Meadow Voles Microtus Pennsylvanicus Research Articles

Restored Wetland Size and Age Influence Small Mammal Communities in West Virginia, USA

Small mammals are important, albeit often overlooked, fauna in wetland restoration projects. However, it is essential to evaluate factors that influence small mammal community metrics in restored wetlands to maximize wetland restoration effectiveness. Previous studies found that vegetation differed as restored wetlands aged and that wetland age may play a role in the presence of amphibians and birds. Therefore, we assessed whether wetland age influenced small mammals. We also evaluated 17 environmental factors in restored wetlands that could influence small mammal communities in these wetlands. To assess and evaluate the effects of age and environmental factors on the small mammal community, we appraised 14 restored wetlands in West Virginia, USA, in the summers of 2020 and 2021 for small mammal community metrics, specifically relative abundance, diversity, richness, and evenness. We captured six species of small mammals: deer mice (Peromyscus maniculatus), white-footed mice (Peromyscus leucopus), meadow voles (Microtus pennsylvanicus), meadow jumping mice (Zapus hudsonius), northern short-tailed shrews (Blarina brevicauda), and eastern chipmunks (Tamias striatus). We found that the relative abundance of deer mice, white-footed mice, and meadow voles decreased with wetland age. However, both species diversity and evenness increased with wetland age. Wetland size influenced the relative abundance of white-footed mice, meadow jumping mice, and all small mammals combined. Although the relative abundance of white-footed mice and total small mammals decreased with wetland size, the relative abundance of meadow jumping mice increased with wetland size. Wetland managers should consider wetland age and size when designing wetlands to facilitate small mammal communities.

Population fluctuations of meadow voles (Microtus pennsylvanicus) in a landscape with cumulative clearcutting

Population fluctuations of meadow voles (Microtus pennsylvanicus) in a landscape with cumulative clearcutting

Comparative analysis of gonadal hormone receptor expression in the postnatal house mouse, meadow vole, and prairie vole brain

The socially monogamous prairie vole (Microtus ochrogaster) and promiscuous meadow vole (Microtus pennsylvanicus) are closely related, but only prairie voles display long-lasting pair bonds, biparental care, and selective aggression towards unfamiliar individuals after pair bonding. These social behaviors in mammals are largely mediated by steroid hormone signaling in the social behavior network (SBN) of the brain. Hormone receptors are reproducible markers of sex differences that can provide more information than anatomy alone and can even be at odds with anatomical dimorphisms. We reasoned that behaviors associated with social monogamy in prairie voles may emerge in part from unique expression patterns of steroid hormone receptors in this species, and that these expression patterns would be more similar across males and females in prairie than in meadow voles or the laboratory mouse. To obtain insight into steroid hormone signaling in the developing prairie vole brain, we assessed expression of estrogen receptor alpha (Esr1), estrogen receptor beta (Esr2), and androgen receptor (Ar) within the SBN, using in situ hybridization at postnatal day 14 in mice, meadow, and prairie voles. We found species-specific patterns of hormone receptor expression in the hippocampus and ventromedial hypothalamus, as well as species differences in the sex bias of these markers in the principal nucleus of the bed nucleus of the stria terminalis. These findings suggest the observed differences in gonadal hormone receptor expression may underlie species differences in the display of social behaviors.

Cell Proliferation and Cell Death Levels in the Dentate Gyrus Correlate with Home Range Size Among Adult Male Meadow Voles

Neurogenesis occurs throughout adulthood within the dentate gyrus, and evidence indicates that these new neurons play a critical role in both spatial and social memory. However, a vast majority of past research on adult neurogenesis has involved experiments with captive mice and rats, making the generalizability of results to natural settings questionable. We assessed the connection between adult neurogenesis and memory by measuring the home range size of wild-caught, free-ranging meadow voles (Microtus pennsylvanicus). Adult male voles (n = 18) were captured, fitted with radio collars, and released back into their natural habitat, where each vole’s home range was assessed using 40 radio-telemetry fixes over the course of 5 evenings. Voles were then recaptured, and brain tissue was collected. Cellular markers of cell proliferation (pHisH3, Ki67), neurogenesis (DCX), and pyknosis were labeled on histological sections and then quantified using either fluorescent or light microscopy. Voles with larger home ranges had significantly higher pHisH3+ cell densities within the granule cell layer and subgranular zone (GCL + SGZ) of the dentate gyrus and higher Ki67+ cell densities in the dorsal GCL + SGZ. Voles with larger ranges also had significantly higher pyknotic cell densities in the entire GCL + SGZ and in the dorsal GCL + SGZ. These results support the hypothesis that cell proliferation and cell death within the hippocampus are involved with spatial memory formation. However, a marker of neurogenesis (DCX+) was not correlated with range size, suggesting that there may be selective cellular turnover in the dentate gyrus when a vole is ranging through its environment.

