The conversion of coastal prairie to farmland in southern Texas has drastically reduced the number of available animal burrows, thereby forcing western Burrowing Owls (Athene cunicularia hypugaea) wintering in southern Texas to use nontraditional roost sites such as roadside culverts. We studied factors influencing the selection of road culverts as roost sites by Burrowing Owls by comparing characteristics of 34 occupied and 100 unoccupied culverts. All occupied culverts were in agricultural habitat. Culverts with small diameters (≤16 cm) and those with an east—west orientation were occupied by Burrowing Owls in greater proportions than were culverts with larger diameters or different orientations. Occupied culverts were also associated with absence of grass, absence of woody vegetation, and presence of crop stubble. Our results provide guidelines for making drainage culverts more attractive to Burrowing Owls, but use of roadside culverts by Burrowing Owls may expose the owls to an increased risk of mortality from vehicle collisions. To avoid this dilemma, our guidelines for culverts could also be adapted as criteria for installation of artificial burrows in habitats suitable for wintering Burrowing Owls.

This study assesses the floristic diversity and affinities of pinyon-juniper (PJ) woodlands in northern Arizona at 2 different scales: regionally within the context of North American floristic patterns and locally within the 2500m elevation gradient of the San Francisco Volcanic Field (SFVF). An analysis based upon 245 North American floras indicates that the PJ woodlands of the SFVF share strong affinities with the adjacent Colorado Plateau and Apachian floristic elements but also show high floristic similarity to the Great Plains. Data suggest that mid-elevation woodlands of the Colorado Plateau share floristic affinities with the Great Plains that are as strong as or stronger than those shared with the Great Basin. A geostatisical analysis provides a spatially explicit depiction of these findings. A comparison of species occurrences between 6 adjacent biotic communities in northern Arizona reveals that the PJ woodlands host the most distinctive flora among local life zones. Despite what their simple woodland structure may suggest, PJ woodlands of the SFVF host a moderately species-rich flora. This study suggests that the floras of PJ woodlands vary in significant and important ways across the range of PJ woodlands in western North America.

We studied herbivory by the desert woodrat (Neotoma lepida) on Joshua trees (Yucca brevifolia) in the Mojave Desert to determine whether N. lepida fed selectively based on leaf nitrogen content. We measured leaf nitrogen content and the location and amount of herbivory by woodrats on Y. brevifolia trees in southwestern Utah, USA. Neotoma lepida removed the outer tips of leaves (⅓ to ⅔ of total leaf length) but left leaf bases, which had lower nitrogen content, uneaten. Herbivory by N. lepida also was concentrated on rosettes that were oriented south, and these had significantly higher nitrogen content than rosettes that were oriented north. Finally, N. lepida fed more on trees that had higher mean leaf nitrogen contents. Thus, N. lepida selectively foraged among leaf parts, among rosettes of leaves, and among trees of Y. brevifolia, and disproportionate foraging was correlated with nitrogen content of leaves.

Because of their high dispersal abilities, birds are expected to manifest marked genetic structuring only at relatively large geographic scales. However, it is not well known how factors like nest site fidelity in a largely resident species could limit gene flow and increase genetic structuring in birds. In this study we use RAPD markers to estimate genetic structuring in a strongly sedentary species of the American tropics, the Russet crowned Motmot (Momotus mexicanus), within a tropical dry forest in central Mexico. Genetic structuring was assessed among 3 populations separated by a mean distance of only 25 km. We report that 12.9% of the total genetic variation is explained by differences among sites, which is quite high for a bird at this geographic scale. We propose that high nest site fidelity, brought on by a scarcity of suitable nest substrates, may be responsible for high genetic structuring in this species.

The eastern woodrat (Neotoma floridana) occurs throughout eastern and central parts of the United States. In Nebraska, 3 of 9 subspecies inhabit the state, including N. f. campestris, N. f. attwateri, and N. f. baileyi. We determined distributional limits of N. f. campestris along 2 river systems in southern Nebraska. As observed with other mammalian species in the Great Plains, we suspected that the distribution of woodrats likely had expanded, reflecting continued regulation of rivers and the concomitant increase in forests along them. We documented N. f. campestris at 7 sites in 5 counties, including a recent (since the 1960s) eastward expansion along the Republican River. We observed little movement along the Platte River. The greatest concentration of houses constructed by woodrats occurred in a shelterbelt near the Republican River; otherwise, abundances of houses tended to be greater along the Platte River. We suspect that the distribution of woodrats will continue to change in Nebraska unless breaks exist or are established in riparian forests along the Platte and Republican rivers.

