Meadow voles and prairie voles differ in the percentage of conspecific marks they over-mark

Many terrestrial mammals scent mark in areas containing the scent marks of conspecifics, and thus, may deposit their own scent marks on top of those that were deposited previously by conspecifics. This phenomenon, known as over-marking appears to play a role in same-sex competition or mate attraction. The present study determines whether meadow and prairie voles avoid over-marking the scent marks of conspecifics, target the scent marks of conspecifics and over-mark them, or randomly over-mark the scent marks of conspecifics. The data show that meadow and prairie voles adjust the number and location of scent marks that they deposit in areas marked previously by particular conspecifics. Male and female meadow and prairie voles target the scent marks of opposite-sex conspecifics and over-mark them. Female meadow and prairie voles also target the scent marks of female conspecifics. In contrast, male meadow and prairie voles over-mark the scent marks of male conspecifics in a random manner. By differentially over-marking the scent marks of conspecifics, voles may be able to communicate particular information to a variety of conspecifics.     

Scent Marking in Female Prairie Voles: a Test of Alternative Hypotheses

We conducted three experiments with females in different stages of reproductive condition to test alternative hypotheses for the function of scent marking in female prairie voles, Microtus ochrogaster . The three reproductive categories were isolated females prior to sexual stimulation (anoestrous), sexually stimulated (oestrous) and lactating. Females in different reproductive condition were given the opportunity to scent mark clean unmarked substrate or areas that had previously been marked by adult females or adult males. The numbers of scent marks deposited by females did not differ statistically for females in different reproductive condition. However, there was a trend for anoestrous females to mark the most, oestrous females less, and lactating females the least. The lack of scent marking by lactating females might be to reduce conspicuousness to conspecifics or predators. Oestrous females tended to mark the most in the area marked previously by males, although the difference was not statistically significant.
Our results provide some support for a mate-attraction hypothesis and a territorial-defense hypothesis, but were most consistent with a self-advertisement hypothesis. Over marking was uncommon and did not differ by experiment or sex of previous donor. Our results suggest that the number and placement of scent marks by females are highly variable and function primarily to convey individual identity.     

Female meadow voles,Microtus pennsylvanicus,do not alter their over-marking in response to female conspecifics that were food deprived

Many terrestrial mammals will deposit scent marks and over-marks, the latter being the overlapping scent marks of two conspecifics. Studies have shown that male rodents that are exposed to the overlapping scent marks of two female conspecifics later spend more time investigating the mark of the top-scent female than that of the bottom-scent female. This suggests that over-marking is a form of competition and that the top-scent female is more likely than the bottom-scent female to be chosen as a potential mate. Thus, females should over-mark the scents of neighboring females at a rate that will maximize their chances of attracting males. However, meadow voles live in areas that may contain patchy food availability and residents may differ in their nutritional status. Females in a better nutritional state may be more likely than those in poorer nutritional states to indicate their presence in an area, signal possession of a territory, and to attract mates. Thus, we tested the prediction that female meadow voles, Microtus pennsylvanicus, that were not food deprived would deposit more over-marks than female voles that were food deprived for 6 h. Food-deprived female voles and female voles that had continuous access to food deposited a similar number of scent marks and used a similar proportion of those marks as over-marks when they encountered the scent marks of female conspecifics. These findings suggest that the nutritional status of female voles does not affect their ability to signal their presence in an area marked by a female conspecific.     