An experimental analysis of density dependence in meadow voles: Within-season and delayed effects.

Wild mammal populations exhibit a variety of dynamics, ranging from fairly stable with little change in population size over time to high-amplitude cyclic or erratic fluctuations. A persistent question in population ecology is why populations fluctuate as they do. Answering this seemingly simple question has proven to be challenging. Broadly, density-dependent feedback mechanisms should allow populations to grow at low density and slow or halt growth at high density. However, experimental tests of what demographic processes result in density-dependent feedback and on what timescale have proven elusive. Here, we used replicated density perturbation experiments and capture-mark-recapture analyses to test density-dependent population growth in populations of meadow voles (Microtus pennsylvanicus) during the summer breeding season by manipulating founding population density and observing the pattern of survival, reproduction, and population growth. High population density had no consistent effect on survival rates but generally negatively influenced recruitment and population growth rates. However, these density-dependent effects varied within the breeding season and across years. Our study provides evidence that density-dependent feedback mechanisms operate at finer time scales than previously believed and that process, additively with delayed year effects, is key to understanding multiyear population demography.

Is chronic stress a causal mechanism for small mammal population cycles? Reconciling the evidence.

Chronic stress has long been hypothesized to play a role in driving population cycles. Christian (1950) hypothesized that high population density results in chronic stress and mass "die-offs" in small mammal populations. Updated variations of this hypothesis propose that chronic stress at high population density may reduce fitness, reproduction, or program aspects of phenotype, driving population declines. We tested the effect of density on the stress axis in meadow voles (Microtus pennsylvanicus) by manipulating population density in field enclosures over three years. Using fecal corticosterone metabolites as a non-invasive measure of glucocorticoid (GC) concentrations, we found that density alone was not associated with GC differences. However, we found that the seasonal relationship of GC levels differed by density treatment, with high-density populations having elevated GC levels early in the breeding season and decreasing towards late summer. We additionally tested hippocampal glucocorticoid receptor and mineralocorticoid receptor gene expression in juvenile voles born at different densities, with the hypothesis that high density may reduce receptor expression, altering negative feedback of the stress axis. We found that females had marginally higher glucocorticoid receptor expression at high density, no effect in males, and no detectable effect of density on mineralocorticoid receptor expression in either sex. Hence, we found no evidence that high density directly impairs negative feedback in the hippocampus, butrather female offspring may be better equipped for negative feedback. We compare our findings with prior studies to attempt to disentangle the complicated relationship between density, seasonality, sex, reproduction and the stress axis.

Postfire salvage logging alters impacts of recent wildfire on small mammal communities in summer

Abstract Wildfire is a natural ecosystem disturbance in forests in North America, yet fires are often at odds with human activity and affect the timber supply. Postfire salvage logging is common practice globally, but the impacts of salvage logging on wildlife, especially small mammal communities, remain unclear. We livetrapped small mammals to determine their population responses to wildfire and postfire salvage logging in central British Columbia, Canada. Postfire regenerating forest provided habitat for deer mice (Peromyscus maniculatus), southern red-backed voles (Myodes gapperi), and meadow voles (Microtus pennsylvanicus). Postfire salvage logging significantly reduced tree basal area and changed small mammal community structure by reducing southern red-backed vole populations and supporting mainly deer mice, a generalist species. Given the large scale and intensity of postfire salvage logging operations across the province, salvage logging has the potential to decrease vole populations and change small mammal communities across the province.

