Neotoma Cinerea Research Articles

Geographic and taxonomic variation in adaptive capacity among mountain-dwelling small mammals: Implications for conservation status and actions

Contemporary climate change is modifying the distribution, morphology, phenology, physiology, evolution, and interspecific interactions of species. Effects of climate change are mediated not only through the magnitude of change experienced (exposure) and an animal's sensitivity to such changes, but also through the ability of the population or species to adjust to climatic variability and change genetically, behaviorally, or spatially (via its distribution) (i.e., adaptive capacity; AC). Here, we used an attribute-based framework to systematically evaluate and compare the AC of American pikas (Ochotona princeps) against four other mountain-dwelling small mammals of North America to determine whether pikas are disproportionately vulnerable to climate change, as has been postulated. Unlike previous analyses, we also compared AC across O. princeps lineages and across three taxonomic (and thus, spatial) scales. Our results indicate that pikas have markedly lower adaptive capacity than all compared species except bushy-tailed woodrats (Neotoma cinerea), and that our assessments of species generally align with earlier characterizations of climate-change vulnerability based on life-history characteristics. Although AC did not differ dramatically among pika lineages, some attributes are likely constraining AC differently in various parts of the geographic range. Comparisons across taxonomic levels of pikas illustrated that, although AC levels were comparable in pika lineages versus range-wide, AC was assessed as lower in interior-Great-Basin pikas than across the entire O.p. schisticeps lineage. We conclude that the comparatively lower AC of pikas results in particularly high susceptibility to anthropogenic climate change, corroborating results from numerous other recent investigations of pikas' climate-responsiveness. Adaptive-capacity evaluations appear useful as a consistent way to identify sentinel species or populations and for conservation prioritization.

Small mammal relative abundance within riparian ecosystems of the Blue Mountains

There is a growing interest and investment in restoring riparian areas in the Pacific Northwest to protect biodiversity and water quality, and to restore quality habitat for threatened fish species. However, these management activities change vegetation conditions and potentially impact terrestrial species in these ecosystems. Our objective was to estimate associations between small mammals and 4 broad cover types—conifers, shrubs, grasses, and forbs—in riparian areas within the Blue Mountains of northeast Oregon, USA. We estimated abundances and spatial association for 10 small mammal species using a multispecies hierarchical abundance model and mark-recapture data collected on 36 sites from 2014 to 2017. We predicted that forest-associated species would be more abundant with greater conifer cover, that increases in shrub cover would favor most species, and that increases in grass and forb cover would favor grassland-associated species. Yellow-pine chipmunks (Tamias amoenus) were positively associated with conifer cover, while long-tailed voles (Microtus longicaudus) and montane voles (Microtus montanus) were negatively associated with conifer cover. Associations with shrub cover were positive for bushy-tailed woodrats (Neotoma cinerea), deer mice (Peromyscus maniculatus), and yellow-pine chipmunks, but negative for montane voles. Bushy-tailed woodrats and montane voles were negatively associated with grass cover. This study is the first to characterize the riparian small mammal communities in this region and provides insights on the effects of restoration activities on riparian ecosystems in dry interior forests and grasslands. We suggest that riparian plantings, a ubiquitous restoration practice, will increase the relative abundances for some, but not all, small mammal species. We also demonstrate use of a new multi-species abundance model that can be a powerful tool for analyzing mark-recapture data because it allowed us to extend the scope of our analysis to data poor species by pooling information with data rich species.

Peridomestic Mammal Susceptibility to Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Wild animals have been implicated as the origin of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but it is largely unknown how the virus affects most wildlife species and if wildlife could ultimately serve as a reservoir for maintaining the virus outside the human population. We show that several common peridomestic species, including deer mice, bushy-tailed woodrats, and striped skunks, are susceptible to infection and can shed the virus in respiratory secretions. In contrast, we demonstrate that cottontail rabbits, fox squirrels, Wyoming ground squirrels, black-tailed prairie dogs, house mice, and racoons are not susceptible to SARS-CoV-2 infection. Our results expand the knowledge base of susceptible species and provide evidence that human–wildlife interactions could result in continued transmission of SARS-CoV-2.

