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At least 649 records · Page 36Linked to original sources

USGS2020

What's in the hump of the humpback chub?

The function of the nuchal hump on adult humpback chub ( Gila cypha ) has been the subject of longtime conjecture. Hypotheses about the purpose of the hump range from it being a feature that confers hydrodynamic advantages in swift water to speculation about how the hump may have reduced predation vulnerability to Colorado pikeminnows ( Ptychocheilus lucius ). We used comparative histology of the head region of captive-reared and wild specimens of humpback chub to evaluate whether histological examination could give insight into the function of the hump. Tissues were sectioned, stained, and photographed under a microscope at 2×, 4×, and 40× magnification. The hump is composed almost entirely of skeletal muscle, with little nervous system innervation or fatty tissue. Hump muscle and dorsal muscle appear very similar in terms of muscle cell size, fat content, and connective tissue content. No apparent differences exist between the hump tissues of wild-caught and captive-reared individuals. Histological analysis and study of the anatomical structure of the head through dissection, along with evidence from other species, suggest that the hump evolved to reduce predation vulnerability. Although the reason for the evolution of the hump in humpback chub remains uncertain, additional information about the composition of the hump can help to support or refute hypotheses related to its function.

Western North American Naturalist↗

USGS2020

First recorded observations of conspecific egg and nestling consumption in common ravens (Corvus corax)

We observed cannibalism, the act of consuming a conspecific, of eggs and nestlings by Common Ravens ( Corvus corax ; hereafter “raven”) by video-monitoring nests in Nevada and California. Specifically, within the sagebrush steppe of Nevada, adult ravens killed and consumed raven chicks from an active nest. Additionally, on the coast of California, we observed adult ravens consume inviable eggs from their own nest following full-term incubation. To our knowledge, these observations represent the first documented cannibalistic behavior by ravens.

California, Nevada↗

USGS2020

Behavioral response to high temperatures in a desert grassland bird: Use of shrubs as thermal refugia

Birds inhabiting hot, arid ecosystems contend with trade-offs between heat dissipation and water conservation. As temperatures increase, passerines engage in various behaviors to reduce exposure to heat, solar radiation and insolation, and reradiation of heat from the ground. These responses to rising temperatures may result in subordination of reproductive urgency or nutrient acquisition to the need for thermoregulation. During studies on Arizona Grasshopper Sparrow ( Ammodramus savannarum ammolegus ) life history and ecology, we noted that these sparrows abandoned territoriality and foraging behaviors under certain circumstances in favor of cooler microsites. In this paper we document the extreme temperatures to which these and other ground-foraging and ground-nesting birds are exposed in southwestern desert grasslands, and we present evidence that A. s. ammolegus avoids exposure to extreme air and ground temperatures by using shrubs as thermal refugia. Our observations have implications for Arizona Grasshopper Sparrows and other desert grassland passerines in the southwestern United States, where the climate is projected to become hotter and drier. We provide some of the only behavioral data, and associated temperature data, associated with the use of thermal refugia by desert grassland birds. We encourage further studies that use more robust methods to supplement our observational data.

Arizona↗

USGS2020

Headwaters fed by subterranean ice: Potential climate refugia for alpine stream communities?

Near-term extirpations of macroinvertebrates are predicted for mountain streams worldwide as a warming climate drives the recession of high-elevation ice and snow. However, hydrological sources likely vary in their resistance to climate change, and thus streams fed by more resistant sources could persist as climate refugia for imperiled biota. In 2015–2016, we measured habitat characteristics and quantified macroinvertebrate community structure along 6 alpine streams in the Teton Range, Wyoming, USA. Strong differences in habitat characteristics (e.g., temperature, bed stability, conductivity) confirmed 3 major stream sources: surface glaciers, perennial snowfields, and subterranean ice. Subterranean ice-fed streams—termed “icy seeps”—appear common in the Teton Range and elsewhere, yet are globally understudied. Midges in the family Chironomidae dominated our study sites, representing 78.6% of all specimens sampled, with nematodes, caddisflies ( Neothremma ), and mayflies ( Epeorus ) also common. At the community scale, glacier- and snowmelt-fed streams differed significantly in multivariate space, with icy-seep communities intermediate between them, incorporating components of both assemblages. Because the thermal environment of subterranean ice, including rock glaciers, is decoupled from large-scale climatic conditions, we predict that icy seeps will remain intact longer than streams fed by surface ice and snow. Furthermore, our results suggest that icy seeps are suitable habitat for many macroinvertebrates occupying streams fed by vulnerable hydrological sources. Thus, icy seeps may act as key climate refugia for mountain stream biodiversity, an idea in need of further investigation.