Another mention of Meadow Vole (<i>Microtus pennsylvanicus</i>) found in pellets of Snowy Owl (<i>Bubo scandiacus</i>) in northern Ungava Peninsula, Canada

The examination of raptor pellets can be used to evaluate Arctic biodiversity. We found the remains of Meadow Vole (Microtus pennsylvanicus) and Ungava Collared Lemming (Dicrostonyx hudsonius) in pellets from Snowy Owl (Bubo scandiacus) nesting in the northern part of the Ungava Peninsula. We differentiated the two species by visual identification and geometric morphometric analysis of molar shape. The results of our study combined with historical data suggest that most commonly used range maps of Meadow Vole should be revised.

Increased Attack Rates and Decreased Incubation Periods in Raccoons with Chronic Wasting Disease Passaged through Meadow Voles

Chronic wasting disease (CWD) is a naturally-occurring neurodegenerative disease of cervids. Raccoons (Procyon lotor) and meadow voles (Microtus pennsylvanicus) have previously been shown to be susceptible to the CWD agent. To investigate the potential for transmission of the agent of CWD from white-tailed deer to voles and subsequently to raccoons, we intracranially inoculated raccoons with brain homogenate from a CWD-affected white-tailed deer (CWDWtd) or derivatives of this isolate after it had been passaged through voles 1 or 5 times. We found that passage of the CWDWtd isolate through voles led to a change in the biologic behavior of the CWD agent, including increased attack rates and decreased incubation periods in raccoons. A better understanding of the dynamics of cross-species transmission of CWD prions can provide insights into how these infectious proteins evolve in new hosts.

Selectivity and Sociality: Aggression and Affiliation Shape Vole Social Relationships.

The formation of selective social relationships is not a requirement of group living; sociality can be supported by motivation for social interaction in the absence of preferences for specific individuals, and by tolerance in place of social motivation. For species that form selective social relationships, these can be maintained by preference for familiar partners, as well as by avoidance of or aggression toward individuals outside of the social bond. In this review, we explore the roles that aggression, motivation, and tolerance play in the maintenance of selective affiliation. We focus on prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) as rodent species that both exhibit the unusual tendency to form selective social relationships, but differ with regard to mating system. These species provide an opportunity to investigate the mechanisms that underlie social relationships, and to compare mechanisms supporting pair bonds with mates and same-sex peer relationships. We then relate this to the role of aggression in group composition in a comparative context.

Island biogeography predicts skull gigantism and shape variation in meadow voles Microtus pennsylvanicus through ecological release and allometry

Island rule describes the graded trend of gigantism in small‐bodied species to dwarfism in large‐bodied species inhabiting islands, but causal explanations remain unresolved. We used geometric morphometrics to quantify cranial morphology of 544 meadow vole Microtus pennsylvanicus samples across 11 island and 3 mainland populations from the Outer Lands of New England (Atlantic) and the Alexander Archipelago of Alaska (Pacific). We compared the thermoregulation and endurance (TRE) and ecological release (ER) hypotheses using all‐subsets linear models employing residual randomization permutation procedures (rrpp), and Akaike information criterion (AIC) for model selection. We decoupled direct and indirect effects of island variables on size using path analysis. We evaluated shape with principal components analysis (PCA) and Procrustes ANOVA on Procrustes shape coordinates, then assessed the impact of static allometry and TRE and ER variables on shape. Six Atlantic island populations exhibit significant signals of gigantism with the largest voles occurring on the smallest islands lacking predators. ER explains 63% of cranial size differences. Island area has a significant total effect on size by influencing the number of mammalian predators, resulting in a 0.011 increase in unit centroid size for a 100 km2 decrease in island area. This corresponds to a predicted 0.9% change in size for every 100 km2. Given static allometry, cranial shape does not respond to insularity independent of size. These results suggest that island rule is a latent evolutionary process whose manifestation depends on nuanced biogeographic and ecological contexts that have important conservation and taxonomic implications.