The relationship between molar morphology and ecology withinNeotoma

AbstractThe extensive diversity in dental form across mammals and its strong relationship with function provides insights into the diet, habitat, and behavior, of both extant and extinct taxa. Understanding the extent of variation in dental morphology across species allows for more accurate identification of fossils and a better ability to infer relationships between form and function and ecology. We examined variation in the size and shape of the first upper molar among the genus Neotoma. We employed elliptical Fourier analysis to quantify differences in the shape of 2D outlines for 23 populations and six species of Neotoma, varying in body size and habitat preference. As expected, molar length is a strong predictor of body size and is significantly and negatively correlated with temperature, particularly in species whose ranges span large latitudinal gradients. We found that differences in molar shape separate species into three general morpho-groups, with no evidence of a phylogenetic signal. While outline analysis could not robustly classify all molars to the species level, it did perform well for Neotoma cinerea, probably because of the greater degree of folding and more acute angling of molar lophs. In contrast, wider lophs with shallower enamel infolding was characteristic of species specializing on softer, more succulent resources (i.e., Neotoma albigula and Neotoma micropus). Neotoma floridana were inaccurately classified to species in the majority of cases, but were the only molars correctly identified to locality 100% of the time, suggesting that dietary specializations at a local level may drive morphological changes within the species as well as across the genus.

Investigating (a)symmetry in a small mammal's response to warming and cooling events across western North America over the late Quaternary

AbstractMany mammalian populations conform spatially and temporally to Bergmann's rule. This ecogeographic pattern is driven by selection for larger body masses by cooler temperatures and smaller ones by warming temperatures. However, it is unclear whether the response to warming or cooling temperatures is (a)symmetrical. Studies of the evolutionary record suggest that mammals evolve smaller body sizes more rapidly than larger ones, suggesting that it may be “easier” to adapt to warming climates than cooling ones. Here, we examine the potential asymmetrical response of mammals to past temperature fluctuations. We use the fossil midden record of the bushy-tailed woodrat, Neotoma cinerea, a well-studied animal that generally conforms to Bergmann's rule, to test the ability of populations to respond to warming versus cooling climate throughout its modern range in western North America over the late Quaternary. We quantified the response to temperature change, as characterized by the Greenland Ice Sheet Project 2 temperature record, using N. cinerea presence/absence and “darwins.” Our results show that populations within the modern range of N. cinerea show little difference between warming and cooling events. However, northern, peripheral populations are absent during older, cooler periods, possibly due to climate or taphonomy. Our study suggests adaptation in situ may be an underestimated response to future climate change.

A winter energetics model for bobcats in a deep snow environment

Understanding basic energetic requirements of wildlife species is critical to evaluate how individuals persist in their current environments as well as to forecast responses to changed climates or habitats. Indeed, northern range limits are often thought to reflect harsh abiotic conditions that exceed the capacity of individuals to stay in energetic balance. Bobcats (Lynx rufus) occur across much of North America; at northern latitudes, they face winter challenges such as deep snows, cold temperatures, and possible food scarcity. We developed an energetics model from field data on movements, body mass, and observed diet of bobcats in mountains of northwest Montana, then evaluated overwinter prey requirements that would enable bobcats to stay in energy balance in this difficult environment. Our model indicated average daily energy expenditures were ~ 1.41× basal metabolic rate. For 90 days from December to February, a 10.5 kg bobcat consuming prey items in proportion with the observed diet for bobcats in this area would need about 2.1 kg of deer (Odocoileus spp.), 7 snowshoe hares (Lepus americanus), 155 red squirrels (Tamiasciurus hudsonicus), 9 woodrats (Neotoma cinerea), and 250 small rodents (Cricetidae). Bobcats have considerable flexibility in diet, movements, and both timing and duration of daily activity to adjust their energetic expenditures in winter.

Ancient DNA provides evidence of 27,000-year-old papillomavirus infection and long-term codivergence with rodents.

The long-term evolutionary history of many viral lineages is poorly understood. Novel sources of ancient DNA combined with phylogenetic analyses can provide insight into the time scale of virus evolution. Here we report viral sequences from ancient North American packrat middens. We screened samples up to 27,000-years old and found evidence of papillomavirus (PV) infection in Neotoma cinerea (Bushy-tailed packrat). Phylogenetic analysis placed the PV sequences in a clade with other previously published PV sequences isolated from rodents. Concordance between the host and virus tree topologies along with a correlation in branch lengths suggests a shared evolutionary history between rodents and PVs. Based on host divergence times, PVs have likely been circulating in rodents for at least 17 million years. These results have implications for our understanding of PV evolution and for further research with ancient DNA from Neotoma middens.

