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USGS2010

Effects of radiotransmitter necklaces on behaviors of adult male western burrowing owls

We studied the behavioral effects of necklace-style radiotransmitters on breeding male western burrowing owls (Athene cunicularia hypugaea) in 2 areas of northwestern Texas, USA, in 2004 and 2005. We tested the hypothesis that transmittered owls would spend time interacting with their necklaces and as a result spend less time in vigilance and resting activities than would nontransmittered owls. Nontransmittered owls (n = 6) spent significantly more time being vigilant (P = 0.007) than did transmittered owls (n = 3) in 2004, who spent significant amounts of time interacting with their necklaces. In 2005, behaviors of transmittered owls (n = 8) were significantly different (P < 0.001) from control individuals (n = 4), but behaviors did not vary consistently by treatment period (prenecklace vs. necklace vs. postnecklace periods). Behavioral activity budgets varied considerably among individuals. Although the owls spent a significant amount of time interacting with their necklaces, they appeared to habituate to the presence of the transmitters within a relatively short period (<1 week), and necklaces did not affect survivorship or fitness in the short-term.

Journal of Wildlife Management↗

USGS1999

Productivity, diets, and environmental contaminants in nesting bald eagles from the Aleutian Archipelago

We studied productivity, diets, and environmental contaminants in nesting bald eagles from the western Aleutian Islands, Alaska, USA, during the summers of 1993 and 1994. Productivity on Adak, Tanaga, and Amchitka Islands ranged from 0.88 to 1.24 young produced per occupied site and was comparable to that of healthy populations in the lower 48 United States. However, productivity on Kiska Island was depressed, averaging 0.67 young per occupied site. The lower reproductive success on Kiska was associated with elevated levels of dichlorodiphenyldichloroethylene and other organochlorine pesticides. Many of the organochlorine pesticides were elevated in bald eagle eggs from the four islands, but concentrations of these contaminants and Hg were significantly higher in eggs from Kiska Island than in eggs from the other islands. In contrast, polychlorinated biphenyl concentrations were higher in eggs from Adak, Amchitka, and Kiska (where military facilities have been installed) than in those from Tanaga (which has had little military activity). The most likely source of these contaminants in bald eagles was from their diets, which were variable spatially and temporally. Fish made up most (56%) of the eagles' diet on Adak and Tanaga Islands, followed by birds (25%) and mammals (19%). In contrast, birds comprised the majority (60%) of bald eagle diets on Amchitka and Kiska Islands, followed by mammals (30%) and fish (10%). The high proportion of seabirds in the diet of eagles from Kiska Island could be the major source of organochlorine and Hg contamination. Elevated concentrations of organochlorines in bald eagle eggs from the Aleutian Archipelago was surprising, because of the distance to agricultural areas. The results indicate that these contaminants can be transported long distances and affect wildlife populations in remote and pristine areas. We also discuss potential sources and transport mechanisms of these contaminants to the Aleutian Islands.

Environmental Toxicology and Chemistry↗

USGS1984

Elk and deer diets in old-growth forests in western Washington

Dietary quality and overlap of sympatric Roosevelt elk ( Cervus elaphus roosevelti ) and Columbian black-tailed deer ( Odocoileus hemionus columbianus ) were investigated in old-growth forests of the Hoh Valley, Olympic National Park, Washington. Diets of both cervids were comprised mainly of common old-growth flora, particularly in winter. High dietary overlap suggested competitive interactions for food, especially in winter when forage resources were least available. Predominant forages in fall and winter diets seemed to afford little opportunity for cervids to select different plant parts. Crude protein (CP), in vitro dry matter digestibility (IVDMD), and phosphorus (P) in important forages varied with phenology, but seasonal trends were more pronounced for shrubs and grasses than forbs and trees. CP, IVDMD, and P in cervid diets also varied seasonally and usually in the following ascending order: winter, fall, summer, spring. CP and P appeared to be adequate in diets, but low IVDMD suggested that digestible energy was limited. Few significant differences in seasonal dietary qualities were demonstrated between elk and deer. The collective cervid population (and its habitat) in the Hoh Valley is unmanaged and probably at equilibrium with its food resource, or at ecological carrying capacity. Results are discussed in light of herbivore--habitat interactions at equilibrium densities.

