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Penstemon haydenii Wats. (blowout penstemon, blowout beardtongue) is an early-succession plant species that is adapted to the dynamic habitats found in sand dunes. Following widespread habitat loss, the species was thought to be extinct from 1940 until it was rediscovered in 1968. It was listed as endangered in 1987 under the Endangered Species Act. At the time, it was only known from the Nebraska Sandhills, where its low numbers were ascribed to habitat loss. It was first discovered in Wyoming in 1996, in the Ferris Dunes of Carbon County. To develop a proxy for historic Wyoming habitat trends and a context for current conditions, we reconstructed the history of dunes where P. haydenii is presently located. Twelve georeferenced aerial photograph sets and digital imagery from 1946 to 2015 were analyzed to trace currently occupied dune areas back over the 70-year period. All currently occupied dunes were continuously present as areas of active sand over the 70-year timespan. Dune migration averaged 2.9 m/year. Dune extent declined 16.1% (2015 compared to the average). The continuity of active sand dune habitat and asynchronous trends in migration and in aerial extent between dunes and over time indicate a dynamic dune system maintained by wind erosion. These results provide critical context for population and habitat data of P. haydenii in Wyoming.
A prediction that has gained considerable traction in the American pika (Ochotona princeps) literature is that because of climate change, high mortality is likely to occur in winters of low or early snowmelt and cause extirpation of local populations. The basis for this prediction is the perception that the absence of an insulative layer of snow to protect pikas from severe winter cold temperatures may cause animals to utilize metabolic reserves through excessive thermoregulation before the spring emergence of fresh vegetation, or die directly from exposure to extreme winter temperatures. The Sierra Nevada of east central California experienced its lowest snowfall in recorded history during the winter of 2014/2015. We observed patch occupancy as a proxy for overwinter survivorship of American pikas in the Sierra Nevada during summer 2015 in comparison to baseline populations at the same sites during summer 2014. In summer 2015, pika presence was documented at 36 of 37 sites where pikas had been observed in summer 2014. Contrary to the low snowfall-high mortality prediction, there was no evidence that the nearly total lack of snow caused unusual overwinter mortality in Sierra Nevada pikas.
Nolina microcarpa (Asparagaceae) is a dioecious monocot shrub found in Arizona, New Mexico, and northern and central Mexico. Leaf rosettes of the species grow in colonies that produce tall inflorescences of small male or female flowers during spring. Dioecious flowering requires pollinating insects to carry pollen from flowers on male colonies to flowers on female colonies. I investigated pollination of female flowers at 12 colonies of N. microcarpa in the Cerbat Mountains in northwestern Arizona during May–June 2017. I examined pollen from male flowers, aspirated insects on female flowers, counted conspecific pollen grains carried by insects, and estimated floral constancies from proportions of conspecific pollen. Pollen on N. microcarpa was prolate and monosulcate with a deep furrow and reticulate sculpturing. The most abundant insect on female flowers was the native beetle Triarius trivittatus (Chrysomelidae), followed by the introduced honey bee Apis mellifera (Apidae). Activities of honey bees, but not beetles, were limited to flowers. Two species of native bees in Halictidae and Megachilidae were also found in low numbers on flowers. Nearly all insects carried N. microcarpa pollen, and conspecific pollen comprised most of the pollen load on most insects. Conspecific pollen loads were highest on A. mellifera, followed by the native bees and T. trivittatus. Amounts of conspecific pollen on A. mellifera and on T. trivittatus males, but not females, were dependent on the distance to the nearest male inflorescence and decreased exponentially as the distance increased. Nolina microcarpa appears to be pollinated primarily by bees and beetles. Pollination by these insects is consistent with pollination of other plants, such as palms (Arecaceae), that similarly produce open inflorescences and small, unisexual, diurnal flowers with nectar.
