Habitat of three rare species of small mammals in juniper woodlands of southwestern Wyoming

Southwestern Wyoming constitutes the northern limit of the ranges of the cliff chipmunk ( Tamias dorsalis ), pinyon mouse ( Peromyscus truei ), and canyon mouse ( P. crinitus ). In addition to trying to determine their presence in the region, we wanted to identify habitat characteristics commonly used by each of these species. We used Sherman live-traps to sample 14 sites representing 2 distinct habitat types in 1998 and 1999: juniper-rocky slopes and juniper cliffs. Seventeen habitat characteristics were measured at capture locations for each species and compared with randomly located points. Best subsets multiple logistic regression was used to construct models that distinguish between used and available habitat for each species. The cliff chipmunk occurred in both rocky slopes and cliffs. The pinyon mouse was also captured in rocky slopes and cliffs and was most often captured in locations in the interior of the juniper woodland with high tree canopy cover, high forb cover, and low density of rock outcrops. The canyon mouse was captured only in cliffs at sites consisting of high forb cover, high rock cover, and high tree density.     

Habitat selection by small mammals in Brazilian Pampas biome

The use of microhabitats by small mammals was investigated in an area of Pampas in southern Brazil. We used 10 transect lines with 12 live-traps during six fieldwork sessions between June 2009 and April 2010. Sixteen environmental variables measured were summarized by a principal component analysis (PCA). Richness, total abundance and abundance of each species captured were correlated with the first two PCA axes. The environmental variables were also correlated with the small-mammal abundance through a canonical correspondence analysis (CCA). The first axis was related to variables that characterize forest environments, such as canopy cover and number of trees, and the second axis (with which the species richness and abundance were associated) was related to water, arthropods and herbaceous vegetation. The CCA and PCA showed a significant effect of microhabitat variables on species occurrence. In view of the great variability of environments in the study area and the correlation of the species with the environment variables measured, the degree of heterogeneity seemed to be an important factor associated with the small-mammal variation among microhabitats.     

Habitat features and predictive habitat modeling for the Colorado chipmunk in southern New Mexico

Two subspecies of Colorado chipmunk (state threatened and federal species of concern) occur in southern New MeXico: Tamias quadrivittatus australis in the Organ Mountains and T. q. oscuraensis in the Oscura Mountains. We developed a GIS model of potentially suitable habitat based on vegetation and elevation features, evaluated site classifications of the GIS model, and determined vegetation and terrain features associated with chipmunk occurrence. We compared GIS model classifications with actual vegetation and elevation features measured at 37 sites. At 60 sites we measured 18 habitat variables regarding slope, aspect, tree species, shrub species, and ground cover. We used logistic regression to analyze habitat variables associated with chipmunk presence/absence. All (100%) 37 sample sites (28 predicted suitable, 9 predicted unsuitable) were classified correctly by the GIS model regarding elevation and vegetation. For 28 sites predicted suitable by the GIS model, 18 sites (64%) appeared visually suitable based on habitat variables selected from logistic regression analyses, of which 10 sites (36%) were specifically predicted as suitable habitat via logistic regression. We detected chipmunks at 70% of sites deemed suitable via the logistic regression models. Shrub cover, tree density, plant proximity, presence of logs, and presence of rock outcrop were retained in the logistic model for the Oscura Mountains; litter, shrub cover, and grass cover were retained in the logistic model for the Organ Mountains. Evaluation of predictive models illustrates the need for multi-stage analyses to best judge performance. Microhabitat analyses indicate prospective needs for different management strategies between the subspecies. Sensitivities of each population of the Colorado chipmunk to natural and prescribed fire suggest that partial burnings of areas inhabited by Colorado chipmunks in southern New Mexico may be beneficial. These partial burnings may later help avoid a fire that could substantially reduce habitat of chipmunks over a mountain range.     

Habitat characteristics of small mammals in southeastern Utah

We describe habitat characteristics of 8 small mammal species occurring in the Manti-LaSal National Forest in southeastern Utah. Thirty-seven grids across 7 vegetation types were sample by live-trapping from May through October 1994 and 1995. Logistic regression models of habitat measurements correctly classified small mammal presence 36%-87% of the time. Except for 1 instance, 4 Peromyscus species present in a specific vegetation type were negatively associated with forb or grass cover. Microtus montanus was present primarily on mesas and was positively associated with tall tree and low shrub cover. Neotoma mexicana was present only in canyons and was found primarily in the pinyon-juniper ( Pinus edulis-Juniperus osteosperma ) vegetation type. Tamias spp. was present in all vegetation types. Our results allow better management of these species by providing greater understanding of their use of habitat within vegetation types.     