Washington↗

USGS2010

Movements of juvenile common ravens in an arid landscape

Movement patterns of juvenile birds are poorly understood, yet critically important ecological phenomena, especially for species with a prolonged juvenile period. We evaluated postfledging movements of juvenile common ravens (Corvus corax) in a western Mojave Desert landscape composed of a mosaic of natural and anthropogenic elements. Generally, ravens do not begin breeding until after their fourth year. We marked 2 annual cohorts of juvenile ravens and followed them from dispersal from their natal territory for up to 33 months. Movements of juvenile common ravens were similar for males and females. Conspecifics and confined livestock feeding operations represented important resources for juvenile ravens, and juveniles were rarely located in open desert. However, initial movements from the natal territory to the nearest communal point subsidy rather than the closest anthropogenic resource suggested juvenile dispersal was influenced by the combination of conspecifics and anthropogenic resources, rather than the distribution of those resources. Land managers concerned with growing raven populations should reduce access to concentrated anthropogenic resources such as landfills and dairies, which serve as important resources for juveniles. Because juvenile ravens rarely venture into open desert, reducing their numbers by lethal removal or other means is unlikely to lessen raven predation of desert tortoises (Gopherus agassizii).

Journal of Wildlife Management↗

USGS2021

Connectivity of Mojave Desert tortoise populations—Management implications for maintaining a viable recovery network

