Meadow Voles (Microtus pennsylvanicus) and Prairie Voles (M. ochrogaster) Differ in Their Responses to Over‐Marks from Opposite‐ and Same‐Sex Conspecifics

Abstract

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.

Perspectives on over-marking: is it good to be on top?

“…To over-mark or not to over-mark: that is the question The literature is replete with observations and anecdotes of mammals depositing their scent marks on or near the scent marks of conspecifics (Johnson 1973;Biben 1980;Macdonald 1980;Hurst 1990a;Johnston et al 1994Johnston et al , 1997aHeymann 1998;Sliwa and Richardson 1998;Brashares and Arcese 1999;Woodward et al 2000;Lewis 2005). These include reports of overmarking in rodents, insectivores, ungulates, carnivores, and primates.…”

“…The fourth hypothesis is that over-marking is a form of mate attraction Hurst and Rich 1999;Woodward et al 2000). In this case, individuals would over-mark marks of opposite-sex conspecifics more than they would the scent marks of same-sex conspecifics (Heymann 1998;Kappeler 1998;Ferkin et al 2004a; but see Smith and Gordon 2002).…”

“…This hypothesis predicts that by over-marking the bottom-scent mark, the top-scent donor is somehow devaluing the features of it to conspecifics (Woodward et al 2000). That is, individuals that investigate such an over-mark would be able to determine that the top-scent donor may have an association with the bottom-scent donor.…”

“…Although this hypothesis raises some interesting issues with regard to how and where some over-marking studies are conducted, there is little empirical evidence that shows that over-marking serves no function. The fact that most of the available literature suggests that mammals over-mark the scent marks of conspecifics (Johnson 1973;Biben 1980;Macdonald 1980;Hurst 1990a;Johnston et al 1994Johnston et al , 1997aHeymann 1998;Sliwa and Richardson 1998;Brashares and Arcese 1999;Woodward et al 2000;Lewis 2005), differ in the proportion of scent marks of particular conspecifics that they over-mark (Ferkin et al 2004a, b), and respond differently to the donors of the top-and bottom-scent marks of an overmark (Johnston et al 1994), suggest that it likely a specialized form of olfactory communication that is inherently different from, or requires special explanation additional to, that for scent marking.…”

“…Second, in some cases, investigating animals later behaved as if the bottom-scent mark was not present Ferkin et al 1999). Third, in other cases, animals behaved as if the bottom-scent mark was present, but it was less salient relative to the top-scent mark (Woodward et al 1999(Woodward et al , 2000. These findings provide no support for the scent-blending hypothesis or the chemical bulletin board hypotheses, but do support the competition hypothesis as the rodents responded selectively toward the top-scent mark.…”