Wyoming↗

USGS2020

Distribution, density, and land cover associations of wintering Golden Eagles in the Southern Great Plains

In addition to its resident Golden Eagles ( Aquila chrysaetos ), the Southern Great Plains of North America receives an influx of migrant Golden Eagles each winter. However, little current or quantitative information is available regarding eagle presence or the species' land cover associations across the region. During the winters of 2014/2015 and 2015/2016, we surveyed Golden Eagles along 51 approximately 55-km-long road survey transects within a 136,800-km 2 area of the Southern Great Plains of eastern New Mexico and the panhandles of Texas and Oklahoma. Our goal was to estimate the winter density of Golden Eagles in the region and to evaluate their land cover associations. Detections were low, with an estimated regional winter density of 0.31 eagles per 100 km 2 . We found that Golden Eagles were detected in rangeland cover types in greater proportion, and in agricultural and other land cover types in lesser proportion, to their availability. Our results provide regulatory agencies with data that may facilitate better-informed decision making for eagle conservation in the region.

New Mexico, Oklahoma, Texas↗

USGS2020

Brood parasitism of greater sage-grouse by California Quail in Idaho

We describe a case of brood parasitism of a Greater Sage-Grouse ( Centrocercus urophasianus ; hereafter, sage-grouse) nest by California Quail ( Callipepla californica ; hereafter, quail) in southwestern Idaho during 2019. We observed one quail egg in the parasitized nest; the egg partially hatched, but the chick was dead upon the final nest check. Of the 6 sage-grouse eggs in the nest, only 2 hatched, although the eggs contained chicks that appeared nearly completely developed. Identification of the quail chick was confirmed using mitochondrial DNA. Additional monitoring and documentation of this behavioral interaction is warranted to better understand its prevalence and any reproductive consequences for sage-grouse.

Idaho↗

USGS2021

Seasonal activity and diets of bats at uranium mines and adjacent areas near the Grand Canyon

Little information exists on the habitat use and feeding ecology of insectivorous bats in arid ecosystems, especially at and near uranium mines in northern Arizona, within the Grand Canyon watershed. In 2015–2016, we conducted mist-netting, nightly acoustic monitoring (>1 year), and diet analyses of bats, as well as insect sampling, at 2 uranium mines (Pinenut and Arizona 1) with water containment ponds. Because of physical barriers and limited general access to areas within the mine yard, mist-netting was limited to outside of the perimeter fence and away from the containment ponds. Mist-netting also occurred at 2 nearby sites that served as proxies to the mines. Bats captured directly at the mines included one pregnant Antrozous pallidus and 3 adult male Parastrellus hesperus . At the proxy sites, we captured 45 individuals identified as A. pallidus , Corynorhinus townsendii , Eptesicus fuscus , Euderma maculatum , Lasionycteris noctivagans , Myotis californicus , Myotis ciliolabrum , P. hesperus , and Tadarida brasiliensis . The nightly and seasonal presence of bats, as shown through acoustic recordings at each mine, coincided with the seasonal migratory and hibernation behaviors of the bat species. Statistical comparisons of acoustic recordings with precipitation data collected over one year show that seasonal monsoon rains generally had a negative effect on the nightly activity and presence of bats. Diets of P. hesperus from both mines were comprised mostly of coleopterans but also included smaller volumes of Hymenoptera, Hemiptera, Lepidoptera, Diptera, and Neuroptera. The diet of A. pallidus was comprised solely of Coleoptera. Diets of bat species from the proxy sites were characteristic of their known feeding ecology, which ranged from the consumption of soft-bodied insects (e.g., moths) by C. townsendii to the consumption of hard-bodied insects (e.g., beetles) by E. fuscus . Ultimately, the increased knowledge of the natural history of bats through multiple methods of data collection allows for a better understanding of complex arid ecosystems. It also provides resources needed for the management of habitat associated with alternative energy, such as uranium mining.

Arizona↗

USGS2021

Cold tolerance of mountain stoneflies (Plecoptera: Nemouridae) from the high Rocky Mountains

How aquatic insects cope with cold temperatures is poorly understood. This is particularly true for high-elevation species, which often experience a seasonal risk of freezing. In the Rocky Mountains, nemourid stoneflies (Plecoptera: Nemouridae) are a major component of mountain stream biodiversity and are typically found in streams fed by glaciers and snowfields, which are rapidly receding due to climate change. Predicting the effects of climate change on mountain stoneflies is difficult because their thermal physiology is largely unknown. We investigated cold tolerance of several alpine stoneflies ( Lednia tumana , Lednia tetonica , and Zapada spp.) from the Rocky Mountains, USA. We measured the supercooling point (SCP) and tolerance to ice enclosure of late-instar nymphs collected from a range of thermal regimes. SCPs varied among species and populations, with the lowest SCP measured for nymphs from an alpine pond, which was much more likely to freeze solid in winter than flowing streams. We also show that L. tumana cannot survive being enclosed in ice, even for short periods of time (<3 h) at relatively mild temperatures (–0.5 °C). Our results indicate that high-elevation stoneflies at greater risk of freezing may have correspondingly lower SCPs, and despite their common association with glacial meltwater, these stoneflies appear to be living near their lower thermal limits.

