Meadow voles (Microtus pennsylvanicus, Arvicolidae) over-mark and adjacent-mark the scent marks of same-sex conspecifics

Scent over-marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific; adjacent-marking occurs when an animal deposits its scent mark next to the scent mark of a conspecific. Given that male rodents usually scent mark more than females and that animals spend more time investigating the odor of the top-scent donor of an over-mark, I tested the following three hypotheses. First, male meadow voles deposit more scent marks than female meadow voles. Second, male meadow voles will deposit more over-marks and adjacent-marks in response to the scent marks of a same-sex conspecific than females would. Third, meadow voles spend more time investigating the odor of the second vole placed in the arena than that of the first vole placed in the arena. To test these hypotheses, two age-matched, like-sex conspecifics (first vole and second vole) were placed successively into an arena in which they were allowed to freely explore and scent mark for 15 min. The first hypothesis was not supported. The first and second vole, independently of sex, deposited a similar number of scent marks. The second hypothesis was also not supported by the data: more conspecific scent marks were over-marked by the second female than by the second male. The third hypothesis was supported by the data. After investigating a scented arena, males and females spent more time investigating the odor of the second vole than that of the first vole. Sex differences in scent-marking behaviors of meadow voles are unlike those reported for other species of rodents