Meadow Jumping Mouse 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.

Wagering with an incomplete deck—refining conservation plans for the New Mexico Meadow Jumping Mouse (Zapus luteus luteus)

Abstract Limited sampling for imperiled taxa inhibits effective management by obscuring windows into ecological and evolutionary processes and ultimately thwarting thoughtful conservation efforts. We report eight new locations for the endangered New Mexico Meadow Jumping Mouse (Zapus luteus luteus) detected across three states that expand their known distribution. When combined with existing curated museum records, we develop an ensemble species distribution model to evaluate persistence of populations over the next 50 years. Predicted distributions indicate complex future changes, including regional expansion and the likelihood that half of the designated critical habitat areas will be unsuitable by 2070. Three of the newly discovered populations occur where predicted climate conditions suggest extirpation is likely. Importantly, indices of historical sampling efforts show that recognized and potential distributions are mismatched, highlighting vast areas that have been insufficiently surveyed. Ongoing habitat degradation and climate disruption are projected to synergistically erode genetic diversity across four of the five divergent phylogroups. Considering these combined results, a holistic sampling strategy is needed to more completely document the distribution of jumping mice and facilitate genomic analyses aimed at establishing a roadmap for improving our understanding of geographic variation and adaptive potential. Current management efforts are not only costly, but they are lacking key biological insights, essentially wagering actions with an incomplete deck of cards.

Courtship Behavior of the Meadow Jumping Mouse (Zapus hudsonius)

We describe the first recorded observations of courtship behavior of the meadow jumping mouse (Zapus hudsonius) made in wild-caught and captive-reared animals. Male meadow jumping mice performed a series of courtship behaviors upon approach to the female, including rapid fanning of the muzzle with the forelimbs, self-grooming, muzzle fanning, retreat, and eventual mounting attempts. During courtship, female jumping mice may retreat, ignore the courting male, or bat at the male with forelimbs until the male retreats. Active rejection of courting males by the female is suggestive of female mate choice in this species.

Breeding and hibernation of captive meadow jumping mice (Zapus hudsonius).

Hibernating mammals exhibit unique metabolic and physiological phenotypes that have potential applications in medicine or spaceflight, yet our understanding of the genetic basis and molecular mechanisms of hibernation is limited. The meadow jumping mouse, a small North American hibernator, exhibits traits–including a short generation time–that would facilitate genetic approaches to hibernation research. Here we report the collection, captive breeding, and laboratory hibernation of meadow jumping mice. Captive breeders in our colony produced a statistically significant excess of male offspring and a large number of all-male and all-female litters. We confirmed that short photoperiod induced pre-hibernation fattening, and cold ambient temperature facilitated entry into hibernation. During pre-hibernation fattening, food consumption exhibited non-linear dependence on both body mass and temperature, such that food consumption was greatest in the heaviest animals at the coldest temperatures. Meadow jumping mice exhibited a strong circadian rhythm of nightly activity that was disrupted during the hibernation interval. We conclude that it is possible to study hibernation phenotypes using captive-bred meadow jumping mice in a laboratory setting.

Hibernation: Insights from Comparative Genomics of Zapus Species

Hibernating mammals employ unique metabolic strategies to survive harsh conditions. They become obese prior to the onset of winter, then conserve their stored energy during a long winter fast by slowing metabolism and becoming deeply hypothermic. Hibernation phenotypes may provide insights into control of metabolism and have applications in medicine, but little is known about the molecular mechanisms or genetic underpinnings of hibernation. We have begun using the meadow jumping mouse (Zapus hudsonius) as a laboratory hibernation model. We sequenced, de novo assembled, and annotated a meadow jumping mouse genome. We further generated whole genome sequences for six additional meadow jumping mice and seven western jumping mice (Zapus princeps), a closely related hibernator. Z. hudsonius uses photoperiod as the cue to initiate fall fattening, while Z. princeps ignores photoperiod and prepares for hibernation based on food availability. Preliminary comparative genomic analysis reveals a subset of ~1700 proteins that are significantly diverged between the species. These diverged proteins are enriched for genes involved in pheromone sensing and reproduction, immunity, and metabolism. Analysis of individual genes yields insights into speciation and may reveal candidate genes that explain the phenotypic differences between the two species.Support or Funding InformationWJI acknowledges support from the Sara and Frank McKnight Fund for Biochemical Research and an NIH Early Independence Award (DP5OD021365).