The amount of time that a meadow vole, Microtus pennsylvanicus, self-grooms is affected by its reproductive state and that of the odor donor

Many hypotheses have been put forth to account for differences in the amount of time that animals engage self-grooming when exposed to conspecifics or their odors, but most ignore the possibility that self-grooming may be associated with olfactory communication between groomers and conspecifics. As yet, we do not know the function of self-grooming and why animals do so when they encounter the odors of conspecifics. The present experiment tests the hypothesis that the amount of time that a meadow vole, Microtus pennsylvanicus, self-grooms is affected by the reproductive state of the odor donor and its own reproductive state. The findings support the hypothesis. Male voles spent more time self-grooming when they were exposed to bedding scented by female voles in postpartum estrus (PPE) compared to that of female voles in other reproductive states and female mice. PPE female voles spent more time self-grooming when they were exposed to bedding scented by testosterone-treated male voles than either to that of gonadectomized male voles and male mice. PPE female voles spent more time than OVX+E and more time than OVX females self-grooming when they were exposed to bedding scented by testosterone-treated male voles. GX+T male voles spent more time than GX male voles self-grooming when they were exposed to bedding scented by PPE female voles. The results suggest that individuals self-groom more in the presence of an odor of a highly receptive potential mate than that of a less receptive mate.     

Self-Grooming as a Tactic Used by Prairie Voles Microtus ochrogaster to Enhance Sexual Communication

Observations of numerous mammals suggest males self-groom more than females in response to the odours of opposite-sex conspecifics. Two experiments tested the hypothesis that self-grooming may be a tactic used by males to attract mates in prairie voles Microtus ochrogaster . In the first experiment, we measured the amounts of time voles self-groomed during exposure either to male-scented cotton bedding, female-scented cotton bedding, or clean cotton bedding. Results from this experiment support the hypothesis and also show that female prairie voles self-groom in response to odours of males. In addition, male prairie voles groom more in response to male odours than to female odours, suggesting that self-grooming also serves a role in male–male competition. In the second experiment, male and female voles spent more time investigating scent marks of opposite-sex conspecifics that recently self-groomed at a higher rate than those of opposite-sex conspecifics that self-groomed at a lower rate. Female, but not male prairie voles, spent more time investigating scent marks of opposite-sex conspecifics that self-groomed at a high rate than those of same-sex conspecifics that self-groomed at a high rate. For prairie voles, self-grooming may increase the detection of their scent marks by conspecifics. By self-grooming, prairie voles may be attempting to attract opposite-sex conspecifics, and males may also be attempting to deter encounters with male conspecifics.     

Age Affects Over-Marking of Opposite-Sex Scent Marks in Meadow Voles, Microtus pennsylvanicus

Models of age-related effects on behavior predict that among short-lived species younger adults are more attractive and attracted to opposite-sex conspecifics than are older adults, whereas the converse is predicted for long-lived species. Although most studies of age-related effects on behavior support these predictions, they are not supported by many studies of scent marking, a behavior used in mate attraction. Over-marking, a form of scent marking, is a tactic used by many terrestrial mammals to convey information about themselves to opposite-sex conspecifics. The present study tested the hypothesis that the age of meadow voles, Microtus pennsylvanicus ; a microtine rodent, affects their over- and scent-marking behaviors when they encounter the marks of opposite-sex conspecifics. Sex differences existed in the over-marking behavior of adult voles among the three different age groups that were tested. Male voles that were 5–7 and 10–12 mo olds over-marked a higher proportion of the marks of females than did 2–3 mo old male voles. Female voles that were 2–3, 5–7, and 10–12 mo old over-marked a similar number of marks deposited by male voles. Overall, the data were not consistent with models predicting the behavior of short-lived animals such as rodents when they encounter the opposite sex. The differences in over-marking displayed by older and younger adult male voles may be associated with life history tradeoffs, the likelihood that they will encounter sexually receptive females, and being selected as mates.     