There is no valid record of cliff chipmunk ( Tamias dorsalis ) in the Sandia Mountains, New Mexico

In the American Southwest, the red squirrel ( Tamiasciurus hudsonicus ) occurs as disjunct populations in coniferous forests on mountaintops. There is a paucity of information concerning the species’ distribution and habitat in western New Mexico. I report new records that document and verify the occurrence of red squirrels in additional montane areas in west central New Mexico, including the Mangas Mountains, Canovas Rim, Turner Mountain, Tularosa Mountains, Elk Mountains, Bearwallow Mountain, and Pinos Altos Mountains. I also report observations of red squirrels from an atypical habitat—low-elevation riparian forests. These new records suggest that the geographic distribution of the species in west central New Mexico is broader than indicated by existing records. However, I also document the apparent extirpation of red squirrels from the Zuni Mountains in northwestern New Mexico. The red squirrel is one of several avian and mammalian species associated with mixed coniferous forests that have become extirpated in this mountain range.     

Grass spider microhabitat use in Organ Pipe Cactus National Monument, Arizona

The grass spider ( Agelena naevia ), commonly found in Organ Pipe Cactus National Monument, Arizona, uses rodent burrows located under a shrub canopy more frequently for web construction than burrows located in the open. The average number of prey available in canopy microhabitat was greater than in open microhabitat, and unequal prey abundance may explain spider microhabitat use.        

Capture locations of two endangered rodents during a 1902 exploration of the Sacramento Mountains, New Mexico

We investigated localities from which Eutamias atristriatus Bailey, 1913 (= Tamias minimus atristriatus ) and Zapus luteus Miller, 1911 (= Zapus hudsonius luteus ) were collected during a 1902 survey in the Sacramento Mountains, New Mexico, by the United States Biological Survey. The locality from which the holotype of Eutamias atristriatus was collected is restricted to James Canyon rather than the Rio Pe?asco. Locality records indicate that the historical distribution of Zapus hudsonius luteus and its obligate wetland habitat were broader than currently realized.     

Habitat affinities of rodents in northeastern Nevada rangeland communities

From May 1978 through September 1980, baseline data for rodent populations were collected by livetrapping in the Saval Ranch area of northeastern Nevada. The objectives of this study were to determine species composition and relative abundance of rodents for the various range sites. The 3 most abundant and uniformly distributed species were deer mice ( Peromyscus maniculatus ), Great Basin pocket mice ( Perognathus parvus ), and least chipmunks ( Neotamias minimus ). Relative abundance indices and densities reported for most species were similar to those reported in other multiyear studies at similar sites. The composition and relative abundance / density of rodent species was variable among habitats and over time. Diverse rodent species within the sagebrush ecosystem have commensurately diverse habitat requirements that should be considered when vegetation management is planned. Annual population fluctuations and differences among similar habitats should be considered when researchers propose to test rodent population responses to livestock grazing or other habitat treatments.     

Influence of experimental habitat manipulations on a desert rodent population in southern Utah

This paper addresses how habitat manipulations in a black sagebrush ( Artemisia nova ) -dominated area, John's Valley of southern Utah, affected resident desert rodent populations. Rodents studied included the deer mouse ( Peromyscus maniculatus ), Great Basin pocket mouse ( Perognathus parvus ), sagebrush vole ( Lagurus curtatus ), Ord's kangaroo rat ( Dipodomys ordii ), and least chipmunk ( Eutamias minimus ). The experimental design involved analyses of treatment and control (nontreatment) plots rather than pre- and posttreatment of all plots. Habitat manipulations emphasized cutting of shrubs (rotobeating), treatment of plants with a herbicide (2,4-D), and reseeding with a mixture of grasses, forbs, and shrubs. Posttreatment trapping indicated the deer mouse was the most abundant rodent in treatment and control plots. Data indicate the prescribed habitat treatments had no significant negative affects on the deer mouse demes on the control or treatment plots. Habitat treatments may have negatively impacted recruitment in pocket mice. Least chipmunks were not captured in plots treated by rotobeating. Our habitat manipulations may have contributed to interspecific competition in this rodent community through the reduction of both food and cover.     