Thirteen species of bats occur in Nebraska, but limited information is available on those inhabiting southwestern parts of the state. We investigated the distribution, abundance, and reproductive activity of bats in 5 counties in extreme southwestern Nebraska (Chase, Hays, Dundy, Hitchcock, and Red Willow). From April 2007 to April 2008, we deployed mist nets on 15 occasions at 8 localities over the Republican River and its tributaries. We captured 100 individuals representing 5 species, including the evening bat (Nycticeius humeralis), eastern red bat (Lasiurus borealis), hoary bat (Lasiurus cinereus), big brown bat (Eptesicus fuscus), and silver-haired bat (Lasionycteris noctivagans). All species raised young in this region of Nebraska, except L. noctivagans, which was documented only during migration. Lactating females of N. humeralis captured on 15 June and volant young captured on 23 June extend known dates of reproductive activity for this species in the state, and an adult female captured on 30 April represents the earliest seasonal record of this species from Nebraska. Our records of evening bats also extend the known distribution of this species farther west in Nebraska than previously reported. Changes in land use throughout the Great Plains during the last century have altered many habitats, such as gallery forests associated with rivers, and distributions of mammals, including bats, have shifted to reflect those ecological changes.

Yellowstone National Park supports a small population (<300) of pronghorn (Antilocapra americana). Some individuals migrate during summer to areas characterized by reduced visibility, mixed habitat types, and a diverse predator community. Across areas selected by migratory and nonmigratory pronghorn, we documented cause-specific mortality of adults and fawns and assessed relative risk of predation by various predators. Coyotes (Canis latrans) accounted for 56% of adult predation and up to 79% of fawn predation. Cougars (Puma concolor) and wolves (Canis lupus) accounted for additional predation of adults, while cougars, black bears (Ursus americanus), and Golden Eagles (Aquila chrysaetos) were documented killing fawns on rare occasions. Our results suggest that even when pronghorn are in the presence of multiple predator species, coyote predation on adults and fawns may predominate for populations inhabiting shrubsteppe habitat. However, the risk of predation by sympatric predators, particularly cougars, may be high for female pronghorn selecting mixed cover types during migration or for birthing purposes. While the direct effect of wolves on overall mortality was low, wolves may indirectly influence survival rates of adult females and fawns by altering the behavior and space use of sympatric predators, particularly coyotes.

Shrub canopy cover can take between 10 and >50 years to recover to predisturbance levels following fire in sagebrush communities. The high degree of unpredictability of shrub recovery following prescribed fires and wildfires makes it difficult to prioritize restoration efforts and develop long-term plans for restoring or maintaining the integrity of sagebrush communities. Our overall goal was to develop a hypothesis based on descriptive data that describes the temporal pattern of recruitment for 2 important shrubs, Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle and Purshia tridentata (Pursh) DC., in the interiors of large burns where little seed input from surviving shrubs occurs. We had 2 primary questions: (1) are there distinct temporal patterns of recruitment in the interiors of large burns that determine the recovery rate of the shrub canopy layer for species largely dependent on seedlings for reestablishment and (2) can we generate hypotheses that explain this variation in shrub recovery rates? To address the question of recruitment, we measured shrub density and age for A. tridentata ssp. vaseyana and P. tridentata in the interiors of 4 large (>400-ha) burns. Time since fire varied from 6 to 41 years. All 4 fires burned in August and were relatively complete with few to no unburned patches. Our data indicate that (1) A. tridentata ssp. vaseyana and P. tridentata seed remained viable up to 4 years postfire and that (2) the rate of shrub recovery is largely determined by the success or failure of seedling establishment in the first 2–3 years following disturbance. From these data we generated a hypothesis describing 2 scenarios of postfire shrub recovery.