Executive Summary The historic distribution of Mojave desert tortoises ( Gopherus agassizii ) was relatively continuous across the range, and the importance of tortoise habitat outside of designated tortoise conservation areas (TCAs) to recovery has long been recognized for its contributions to supporting gene flow between TCAs and to minimizing impacts and edge effects within TCAs. However, connectivity of Mojave desert tortoise populations has become a concern because of recent and proposed development of large tracts of desert tortoise habitat that cross, fragment, and surround designated conservation areas. This paper summarizes the underlying concepts and importance of connectivity for Mojave desert tortoise populations by reviewing current information on connectivity and providing information to managers for maintaining or enhancing desert tortoise population connectivity as they consider future proposals for development and management actions. Maintaining an ecological network for the Mojave desert tortoise, with a system of core habitats (TCAs) connected by linkages, is necessary to support demographically viable populations and long-term gene flow within and between TCAs. There are four points for wildlife and land-management agencies to consider when making decisions that could affect connectivity of Mojave desert tortoise populations (for example, in updating actions in resource management plans or amendments that could help maintain or restore functional connectivity in light of the latest information): Management of all desert tortoise habitat for persistence and connectivity . Desert tortoise populations continue to decline within most TCAs, and it is unlikely that trends are better in populations outside protected areas. Fragmentation exacerbates negative population trends by breaking large continuous populations into smaller isolated populations. Connectivity within large populations can enhance resilience to localized disturbances due to rescue by neighboring individuals. In contrast, smaller fragmented populations are resistant to rescue by their isolation and thus could suffer irreversible declines to extirpation from a variety of threats and stochastic events. Enhanced threat reduction to reverse declines within TCAs and to maintain occupied habitat in the surrounding matrix would help reduce the variability in population growth rates and improve the resilience of protected populations even while implementing efforts to improve connectivity. Each TCA has unique strengths and weaknesses regarding its ability to support minimum sustainable populations based on areal extent and its ability to support population increases based on landscape connection with adjacent populations. Considering how proposed projects (inside or outside of TCAs) affect connectivity and the ability of TCAs to support at least 5,000 adult tortoises (the numerical goal for each TCA) could help managers to maintain the resilience of TCAs to population declines. The same project, in an alternative location, could have very different impacts on local and regional populations. For example, within the habitat matrix surrounding TCAs, narrowly delineated corridors may not allow for natural population dynamics if they do not accommodate overlapping home ranges along most of their widths so that tortoises reside, grow, find mates, and produce offspring that can replace older tortoises. In addition, most habitat outside TCAs may receive more surface disturbance than habitat within TCAs. Therefore, managing the entire remaining matrix of desert tortoise habitat for permeability may be better than delineating fixed corridors. These concepts apply, especially given uncertainty about long-term condition of habitat, within and outside of TCAs under a changing climate. Ultimately, questions such as “ What are the critical linkages that need to be protected ?” could be better framed as “ How can we manage the remaining habitat matrix in ways that sustain ecological processes and habitat suitability for special status species ?” Land-management decisions made in the context of the latter question may be more conducive to maintenance of a functional ecological network. Limitations on landscape-level disturbance across habitat managed for the desert tortoise Clearly delineating habitat linkages and differentiating them from non-delineated areas by the uses that are permitted or prohibited within them by specific management guidelines can help achieve functional connectivity. Such guidelines would be most effective if they considered and accounted for all surface disturbances (for example, temporary disturbances such as fiberoptic lines or off-highway vehicle routes, right-of-ways, utility-scale solar development, urbanization) to the extent possible. A weighted framework that varies with the permanence or severity of the disturbance, and can be additive to quantify cumulative effects, could be useful (Xiong, 2020). For example, minor roads can alter tortoise movements independently of other features (Peaden and others, 2017; Hromada and others, 2020), but if the isolated dirt road is accompanied by a powerline that encourages raven predation (Xiong, 2020), then the two features together may be additive. Ignoring minor or temporary disturbance on the landscape could result in a cumulatively large impact that is not explicitly acknowledged (Goble, 2009); therefore, understanding and quantifying all surface disturbance on a given landscape is prudent. In California, the Bureau of Land Management established 0.1–1.0 percent caps on new surface-disturbance for TCAs and mapped linkages that address the issues described in number 1 of this list. Nevada, Utah, and Arizona currently do not have surface-disturbance limits. Limits comparable to those in the Desert Renewable Energy Conservation Plan (DRECP) would