The hormone oxytocin is known to regulate a range of behaviours in mammals, particularly in females. In addition to the known reproductive functions, studies in mice show that oxytocin released centrally in the brain influences a range of social behaviours. In females, for example, these include social preferences for mates of the opposite and same sex. A study at the University of Liverpool published with the participation of the University of Veterinary Medicine Vienna now shows that female mice benefit from higher levels of oxytocin in the rearing of their offspring through improved co-operation.

In their study, the scientists investigated the behaviour of related female house mice (Mus musculus domesticus). Female house mice can choose whether to raise their young in so-called communal nests with another female and her young, or alone in a single nest. In the study, they found that when females reared their young together, mice with higher central oxytocin levels had more egalitarian and successful co-operative relationships. ‘The cooperation of two sisters with high oxytocin concentrations in the paraventricular nucleus (PVN) of the hypothalamus resulted in a communal nest in which the sisters produced more offspring together, had more equal contributions to the number of young and spent more equal proportions of time in the nest,’ says study joint first author Stefan Fischer from the Konrad Lorenz Institute of Ethology (KLIVV) at Vetmeduni .

Influence of oxytocin sheds new light on the evolution of egalitarian social relationships

In contrast to the relationship between oxytocin concentrations and the number of offspring produced in a communal nest, oxytocin concentrations were not related to the number of weaned offspring produced in a single nest without co-operation. In addition, oxytocin levels did not differ with regard to the availability of preferred nest sites or social competition with other groups of mice. ‘Given that we associate the positive effects of co-operation with oxytocin, our results have far-reaching implications for understanding the evolution of egalitarian social relationships,’ explains Fischer.

Despotic or egalitarian: social systems are characterised by a tension between competition and cooperation

According to Fischer, social competition and cooperation fundamentally characterise the social systems of animals living in groups. Sociality is always the outcome between the tension of group members to fight or co-operate for resources and reproduction. Whether group members tend to fight or co-operate depends on the relatedness of the interacting animals and the benefits of cooperation. This tension is reflected in the differential distribution of the benefits of cooperative behaviour between group members. In egalitarian social systems, the benefits are distributed relatively evenly according to the effort invested, whereas in despotic social systems the benefits tend to accrue to the dominant individuals - at the expense of the others. ‘Our study is of particular interest because it provides evidence for differences in the balance between egalitarian and despotic behaviour that are related to central oxytocin levels of cooperating individuals. If similar variations are replicated in other social species, this could help us to understand the proximate factors that influence egalitarian and despotic social behaviour and thus provide a comprehensive insight into the diversity of social systems,’ emphasises Fischer.

The article „Egalitarian cooperation linked to central oxytocin levels in communal breeding house mice“ by Stefan Fischer, Callum Duffield, William T. Swaney, Rhiannon L. Bolton, Amanda J. Davidson, Jane L. Hurst and Paula Stockley was published in „Communications biology“.

Scientific article