Montana, Wyoming↗

USGS2021

Effects of elk and bison herbivory on narrowleaf cottonwood

Ungulate browsing influences the structure and composition of woody plant communities, including species composition and biomass production as well as age distribution, recruitment, and mortality. We evaluated effects of elk and bison herbivory on narrowleaf cottonwood ( Populus angustifolia ) communities in a semiarid ecosystem in southern Colorado. Cottonwoods in this ecosystem have been aged at ≥300 years old and are among the oldest cottonwood trees in North America. We compared browsing intensity and structural and productivity responses of cottonwood to ungulate herbivory. We compared responses in sites with elk and bison, sites with elk but no bison, and sites where both ungulates were excluded. We found that the majority of browsing on cottonwood occurred during summer in this high desert ecosystem. Areas with both elk and bison had higher browse utilization than areas with only elk, but diet data indicated that elk consumed a much greater proportion of cottonwood than bison. Overall, browse utilization observed in this study was low to moderate compared to other studies, and our results may not be representative of sites experiencing intense year-round herbivory. Removal of all ungulate herbivory led to taller and denser cottonwood suckers; however, other environmental factors, in addition to herbivory, still strongly limit cottonwood growth and recruitment in this ecosystem.

Colorado↗

USGS2021

First record and diet of the tricolored bat (Perimyotis subflavus) from Guadalupe National Park and Culberson County, Texas

The tri-colored bat ( Perimyotis subflavus ) occurs throughout the eastern United States, from Canada to south Florida and westward to eastern New Mexico, central Colorado, and western Texas. In this study, we document the first record of P . subflavus for both Guadalupe Mountains National Park and Culberson County, Texas. Our record extends the range of P. subflavus into the Trans-Pecos region of Texas. We also examined the diet of this individual and observed that it consisted of Lepidoptera, Coleoptera, and Hemiptera. Our observations of the diet of P. subflavus correspond with results of previous studies from more eastern portions of the species' range.

Texas↗

USGS2021

Southwestern bats and their external bacteria

Bat species diversity within the United States is greatest in the Southwest, with approximately 30 species present. At least 16 of these bat species hibernate and are susceptible to white-nose syndrome (WNS), which is caused by the fungus Pseudogymnoascus destructans . Since 2006, millions of bats from 35 U.S. states and 7 Canadian provinces have died from WNS. In previous studies of external surfaces of bats sampled from southwestern states, Actinobacteria were detected that were shown to have antifungal properties against P. destructans in laboratory testing. These studies motivated us to expand our research to sites that represent possible gateways for P. destructans to enter the Southwest so that we could establish a baseline of bat microbiota before the arrival of WNS. We surveyed for the presence of bats and their external microbiota at 3 national parks and monuments located in southeastern Colorado and northeastern New Mexico. Our results document new occurrence records of bat species and their external bacteria at each sampling location. Additionally, we provide insight on the composition of bat external microbiota in the absence of P. destructans , while revealing information about the Streptomyces and other possible native defenses of bats against P. destructans at a gateway into the Southwest.

Western North American Naturalist↗

USGS2021

Predictability of invasive Argentine ant distribution across Mediterranean ecoregions of southern California

The invasiveness of nonnative taxa can vary across a landscape due to environmental gradients, suggesting that location-dependent management strategies may be more effective at reducing spread compared to a “one size fits all” approach across the entire introduced range. Using bait stations placed along linear transects within habitat preserves, we tested for effects of ecoregion, vegetation, soil moisture, habitat edge type (i.e., moisture source), and distance from edges on the presence of the invasive Argentine ant Linepithema humile in San Diego County, California, a region with high indigenous biodiversity and numerous rare and protected species. Our results showed an inverse relationship between the presence of native ant species and the presence of the Argentine ant across ecoregions, with the latter reaching peak abundance in the coastal terrace. Argentine ant presence was negatively associated with distance from all edge types regardless of location, but the magnitude of this effect varied among ecoregions. In the xeric foothill and inland valleys, the probability of occurrence was nearly 0 at distances of 200 m and 750 m from moisture edges, respectively, whereas in the coastal terrace, the probability remained above 0.80 at distances up to 1.25 km. When compared to previous studies at different spatial scales, these findings provide an alternative perspective on the invasiveness of the Argentine ant at the landscape level. Our results further suggest that efforts to control spread in regions with a Mediterranean climate may be more successful in inland areas, where the ant is likely to have lower environmental tolerance and native ant species may be better able to generate biotic resistance. In contrast, different tactics and expectations may be necessary for coastal areas, where the same constraints are diminished or absent.