be 0.5 percent within TCAs and 1 percent within the linkages modeled by Averill-Murray and others (2013). Limits in some areas of California within the Desert Renewable Energy Conservation Plan, such as Ivanpah Valley, are more restrictive, at 0.1 percent. Continuity across the state line in Nevada could be achieved with comparable limits in the adjacent portion of Ivanpah Valley, as well as the Greater Trout Canyon Translocation Area and the Stump Springs Regional Augmentation Site. These more restrictive limits would help protect remaining habitat in the major interstate connectivity pathway through Ivanpah Valley and focal areas of population augmentation that provide additional population connectivity along the western flank of the Spring Mountains. In a recent study that analyzed 13 years of desert tortoise monitoring data, nearly all desert tortoise observations were at sites in which 5 percent or less of the surrounding landscape within 1 kilometer was disturbed (Carter and others, 2020a). To help maintain tortoise habitability and permeability across all other non-conservation-designated tortoise habitat, all surface disturbance could be limited to less than 5-percent development per square kilometer because the 5-percent threshold for development is the point at which tortoise occupation drops precipitously (Carter and others, 2020a). However, although individual desert tortoises were observed at development levels up to 5 percent, we do not know the fitness or reproductive characteristics of these individuals. This level of development also may not allow for long-term persistence of healthy populations that are of adequate size needed for demographic or functional connectivity; therefore, a conservative interpretation suggests that, ideally, development could be lower. Lower development levels would be particularly useful in areas within the upper 5th percentile of connectivity values modeled by Gray and others (2019). Reducing ancillary threats in places where connectivity is restricted to narrow strips of habitat, for example, narrow mountain passes or vegetated strips between solar development, could enhance the functionality of these vulnerable linkages. In such areas, maintaining multiple, redundant linkages could further enhance overall connectivity. Minimization of mortality from roads and maximization of passage under roads . Roads pose a significant threat to the long-term persistence of local tortoise populations, and roads of high traffic volume lead to severe population declines, which ultimately fragments populations farther away from the roads. Three points (a.–c.) pertain to reducing direct mortality of tortoises on the many paved roads that cross desert tortoise habitat and to maintaining a minimal level of permeability across these roads: Tortoise-exclusion fencing tied into culverts, underpasses, overpasses, or other passages below roads in desert tortoise habitat, would limit vehicular mortality of tortoises and provide opportunities for movement across the roads. Installation of shade structures on the habitat side of fences installed in areas with narrow population-depletion zones would limit overheating of tortoises that may pace the fence. Passages below highways could be maintained or retrofitted to ensure safe tortoise access, for example, by filling eroded drop-offs or modifying erosion-control features such as rip-rap to make them safer and more passable for tortoises. Wildlife management agencies could work with transportation departments to develop construction standards that are consistent with hydrologic/erosion management goals, while also incorporating a design and materials consistent with tortoise survival and passage and make the standards widely available. The process would be most effective if the status of passages was regularly monitored and built into management plans. Healthy tortoise populations along fenced highways could be supported by ensuring that land inside tortoise-exclusion fences is not so degraded that it leads to degradation of tortoise habitat outside the exclusion areas. For example, severe invasive plant infestations inside a highway exclusion could cause an increase of invasive plants outside the exclusion area and degrade habitat; therefore, invasive plants inside road rights of way could be mown or treated with herbicide to limit their spread into adjacent tortoise habitat and minimize the risk of these plants carrying wildfires into adjacent habitat. Adaptation of management based on new information . Future research will continue to build upon and refine models related to desert tortoise population connectivity and develop new ones. New models could consider landscape levels of development and be constructed such that they share common foundations to support future synthesis efforts. If model development was undertaken in partnership with entities that are responsible for management of desert tortoise habitat, it would facilitate incorporation of current and future modeling results into their land management decisions. There are specific topics that may be clarified with further evaluation: The effects of climate change on desert tortoise habitat, distribution, and population connectivity; The effects of large-scale fires, especially within repeatedly burned habitat, on desert tortoise distribution and population connectivity; The ability of solar energy facilities or similar developments to support tortoise movement and presence by leaving washes intact; leaving native vegetation intact whenever possible, or if not possible, mowing the site, allowing vegetation to re-sprout, and managing weeds; and allowing tortoises to occupy the sites; and The design and frequency of underpasses necessary to maintain functional demographic and genetic connectivity across linear features, like highways.