Mountain lions (Puma concolor) were captured and radio-collared in the Sierra National Forest between 1983 and 1992 to study the species' seasonal spatial patterns in a location where migratory mule deer (Odocoileus hemionus) are its primary prey. Some mountain lions displayed seasonal migratory shifts in elevation that mirrored those of their migratory prey; others resided at lower elevations year-round. Home range size for all mountain lions was larger in summer ( = 231 km2) than in winter ( = 110 km2), whether or not an individual exhibited seasonal migratory shifts in elevation. Due to seasonal shifts in home range size and, for part of the mountain lion population, in elevation, minimum density of mountain lions in the study area also differed seasonally (summer, 0.87 per 100 km2; winter, 1.42 per 100 km2). Overall, these findings demonstrate differing space use strategies (migratory vs. resident) within a large carnivore population that have important management implications for large carnivores because these strategies provide context for population monitoring and conflict mitigation efforts.
Juvenile survival and growth are critical determinants of evolutionary fitness in most organisms. However, specific effects of population density and habitat quality on survival and growth of larvae vary widely among amphibian species. The Columbia spotted frog (Rana luteiventris), like many amphibians in the arid western United States, is a species of conservation concern, especially in the southern part of its range. To determine how density and habitat affect vital rates of Columbia spotted frog during the larval period, we performed a controlled experiment. Larval growth and survival in the Columbia spotted frog are determined by density of conspecifics and pond habitat. Density of conspecifics is the most important determinant of larval growth, and pond habitat type is the most important determinant of larval survival. Recommendations for repatriation efforts include starting populations with intermediate densities of larvae to optimize the size-versus-number trade-off.
Bat populations are being impacted by many threats, including white-nose syndrome, wind energy development, and hibernaculum disturbance and modification. Understanding the use of caves as hibernacula by bats in the western United States is necessary for the conservation and management of these mammals and their habitat, as well as for monitoring the arrival of white-nose syndrome. We identified biologically important hibernacula from 304 winter surveys (1 November–31 March) in 64 caves from 1984 to 2016 in southern Idaho, USA. During surveys researchers counted 37,693 bats representing 6 species. Townsend's big-eared bats (Corynorhinus townsendii townsendii) comprised 96.1% (36,237 individuals in 58 caves) and western small-footed myotis (Myotis ciliolabrum ssp.) comprised 3.8% (1432 individuals in 22 caves). Thirty of the 64 caves were biologically important for Townsend's bigeared bats (maximum count ≥20 individuals), and the largest hibernating colony of that species occupied cave C34 (8 surveys, = 1610 individuals, SD 415, range 962–1994). Thirteen caves were biologically important hibernacula for western small-footed myotis (maximum count ≥5 individuals), and the largest hibernating colony of that species occupied cave C24 (6 surveys, = 98 individuals, SD 53, range 32–152). Ten caves were biologically important hibernacula for both species. Our results indicate that Townsend's big-eared bats are the predominant species that hibernate on the Snake River Plain in southern Idaho, and that this area has a high density of hibernacula—and the largest reported hibernaculum—for Townsend's big-eared bats and western small-footed myotis in western North America. We recommend that biologists prioritize monitoring the 13 biologically important hibernacula of western small-footed myotis as well as the 10 caves used by both species for the potential arrival of white-nose syndrome in this area and to track the abundance of Townsend's big-eared bats. Our results will help biologists with the management and conservation of bats and their habitat as well as aid in land use planning in this área.
The western red bat (Lasiurus blossevillii) is a foliage-roosting species of riparian habitats in arid regions of the southwestern United States. Only limited published anecdotal observations exist for roost sites used by this species. Western red bats were split taxonomically from the eastern red bat (Lasiurus borealis) in 1988, but summaries of roosting behaviors for western red bats still appear to stem from former associations with the commonly studied eastern red bat. Our study represents the first comprehensive research on the roosting ecology of western red bats. We radio-tracked 14 adult bats to 19 different day roosts along the Mimbres River of southwestern New Mexico. While we documented that western red bats had an affinity for densely foliated trees (79%), we did not detect any selection for tree species or size. At our study site, western red bats roosted in cottonwoods (47%, Populus spp.), velvet ash (21%, Fraxinus velutina), box elder (16%, Acer negundo), and red mulberry (16%, Morus rubra). We also described clustering behavior, where groups of 2–3 adults roosted in direct contact with one another. Although the species was deemed to roost solitarily, the frequency of clustering behavior in our study suggests otherwise. If bats were observed in clusters, they typically exhibited greater roosting fidelity than solitary individuals. Because arid riparian corridors in the southwestern United States generally are considered threatened systems, protection and preservation of mechanisms that create and maintain the diversity of these riparian corridors is necessary for the survival of this uncommon and poorly understood species.
