Implications of breaking mother–young social bonds

Abstract

Whereas mammalian mothers and young may retain long-term social affiliations in nature, the management of animals in captivity typically dictates that offspring are abruptly and permanently separated from their mothers at a relatively early age, often prior to the time of natural weaning. For animal breeders, this strategy can enhance the yield of offspring from a breeding population. Morbidity and mortality can also precipitate severance of mother–young bonds. Although it is recognized that early weaning provides nutritional challenges for the young, relatively little attention has been paid to the psychological consequences and long-term impacts of breaking the mother–young bond in non-human mammals. Furthermore, whereas great strides are being made in our understanding of the neurobiological and genetic underpinnings of social bonding, the mechanisms underlying the process of detachment following establishment of a mother–young bond remain relatively unexplored, although parallels can be drawn with processes involved in withdrawal from addictive substances. In this review, we outline mechanisms involved in social bonding. We consider the diversity in extent and duration of mother–young attachment across mammalian lineages and implications for predicting the outcome of severing ties between mothers and young at different times post-partum. We identify characteristics signalling emotional distress resulting from separation of mothers and young and discuss strategies for mitigating separation-induced distress. These include postponement of separation, ensuring high-quality maternal care of young prior to separation, providing bonded individuals with opportunities to separate voluntarily for brief periods prior to permanent separation, use of anti-suck devices prior to separation, allowing a period of partial (fence line) contact prior to full separation, providing substitutes for stimuli previously exchanged between mother and young, providing social buffers, gradual introduction to new housing arrangements, and pharmacological intervention. Areas for future research are proposed, including the use of functional neuroimaging technologies and functional genomics approaches, in combination with behavioural assessments of reinstatement motivation, individual recognition memory and long-term consequences of early separation, to shed further light on the nature of mother–young bonding and detachment in animals.