California↗

USGS2024

Diet of Myotis ciliolabrum from six sites in the southwestern United States

With bat populations declining in many parts of the world, detailed life history information will be critical for assessing vulnerabilities of bat populations and associated trophic effects. Myotis ciliolabrum (western small-footed bat) is a species of insectivorous bat distributed from the Great Plains to the Pacific Coast and from British Columbia to Central Mexico. The species is spottily distributed within this wider range but is locally abundant in areas containing appropriate rocky habitat. Despite M. ciliolabrum being relatively common, little information is available about its feeding ecology. Earlier studies have suggested that skull morphology can be used to determine whether insectivorous bats select for soft- or hard-bodied prey, but we hypothesized that M. ciliolabrum may feed opportunistically on a variety of insect types. To test this hypothesis, we examined the feeding habits of western small-footed bats captured during 2000–2022 at 6 national parks and 1 national conservation area across the Southwest. Visual analysis of prey remains in guano revealed that western small-footed bats within our study area consumed insects belonging to 7 orders (Lepidoptera, Coleoptera, Hymenoptera, Hemiptera, Neuroptera, Diptera, and Odonata) and 20 families. Diet varied over time and across geographic space, though we observed a general trend in which the orders Lepidoptera, Coleoptera, and Hymenoptera were consumed at the highest volumes. This varied diet indicates opportunistic feeding in which M. ciliolabrum makes use of locally abundant resources.

Colorado, New Mexico, Texas↗

USGS2025

Sprague’s Pipits (Anthus spragueii) occupying high-elevation intermontane valley habitat throughout the breeding season in southwest Montana

Sprague's Pipit ( Anthus spragueii ) is an imperiled bird species that breeds in grasslands of the northern Great Plains of North America. While conducting avian surveys in the Centennial Valley, Beaverhead County, southwest Montana, during spring and summer 2023, we detected approximately 10 male Sprague's Pipits performing aerial displays. These represent the first detailed observations of Sprague's Pipits in Beaverhead County, Montana, and the first confirmed observations of territorial displays therein. Subsequent detections included multiple adults, one of which was seen flying with food in its bill. We hypothesize that these observations represent a small but previously undescribed breeding population occurring above 2000 m elevation, which is higher than elevations at which this species is generally thought to breed. Our discovery also expands the known breeding habitat of this species to include intermontane valley bottoms, raising questions of whether the historical range included this habitat prior to its large-scale modifications across western North America and contemporary global change. These additions to our understanding of Sprague's Pipit ecology may be important for both land managers in the region and conservation efforts for this species. The evidence described here, of a breeding population of Sprague's Pipits in the Centennial Valley, Montana, may warrant further investigations in intermontane valleys throughout the region to better understand the breeding extent and the management actions needed to conserve this species and its habitat.

Montana↗

USGS2025

Comparative life history of mud turtles (genus: Kinosternon) from the North American deserts

The warm deserts of North America are characterized by diverse environments that include the transition zone between tropical and temperate regions on the continent. This vast region includes the Sonoran and Chihuahuan deserts, which have different precipitation regimes and are composed of different floras and faunas, separated by the Cochise Filter Barrier. Inhabiting these deserts are 7 mud turtles (representing 4 separate clades within the genus Kinosternon ), and we compared their basic ecology, life history, and estivation time to test for variation between deserts. We used phylogenetic comparative methods to correlate the life history traits with environmental variables (temperature and precipitation) to test for variation between deserts. Life history strategies (clutch size, egg size, and reproductive phenology) of mud turtles were similar across both deserts, with negative correlations of clutch size and age of maturity with both aridity and temperature variables. Maximum estivation time was correlated with the seasonality of each included locality. Overall, life history strategies were quite similar, with small local specializations to avoid high temperatures and periodic lack of water. From a population ecology perspective, populations showed varied sex ratios biased toward males or females, along with different population structure among populations and species. However, most published studies lacked data for hatchlings. Phylogenetic signal is high in traits related to body size, including sexual size dimorphism. Overall, mud turtles from the southwest deserts are adapted to regional seasonality and precipitation regimes, with minor adjustments to fit local conditions.