The La Sal daisy, Erigeron mancus, is endemic to treeline ecotone and alpine meadow habitats of the La Sal Mountains in Utah, an insular, laccolithic mountain range on the Colorado Plateau in southeastern Utah. From 2009 to 2011 we established elevational transects through upper spruce-fir forest, treeline ecotone, and alpine meadow habitats on Laurel Ridge in the Middle Mountain group of the La Sal Mountains to measure (1) periodic changes in E. mancus population density, (2) changes in the elevation of the E. mancus population centroid, (3) changes in patch size occupied by E. mancus, and (4) changes in frequency of occurrence in herbaceous plant species associated with E. mancus along these transects. We measured both E. mancus density and vascular plant species composition within 1-m × 1-m square frames in mid-July, near peak alpine plant flowering time. The E. mancus population density on Mt. Laurel ridge did not significantly change from 2009 to 2015, but the species was most abundant in alpine meadow habitat for both years. Changes in patch width, centroid elevation, and frequency of occurrence of 30 associated plant species were also not statistically significant. Like E. mancus, most species show changes in frequency of occurrence between upper spruce-fir forest, treeline ecotone, and alpine meadow habitats. Individual plants of E. mancus are probably long-lived perennials, so changes in population density and distribution due to global warming are expected to be gradual and/or have an unknown lag time. Although there is no evidence of ongoing change in the Laurel Ridge population of E. mancus, having this information will provide a solid statistical basis for determining significant future changes.
Granivorous rodents commonly exhibit preferences for seeds of particular plant species. However, among buried seeds that are available, rodents may find that alternate, less desirable seeds are more easily located by olfaction than preferred seeds. Seeds of Indian ricegrass (Achnatherum hymenoides) are a highly preferred food resource for seed-caching desert heteromyid rodents. We tested relative abilities of heteromyids to locate buried caches of Indian ricegrass seeds versus seeds of another plant species (cheatgrass, Bromus tectorum) that are common in heteromyid diets at a western Nevada field site. Rodents located more cheatgrass than Indian ricegrass seed caches in the field when seeds were unaltered. When ground, however, detectability of preferred Indian ricegrass seeds increased, presumably due to release of volatile compounds inside seeds, and more ground Indian ricegrass seed caches were found and removed compared with ground cheatgrass caches. Grinding cheatgrass seeds did not affect harvest rates of cheatgrass caches. Results of a laboratory cache removal experiment using 2 heteromyid species, Merriam's kangaroo rats (Dipodomys merriami) and long-tailed pocket mice (Chaetodipus formosus), mirrored field cache removal results. Dispersal of Indian ricegrass seeds and establishment of new seedlings occurs largely through emergence of seedlings from heteromyid scatterhoard caches. Our results suggest that Indian ricegrass seeds may have been selected for reduced olfactory detectability to minimize the probability that they are recovered by rodents for later consumption once they have been cached.
Facultative spawning in lakes is an uncommon and notable behavior among catostomids and other fish species that typically spawn in streams. I describe what may be the first documented case of lake-spawning behavior by mountain suckers (Catostomus platyrhynchus).
Kangaroo rats are reported to have a mutualistic relationship with harvester ants through facilitation of burrow establishment, creation, and persistence. The relationship can, however, become more complex. We report observations of the giant kangaroo rat (Dipodomys ingens), a state and federally listed endangered species, repeatedly kleptoparasitizing harvester ants from a nearby nest in the Carrizo Plain, California. Though the relationship between kangaroo rats and harvester ants has been studied extensively and is believed to be mutualistic, under certain conditions this relationship can follow an alternate path of parasitism.
