Perhaps, living with conspecifics is part of an overall evolutionary strategy to enhance the survival in a highly social species like the Indian house crow.