Arctic fox winter dietary response to damped lemming cycles estimated from fecal DNA

Abstract Climate-caused changes in prey abundance may alter predator–prey dynamics in the Arctic food web. Lemmings (Dicrostonyx spp.) are important prey for Arctic foxes (Vulpes lagopus) and their annual population fluctuations drive fox reproduction, creating strongly linked predator–prey population cycles. Winter diet directly impacts Arctic fox reproductive success, but winter prey diversity on the tundra is low. Strategies such as using the marine environment to scavenge seals have allowed Arctic foxes to persist during years of low lemming abundance. However, warming winters have decreased snowpack quality, preventing lemmings from reaching their previous high abundances, which may reduce their impact on predator dynamics. We investigated Arctic fox dietary response to lemming abundance by reconstructing Arctic fox winter diet in the low Arctic. Next-generation sequencing of fecal DNA, from samples (n = 627) collected at dens in winters of 2011–2018, identified prey both from terrestrial and marine environments. Despite lemming cycle damping, Arctic foxes still increased lemming consumption during years of higher lemming abundance. Alternative prey such as marine resources were consumed more during years of low lemming abundance, with up to 45% of samples containing marine resources in low lemming years. In addition, Arctic foxes consumed high proportions of meadow voles (Microtus pennsylvanicus), which may represent a new alternative prey, suggesting climate change may be creating new foraging opportunities. Changes in prey abundance illustrate how climate-caused disturbances are altering Arctic food-web dynamics. Dietary flexibility and availability of alternative prey may become increasingly important for Arctic predators as the Arctic continues to change.

Using Long‐Term Data to Compare Two Sizes of Sherman Trap

ABSTRACTLive traps are commonly used to inventory, monitor, and sample populations of small mammals. Due to the variety of available trap types, understanding differences between traps is important to minimize bias and plan future studies. Sherman traps (H. B. Sherman Trap, Inc., Tallahassee, FL, USA; hereafter Sherman traps) are a popular live trap that come in a variety of sizes. However, studies comparing the relative efficacy of different‐sized Sherman traps often focus on a single species or are limited by a lack of temporal and spatial replication, leading to contradictory or ambiguous results. Therefore, to better understand the relative efficacy of two commonly‐used sizes, we used a paired design and 10 years of trapping data to compare species richness, capture numbers, and mortality rates between small Sherman traps (5.1 × 6.4 × 16.5 cm) and large Sherman traps (7.6 × 8.9 × 22.9 cm) across 55 preserves in northeastern Illinois. Despite wide annual variation, we captured more small mammals in large traps except for the smallest taxa (Sorex spp.), the proportion of captures in large traps increased with body size, and large traps significantly reduced mortality rates for Peromyscus spp., meadow voles (Microtus pennsylvanicus), and short‐tailed shrews (Blarina brevicauda). We recommend the 7.6 × 8.9 × 22.9 cm Sherman trap for monitoring surveys in the midwestern USA when research or monitoring objectives include maximizing captures and species richness while minimizing mortality. However, we note the smaller‐sized trap may be useful to minimize bycatch when smaller species are being targeted. Finally, managers and biologists conducting short‐term or pilot studies should be wary of year effects, as we found substantial annual variation in relative capture rates between trap sizes. © 2021 The Wildlife Society.

A mechanism for population self-regulation: Social density suppresses GnRH expression and reduces reproductivity in voles.

Nearly 100years ago, Charles Elton described lemming and vole population cycles as ecological models for understanding population regulation in nature. Yet, the mechanisms driving these cycles are still not fully understood. These rodent populations can continue to cycle in the absence of predation and with food supplementation, and represent a major unsolved problem in population ecology. It has been hypothesized that the social environment at high population density can drive selection for a low-reproduction phenotype, resulting in population self-regulation as an intrinsic mechanism driving the cycles. However, a physiological mechanism for this self-regulation has not been demonstrated. We manipulated population density in wild meadow voles Microtus pennsylvanicus using large-scale field enclosures over 3years and examined reproductive performance and physiology. Within the field enclosures, we assessed the proportion of breeding animals, mass at sexual maturation, and faecal androgen and oestrogen metabolites. We then collected brain tissue from juvenile voles born at high or low density, quantified mRNA expression of gonadotropin-releasing hormone (GnRH) and oestrogen receptor alpha (ERα) and measured DNA methylation at six CpG sites in a region that was highly conserved with the mouse GnRH promoter. At high density, there was a lower proportion of reproductive animals. Juvenile voles born at high densities had reduced expression of GnRH in the hypothalamus, accompanied by marginally lower faecal sex hormone metabolites. Female juvenile voles born at high density also had higher methylation levels at two CpG sites while males did not, aligning with prior observations that females (but not males) from high-density environments retain reduced reproduction long term. Our results support a physiological basis for population self-regulation in vole cycles, as altering population density alone induced reproductive downregulation at the hypothalamic level. Our results demonstrate that altering the early-life social environment can fundamentally impact reproductive function in the brain. This, in turn, can drive population demography changes in wild animals.