Landscape Scale and Microhabitat of the Endangered New Mexico Meadow Jumping Mouse in the White Mountains, Arizona

Abstract The New Mexico meadow jumping mouse Zapus hudsonius luteus was listed as endangered under the U.S. Endangered Species Act in 2014, with critical habitat designated in 2016. Despite these recent conservation actions, there is a paucity of published information regarding its habitat associations. The taxon is a riparian obligate that occurs along both low-elevation rivers and high-elevation headwater streams in several disjunct areas of the American Southwest. Habitat information from one region might not apply to others. The distribution and habitat preferences of the New Mexico meadow jumping mouse in the White Mountains in eastern Arizona are poorly known. Objectives of this study were to 1) identify and resurvey historical locations in the White Mountains, 2) survey for new populations in areas with potentially suitable habitat in the White Mountains, and 3) use quantitative data to evaluate habitat associations at the landscape and microhabitat scales and to compare habitat at sites where I captured or did not capture the New Mexico meadow jumping mouse. I found 123 historical records of the New Mexico meadow jumping mouse from 21 locations in the White Mountains, indicating a formerly broad distribution. I conducted field surveys and collected habitat data at 35 sites (14 historical, 21 new) and caught 37 (39 total captures) New Mexico meadow jumping mice at 12 sites, including 6 of 12 historical locations surveyed. The overall capture rate was 0.36%, with an average capture rate at sites where it was present of 1.28% (range = 0.25–2.5%). All historical sites where I caught the New Mexico meadow jumping mouse were in the drainage of the Black River. The six new sites included the first records for Nutrioso Creek and Corduroy Creek and confirmed persistence of the taxon in the East Fork Little Colorado River, San Francisco River, and Blue River watersheds. Habitat used by the New Mexico meadow jumping mouse in the White Mountains was similar to that reported for other montane populations, characterized by tall, dense herbaceous vegetation composed primarily of forbs and sedges on saturated soil in close proximity to flowing water. However, there was significantly more cover provided by alders Alnus spp. at capture sites at both the stream reach and microhabitat scales. All sites where I captured the New Mexico meadow jumping mouse had no authorized livestock grazing, and the taxon was more likely to occur at sites where there were no signs of unauthorized livestock grazing. Further, there was a significant positive relationship between alder cover and time since an area was excluded from livestock grazing. The widespread exclusion of livestock from riparian areas in the White Mountains may have contributed to the higher rate of population persistence of the New Mexico meadow jumping mice in the White Mountains compared with the Jemez and Sacramento mountains, New Mexico. Although the overall persistence rate in the White Mountains (47%) was higher than other populations, the population is at risk of further losses due to small, isolated occupied areas and ongoing threats.

The Meadow Jumping Mouse as a Laboratory Model of Hibernation

Hibernating mammals exhibit great metabolic flexibility. They experience seasonal obesity and employ heterothermy as a survival strategy. During hibernation in cold climates, small mammalian hibernators enter a state of metabolic torpor and profound hypothermia. The significant (>95%) reduction of metabolic rate during torpor allows the hibernator to subsist on body fat for up to six months. The physiological flexibility of hibernators and their ability to suppress metabolic rate and survive hypothermia are of interest to human medicine; however, the molecular mechanisms underlying these phenotypes are not well understood and most current hibernating model organisms are not conducive to genetic approaches due to long generation times. The goal of this research has been to establish the meadow jumping mouse (Zapus hudsonius) as a convenient laboratory model of hibernation. Meadow jumping mice are small North American rodents with a ‘true’ hibernation phenotype: they fatten prior to hibernation and undergo multi‐day bouts of torpor that are interrupted by short interbout arousals. Crucially, meadow jumping mice breed multiple times per summer in the wild, and they cue their transition from summer reproduction to fall fattening and hibernation largely on day length. We established a breeding colony using wild‐caught animals that were trapped in Massachusetts in the summers of 2014 and 2015. The animals remain in a lean breeding condition year‐round when housed at long photoperiod (16 hours light, 8 hours dark). Obesity and torpor can be induced by exposure to short photoperiod (8 hours light, 16 hours dark) and reduced temperature. We have generated the first meadow jumping mouse transcriptome data and expect that completion of ongoing genome sequencing efforts will increase the utility of this model. The meadow jumping mouse appears to be suitable for investigation of hibernation metabolism in the laboratory, and its short generation time may open the door to future genetic studies of hibernation phenotypes.Support or Funding InformationWJI acknowledges support from the Sara and Frank McKnight Fund for Biochemical Research and an NIH Early Independence Award (DP5OD021365).