Arizona, California, Nevada↗

USGS2006

Persistence of Pasteurella multocida in wetlands following avian cholera outbreaks

Avian cholera, caused by Pasteurella multocida, affects waterbirds across North America and occurs worldwide among various avian species. Once an epizootic begins, contamination of the wetland environment likely facilitates the transmission of P. multocida to susceptible birds. To evaluate the ability of P. multocida serotype-1, the most common serotype associated with avian cholera in waterfowl in western and central North America, to persist in wetlands and to identify environmental factors associated with its persistence, we collected water and sediment samples from 23 wetlands during winters and springs of 1996a??99. These samples were collected during avian cholera outbreaks and for up to 13 wk following initial sampling. We recovered P. multocida from six wetlands that were sampled following the initial outbreaks, but no P. multocida was isolated later than 7 wk after the initial outbreak sampling. We found no significant relationship between the probability of recovery of P. multocida during resampling and the abundance of the bacterium recovered during initial sampling, the substrate from which isolates were collected, isolate virulence, or water quality conditions previously suggested to be related to the abundance or survival of P. multocida. Our results indicate that wetlands are unlikely to serve as a long-term reservoir for P. multocida because the bacterium does not persist in wetlands for long time periods following avian cholera outbreaks.

Journal of Wildlife Diseases↗

USGS2025

Factors associated with survival, recovery, and movements in the western Gulf Coast population of mottled ducks

The mottled duck ( Anas fulvigula ) is nonmigratory and a priority species for regional conservation and management because of its limited range and declining population trajectory in the western Gulf Coast (WGC) of Louisiana and Texas, USA. We developed multistate dead-recovery models for banding and recovery data (1997–2020) to evaluate potential drivers of survival, recovery, and post-summer movements for the WGC population of mottled ducks in Louisiana and Texas. Annual survival was most strongly associated with sex and year, with females having lower survival ( ± = 0.544 ± 0.114) than males (0.619 ± 0.062). Of the 32 environmental covariates tested, fall precipitation was the factor most strongly associated with survival. Conditional recovery probability (i.e., given mortality, the probability a bird had been shot by a hunter, retrieved, and had their band number reported) varied by sex, age, geographic state, and year, with juvenile males generally having highest conditional recovery (0.303 ± 0.072), followed by juvenile females (0.201 ± 0.100), adult males (0.156 ± 0.038), and adult females (0.095 ± 0.057). Estimates of harvest probabilities followed similar patterns as conditional recovery. Models containing effects of harvest regulations on conditional recovery were not competitive compared to models with general year effects; however, post hoc analyses suggested conditional recovery and harvest probabilities for adult and juvenile females decreased with the daily bag limit reduction in Louisiana and, for juvenile females, implementation of the 5-day closure regulation in Texas. Post-summer movement was substantially higher in the direction of Texas to Louisiana, decreased with distance to the Louisiana–Texas border, was higher for males than females, and varied with winter precipitation. These results contribute to a better understanding of the factors influencing demographic performance, harvest, and movement between states with differing harvest regulations and environmental pressures, which is important for mottled duck conservation planning. Wildlife managers can consider expanding banding effort throughout the full range of the WGC population and collecting and reporting live-recapture data to allow for stronger population-level inferences and increased power to detect differences in important demographic parameters at more refined spatial scales.

Louisiana, Texas↗

USGS2012

Spring snow goose hunting influences body composition of waterfowl staging in Nebraska

A spring hunt was instituted in North America to reduce abundance of snow geese ( Chen caerulescens ) by increasing mortality of adults directly, yet disturbance from hunting activities can indirectly influence body condition and ultimately, reproductive success. We estimated effects of hunting disturbance by comparing body composition of snow geese and non-target species, greater white-fronted geese ( Anser albifrons ) and northern pintails ( Anas acuta ) collected in portions of south-central Nebraska that were open (eastern Rainwater Basin, ERB) and closed (western Rainwater Basin, WRB; and central Platte River Valley, CPRV) to snow goose hunting during springs 1998 and 1999. Lipid content of 170 snow geese was 25% (57 g) less in areas open to hunting compared to areas closed during hunting season but similar in all areas after hunting was concluded in the ERB. Protein content of snow geese was 3% (14 g) less in the region open to hunting. Greater white-fronted geese had 24% (76 g; n = 129) less lipids in the hunted portion of the study area during hunting season, and this difference persisted after conclusion of hunting season. We found little difference in lipid or protein content of northern pintails in relation to spring hunting. Indirect effects of spring hunting may be considered a collateral benefit regarding efforts to reduce overabundant snow goose populations. Disrupted nutrient storage observed in greater white-fronted geese represents an unintended consequence of spring hunting that has potential to adversely affect reproduction for this and other species of waterbirds staging in the region.

Nebraska↗

USGS2007

Comparison of immune responses of brown-headed cowbird and related blackbirds to West Nile and other mosquito-borne encephalitis viruses

The rapid geographic spread of West Nile virus (family Flaviviridae , genus Flavivirus , WNV) across the United States has stimulated interest in comparative host infection studies to delineate competent avian hosts critical for viral amplification. We compared the host competence of four taxonomically related blackbird species (Icteridae) after experimental infection with WNV and with two endemic, mosquito-borne encephalitis viruses, western equine encephalomyelitis virus (family Togaviridae , genus Alphavirus , WEEV), and St, Louis encephalitis virus (family Flaviviridae , genus Flavivirus , SLEV). We predicted differences in disease resistance among the blackbird species based on differences in life history, because they differ in geographic range and life history traits that include mating and breeding systems. Differences were observed among the response of these hosts to all three viruses, Red-winged Blackbirds were more susceptible to SLEV than Brewer's Blackbirds, whereas Brewer's Blackbirds were more susceptible to WEEV than Red-winged Blackbirds. In response to WNV infection, cowbirds showed the lowest mean viremias, cleared their infections faster, and showed lower antibody levels than concurrently infected species. Brown-headed Cowbirds also exhibited significantly lower viremia responses after infection with SLEV and WEEV as well as coinfection with WEEV and WNV than concurrently infected icterids. We concluded that cowbirds may be more resistant to infection to both native and introduced viruses because they experience heightened exposure to a variety of pathogens of parenting birds during the course of their parasitic life style.