Western North American Naturalist↗

USGS2006

Transverse and longitudinal variation in woody riparian vegetation along a montane river

This study explores how the relationship between flow and riparian vegetation varies along a montane river. We mapped occurrence of woody riparian plant communities along 58 km of the San Miguel River in southwestern Colorado. We determined the recurrence interval of inundation for each plant community by combining step-backwater hydraulic modeling at 4 representative reaches with Log-Pearson analysis of 4 stream gaging stations. Finally, we mapped bottomland surficial geology and used a Geographic Information System to overlay the coverages of geology and vegetation. Plant communities were distinctly arrayed along the hydrologic gradient. The Salix exigua Nuttall (sand-bar willow) community occurred mostly on surfaces with a recurrence interval of inundation shorter than 2.2 years; the Betula occidentalis Hooker (river birch) community peaked on sites with recurrence intervals of inundation between 2.2 and 4.6 years. The hydrologic position occupied by communities dominated by Populus angustifolia James (narrowleaf cottonwood) was strongly related to age of trees and species composition of understory shrubs. The fraction of riparian vegetation on surfaces historically inundated by the river decreased in the upstream direction from almost 100% near Uravan to <50% along the South Fork of the San Miguel River. In upstream reaches much of the physical disturbance necessary to maintain riparian vegetation is provided by valley-side processes including debris flows, floods from minor tributaries, landslides, and beaver activity. Where valley-side processes are important, prediction of riparian vegetation change based on alterations of river flow will be incomplete.

Western North American Naturalist↗

USGS2006

Evaluating plant invasions from both habitat and species perspectives

We present an approach to quantitatively assess nonnative plant invasions at landscape scales from both habitat and species perspectives. Our case study included 34 nonnative species found in 142 plots (0.1 ha) in 14 vegetation types within the Grand Staircase–Escalante National Monument, Utah. A plot invasion index, based on nonnative species richness and cover, showed that only 16 of 142 plots were heavily invaded. A species invasive index, based on frequency, cover, and number of vegetation types invaded, showed that only 7 of 34 plant species were highly invasive. Multiple regressions using habitat characteristics (moisture index, elevation, soil P, native species richness, maximum crust development class, bare ground, and rock) explained 60% of variation in nonnative species richness and 46% of variation in nonnative species cover. Three mesic habitats (aspen, wet meadow, and perennial riparian types) were particularly invaded (31 of 34 nonnative species studied were found in these types). Species-specific logistic regression models for the 7 most invasive species correctly predicted occurrence 89% of the time on average (from 80% for Bromus tectorum , a habitat generalist, to 93% for Tamarix spp., a habitat specialist). Even with such a modest sampling intensity (<0.1% of the landscape), this multiscale sampling scheme was effective at evaluating habitat vulnerability to invasion and the occurrence of the 7 most invasive nonnative species. This approach could be applied in other natural areas to develop strategies to document invasive species and invaded habitats.

Utah↗

USGS2007

Effects of exotic grasses on soil seed banks in Southeastern Arizona grasslands

At the Appleton-Whittell Research Ranch, an ungrazed grassland preserve in southeastern Arizona, soil seed banks were sampled in June, August, and October 2002 and June 2003. Wildfire had previously burned 90% of the research ranch in May 2002. Seed density and species richness in burned native grassland (2 plots) were compared to those in burned exotic grassland (2 plots). Averaged over 4 sample dates, seed densities were as follows: burned native grassland, 591 ± 243.1 seeds ·m −2 and 784 ± 334.9 seeds ·m −2 ; burned exotic grassland, 501 ± 198.9 seeds ·m −2 and 196 ± 123.8 seeds ·m −2 . Species richness in the seed bank, also averaged over 4 sample dates, was as follows: burned native grassland, 16.3 ± 1.7 species ·m −2 and 19.5 ± 1.0 species ·m −2 ; burned exotic grassland, 12.0 ± 3.4 species ·m −2 and 11.06 ± 2.5 species ·m −2 . The seed bank of burned exotic grassland contained significantly fewer seeds and species than that of burned native grassland. In addition, the seed bank in burned exotic grassland comprised mainly exotic grasses, whereas annual and perennial herbs, most of them native, dominated the seed bank of burned native grassland. Of the 50 species detected in soil samples, only 20 had a persistent seed bank, and only 1 of these was a native perennial bunchgrass. The preponderance of transient species means that eradication of exotic grasses must be followed by reseeding of native grasses and herbs, perhaps repeatedly, if native grassland is to replace exotic grassland.

Arizona↗