The tricolored bat (Perimyotis subflavus) is widely distributed throughout eastern North America. However, this species has also undergone severe population declines in areas where white-nose syndrome has taken hold. Previous records in Colorado showed what appeared to be vagrant individuals with no evidence of established populations. Herein we provide new records for Boulder and Weld Counties, Colorado. We also provide evidence of reproduction supporting the hypothesis of westward expansion of this species. Because the tricolored bat has been significantly impacted by white-nose syndrome in eastern North America, the Rocky Mountain West may provide at least a temporary refugium from this disease.
From late February to early April the Central Platte River Valley in Nebraska is home to the largest gathering of Sandhill Cranes (Antigone canadensis) in the world and increasingly serves as a foraging ground for migrating Bald Eagles (Haliaeetus leucocephalus). On 7 March 2017, we documented a subadult Bald Eagle depredating an adult Sandhill Crane. Though evidence suggests that Bald Eagles depredate Sandhill Cranes on rare occasion, the process of that depredation has not been described in the scientific literature. The Sandhill Crane effectively defended itself several times against hovering attacks from the Bald Eagle by utilizing wing-spread displays and “bill stab” attacks. However, the Bald Eagle was eventually able to land on the Sandhill Crane's neck and back with its talons, push the crane's head under water, and drown its prey. Following submersion, the Sandhill Crane was only momentarily responsive before floating on its back down the river. We also documented 5 subadult Bald Eagles competing for access to a second Sandhill Crane carcass. As Bald Eagle populations continue to recover, Sandhill Cranes may become more frequently depredated by Bald Eagles during the spring migration-staging period in the Central Platte River Valley.
We present a review of cougar dispersal literature and the first evidence of natural (i.e., unmanipulated) homing behavior by a dispersing male cougar (Puma concolor) that sustained severe injuries crossing the northern Mojave Desert. Based on Global Positioning System and ground tracking data, the male traveled a total distance of 981.1 km at 5.03 km/d, including 170.31 km from the Desert National Wildlife Refuge to the northwestern Grand Canyon, where he sustained severe injuries. The interkill interval increased from 7.1 ± 2.7 d while he was in his natal range to 17.5 ± 4.9 d during dispersal. While homing, the male appeared to consume only reptiles until he died, 33.7 km from his capture site. In desert environments where prey availability is low, homing behavior may be an important strategy for dispersing cougars, providing a mechanism for persistence when the best quality habitats they encounter are already occupied by adult residents. Therefore, managing for habitat connectivity can ensure successful homing as well as dispersal on a greater scale than has been previously suggested. Elucidating the mechanisms that trigger homing during dispersal may provide critical insight into animal movements often overlooked as mundane behavior.
Freshwater gastropods comprise a diverse and highly imperiled taxonomic group that is threatened by anthropogenic factors including the introduction of nonnative species. We surveyed 10 wetland ponds in Turnbull National Wildlife Refuge to assess the possible expansion of the nonnative European ear snail (Radix auricularia) and to determine the genus richness and relative abundance of native gastropods. D-frame dip nets were used to sample gastropods at 4 locations in each pond. Six genera of gastropods were found, including R. auricularia in 6 ponds where it was not previously known. Radix auricularia is now the dominant genus in Middle Pine and Lower Pine Lakes, with relative abundances of 84.13% and 92.31%, respectively. Due to the high abundance and spread of R. auricularia in Turnbull National Wildlife Refuge, resource managers need to investigate the snail's impacts and implement strategies to reduce possible negative effects of this nonnative snail on native gastropods and other wildlife.
We report the northernmost Atlantic Coast record of the Cloudy Snail Sucker (Sibon nebulatus) from the state of Hidalgo, at a straight-line distance of about 185-km from the nearest historical locality in Sierra Norte de Puebla, Mexico. We assess the potential distribution of this species and compare morphological characteristics of specimens from Mexico and Central America. No significant morphometric or meristic differences were found. A species distribution model suggests that S. nebulatus is widely distributed on both coasts of Mexico, with a high probability of occurrence at a wider range of latitudes than current records indicate.