Journal of Wildlife Diseases↗

USGS2018

Biodiversity of amphibians and reptiles at the Camp Cady Wildlife Area, Mojave Desert, California and comparisons with other desert locations

We examined the biodiversity of amphibian and reptile species living in and near constructed ponds in the riparian area at the Camp Cady Wildlife Area (CCWA) in the Mojave Desert of San Bernardino County, California, based on field work from 1998-1999, 2016-2017, review of the literature, and searches for museum specimens using VertNet.org. A total of 11 species (201 captures), including two frogs and toads (one non-native frog), one turtle, three snakes, and five lizards were captured at terrestrial drift fences with pitfall traps encircling two ponds (0.5 hectares total) on the property in 1999. Four additional species (one frog, one lizard, and two snakes) were previously reported in 1978 from a ranch 1.6 km southwest from CCWA for a total of 15 species in the local area. The southwestern pond turtle (Actinemys pallida), was commonly observed at CCWA from 1998 to 1999 and documented as a breeding population. However, the species was extirpated at CCWA sometime after 2014 when the last individuals were photographed, and none have been detected since then despite significant efforts to do so. Biodiversity of amphibians and reptiles at CCWA is relatively low compared with sites elsewhere in the Mojave Desert with more elevational diversity. The 14 native species documented at CCWA accounts for approximately 21% of the native reptile and amphibian species reported by Stewart (1994) for the entire Mojave Desert, including peripheral species. Our smaller sample likely represents a group of easily detected species and is biased toward those found in or near water, especially amphibians. However, the relative proportion of amphibians vs. reptiles that inhabited CCWA in the last 40 years is not significantly different from the recently compiled proportions at five military installations in the California deserts. The herpetofauna inhabiting CCWA is notable for including riparian obligates like the western toad (Anaxyrus boreas), Northern Baja California treefrog (Pseudacris h. hypochondriaca), and A. pallida that are otherwise absent from large portions of the Mojave Desert. Other species are typical of those that are expected in the low-elevation creosote scrubdominated ecosystem in the area.

California↗

USGS2015

Observations of territorial breeding common ravens caching eggs of greater sage-grouse

Previous investigations using continuous video monitoring of greater sage-grouse Centrocercus urophasianus nests have unambiguously identified common ravens Corvus corax as an important egg predator within the western United States. The quantity of greater sage-grouse eggs an individual common raven consumes during the nesting period and the extent to which common ravens actively hunt greater sage-grouse nests are largely unknown. However, some evidence suggests that territorial breeding common ravens, rather than nonbreeding transients, are most likely responsible for nest depredations. We describe greater sage-grouse egg depredation observations obtained opportunistically from three common raven nests located in Idaho and Nevada where depredated greater sage-grouse eggs were found at or in the immediate vicinity of the nest site, including the caching of eggs in nearby rock crevices. We opportunistically monitored these nests by counting and removing depredated eggs and shell fragments from the nest sites during each visit to determine the extent to which the common raven pairs preyed on greater sage-grouse eggs. To our knowledge, our observations represent the first evidence that breeding, territorial pairs of common ravens cache greater sage-grouse eggs and are capable of depredating multiple greater sage-grouse nests.