Self-Discrimination in Meadow Voles, Microtus pennsylvanicus

Particular features of the signaling characteristics of the scent marks of temperate zone, seasonally breeding mammals may reflect differences in their reproductive state and, hence, be variable. Consequently, an individual's perception of self may depend more on the condition independent than on the condition-dependent signaling characteristics of the scent marks. Yet, we do not know whether an individual responds to changes in the signaling characteristics of its own scent marks, such as those associated with changes in an individual's reproductive state. Such changes may affect how and where an animal scent marks. Here we report on a series of experiments designed to test the hypothesis that individual meadow voles, Microtus pennsylvanicus , distinguish between scent marks they deposited when they were in different reproductive states. Results showed that voles discriminated their own scent marks from those of unfamiliar, same-sex conspecifics, and the scent marks of siblings. Voles did not behave as if they could distinguish between their own scent marks if the marks were deposited when the voles were in the same reproductive state, although the two scent marks used as stimuli differed in age by 30 d. However, they did so distinguish if they were exposed to scent marks taken when they were in different reproductive states. Overall, these findings suggest that voles behave as if their novel and familiar scent marks shared the similar signaling features. If, however, the reproductive condition of the voles differed when it provided the two scent marks, they behaved as if their own scent marks had different signal characteristics, which may have induced voles to treat the two scent marks as not being the same or having been deposited by two different donors. We speculate that the scent marks of individuals may have unique signaling characteristics that may be associated with that individual's 'current template for self'.     

Olfactory Experience Affects the Response of Meadow Voles to the Opposite‐Sex Scent Donor of Mixed‐Sex Over‐Marks

Scent marking and over‐marking are important forms of communication between the sexes for many terrestrial mammals. Over the course of three experiments, we determined whether the amount of time individuals investigate the scent marks of opposite‐sex conspecifics is affected by 4 d of olfactory experience with those conspecifics. In Experiment 1, female meadow voles, Microtus pennsylvanicus, spent more time investigating the scent mark of the novel male conspecific than that of the familiar male donor, whereas male voles spent similar amounts of time investigating the scent mark of the familiar female and a novel female conspecific. In Experiment 2, voles were exposed to a mixed‐sex over‐mark in which subjects did not have 4 d of olfactory experience with either the top‐scent donor or the bottom‐scent donor. During the test phase, male and female voles spent more time investigating the scent mark of the opposite‐sex conspecific that provided the top‐scent mark than that of a novel, opposite‐sex conspecific. Male and female voles spent similar amounts of time investigating the scent mark of the bottom‐scent donor and that of a novel opposite‐sex conspecific. In Experiment 3, voles were exposed to a mixed‐sex over‐mark that contained the scent mark of an opposite‐sex conspecific with which they had 4 d of olfactory experience. During the test phase, male voles spent more time investigating the mark of the familiar, top‐scent female than the scent mark of a novel female donor but spent similar amounts of time investigating the mark of the familiar, bottom‐scent female and that of a novel female donor. In contrast, female voles spent more time investigating the mark of a novel male donor than that of either the familiar, top‐scent male or that of the familiar, bottom‐scent male. The sex differences in the responses of voles to scent marks and mixed‐sex over‐marks are discussed in relation to the natural history and non‐monogamous mating system of meadow voles.     

Over-marking and Adjacent Marking are Influenced by Sibship in Male Prairie Voles,Microtus ochrogaster

Scent over-marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific. Over-marking may provide advantages in the transfer of information to the individual whose scent is on top but not to the individual whose scent is on the bottom. We tested the hypothesis that over-marking is a competitive form of olfactory communication and that male prairie voles would over-mark the scent marks of same-sex conspecifics more than those of same-sex siblings. Two age-matched male voles (first male and second male) were placed successively into an arena in which they were allowed to explore freely and scent mark for 15 min at age 12, 20, 28, 36, 44, and 52 d. The first male was placed into a clean arena, whereas the second male was placed into an arena containing either the scent marks of an age-matched male sibling or nonsibling. Age affected the total number of scent marks deposited by the voles; 12-20-d-old voles deposited fewer scent marks, over-marks and adjacent marks than did 28-52-d-old voles. Sibship did not affect the total number of scent marks deposited by the first and second voles but did affect the number of over-marks and adjacent marks deposited by the second vole. Siblings received significantly fewer over-marks and adjacent marks than did nonsiblings; this effect was most dramatic after the voles reached 28 d of age, a time coincident with the onset of puberty. Males separated from siblings and housed singly at 44-d-old and tested at 52-d-old, deposited significantly more over-marks and adjacent marks in arenas if the first vole was a nonsibling than if it was a sibling. This differential scent-marking supports the hypothesis that over-marking and adjacent marking are used as competitive forms of olfactory communication by male prairie voles.     