A review of the flea genus Phalacropsylla Rothschild, 1915 (Siphonaptera, Ctenophthalmidae, Neopsyllinae, Phalacropsyllini) with new host and distributional records.

A redescription of the genus Phalacropsylla Rothschild is provided. Six species are recognized: Phalacropsylla allos Wagner, P. hamata Tipton and Mendez, P. morlani Eads and Campos, P. nivalis Barrera and Traub, P. oregonensis Lewis and Maser, and P. paradisea Rothschild. Phalacropsylla hamata is designated herein as a junior synonym of P. paradisea. The distribution of P. paradisea is more extensive than previously thought, extending from Arizona through southern Colorado, into New Mexico, Texas, and northern Mexico (State of Nuevo León). It is the least host-specific of all species of Phalacropsylla, occurring on 13 different host species including cricetid, heteromyid, murid, and sciurid rodents and several carnivores, although it most commonly occurs on Neotoma albigula Hartley. The range of P. oregonensis is expanded from eastern Oregon to southeastern Idaho. Numerous records are documented for the most common and ubiquitous species, P. allos, which is found in British Columbia, central to northern California, Idaho, Montana, Colorado, Nevada, Utah, Wyoming, Arizona, and New Mexico. Neotoma cinerea Ord is the principal host of P. allos. Phalacropsylla allos is a winter flea west of the Rocky Mountains, but it has been reported in warmer months of the year on the eastern slopes of the Rocky Mountains in Larimer County, Colorado. A distribution map and key are provided for all species in the genus Phalacropsylla.

The Mescal Cave Fauna (San Bernardino County, California) and testing assumptions of habitat fidelity in the Quaternary fossil record

The late Pleistocene and Holocene vertebrate fossil record for the northern Mojave Desert (southwestern USA) is known primarily from five sites. Until now, only two of these have been radiometrically dated, and temporal placement of the others has been based on stratigraphic or biostratigraphic correlation, leading to circular interpretations of mammal extirpations in the Mojave. Here, I report a revised and complete faunal list for Mescal Cave, along with 22 AMS radiocarbon dates from 5 vertebrate taxa recovered from its deposits. The results reported here demonstrate time-averaging in Mescal Cave encompassing around ~34ka, a maximum age 14ka older and minimum age 10ka younger than previously thought. Furthermore, radiocarbon analyses suggest local extirpation of Marmota flaviventris around 3.6calka BP, considerably younger than expected based on regional patterns of warming and aridification in the Mojave. Conversely, radiocarbon dates from another presumably boreal species, Neotoma cinerea, are considerably older than expected, suggesting either that climate change at this site did not directly mirror regional patterns, that habitat requirements for these two species are not strictly boreal or cool/mesic as has often been assumed, or that local edaphic conditions and/or competitive interactions overrode the regional climatic controls on theses species' distribution.

Patterns of Evolutionary Divergence and Convergence in the Bushy-Tailed Woodrat (Neotoma cinerea) Across Western North America

The degree of concordance between patterns of divergence in genetic and morphological characters provides insight into the process of evolutionary diversification. We analyzed species-wide morphological variation in a broadly distributed species of small mammal, the bushy-tailed woodrat (Neotoma cinerea), for comparison against a recently developed mitochondrial phylogeny. We focused our analyses on patterns of qualitative and quantitative craniodental morphological variation throughout the distribution of this taxon. We found strong concordance between the morphology of one prominent craniodental feature (sphenopalatine vacuity) and the major mitochondrial lineages, but only minimal differentiation in overall morphometric variation between these clades. Further, in contrast to the largely east–west subdivision of mitochondrial and sphenopalatine vacuity variation, cluster analyses of morphometric variation revealed a north–south morphological subdivision irrespective of mitochondrial clade. Our combined character sets are best explained by a deep history of evolutionary divergence within this taxon accompanied or followed by broad-scale convergent or parallel evolution.