Idaho, Nevada↗

USGS2015

Laboratory investigations of African Pouched Rats ( Cricetomys gambianus ) as a potential reservoir host species for Monkeypox Virus

Monkeypox is a zoonotic disease endemic to central and western Africa, where it is a major public health concern. Although Monkeypox virus (MPXV) and monkeypox disease in humans have been well characterized, little is known about its natural history, or its maintenance in animal populations of sylvatic reservoir(s). In 2003, several species of rodents imported from Ghana were involved in a monkeypox outbreak in the United States with individuals of three African rodent genera ( Cricetomys , Graphiurus , Funisciurus ) shown to be infected with MPXV. Here, we examine the course of MPXV infection in Cricetomys gambianus (pouched Gambian rats) and this rodent species’ competence as a host for the virus. We obtained ten Gambian rats from an introduced colony in Grassy Key, Florida and infected eight of these via scarification with a challenge dose of 4X10 4 plaque forming units (pfu) from either of the two primary clades of MPXV: Congo Basin (C-MPXV: n = 4) or West African (W-MPXV: n = 4); an additional 2 animals served as PBS controls. Viral shedding and the effect of infection on activity and physiological aspects of the animals were measured. MPXV challenged animals had significantly higher core body temperatures, reduced activity and increased weight loss than PBS controls. Viable virus was found in samples taken from animals in both experimental groups (C-MPXV and W-MPXV) between 3 and 27 days post infection (p.i.) (up to 1X10 8 pfu/ml), with viral DNA found until day 56 p.i. The results from this work show that Cricetomys gambianus (and by inference, probably the closely related species, Cricetomys emini ) can be infected with MPXV and shed viable virus particles; thus suggesting that these animals may be involved in the maintenance of MPXV in wildlife mammalian populations. More research is needed to elucidate the epidemiology of MPXV and the role of Gambian rats and other species.

PLoS Neglected Tropical Diseases↗

USGS2018

Prevalence and risk factors of Trichomonas gallinae and trichomonosis in golden eagle (Aquila chrysaetos) nestlings in western North America

Avian trichomonosis, caused by the protozoan Trichomonas gallinae , affects bird-eating raptors worldwide. Raptors can develop trichomonosis by feeding on infected prey, particularly Rock Pigeons (C olumba livia ), which are a reservoir for T. gallinae . Raptors may be particularly vulnerable to T. gallinae infection in degraded habitats, where changes in resources may cause raptors to switch from foraging on native prey to synanthropic avian species such as Rock Pigeons. Golden Eagles ( Aquila chrysaetos ) typically forage on mammals; however, habitat across much of their range is experiencing degradation through changes in land use, climate, and human encroachment. In 2015, we examined the prevalence of T. gallinae infection in Golden Eagle nestlings across western North America and conducted an intensive study on factors associated with T. gallinae infection and trichomonosis in southwestern Idaho. We found T. gallinae infection in 13% (12/96) of eagle nestlings across 10 western states and in 41% (13/32) of nestlings in southwestern Idaho. At the Idaho site, the probability of T. gallinae infection increased as the proportion of Rock Pigeons in nestling diet increased. Nestlings with diets that consisted of ≥10% Rock Pigeons had a very high probability of T. gallinae infection. We compared historical (1971–81) and recent (2014–15) diet data and incidence of trichomonosis lesions of nestling eagles in Idaho and found that the proportion of Rock Pigeons in eagle diets was higher in recent versus historical periods, as was the proportion of eagle nestlings with trichomonosis lesions. Our results suggested that localized shifts in eagle diet that result from habitat degradation and loss of historical prey resources have the potential to affect Golden Eagle nestling survival and supported the hypothesis that land use change can alter biologic communities in a way that might have consequences for disease infection and host susceptibility.

Journal of Wildlife Diseases↗

USGS1999

Reference intervals and physiologic alterations in hematologic and biochemical values of free-ranging desert tortoises in the Mojave Desert