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.     

Sex differences in scent marking in Propithecus edwardsi of Ranomafana National Park, Madagascar

In this study we compared the scent-marking rates of females with those of males. Specifically, we examined the ability of season, dominance status, and natal status to explain the frequency of scent marking in female sifakas living wild in Ranomafana National Park, Madagascar, and compared the results with those published for males [Pochron et al., American Journal of Primatology, in press]. We also sought to determine whether vulnerability to infanticide affects marking frequency in adults of either sex, and whether female reproductive status affects female marking behavior. We found that males marked at twice the rate of females, and like males, females in single-female groups marked at the highest rates. Dominant females and non-natal females marked at higher rates than did subordinate females and natal females, a pattern also seen in males. This suggests that scent marks may convey important information about status. Neither females nor males varied their marking frequency with the presence of vulnerable infants. Females did not alter marking frequency with reproductive state, and like males, they marked at higher rates in the period prior to the mating season than they did in the mating season itself. This implies that females may use scent marks more for intrasexual aggression or territoriality than for mate attraction.     

Scent marking and mate choice in the prairie vole, Microtus ochrogaster

Scent marking is common among male and female rodents and might be used in male-male competition and as a mechanism for mate attraction. I tested the hypotheses that females would choose males based on their frequency and placement of scent marks, and that a female would advertise interest in a particular male by placing her scent marks on or near those of a preferred mating partner. In a series of experiments conducted with prairie voles, Microtus ochrogaster, females did not choose mates based on the frequency or placement of scent marks by males nor did they advertise their interest in a particular male through the frequency or placement of scent marks. The number of males chosen that scent-marked more than their opponents did not differ significantly between females exposed (11 of 15) and not exposed (10 of 15) to scents of males. Females exposed and not exposed to scents of males preferred seven of the same males that had scent-marked more than their opponents. When a third group of females was exposed to four times more scent of the less preferred than preferred males, they still chose the preferred males. Thus, the frequency and placement of scent marks by males were not used to assess males for mate choice nor did female prairie voles use scent to advertise their preference for a mating partner. In that scent marking is common in male and female mammals, scent quality might be more important than quantity in male-male competition and mate attraction.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .     

Male and Female Meadow Voles,Microtus pennsylvanicus,Differ in Their Responses to Heterospecific/Conspecific Over‐Marks

Voles use runways, paths, and trails that may also be used by rabbits and mink. These shared areas could contain the scent marks of conspecifics and heterospecifics. Thus, it is likely that the scent marks of heterospecifics may overlap or be overlapped by those of voles, forming over‐marks. Much is known about how voles respond to over‐marks of two different conspecifics. However, we do not know how they would respond to an opposite‐sex conspecific whose scent marks are in an over‐mark with the scent marks of predator or the scent marks of a non‐predator heterospecifics. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, differ in their response to the scent mark of the opposite‐sex conspecific if the scent mark was overlapped by that of a mink, a vole predator, or rabbit, a vole non‐predator. We found that female but not male voles showed a preference for the scent marks of the opposite‐sex conspecifics that were part of the mink‐vole over‐mark when compared to those of opposite‐sex conspecifics that were not part of the over‐mark. This preference by female voles was independent of whether the male vole was the top‐scent donor or bottom‐scent donor of the over‐mark. Male and female voles showed no preference between the scent marks of the opposite‐sex conspecifics whose marks were part of or not part of the rabbit‐vole over‐mark. Sex differences in the manner that meadow voles respond to rabbit‐vole and mink‐vole over‐marks are discussed.     