Fire has been a critical influence on forest dynamics over much of western North America, and knowledge of historical fire regimes provides a valuable reference point for guiding ecosystem management. Spatial and temporal variations in historical (1550–1997) fire frequency were quantified for a 145-km2 area straddling the McKenzie River in the central western Cascades of Oregon. Fire-scar and tree-origin years estimated from cut stumps in 63 clear-cut sites were used to approximately date fires. The estimated natural fire rotation was 162 years for the presettlement period (1550–1849). Natural fire rotation varied considerably over the period of record, ranging from 40 years for the Euro-American settlement period (1850–1924) to 504 years for the recent (1925–1997) fire-suppression period. Such temporal variation in fire regime may be attributed to a combination of climatic and anthropogenic influences. The study area also experienced 2 periods of widespread fire recorded at a majority of sample sites: one in the mid-1500s and the other from 1850 to 1925. Historical fire frequency has also varied spatially over at least 2 distinct scales. At the slope-facet scale, fire frequency was greatest on the generally south-facing slope to the north of the McKenzie River. At the finer scale of individual 4-ha sites, local topographic influences varied according to a site's broad geographical context north or south of the river. Results suggest that meaningful fire-regime characterization may require information derived from multiple spatial scales.

Variation at 21 allozyme loci and 10 restriction enzymes within the mitochondrial DNA control region was assessed among 3 allopatric populations of montane vole (Microtus montanus) in the American Southwest. Among populations of M. montanus, the population from the White Mountains, Arizona, was most genetically divergent. Genetic and biogeographic evidence supported recognition of the White Mountains population as a distinct subspecies, M. m. arizonensis. Results also supported recognition of the Mogollon vole (Microtus mogollonensis) as distinct from the Mexican vole (Microtus mexicanus).

Biological invasions are one of the greatest threats to native species in natural ecological systems. One of the most successful invasive species is Bromus tectorum L. (cheatgrass), which is having marked impacts on native plant communities and ecosystem processes. However, we know little about the effects of this invasion on native animal species in the Intermountain West. Because ants have been used to detect ecological change associated with anthropogenic land use, they seem well suited for a preliminary evaluation of the consequences of cheatgrass-driven habitat conversion. In our study, we used pitfall traps to assess ant community assemblages in intact sagebrush and nearby cheatgrass-dominated vegetation. Ant abundance was about 10-fold greater in cheatgrass-dominated plots than in sagebrush plots. We also noted differences in diversity and evenness between habitat types at both the species and the functional-group levels of organization. At the species level, Shannon's diversity index was greater in sagebrush plots than in cheatgrass-dominated plots. However, at the functional-group level, Simpson's and Shannon's diversity indices and the Brillouin evenness index were greater in cheatgrass-dominated plots than in sagebrush plots. Further, common species / functional groups tended to be more abundant while less common species / functional groups tended to be less abundant in cheatgrass-dominated plots compared to intact sagebrush plots. Patterns appear to be at least partially related to resource availabilities. This initial survey of ant communities from intact-native and altered vegetation types may be indicative of similar trends of biodiversity shifts throughout the Intermountain West where cheatgrass has successfully replaced native species. We also discuss the implications of ant communities on land management activities, specifically in the context of aridland restoration.

Little is known about how avian relationships to tracts of native sod prairie compare with avian relationships to single and multiple species of cool- and warm-season grassland plantings. We compared grassland bird species richness and density in 5 grassland cover types (n = 97) in the tallgrass prairie region of eastern South Dakota and western Minnesota, 2001–2004. Grassland bird species richness was significantly higher in native sod prairies than it was in all planted cover types except warm-season mixes. Grasslands dominated by exotic species did not support as many grassland bird species or have species densities as high as grasslands containing native species. Intermediate wheatgrass monotypes and cool-season mixes comprised of exotic species contained 40%–60% fewer grassland bird species than native sod prairie. Bobolink (Dolichonyx oryzivorus) density was 68% and 51% lower in intermediate wheatgrass monotypes and cool-season mixes, respectively, than it was in switchgrass monotypes. Clay-colored Sparrow (Spizella pallida) density was 75%–91% higher in native sod prairies than it was in any other cover type. Savannah Sparrow (Passerculus sandwichensis) density was 72% higher in native prairie than it was in grasslands dominated by exotic species. We recommend incorporating a diversity of native plant species into grassland plantings for biomass fuels or wildlife, rather than using monotypes or exotic species, to provide habitat for grassland birds. Although replacing croplands with planted grasslands would benefit grassland bird populations, we caution that replacing existing native sod tracts with planted grasslands would be detrimental to populations of several grassland bird species.