Effects of an ongoing oak savanna restoration on small mammals in Lower Michigan

Oak (Quercus spp.) savannas have declined drastically in the midwestern United States since European settlement. Oak savanna restoration projects are primarily driven by species closely linked to this habitat type, such as the federally endangered Karner blue butterfly (Lycaeides melissa samuelis). However, it is essential that other species are monitored during restoration. Small mammals, due to their importance in ecosystem function, are particularly useful to study. The United States Forest Service is currently conducting an oak savanna restoration in the Manistee National Forest in Lower Michigan using forest thinning and prescribed burning. To understand management impacts on small mammal communities, we live trapped small mammals in each of the mechanically thinned plots (i.e., bulldozer, masticator, and shear cutter) and control plots in five blocks over six years (2008–2013), as well as measured vegetation variables each year. Initially, we used a permutation multivariate analysis of variance (perMANOVA) to determine if there were treatment and year interactions for both small mammal community assemblages and vegetation variables. We then compared changes in small mammal diversity, relative abundance, and vegetation variables among treatments using exploratory randomized block design analysis of variances (ANOVAs). Canopy cover was significantly lower in bulldozer and shear cutter thinned plots than control plots five years following thinning. We observed significant treatment by year interactions in how the small mammal community responded. A large increase in relative abundance of white-footed mice occurred one year post-thinning in all treatments. Within 1–2years of treatment, thirteen-lined ground squirrels and meadow jumping mice, both open-canopy grassland species became established on thinned plots. The retention of brush piles in bulldozer and shear cutter plots provided important refuge habitat for small mammals following thinning. Restoration efforts were beneficial to the small mammal community overall and promoted grassland species to immigrate into the restored area.

Small Mammal Habitat Preferences in a Patchwork of Adjacent Reconstructed Grasslands Subject to Semiannual Burns

This study used small mammal capture-recapture methods within a mosaic of side-by-side prairie reconstructions to evaluate the relationship between floristic diversity, the effect of prescribed burns, and habitat use. This unique 10.4 ha study of opportunity consisted of multiple plots of three habitat types: low floristic diversity exotic cool-season grasses (CSG), low floristic diversity grass plantings dominated by native warm-season grasses (WSG), and floristically diverse, mixed prairie (MP) plantings with 45 species of forbs. Data for calculating small mammal abundances (new captures/trap effort) were determined by trapping in August following spring burns in 2002 and 2004, and unburned years in 2003 and 2005. Fire-positive species (meadow jumping mice, Peromyscus spp.) preferred fields with a more open understory (MP plantings), and a reduced thatch thickness and leaf litter layer (burned fields). Fire-negative species (meadow voles, northern short-tailed shrews) populated all restorations (CSG, WSG, MP plantings) but only during the unburned years when the fields provided a high density of vegetative cover. Even though the distinct floristic diversity found within the three reconstruction types influenced small mammal foraging preferences, the effect of semiannual burns on floristic structures had a noteworthy impact on their distributions. The results of this study demonstrate an important take home message for restoration practitioners: techniques that promote differences in structural characteristics are just as important as creating plantings with high floristic diversity.

Habitat Selection by the Endangered New Mexico Meadow Jumping Mouse on an Irrigated Floodplain

Abstract The New Mexico meadow jumping mouse Zapus hudsonius luteus is endemic to the American Southwest. It has undergone severe declines in distribution over the past century and it has been listed as endangered under the Endangered Species Act. The goal of this study was to determine current status and habitat selection by the New Mexico meadow jumping mouse at three spatial scales (landscape, macrohabitat, microhabitat) on a managed high-order floodplain. We hypothesized that the New Mexico meadow jumping mouse is a habitat specialist that might rely on specific habitat components at multiple spatial scales. The study occurred at Bosque del Apache National Wildlife Refuge, New Mexico. In comparison with the status of the species 2 decades ago, the New Mexico meadow jumping mouse was rare, with only 29 individuals captured. Trapping results and radiotelemetry of 20 individuals revealed that the current population existed along 2.7 km of a single irrigation canal. At the landscape scale, the distribution of the New Mexico meadow jumping mouse was determined by selection of canals, water, foxtail barley Hordeum jubatum herbaceous temporarily flooded association, and narrowleaf willow Salix exigua mesic graminoids shrubland association. At the macrohabitat scale, jumping mice selected canals and Hordeum jubatum herbaceous temporarily flooded association. At the microhabitat scale, jumping mice selected areas that were near water and contained moist soils, dense herbaceous canopy cover, dogbane Apocynum cannabinum, foxtail barley, and common threesquare Schoenoplectus pungens; jumping mice avoided habitats represented by eight plant species, including mule-fat Baccharis salicifolia, kochia Bassia scoparia, and saltcedar Tamarix ramosissima. Jumping mice only occurred where there is an overlap of the required habitats at all three scales and this may be a key limiting factor for the New Mexico meadow jumping mice at Bosque del Apache National Wildlife Refuge. Habitats used by jumping mice during maternal nesting and hibernation contained more woody plants and woody debris than at other times of their life cycle. Information gained from this study can help land managers protect and create habitat conditions required by the New Mexico meadow jumping mouse.