Scent-marking behaviour by male prairie voles,Microtus ochrogaster,in response to the scent of opposite- and same-sex conspecifics

We conducted an experiment using the prairie vole (Microtus ochrogaster) to test predictions associated with the proposed functions of scent marking as a sexual attractant, in reproductive competition, and as a self-advertisement. We allowed an oestrous female, an anoestrous female, and an adult male to scent mark three portions of a clean substrate and then exposed a second male to this substrate for secondary marking. We did not support a sexual attraction hypothesis in that males did not place more scent marks in response to oestrous than anoestrous females. Similarly, we did not support a reproductive competition hypothesis in that males did not place more scent marks in response to marks of males than to those of females or bare substrate. Males did not overmark the scent of males or females and thus we did not support a scent-masking or scent-blending hypothesis. In that males deposited scent similarly in response to males, females, and on bare substrate, our results suggest that the frequency and placement of scent marks by males function primarily to advertise individual identity in an area.     

Sex differences in olfactory social recognition memory in meadow voles,Microtus pennsylvanicus

Terrestrial mammals, like rodents, use odors, and scent marks to indicate their presence in an area to conspecifics. These odors convey information about the scent donor's genotype, sex, condition, and age. The ability to discriminate among the scent marks of conspecifics and later recollect the identity of the donor is essential for choosing between familiar and unfamiliar mates. We tested the hypothesis that the promiscuous meadow vole (Microtus pennsylvanicus) can recollect the odor of a familiar, opposite-sex conspecific and distinguish it from that of an unfamiliar, opposite-sex conspecific. We also hypothesized that because reproductive success is highly skewed among male meadow voles and competition for mates is intense, males will be more likely than females to recollect the odor of a familiar, opposite-sex conspecific and distinguish it from that of an unfamiliar, opposite-sex conspecific, for a longer period of time. Using a habituation task, we first exposed the voles, 4 times successively, to the anogenital area scent of an opposite-sex conspecific. Then, 1 hr, 24 hrs, 72 hrs, or 96 hrs after the fourth exposure, voles were presented with the odor of the donor from the exposure phase (familiar donor) and that of an unfamiliar, opposite-sex conspecific. Female meadow voles spent similar amounts of time investigating the scent of the familiar male donor and that of an unfamiliar male donor after the 1-hr and 24-hr intervals. Male meadow voles, however, spent more time with the scent of an unfamiliar female donor than that of the familiar female donor after the 1-hr, 24-hr, and 72-hr intervals, suggesting that male voles could recollect the scent mark of a familiar female for at least three days. The implications of these sex differences in social memory may reflect the different strategies male and female meadow voles use in the recognition of previous and potential mates. Recognition of an individual's scents may enhance fitness by allowing animals to direct appropriate behaviors toward those individuals.     

Scent Marking in Voles: A Reassessment of Over Marking, Counter Marking, and Self-Advertisement

We conducted a series of experiments to discern among the counter-marking, over-marking, and self-advertisement hypotheses for secondary marking in male prairie voles, Microtus ochrogaster , and meadow voles, M. pennsylvanicus . Secondary scent marks (those placed in an area that has already been marked by a conspecific) were not significantly greater than initial marks placed on clean substrate (a substrate without any previous scent marks) for either species and thus did not support a counter-marking hypothesis. Similarly, overlapping of initial scent marks with secondary marks occurred less often than expected by chance and did not support an over-marking hypothesis. Secondary marks tended to avoid overlap with scent marks previously deposited by a potential competitor. Our results suggest that secondary scent marking functions to self-advertise by maximizing individual identity and avoiding masking or blending with previous donors. Future studies on secondary marking should be designed to quantify the observed and expected frequency and placement of original and secondary marks to discern among alternative hypotheses for the adaptive significance of secondary marking.     