It has been suggested that Nearctic pikas (Ochotona spp.) are good biogeographic indicators of regions containing rocky, mesic, and cool habitat characterized by long winters and short summers. I examined whether populations of pikas inhabiting distinct low-elevation locales (121–255 m) are faithfully restricted to long-winter and short-summer conditions by monitoring the climate associated with American pikas (Ochotona princeps) in the southern part of the Columbia River Gorge, Oregon. Ambient air temperatures and weather conditions in the vicinity of 4 pika-occupied rockslides were monitored with remote temperature loggers and weather stations from June 2000 to June 2001. Temperatures were compared to long-term averages recorded within the area. I detected pikas inhabiting locales where some temperatures lie outside of the limiting climatic values previously calculated for regions containing pikas. Mild winter temperatures at these pika locations show that long-winter temperatures and snow accumulation associated with typical habitat may not be requirements for pikas in some low-elevation habitat. When using climatic conditions experienced by extant pikas to estimate local paleoenvironments surrounding fossil sites and to anticipate effects of climate change on future pika distributions, I determined that pika sites in the Columbia River Gorge indicate that the association of pikas with long-winter habitat should be considered uncertain. These results highlight the need for further investigation into how local temperatures affect the distribution, behavior, and persistence of low-elevation pikas.

We report a population of the mussel the black sandshell (Ligurnia recta [Lamarck, 1819]) from the Carrot River in Saskatchewan, far north of the species' known range in southern Manitoba and northwestern Ontario. Ligumia recta is reported to be declining substantially in its abundance and range, and this occurrence provides valuable information for the construction of a species status report in Canada.

The collared peccary (Tayassu tajacu) is undergoing range expansion in the southwestern United States. Here we report sightings of the collared peccary from locations outside the known ranges of either of the subspecies, T. t. sononensis and T. t. angulatus, in south central New Mexico. Sightings include multiple individuals of different ages. This indicates that the collared peccary is expanding into previously unoccupied areas between the documented ranges of the 2 subspecies. We suggest that the possibility of gene flow between the 2 historically separate subspecies may have important evolutionary consequences.

Salmincola californiensis is a parasitic copepod in the Lernaeopodidae family that commonly parasitizes salmonid fishes (Oncorhynchus spp.) by attaching near the fins and on gill filaments. Historically their distribution was limited to streams that emptied into the Pacific Ocean. During the summer of 2006, several rainbow trout (Oncorhynchus mykiss) captured in Lake Tahoe were infested with S. californiensis. This is the first known record of S. californiensis in Lake Tahoe.

We captured >2000 Crawford's gray shrews (Notiosorex crawfordi) in a riparian forest mainly consisting of cottonwoods (Populus deltoides) along the Rio Grande in central New Mexico. Little has been published about abundance and habitat of Crawford's gray shrew throughout its distributional range. During 7 summers, we captured shrews in pitfall traps at 13 study sites in Bernalillo, Valencia, and Socorro counties. Capture rates of shrews were greatest in August and September, and we did not detect a response of shrews to restoration treatments that removed nonnative plants from riparian forests. Results from our study indicate that (1) Crawford's gray shrews are more abundant in riparian habitats than historically presumed and (2) pitfall traps with drift fences are an effective means to capture shrews.

Cold air temperatures may have killed several emerging nymphs and adult Pteronarcys californica on the Jocko River, Montana. Some aquatic insect taxa emerge early on the Jocko River, likely due to warm water temperatures in winter and spring. At this location, P. californica emerges approximately 5–7 weeks earlier than it does on many other streams or rivers across the United States. We hypothesize that this earlier emergence may be a mortality factor when cold fronts cause air temperatures to drop below freezing. Other mortality factors are also discussed.

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 Peñasco. Locality records indicate that the historical distribution of Zapus hudsonius luteus and its obligate wetland habitat were broader than currently realized.

Solifugids (camel spiders) are widespread throughout arid regions of western North America and are thought to be important in structuring desert arthropod communities. Despite the ubiquity of camel spiders, little is known about their ecology. Black-tailed prairie dogs (Cynomys ludovicianus) are also widespread in western North America and are important ecosystem engineers, but they have been reduced in extent because of human activity. Here we report significantly greater numbers of camel spiders on black-tailed prairie dog colonies in southern New Mexico. The difference in vegetation structure created by prairie dog activity is likely the reason for the increased prevalence of camel spiders on colonies. Because camel spiders are important predators and prey, the observation that colonies support higher numbers of these animals provides a mechanism explaining differences in arthropod communities on and off colonies and explaining the preferential foraging behavior of vertebrates associated with prairie dog colonies.