PARENTAL INVESTMENT IN SOCIAL VOLES VARIES AND IS RELATIVELY INDEPENDENT OF LITTER SIZE

The spatial-and-ethological population structure, cooperation, and the evolution of sociality in rodents

There are two types of complex social units — aggregations and family groups — in rodent populations, with an essential difference in their social organization. The impact of ecological factors on the evolution of sociality in rodents (the transition from solitary towards family-group lifestyle) is still unclear. The inter-specific comparative analysis based on quantification of social traits related to the spatial-and-ethological population structure and cooperation allows author to propose a new conceptual approach to the assessment of differences between the species under consideration in terms of the evolution of sociality. A new conceptual model of the evolution of sociality in rodents should incorporate ecological conditions and social factors, including cooperation, operating as a complex of selective forces promoting formation of family groups.

Who are the bosses? Group influence on the behavior of voles following owl attack

Individual members of a group must conform to the group norms, as they may otherwise become isolated from the group or the group may split. On the other hand, social groups usually comprise various social ranks and display a differential division of labor and consequently different behaviors. The present study was aimed at examining how the above factors are manifested in social voles that had experienced owl attack. Here, we reconfirm the findings of past studies: that grouped voles converge to display similar behavior after owl attack. In addition, we found that high-mass voles were more active in the open sectors of the experimental set-ups both before and after the owl attack, whereas low-mass voles dichotomized to those that increased and those that decreased their activity in the open following owl attack. Taking body mass as a proxy for social rank, it is suggested that as a consequence of their larger size and of their experience and physical strength, high-mass voles both presented an exemplary model for the low-mass voles and, accordingly, assumed leadership and stabilized their group's behavior. We also suggest a hypothetical model for the propagation of behavior in hierarchical groups.