Ferkin, M. H. 2000: Meadow voles (Microtus pennsylvanicus) and prairie voles (M. ochrogaster) dier in their responses to over-marks from opposite-and same-sex con-speci®cs. Ethology 106, 979Ð992. AbstractOver-marking occurs when one individual deposits its scent mark on the scent mark of a conspeci®c. Previous studies have shown that meadow voles (Microtus pennsylvanicus) and prairie voles (M. ochrogaster) that were exposed to an overmark of two same-sex conspeci®cs, later responded similarly to the top-scent mark but diered in their response to the bottom-scent mark. In the present study, we examined the responses of meadow voles and prairie voles to same-sex and mixedsex over-marks to ascertain whether their responses re¯ect the dierent tactics which males and females in promiscuous (meadow voles) and monogamous (prairie voles) species use to attract opposite-sex conspeci®cs and to compete with same-sex conspeci®cs. Males and females of both species spent more time investigating the mark of the top-scent donor than that of the bottom-scent donor of an over-mark. Meadow voles exposed to a mixed-sex over-mark spent more time investigating the mark of the opposite-sex conspeci®c independently of whether it was from the top-or bottom-scent donor. In contrast, prairie voles spent more time investigating the mark of the opposite-sex donor if it was from the top-scent donor. These results suggest that: (i) over-marking serves a competitive function; (ii) the scent marks of individuals attract multiple mates in promiscuous species such as the meadow vole; and (iii) the scent marks of individuals establish and maintain pair bonds between familiar opposite-sex conspeci®cs in monogamous species such as the prairie vole.

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.