Winter and early spring bird communites in grasslands, shrubsteppe, and juniper woodlands in central Oregon

We compared winter (December, January, and February) and early spring (March and April) bird communities among 4 successional stages that included grassland, shrubsteppe, juniper-shrubsteppe, and old-growth juniper woodland in central Oregon. Birds were surveyed monthly from December through April in 1998/1999 and 1999/2000 using the point count method to estimate relative abundance of birds (individuals ? transect –1 year –1 ). We used distance sampling to correct for potential bias in estimating abundance and density among successional stages. A total of 4513 birds (32 species) were detected. Relative abundance of total birds (all species combined) was similar in the juniper-shrubsteppe and old-growth woodland (48.7 and 48.9 individuals ? transect –1 , respectively) but 6 times greater than in the grassland and shrubsteppe (8.0 and 7.7 individuals ? transect –1 , respectively) during the 5-month period. Total density of birds was greater in old-growth juniper woodland and juniper-shrubsteppe than in grassland or shrubsteppe. However, median bird species richness in 1998/1999 was highest in grassland and lowest both in shrubsteppe and juniper-shrubsteppe, and in 1999/2000 it was highest in shrubsteppe and lowest in juniper-shrubsteppe and oldgrowth juniper woodland. American Robins and Townsend's Solitaires were the most abundant species in junipershrubsteppe and old-growth juniper woodland during the winter months. Sage Sparrows and Horned Larks were the most abundant species in shrubsteppe during winter, and Horned Larks were most abundant in grasslands during the early spring transition period prior to nesting. Our results indicate that a different suite of species use these successional stages during the nonbreeding season. If avifauna conservation is a part of long-term management goals, a broad range of successional stages should be maintained on the landscape to provide habitat for a variety of avian species throughout the year.     

Winter habitat selection by reintroduced pronghorn on Antelope Island, Great Salt Lake, Utah

The recent and future introduction of several ungulate species on Antelope Island necessitates knowledge of habitat use by each species. In this study habitat preferences reintroduced pronghorn ( Antilocapra americana ) on Antelope Island were evaluated during February-March 1993 and January-March 1994. Elevation, slope, physiography, aspect, and habitat type of sites used by pronghorn were compared to similar data collected from random points. During the severe winter of 1993, pronghorn preferred terrain that was 1281-1380 m in elevation and was relatively flat or at the base of a hill. Slopes greater than 30% were avoided. South-facing slopes were preferred; west-facing slopes were avoided. Pronghorn preferred sagebrush habitats and avoided grasslands. During the mild winter of 1994, pronghorn showed preferences for slightly higher elevations, avoided slopes greater than 30%, but used other habitat features in proportion to their availability. Future winter studies of pronghorn should include considerations of snowfall patterns and the availability, versus the abundance, of sagebrush.     

Rodent populations, biomass, and community relationships in Artemisia tridentata, Rush Valley, Utah

Three desert Artemisia tridentata communities in Rush Valley, Utah, were trapped for small rodents during the summer of 1970, and population densities were estimated for each population category using Lincoln's index. Animals were weighed and rodent biomass calculated by species throughout the summer. Population, biomass, and other data were then analyzed to gain an understanding of the community relationships of the three study areas to each other as well as to the A. tridentata community types of the Great Basin. Peromyscus maniculatus, Eutamias minimus, and Reithrodontomys megalotis were common to area 1, whereas P. maniculatus, E. minimus, and Perognathus parvus were common to areas 2 and 3. The peak estimated standing crops were 182.8 (74.0). 143.1 (57.9), and 129.7 g/acre (52.5 g/ha) for areas 2, 1, and 3 respectively. The population and biomass of area 2 peaked in midsummer, area 1 early summer, and area 3 late summer.     

