Scent over-marking occurs when one individual places its scent mark on top of one deposited by a conspecific. Studies have shown that animals investigating an over-mark later behave as if the top-scent mark is more important than the bottom-scent mark. Differences in response to over-marks may reflect differences in social and mating systems. Here, we ascertained the length of time that meadow voles (Microtus pennsylvanicus) and prairie voles (Microtus ochrogaster), exposed to an over-mark, maintain a preference for the mark of the top-scent donor compared with that of the bottom-scent donor. If voles had no previous sexual experience with their top-scent and bottom-scent donors, male and female meadow voles maintained a preference for their top-scent donor’s mark over their bottom-scent donor’s mark for 48 h. In contrast, male and female prairie voles maintained such preferences for 24 h and 12 h, respectively. If voles had prior sexual experience with either their top- or bottom-scent donor, such experience did not affect the length of time meadow voles and male prairie voles maintained a preference for their top-scent donor. Female prairie voles maintained a 12-h preference for the top-scent mark if it belonged to the mate. If the mate was the bottom-scent donor, female prairie voles showed no preference for it or the top-scent mark. These findings are discussed within the framework that an association may exist between the manner in which voles respond to over-marks and their social and mating systems.