Social vole parents force their mates to baby-sit.

Parental care has been categorized into direct and indirect investment. The former includes direct contact with the offspring, as in lactation or huddling with the pups, and the latter includes activities such as nest building or hoarding food for the guarding mate. We report here an unfamiliar type of parental behavior in which one parent aggressively forces its mate to stay in the nest with the pups. In this "forced baby-sitting," one parent grasps the fur of its mate and drags it toward the nest. The behavior was observed in 6 of 10 pairs of the social vole (Microtus socilalis guentheri) and was typically executed by the male. Dragging the mate to the nest was not correlated with other parental behaviors; neither could we explain why/when it occurred. However, this behavioral pattern was eye catching, and its goal was obviously to enforce the mate to stay in the nest with the pups.