Herbeal Feeding Behavior of the New Mexico Meadow Jumping Mouse (Zapus hudsonius luteus)

Abstract. We report the first observations of feeding behavior by free-ranging New Mexico meadow jumping mice (Zapus hudsonius luteus). We made observations during a radiotelemetry study of Z. h. luteus in the floodplain of the Rio Grande at Bosque del Apache National Wildlife Refuge, Socorro Co., New Mexico, in 2009 and 2010. We observed Z. h. luteus eat the achenes or seeds of the order Cyperales: common threesquare (Schoenoplectus pungens), spikerush (Eleocharis spp.), saltgrass (Distichlis spicata), foxtail barley (Hordeum jubatum), Saunder's wildrye (Elymus saundersii), Japanese brome (Bromus japonicus), slender wheatgrass (Elymus trachycaulus), and knotgrass (Paspalum distichum). Mice frequently foraged 0.5–1 m above the ground in the canopy of herbaceous vegetation. Seed heads for consumption were harvested in several ways.

Using a temporal symmetry model to assess population change and recruitment in the Preble's meadow jumping mouse (Zapus hudsonius preblei)

The Preble’s meadow jumping mouse (Zapus hudsonius preblei [PMJM]) is a rare rodent of southeastern Wyoming and central Colorado that has been the center of debates regarding subspecies’ genetic identity and the application of the Endangered Species Act. I analyzed a 7-year PMJM mark–recapture data set using a temporal symmetry model (Pradel model) to estimate apparent survival (u), recruitment ( f ), population change (k), and vital rate influence on k. Deer mouse (Peromyscus maniculatus) captures depressed u, suggesting that competition for resources may decrease PMJM survival. Vole-mediated habitat changes or voles’ affinity for quality riparian habitats may explain why PMJM u and f increased with meadow vole (Microtus pennsylvanicus) captures. Based on early-summer and late-summer sampling from 2000 to 2006, k estimates were 0.87 6 0.06 SE and 0.87 6 0.11 SE, respectively, and f had a greater influence on k than did u. This PMJM population is losing connectivity to eastern, northern, and southern tributaries from habitat degradation and storm-water and municipal runoff erosion. The loss of the adjoining habitat and the PMJMs that were supported by this habitat prevents new recruitment via immigration. Because of the importance of recruitment to PMJM population stability, tributaries and the riparian habitat along these tributaries are vital to PMJM conservation. Scaleappropriate habitat sampling, assessments of reproductive success, and detailed demographic studies to estimate vital demographic parameters will help identify how particular habitat components impact fecundity and immigration.

Evidence for an Historical Occurrence of the Meadow Jumping Mouse (Zapus Hudsonius Luteus) in the Verde River Watershed, Arizona

The meadow jumping mouse (Zapus hudsonius luteus) is a riparian obligate with a fragmented distribution in the American Southwest. Because of recent rapid declines in populations, it is a candidate for federal protection under the Endangered Species Act. In Arizona, its known distribution has been restricted to the White Mountains region in the east central part of the state. I present evidence for an historical occurrence of jumping mice in the Verde River watershed, Yavapai County, in west central Arizona. Evidence includes record of a specimen collected by Edgar Mearns in the 1880s, a 1944 report of parasites collected from jumping mice in Yavapai County, and a phylogeographic history that is consistent with an occurrence in the region, including an ecological niche model that predicted suitable conditions for Z. h. luteus in the upper Verde River watershed during the last glacial maximum. Field surveys should be conducted to determine if Z. h. luteus currently exists within the Verde River watershed.