The effect of social odour context on the amount of time male meadow voles, Microtus pennsylvanicus, self-groom

Abstract Communicational behaviours by individuals provide information for not only the intended target(s) of the signal but any non-target individual(s) that may be nearby. For terrestrial mammals a major form of communication and social information is through odours via scent marking and self-grooming. Self-grooming is a ubiquitous behaviour in mammals with the function thought to primarily be centred on personal care. But it has been found in rodents that self-grooming will occur in the presence of social odours thus potentially serving a communicative role. For example, male meadow voles (Microtus pennsylvanicus) self-groom in the presence of a female conspecific odour but not a male conspecific odour. Most studies examining self-grooming as a form of olfactory communication have used single odour donors but in a natural environment individuals will come across complex social odour situations. Therefore, we examined how male meadow voles respond to complex social odours with regards to their self-grooming behaviour. We tested the hypothesis that self-grooming can act as a form of olfactory communication and that male meadow voles will control this behaviour measured by differences in self-grooming rates based on social contexts. Male meadow voles did not show differences in the amount of time spent self-grooming to social odours that contained a female and varying number of rival males (0, 1, 3, or 5) or if the social odour contained an acquainted or novel male. Male meadow voles did self-groom more to a social odour that contained a female and a younger male compared to when the social odour contained a female and older male. Male meadow voles appear to adjust their self-grooming behaviour based on the context of the social information. This may be a strategy that can maximize that individual’s fitness by adjusting how much information is provided to potential rivals and mates.

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

AbstractTerrestrial 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.

Time‐Averaging Voles Match Density with Long‐Term Habitat Quality

Photo 1. The Lakehead University Habitron in northern Ontario, Canada. The Habitron consists of 24 interconnected rodent-proof enclosures, a small office, outdoor field laboratory, and three storage sheds. Enclosures have small gates that can be opened to enable dispersal among habitats. Field biologists control rodent densities, age distributions and sex ratios, and determine whether enclosures receive supplemental resources, and whether animals can move from one enclosure to others. Photo credit: Douglas Morris. Photo 2. Circular foraging trays used to calculate giving-up densities (GUDs) located under a clear polyethylene cover (risky foraging site) and a nearby plywood cover (safe foraging site). Trays are filled with 1.5 L of sieved silica sand thoroughly mixed with 8 g of whole oats and are foraged in by free-ranging meadow voles (Microtus pennsylvanicus). The difference in GUD between paired risky and safe trays provides an estimate of predation risk. Photo credit: Douglas Morris. Photo 3. A risky open foraging tray with an automatic radio frequency identification (RFID) antenna attached to an event recorder. The recorder logs the entrance and departure times of all RFID-tagged rodents that forage in the tray. Total foraging time is a simple cumulation of the respective foraging intervals. Photo credit: Douglas Morris. Photo 4. A closed safe foraging station with an automated RFID antenna (hidden from view under the cover) and its event recorder. Covers are suspended on small wooden supports to allow entry by voles. The supports are located parallel to the RFID antenna in order to eliminate false recordings of animals that might be resting or moving adjacent to the antenna, rather than foraging in the sand-filled tray. Photo credit: Douglas Morris. Photo 5. Power and communication cables connect a series of electrical transformers and control units to eight data recorders (not in the photo) at the Lakehead University Habitron in northern Ontario, Canada. The middle platform serves as a field desk for a laptop computer used to download data on the identities and foraging activities of RFID-tagged meadow voles. Photo credit: Douglas Morris. These photographs illustrate the article “Time-averaging voles match density with long-term habitat quality” by Douglas W. Morris published in Ecology. https://doi.org/10.1002/ecy.3036