The Bonneville Estates Rockshelter rodent fauna and changes in Late Pleistocene–Middle Holocene climates and biogeography in the Northern Bonneville Basin, USA

Excavations at Bonneville Estates Rockshelter, Nevada recovered rodent remains from stratified deposits spanning the past ca. 12,50014CyrBP (14,800calyrBP). Specimens from horizons dating to the late Pleistocene and early Holocene include species adapted to montane and moist and cool habitats, including yellow-bellied marmot (Marmota flaviventris) and bushy-tailed woodrat (Neotoma cinerea). Shortly after 900014CBP (10,200calyrBP) these mammals became locally extinct, or nearly so, taxonomic diversity declined, and the region became dominated by desert woodrats (Neotoma lepida) and other species well-adapted to xeric, low-elevation settings. The timing and nature of changes in the Bonneville Estates rodent fauna are similar to records reported from nearby Homestead and Camels Back caves and provide corroborative data on terminal Pleistocene–early Holocene environments and mammalian responses to middle Holocene desertification. Moreover, the presence of northern pocket gopher (Thomomys talpoides) at Bonneville Estates adds to a sparse regional record for that species and, similar to Homestead Cave, it appears that the ca. 950014CyrBP (10,800calyrBP) replacement of the northern pocket gopher by Botta's pocket gopher in the Great Salt Lake Desert vicinity was also in response to climate change.

Stable isotopes reflect the ecological stability of two high-elevation mammals from the late Quaternary of Colorado

The vertebrate fossil record of Cement Creek Cave, Colorado, spans from >45,000yr ago to the present and represents the richest stratified series of high-elevation (>2900m) mammal remains known from the late Quaternary of North America. Stable carbon and oxygen isotope analyses of tooth enamel were used to assess potential ecological responses of two species found commonly throughout the cave, Yellow-bellied marmots (Marmota flaviventris) and Bushy-tailed woodrats (Neotoma cinerea), to late Quaternary climate and environmental changes of the Southern Rocky Mountains. Results indicate that despite such perturbations, the dietary ecologies of both species were maintained across this period. Neither taxon shifted to consuming C4 taxa or different C3 functional groups; similarly, no significant shifts in surface water use were detected. Variations in enamel δ13C were observed, however, that represent the physiological responses of high-elevation plants to changing levels of late Quaternary atmospheric CO2. While our findings extend both the geographic and elevational record of this plant CO2 response, they simultaneously highlight the ecological stability of high-elevation M. flaviventris and N. cinerea during climate changes of late Quaternary magnitude.

From Desert to Rainforest: Phenotypic Variation in Functionally Important Traits of Bushy-Tailed Woodrats (Neotoma cinerea) Across Two Climatic Extremes

Changes in body size inversely related to ambient temperatures have been described in woodrats (Neotoma) over time scales ranging from decades to millennia. However, climate-mediated variation in other traits has not been evaluated, and the effects of precipitation have been overlooked. We assessed variation in skull morphology among bushy-tailed woodrats (Neotoma cinerea) over two sampling transects spanning coastal rainforest and interior desert environments to determine whether skull morphology varied with climate. We also tested whether previously described size-temperature relationships could be generalized to our study populations. In both transects, linear measurements of functionally significant traits differed between coastal and interior populations. Geometric morphometric analyses of shape confirmed some of those differences and revealed additional patterns of skull variation. Variation in some linear measurements, including body size, was predicted by climate. However, body and skull size, as well as measurements of skull components, displayed varying responses. Although longitudinal patterns of body size variation supported Bergmann’s rule, skull size variation was only weakly associated with climate. The strongest phenotypic responses to climate were those of auditory, dental, and palatal skull traits. Altogether, our findings suggest that geographic variation in temperature and precipitation mediated selective heterogeneity and plasticity in skull traits associated with food processing and sensory organs in N. cinerea. This was consistent with our expectation of resource-dependent phenotypic variation among populations in environments with highly contrasting climatic regimes.

