The highly social subterranean voles of genus Ellobius (mole vole) represent a unique model to compare with both social bathyergids and surface-dwelling voles. Unlike most arvicolines, mole voles display the prolonged obligatory delay of dispersal. In subterranean rodents, this delay may be associated with benefits of cooperation (weaned offspring help their parents), an extended parental investment (parents care for weaned offspring), or both. To identify the role offspring aged