The behavior of female meadow voles,Microtus pennsylvanicus,during postpartum estrus and the responses of males to them

For numerous species of terrestrial mammals, postpartum estrus, PPE, is a period of heightened attractivity, proceptivity, and receptivity that occurs shortly after the female delivers her litter. Many mammals mate almost exclusively during PPE. However, we know little about the behavior of PPE females and how male conspecifics behave toward them. This review focuses on the results of recent studies that tried to examine systematically the behavior of PPE female meadow voles, Microtus pennsylvanicus, and the responses of males to them. Our review is divided in five parts. First, we introduce the topic of PPE in rodents. Second, we discuss the outcome of studies showing that PPE female voles were more attractive to males, directed more proceptive behaviors toward males, and were more sexually receptive and likely to get pregnant compared to females that were not in PPE. Third, we discuss studies that examined how male voles respond and adjust their behavior when they encounter PPE females. Males increase the likelihood of mating with PPE females by recalling the reproductive state of females and the location of their nests, and by anticipating how long or when each of these females would be in PPE. Fourth, we focus in how food availability, an ecological constraint facing gestating female voles, affected their attractivity, proceptivity, and receptivity postpartum. Fifth, we revisit the benefits of seeking out and mating with PPE females and introduce the costs of doing so for both males and PPE females. We close our review with a list of questions that can be used to formulate testable hypotheses surrounding the behavior of PPE females and the responses of male conspecifics to them.     

Female prairie voles do not choose males based on their frequency of scent marking

We conducted an experiment to test three alternative hypotheses for the function of frequency of scent marking in male prairie voles, MICROTUS OCHROGASTER: (1) sexual attraction (to advertise male quality for mating); (2) reproductive competition; and (3) self-advertisement or individual identity. In laboratory experiments, males deposited scent on all areas of a bare substrate, and more in an area next to a stimulus animal than other areas, regardless of the stimulus animal's sex. Females did not choose mates based on their frequency of scent marking and scent marking did not antagonize or stimulate aggression between males. The frequency of scent marking by males supports the individual identity hypothesis, and is less consistent with the sexual attraction or reproductive competition hypotheses. Mate choice is likely based on a complex suite of characters, but at least in prairie voles, the frequency of scent marking by males does not appear to be one of them.     

Temporal and Spatial Distribution of Male Scent Marks in the Polygynous Greater Sac-Winged Bat

Scent marks are relatively long-lived signals that can be perceived by conspecifics when the producer is absent. Therefore, it is often not obvious to whom the signal is directed. In daytime roosts of the polygynous greater sac-winged bat, males scent mark territories with facial gland secretions. Territories are a valuable resource for males, as they offer exclusive courtship opportunities, which results in increased male reproductive success and, consequently, increased male–male competition over territories. The information encoded in male scent marks could, therefore, be either directed at females as part of an olfactory courtship display or at male competitors as part of territorial behaviour. We expected territorial males to scent mark in the morning, shortly before females return to the territory and close to female roosting sites, if scent marks are directed at females as part of the courtship display. And we expected harem males to scent mark at the territory boundaries, where male–male encounters are most likely to occur, if scent marks are directed at male competitors. We found that males marked more frequently in the afternoon, at a time when all females have already left the territory, and harem males marked at the territory boundaries and not inside their territory in the area where females roost. At boundaries males fan volatiles from specialised wing sacs towards competitors outside the territory. Scent marking of male Saccopteryx bilineata might therefore be congruent with the assessment-hypothesis, which states that scent marks offer intruders the possibility to make an olfactory assessment of the territory owner without direct physical interaction. Thus, scent marks of male S. bilineata are most likely influenced by male–male competition and not by female choice.     

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

Over‐marking occurs when one individual deposits its scent mark on the scent mark of a conspecific. Previous studies have shown that meadow voles (Microtus pennsylvanicus) and prairie voles (M. ochrogaster) that were exposed to an over‐mark of two same‐sex conspecifics, later responded similarly to the top‐scent mark but differed 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 mixed‐sex over‐marks to ascertain whether their responses reflect the different tactics which males and females in promiscuous (meadow voles) and monogamous (prairie voles) species use to attract opposite‐sex conspecifics and to compete with same‐sex conspecifics. 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 conspecific 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 conspecifics in monogamous species such as the prairie vole.