Differential regional response of the bushy‐tailed woodrat (Neotoma cinerea) to late Quaternary climate change

AbstractAim To reconstruct the regional biogeographical history of the bushy‐tailed woodrat, Neotoma cinerea (Rodentia: Cricetidae), across its distribution using multiple sources of information, including genetic data, ecological niche models and the palaeorecord.Location Western North America.Methods We analysed complete cytochrome b gene (1143 bp) sequences from 182 specimens of N. cinerea using Bayesian and coalescent methods to infer phylogenetic relationships, time of major divergences, and recent demographic trends. For comparison, we developed clade‐specific ecological niche models for groups of interest and analysed spatial trends of N. cinerea in the palaeorecord as well as temporal frequency trends across strata of individual palaeomiddens.Results We found two largely allopatric clades within N. cinerea, with several regionally distinct subclades showing contrasting recent population dynamics. Niche models showed consistent habitat at the Last Glacial Maximum (LGM) and modern times in the Rocky Mountains and northern United States, while the Great Basin may have been markedly less suitable at the LGM than today. The palaeorecord showed great spatio‐temporal variability in the presence of N. cinerea, but documents broad‐scale patterns of occupancy and regional population trends.Main conclusions The Quaternary dynamics and evolutionary history of N. cinerea appear to have been shaped by both vicariant events associated with geographical barriers and the availability of suitable habitat through time. Divergence of the two major clades dates to the Pliocene–Pleistocene transition, with clades separated by the Green and Colorado rivers and northern Rocky Mountain Pleistocene glaciations. We found largely concordant genetic, niche model and palaeorecord patterns suggesting long‐term population stability in the Rocky Mountains, while extant clades in the Great Basin and far north appear to have expanded or re‐expanded into these regions relatively recently. Furthermore, disjunct haplotype distributions, regional demographic history, and historical distribution of suitable habitat suggest that the Great Basin has been a particularly dynamic region.

A tale of two species: Extirpation and range expansion during the late Quaternary in an extreme environment

Death Valley, California is today the hottest hyperarid area in the western Hemisphere with temperatures of 57 °C (134 °F) recorded. During the late Quaternary, pluvial Lake Manly covered much of the Valley and contributed to a much more moderate climate. The abrupt draining of Lake Manly in the mid-Holocene and coincident dramatic shifts in temperature and aridity exerted substantial selection pressure on organisms living in this area. Our research investigates the adaptive response of Neotoma (woodrats) to temperature change over the late Quaternary along a steep elevational and environmental gradient. By combining fieldwork, examination of museum specimens, and collection of paleomiddens, our project reconstructs the divergent evolutionary histories of animals from the valley floor and nearby mountain gradients (− 84 to > 3400 m). We report on recent paleomidden work investigating a transition zone in the Grapevine Mountains (Amargosa Range) for two species of woodrats differing significantly in size and habitat preferences: N. lepida, the desert woodrat, and N. cinerea, the bushy-tailed woodrat. Here, at the limits of these species' thermal and ecological thresholds, we demonstrate dramatic fluctuations in the range boundaries over the Holocene as climate shifted. Moreover, we find fundamental differences in the adaptive response of these two species related to the elevation of the site and local microclimate. Results indicate that although N. cinerea are currently extirpated in this area, they were ubiquitous throughout the late Pleistocene and into the middle Holocene. They adapted to climate shifts over this period by phenotypic changes in body mass, as has been demonstrated for other areas within their range; during colder episodes they were larger, and during warmer intervals, animals were smaller. Their presence may have been tied into a much more widespread historical distribution of juniper ( Juniperus sp.); we document a downward displacement of approximately 1000 m relative to juniper's modern extent in the Amargosa Range. These results suggest a cooler and more mesic habitat association persisting for longer and at lower elevations than previously reported.