Spatial, temporal, and biological factors associated with Preble's meadow jumping mouse (Zapus hudsonius preblei) home range

Knowledge of animal movement is fundamental to several biological disciplines, including wildlife conservation, yet animal movement remains one of the least understood behaviors and is critical for establishing and implementing effective management strategies. Thus, our goal was to compare the spatial, temporal, and biological factors that may influence the home ranges of Preble’s meadow jumping mouse (Zapus hudsonius preblei), a federally threatened subspecies with relatively little known about its movement behavior. We radiotracked 187 individuals for 3 monthly sessions from 1998 to 2002 at 3 sites with varying hydrologic and vegetation characteristics in Colorado. A nonparametric kernel home-range estimator, local convex hull (LoCoH), was applied to estimate 50% and 95% home-range sizes for each individual. The 50% home ranges varied by session, site, and annual precipitation (P , 0.05). The broader, 95% home ranges were influenced by session and sex (P , 0.001) and slightly influenced by year. The 95% home ranges for males (X ¯ 5 6,342 m 2 , SE 5 520 m 2 ) were greater than for females (X ¯ 5 4,026 m 2 , SE 5 358 m 2 ). Individuals located at the site with the widest 100-year floodplain used twice the area compared to those at the 2 narrower 100-year floodplain sites. This information improves our ability to design management strategies to conserve and restore populations of Z. h. preblei by increasing our understanding of how biological, spatial, temporal, and environmental factors may influence movement patterns and ultimately persistence of this subspecies.

Effects of disturbance on small mammal community structure in the New Jersey Pinelands, USA

We compared small mammal community composition among undisturbed habitats and habitats disturbed by military operations on Warren Grove Gunnery Range (WGR) in the New Jersey Pinelands. WGR is one of the largest tracts of protected land within this globally rare ecosystem. Disturbance in the form of fire, mowing, soil disruption and logging has had a large effect on small mammal occurrence and distribution. Of the 14 small mammal species that occur in the Pinelands, 9 live on WGR, including large populations of the southern bog lemming (Synaptomys cooperi Baird, 1858) and meadow jumping mouse [Zapus hudsonius (Zimmermann, 1780)]. Simpson's Index of Diversity was 0 for most disturbed sites and was generally greater in wetlands than in uplands. White-footed mouse [Peromyscus leucopus (Rafinesque, 1818)] was the most common species on WGR and had a dominant effect on species diversity and community similarity indices. It dominated upland habitats and was the only species to occur in several disturbed habitats, whereas all 9 species occurred in wetlands. Principal components analysis indicated that most variation in species diversity was explained by disturbance and differences between upland and wetland habitats, due to presence of white-footed mice in disturbed and upland sites. Meadow jumping mice, southern bog lemmings and red-back voles [Myodes gapperi (Vigors, 1830)] were positively correlated with wetland habitats, and pine voles [Microtus pinetorum (Le Conte, 1830)], short-tail shrews [Blarina brevicauda (Say, 1823)] and eastern chipmunks [Tamias striatus (Linnaeus, 1758)] were associated with uplands. Habitat heterogeneity at WGR, including extensive undisturbed wetlands and uplands supported a rich diversity of small mammal species.

Spatial distribution of meadow jumping mice ( Zapus hudsonius) in logged boreal forest of northwestern Canada

Most studies of small mammal responses to habitat alterations focus on dominant species, with a resulting lack of information for rare species. Jumping mice (Order Rodentia: Dipodidae) tend to be rare in small mammal trapping studies; thus, little is known of their response to habitat alterations, such as clear-cut logging. We examined the spatial distribution of meadow jumping mice ( Zapus hudsonius) captured in 3 upland habitat types (forest interior, forest edge, and logged forest) in the boreal forest of southeastern Yukon, Canada. Meadow jumping mice were the third most common rodent captured, and consistently constituted 19.7% of captures in all of the habitat types. Meadow jumping mice may not be rare in some boreal mammal assemblages. Significantly less animals were captured in the forest interior compared to the forest edge or logged forest ( P < 0.05). A preference or avoidance of sharp habitat edges created by logging was not detected. Logged areas may be more preferred over unlogged areas by meadow jumping mice because they provide relatively diverse and abundant food resources and cover. To provide data more useful for biodiversity conservation, we suggest that studies of small mammals in forest ecosystems deploy a variety of trap types and sample at sufficient intensity to provide information on both dominant and rare species.