Physical characteristics of Blue Grouse winter use-trees and roost sites

Physical characteristics of winter use-trees and roost sites of Blue Grouse ( Dendragapus obscurus ) were studied in northeastern Utah. Blue Grouse selectively roosted in the largest Douglas-fir ( Pseudotsuga menziesii ) trees during the day and subalpine fir ( Abies lasiocarpa ) trees at night. Diurnal and nocturnal roosts were typically adjacent to tree trunks in the lower two-thirds of trees. Nocturnal roosts provided greater canopy and denser shelter than diurnal roosts. Roost site selection was consistent with occupation of favorable microhabitat, particularly at night, and foraging strategy during the day. Timber management strategies should perpetuate large trees within Douglas-fir-subalpine fir habitat in areas occupied by wintering Blue Grouse.     

Changes in kit fox–coyote–prey relationships in the Great Basin Desert, Utah

Variation in kit fox ( Vulpes macrotis ) population parameters can be influenced by vegetative cover and the distribution and abundance of other predator and prey species. Dramatic changes to Great Basin Desert habitats, which can potentially impact mammalian species, have occurred in some areas in Utah. We examined kit fox demographics and prey populations from 1999 to 2001 on Dugway Proving Ground (DPG), a U.S. Army facility in Utah, and compared some parameters to historical levels (1956–1958, 1966–1969). Adult survival rates were fairly consistent between 1999 and 2000 and between 1999 and 2001; however, survival was greater in 2001 than in 2000. Reproductive rates ranged from 1.0 to 3.8 pups per female in 1999–2000 and were similar to historical numbers (1.0–4.2 pups per female). We found a decrease in pre-whelping kit fox density from the 1960s (0.12 foxes ? km –2 ) to 1999–2001 (0.04 foxes ? km –2 ); however, densities were similar between the current study and the 1950s (0.08 foxes ? km –2 ). Using 9 years of data, we found density dependence between reproductive rates of the current year and annual fox density from the previous year. Using 7 years of data, we found a slight correlation between kit fox annual density and a 1-year lag in leporid abundance, even though leporid abundance was lower during the present study than it was historically. Compared to historical levels, current small mammal abundance and species composition has changed in several habitats. Kit fox breeding density and annual density were inversely correlated with coyote ( Canis latrans ) density. Changes to the landscape at DPG, especially due to invasion of cheatgrass ( Bromus tectorum ) and addition of artificial water sources, have caused a change in available kit fox habitat and prey species, and have increased the abundance of coyotes, the kit fox's major competitor.     

Competition for food and space in a heteromyid community in the Great Basin Desert

A series of removal experiments were performed on Dipodomys merriami, D. microps, and Perognathus longimembris to test for the importance of competition for food and microhabitats in a heteromyid community in the Great Basin Desert. Each of these species was removed singly to determine the short-term effects on the microhabitat preferences of the remaining species. We correctly predicted, based on differences in diet, that the removal of D. microps (a foliovore) would have no effect on D. merriami or P. longimembris (granivores). Using the dominance hierarchy theory, we correctly predicted that removal of a larger heteromyid, D. merriami, would have an effect on the microhabitat use of the smaller P. longimembris, but not vice versa. While our results offer strong evidence of competition for food and microhabitats, the short-term reactions were weak compared to the long-term reactions found in other studies of heteromyids.     

A classification of aquatic plant communities within the Nothern Rocky Mountains

A synecological study of aquatic macrophyte plant communities was conducted across northern Idaho and western Montana during the summers of 1997, 1998, and 1999. A total of 111 natural and man-made water bodies were sampled based on a stratification of environmental variables thought to influence plant species distribution (i.e., elevation, landform, geology, and water body size). Plant species foliar cover data were used to develop a hierarchical, floristic-based community type classification with TWINSPAN and DECORANA software. Six planmergent (conspicuous portion of vegetative plant body on the water surface) and 24 submergent (vegetative plant body found primarily underwater) community types were identified. Multivariate analysis indicated that all community types displayed significant differences in plant species composition, and the Sorensons floristic similarity between communities averaged 10% for planmergent and 8% for submergent types. Canonical correspondence analysis was used to inspect relationships between abiotic factors and plant species abundance. Results of this analysis indicated some relationships between species distributions and abiotic factors; however, chance introduction of plant species to water bodies is a process considered to be equally important to the presence of the community types described.     