Small‐Mammal Microhabitat Associations and Response to Grazing in Oregon

Abstract: Livestock grazing is common and widespread throughout North America, yet few studies have evaluated its effects on small mammals. We studied small mammals in mixed‐conifer forests and oak woodlands on the Cascade‐Siskiyou National Monument in southern Oregon, USA, to 1) evaluate small‐mammal microhabitat associations, 2) identify riparian‐associated species, and 3) test the hypothesis that grazing does not influence small mammals after accounting for microhabitat associations. We live‐trapped small mammals at 16 study sites and used logistic regression to model probability of capture on measured habitat characteristics at each trap station and to evaluate effects of grazing. Over 2 years, we trapped 1,270 individual small mammals representing 18 species. Odds of capturing western harvest mice (Reithrodontomys megalotis), dusky‐footed woodrats (Neotoma fuscipes), and long‐tailed voles (Microtus longicaudus) were lower (P < 0.05) on heavily versus lightly grazed sites. Odds of capture for deer mice (Peromyscus maniculatus) were lower (P < 0.05) on heavily versus lightly grazed sites in woodlands, but there was less difference in the odds of capture between grazing intensities in conifer forests. Odds of capturing Townsend's vole (Microtus townsendii) were lower on heavily versus lightly grazed riparian areas. Western harvest mice, long‐tailed voles, and Townsend's voles were associated with, but not obligated to, riparian areas. Deer mice were ubiquitous, but captures were also higher (P < 0.05) in riparian areas compared with uplands. Siskiyou chipmunks (Tamias siskiyou) and piñon mice (Peromyscus truei) were associated with uplands (P < 0.05) rather than riparian areas. Trowbridge's shrews (Sorex trowbridgii), Siskiyou chipmunks, and bushy‐tailed woodrats (Neotoma cinerea) were positively associated with coarse woody debris. Land managers should anticipate that small mammals associated with herbaceous or shrub cover, particularly in riparian areas, will decline when cattle remove this cover.

Range Extension of the Northern Long-eared Bat (Myotis septentrionalis) in the Yukon

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Haying Behavior in a Rodent, the Bushy-tailed Woodrat (Neotoma cinerea)

Haying Behavior in a Rodent, the Bushy-tailed Woodrat (Neotoma cinerea)

Pollen, Plant Macrofossils, and Insects from Fossil Woodrat (Neotoma Cinerea) Middens in British Columbia

Bushy-tailed woodrats (Neotoma cinerea) occur commonly in cliffs, rock talus, and caves in the open Pseudotsuga menziesii and Pinus ponderosa forests throughout interior British Columbia. Fossil N. cinerea middens from two sites in central British Columbia were radiocarbon dated and examined for pollen, plant macrofossils and insect remains. The Oregon Jack Creek site contains a midden that is dated 1150 ± 80 (WAT-1764) radiocarbon years ago. Pollen analyses reveal an abundance of Cupressaceae (Juniperus) and Pinus. Shrub and herb pollen types include Artemisia. Fabaceae, Poaceae, and Asteraceae. Juniperus scopulorum leaves, Pseudotsuga menziesii needles, Chenopodiaceae seeds. Rosa thorns and Artemisia leaflets are the main plant macrofossils. The remains of three beetle genera, Cryptophagus, Lathridius, and Enicmus represent insects that probably lived in the midden, eating decaying organic matter or moulds. Click beetle (Limonius) remains were probably brought into the midden from nearby soil or plant material. The Bull Canyon site contains a midden that dates to 700 ± 80 (WAT-1765) years BP. Pollen and plant macrofossil assemblages are similar to those at the Oregon Jack Creek site. Woodrat middens offer a new dimension in reconstructing Holocene paleoenvironments in the arid interior of British Columbia, in much the same way as they do in the southwest United States.

Effects of a stand-replacing fire on small-mammal communities in montane forest

Wildfire, ubiquitous and recurring over thousands of years, is the most important natural disturbance in northern coniferous forest. Accordingly, forest fires may exert a strong influence on the structure and functioning of small-mammal communities. We compared the composition of rodent and shrew communities in burned and unburned patches of a Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco) – western larch ( Larix occidentalis Nutt.) forest in western Montana, USA. Trapping was conducted during two consecutive summers after a wildfire. Four trapping sites were sampled in areas that burned at high severity and two in unburned forest. Small-mammal communities in burned sites were characterized by strong numerical dominance of deer mice ( Peromyscus maniculatus (Wagner, 1845)) and greatly reduced proportion of southern red-backed voles ( Clethrionomys gapperi (Vigors, 1830)) and red-toothed shrews (genus Sorex L., 1758). Relatively rare species such as northern flying squirrels ( Glaucomys sabrinus (Shaw, 1801)) and bushy-tailed woodrats ( Neotoma cinerea (Ord, 1815)) were largely restricted to unburned areas. The numbers of chipmunks (genus Tamias Illiger, 1811) were similar in burned and unburned areas. Rodent diversity was higher in unburned forest, but only during the 1st year after fire. Overall, the fire shifted small-mammal communities away from more specialized red-backed voles and shrews and towards greater abundance of generalist deer mice.