The Meadow Jumping Mouse on Konza Prairie Biological Station, Kansas

We report specific locations, habitat associations and attributes of meadow jumping mice (Zapus hudsonius) captured over a 28-year period on the Konza Prairie Biological Station, Kansas. We used large Sherman live traps to survey small mammals in native tallgrass prairie habitats (by traplines and grids), woodland habitats (by traplines and grids) and planted brome fields (traplines only). Fifteen meadow jumping mice were captured over the 28 years of surveys (a total of >300,000 trap nights). Nine males and six females were captured between late June and October; only a single male was scrotal and no females were visibly reproductively active. Furthermore, meadow jumping mice were from young adult-to-adult body size (13.5–21.0 g), except for a 9.5 g male trapped in mid-October. In terms of habitat association, more meadow jumping mice were captured in woodland habitats than in native prairie (standardized to trapping efforts in each habitat). No jumping mice were captured in brome fields. We conclude tha...

Multiscale Perspectives on Occupancy of Meadow Jumping Mice in Landscapes Dominated by Agriculture

Abstract Previous studies of distribution and habitat use by meadow jumping mice (Zapus hudsonius) have focused on local habitat associations. Our objectives were to predict occupancy of meadow jumping mice and identify local-, patch-, and landscape-specific factors correlated with the species' occurrence. We livetrapped for 5 consecutive days at each of 922 sites during summers of 2001–2003 in thirty-five 23-km2 landscapes located across the upper Wabash River basin, Indiana. At 474 of these sites (300 forest and 174 grassland), we measured local habitat variables and computed metrics of patch size, shape, and isolation. Meadow jumping mice were captured 242 times at 69 of the 474 sites. The species did not associate with grassland habitat more frequently than forest habitat and was slightly more likely to be captured in forested corridors than in forest patches. Occupancy models fitted separately for grassland and forest sites revealed positive effects of stem density <1 m (forest) and 1–2 m (grassland)...

Decline of the Meadow Jumping Mouse (Zapus hudsonius luteus) in two Mountain Ranges in New Mexico

The New Mexico meadow jumping mouse (Zapus hudsonius luteus) is endemic to riparian habitats in the American Southwest. We evaluated current status and habitat of this species in the Jemez and Sacramento mountains, New Mexico. We compiled historical capture localities and conducted field surveys at historical and potential new localities during 2005 and 2006. We did not find the species or its habitat at 73% of historical localities surveyed in the Jemez Mountains and 94% of historical localities surveyed in the Sacramento Mountains. It persisted in two drainages (five localities) in the Jemez Mountains and two small, isolated localities in the Sacramento Mountains. Zapus h. luteus was associated with tall, dense, herbaceous riparian vegetation, especially areas dominated by sedges. The lower bound to the 95% confidence interval for vertical cover at localities where Z. h. luteus was captured was 63 cm. Decline in distribution was due to loss of this habitat, primarily as a result of livestock grazing. However, drought, development, recreation, forest fire, and loss of the American beaver (Castor canadensis) also contributed. We recommend that conservation of Z. h. luteus will require establishment of refugial areas of suitable habitat through protection from livestock grazing.

Body Mass and Winter Severity as Predictors of Overwinter Survival in Preble's Meadow Jumping Mouse

Meadow jumping mice (Zapus hudsonius) reduce their metabolism substantially during hibernation and use stored fat reserves for overwinter energy needs. Preble’s meadow jumping mouse (Z. h. preblei; PMJM) occurs along the Front Range of Colorado, north into southeastern Wyoming, and is listed as a threatened species under the Endangered Species Act because of the conversion and degradation of riparian habitats. To better understand how increasing fat and body mass before hibernation impact overwinter survival, we conducted a mark–recapture study of PMJM at the United States Air Force Academy, El Paso County, Colorado. We used environmental covariates and individual covariates, such as body mass and fat mass, to improve survival estimates. Overwinter survival of female PMJM was higher during long, cold winters, whereas overwinter survival of males was lower during winters with much snowfall. For both sexes, heavier individuals had higher overwinter survival. A combination of large body mass and colder winters may allow PMJM to conserve valuable fat resources. Because periodic arousal from hibernation is the most energetically expensive activity over winter, increasing body size (reducing surface area-to-volume ratio) should increase energy conservation and probability of survival.