Niche pattern in a Great Basin rodent fauna

Niche pattern of a desert rodent community in shrub habitats of central Utah was examined in the canonical space formed by the first four principal components of trapsite, microhabitat. Positions of species centroids differed significantly (P 1 ) increased with niche breadth (v 1 ) and decreased with increasing difference of centroids of a species from the overall mean habitat (d 1 ). V 1 was positively related to d 1 . Differences between niche pattern of this community and that of deciduous forest small mammals are discussed.     

Black bears ( Ursus americanus ) harvest Jeffrey pine ( Pinus jeffreyi ) seeds from tree canopies

Despite much attention to the foraging habits and hibernation patterns of food-storing mammals, little is known about the contents of winter larders under natural conditions or how animals prepare a winter larder. Here we describe the contents of 15 yellow-pine chipmunk ( Tamias amoenus ) winter larders from 3 different years and describe the movement of scatter-hoarded seeds into larders. We found larders by locating 14 radio-collared chipmunks in their winter dens. One additional larder was found by tracking the movement of seeds labeled with radioactive scandium-46 from scattered caches into the larder. Chipmunks formed winter dens and rapidly provisioned winter larders in the fall, just before the onset of winter. Surface caches were dynamic, with seeds residing in 1–6 cache sites (mean = 2.6, SD = 1.1) before being found in the larder. Distances from scattered caches to the winter larder were 34.5 m (SD = 17.1). Contents of winter larders consisted of pine and shrub seeds. In 14 of the 15 larders, pine seeds contributed most to the size and caloric content of larders. Pine seeds and other seeds found in winter larders were produced by plants 2–4 months before the onset of winter. We conclude that if yellow-pine chipmunks did not scatter-hoard seeds during summer and autumn, seeds would not have been available for use in winter larders.     

Tree size and understory phytomass production in a western juniper woodland

Understory phytomass production in a western juniper ( Juniperus occidentalis ) woodland was examined relative to tree size in central Oregon in 1983 and 1984. Vegetation was sampled in two zones, the canopy zone (beneath the canopy) and the intercanopy zone (the space between canopies), on two adjacent sites—a lower slope site with shallow soil and an upper slope site with deeper soil. Sampling was stratified into three tree size classes. Individual species production was significantly affected by tree size and location relative to tree canopy. Production of bottlebrush squirreltail, bluebunch wheatgrass, cheatgrass, miscellaneous annual grasses, perennial forbs, and annual forbs increased with increasing tree size. Sandberg bluegrass production was greater in the intercanopy than the canopy zone, while production of bottlebrush squirreltail, bluebunch wheatgrass, miscellaneous annual grasses, and both perennial and annual forbs was greater in the canopy zone. Production of cheatgrass was determined by the interaction of tree size and zone. Phytomass relationships were expressed to a greater degree on the upper slope site, where total production exceeded that of the lower slope site by approximately 50% the second year of the study. Individual trees appear to exert a great influence on associated vegetation as western juniper woodlands progress from the seedling (tree establishment) phase to closed stands of mature trees. Original community dominants appear to be spatially segregated beneath tree canopies and associated with large trees, while formerly less common species, such as cheatgrass, come to dominate the entire site.     

Formation and contents of yellow-pine chipmunk ( Tamias amoenus ) winter larders

Despite much attention to the foraging habits and hibernation patterns of food-storing mammals, little is known about the contents of winter larders under natural conditions or how animals prepare a winter larder. Here we describe the contents of 15 yellow-pine chipmunk ( Tamias amoenus ) winter larders from 3 different years and describe the movement of scatter-hoarded seeds into larders. We found larders by locating 14 radio-collared chipmunks in their winter dens. One additional larder was found by tracking the movement of seeds labeled with radioactive scandium-46 from scattered caches into the larder. Chipmunks formed winter dens and rapidly provisioned winter larders in the fall, just before the onset of winter. Surface caches were dynamic, with seeds residing in 1–6 cache sites (mean = 2.6, SD = 1.1) before being found in the larder. Distances from scattered caches to the winter larder were 34.5 m (SD = 17.1). Contents of winter larders consisted of pine and shrub seeds. In 14 of the 15 larders, pine seeds contributed most to the size and caloric content of larders. Pine seeds and other seeds found in winter larders were produced by plants 2–4 months before the onset of winter. We conclude that if yellow-pine chipmunks did not scatter-hoard seeds during summer and autumn, seeds would not have been available for use in winter larders.