Northern Harriers Have a Geographically Broad Four-Year Migration Cycle

We used observation data from major hawk-watch sites in northeastern North America to assess multiyear cycles in breeding productivity of the Northern Harrier (Circus hudsonius). We found that autumn totals of migrating harriers for 1983–2017 autocorrelated positively at the 4-yr lag for interior, but not Atlantic coastal, counts. The autocorrelation was especially high for harriers counted in October. The autumn counts of south-bound harriers were not correlated with counts of north-bound harriers in the previous spring. Interannual differences in atmospheric circulation during migration in 1983–2017, as expressed by the autumn North Atlantic Oscillation Index, correlated with the autumn harrier counts but did not have a 4-yr cycle. The temporal pattern revealed in this study should be considered when using counts of autumn migrants to infer regional population trends. Future research could focus on the cause of the cyclic pattern in harrier numbers. One obvious question concerns the relationship between spring populations of meadow voles (Microtus pennsylvanicus), which are important prey for harriers during breeding, and harrier numbers reported during the subsequent autumn migration.

A precarious future for distinctive peripheral populations of meadow voles (Microtus pennsylvanicus)

Abstract Conservation efforts rely on robust taxonomic assessments that should be based on critical assessment of interspecific boundaries, infraspecific variation, and potentially distinctive peripheral populations. The meadow vole (Microtus pennsylvanicus) is widely distributed across North America, including 28 morphologically defined subspecies and numerous isolated populations. Because some subspecies are of high conservation concern, we examined geographic variation across the range of the species to test existing infraspecific taxonomy in terms of local and regional diversification. We sequenced mitochondrial DNA (mtDNA) from 20 subspecies of M. pennsylvanicus and contextualized infraspecific variation through comparison of pairwise genetic distances derived from an extended data set of 63 species of Microtus. We found strong support for at least three divergent clades within M. pennsylvanicus, with observed intraspecific clade divergence exceeding that between several pairwise comparisons of sister species within Microtus. Six nuclear genes were then sequenced to test the validity of mtDNA structure and to further evaluate the possibility of cryptic, species-level diversity using Bayes factor species delimitation (BFD) analyses. BFD consistently and decisively supported multiple species based on the multilocus approach. We propose that taxonomic revision of the meadow vole is required, with the eastern clade now identified as M. pennsylvanicus (Ord 1815), the western clade as M. drummondii (Audubon and Bachman 1853), and the coastal Florida clade as M. dukecampbelli (Woods, Post, and Kilpatrick 1982). We suggest that such an arrangement would more closely reflect evolutionary history and provide critical context for further examination of distinctive southern peripheral populations that harbor novel evolutionary legacies and adaptive potential.

Assessing space use in meadow voles: the relationship to reproduction and the stress axis

Abstract Voles are key mammals in understanding how social interactions can affect large-scale population processes. Previous studies have shown that at high population densities, meadow voles (Microtus pennsylvanicus) have a lower proportion of breeding animals, higher average corticosterone levels, and can be limited by female territorial spacing. Based on this, we compared corticosterone levels and spatial use between breeding and nonbreeding free-ranging adult meadow voles within populations. We measured intrasexual spatial overlap to examine if breeding females minimize occupying the same areas as other females, and noninvasively assessed corticosterone levels using fecal corticosterone metabolites (FCMs). We found that female meadow voles have much lower intrasexual spatial overlap than males, even though both sexes have similar range sizes, and that females have generally higher FCM levels than males. However, breeding and nonbreeding females did not differ from one another in spatial use or in FCM levels. Conversely, reproductive classes of males differed greatly in all measures: nonbreeding males had FCM levels that were two times higher than those of breeding males, occupied a smaller range, and had lower spatial overlap, indicating they were moving less widely than breeding males. We additionally validated an enzyme immunoassay for noninvasively measuring FCMs in meadow voles. The assay was successful in detecting an increase in corticosterone stimulated by adrenocorticotropic hormone injection; however, dexamethasone did not induce negative feedback. FCMs reflect circulating corticosterone levels approximately 5 h prior. These results highlight differences in FCMs and spacing in meadow voles related to sex and reproductive status, and reflect the respective strategies males and females employ during the breeding season.