Desert tortoise ( Gopherus agassizii ) populations have experienced precipitous declines resulting from the cumulative impact of habitat loss, and human and disease-related mortality. Evaluation of hematologic and biochemical responses of desert tortoises to physiologic and environmental factors can facilitate the assessment of stress and disease in tortoises and contribute to management decisions and population recovery. The goal of this study was to obtain and analyze clinical laboratory data from free-ranging desert tortoises at three sites in the Mojave Desert (California, USA) between October 1990 and October 1995, to establish reference intervals, and to develop guidelines for the interpretation of laboratory data under a variety of environmental and physiologic conditions. Body weight, carapace length, and venous blood samples for a complete blood count and clinical chemistry profile were obtained from 98 clinically healthy adult desert tortoises of both sexes at the Desert Tortoise Research Natural area (western Mojave), Goffs (eastern Mojave) and Ivanpah Valley (northeastern Mojave). Samples were obtained four times per year, in winter (February/March), spring (May/June), summer (July/August), and fall (October). Years of near-, above- and below-average rainfall were represented in the 5 yr period. Minimum, maximum and median values, and central 95 percentiles were used as reference intervals and measures of central tendency for tortoises at each site and/or season. Data were analyzed using repeated measures analysis of variance for significant ( P < 0.01) variation on the basis of sex, site, season, and interactions between these variables. Significant sex differences were observed for packed cell volume, hemoglobin concentration, aspartate transaminase activity, and cholesterol, triglyceride, calcium, and phosphorus concentrations. Marked seasonal variation was observed in most parameters in conjunction with reproductive cycle, hibernation, or seasonal rainfall. Year-to-year differences and long-term alterations primarily reflected winter rainfall amounts. Site differences were minimal, and largely reflected geographic differences in precipitation patterns, such that results from these studies can be applied to other tortoise populations in environments with known rainfall and forage availability patterns.

Journal of Wildlife Diseases↗

USGS2016

Susceptibility and antibody response of Vesper Sparrows ( Pooecetes gramineus ) to West Nile virus: A potential amplification host in sagebrush-grassland habitat

West Nile virus (WNV) spread to the US western plains states in 2003, when a significant mortality event attributed to WNV occurred in Greater Sage-grouse ( Centrocercus urophasianus ). The role of avian species inhabiting sagebrush in the amplification of WNV in arid and semiarid regions of the North America is unknown. We conducted an experimental WNV challenge study in Vesper Sparrows ( Pooecetes gramineus ), a species common to sagebrush and grassland habitats found throughout much of North America. We found Vesper Sparrows to be moderately susceptible to WNV, developing viremia considered sufficient to transmit WNV to feeding mosquitoes, but the majority of birds were capable of surviving infection and developing a humoral immune response to the WNV nonstructural 1 and envelope proteins. Despite clearance of viremia, after 6 mo, WNV was detected molecularly in three birds and cultured from one bird. Surviving Vesper Sparrows were resistant to reinfection 6 mo after the initial challenge. Vesper sparrows could play a role in the amplification of WNV in sagebrush habitat and other areas of their range, but rapid clearance of WNV may limit their importance as competent amplification hosts of WNV.

Nevada↗

USGS2010

Identifying sites for elk restoration in Arkansas

We used spatial data to identify potential areas for elk ( Cervus elaphus ) restoration in Arkansas. To assess habitat, we used locations of 239 elk groups collected from helicopter surveys in the Buffalo National River area of northwestern Arkansas, USA, from 1992 to 2002. We calculated the Mahalanobis distance ( D 2 ) statistic based on the relationship between those elk-group locations and a suite of 9 landscape variables to evaluate winter habitat in Arkansas. We tested model performance in the Buffalo National River area by comparing the D 2 values of pixels representing areas with and without elk pellets along 19 fixed-width transects surveyed in March 2002. Pixels with elk scat had lower D 2 values than pixels in which we found no pellets (logistic regression: Wald χ 2 = 24.37, P < 0.001), indicating that habitat characteristics were similar to those selected by the aerially surveyed elk. Our D 2 model indicated that the best elk habitat primarily occurred in northern and western Arkansas and was associated with areas of high landscape heterogeneity, heavy forest cover, gently sloping ridge tops and valleys, low human population density, and low road densities. To assess the potential for elk–human conflicts in Arkansas, we used the analytical hierarchy process to rank the importance of 8 criteria based on expert opinion from biologists involved in elk management. The biologists ranked availability of forage on public lands as having the strongest influence on the potential for elk–human conflict (33%), followed by human population growth rate (22%) and the amount of private land in row crops (18%). We then applied those rankings in a weighted linear summation to map the relative potential for elk–human conflict. Finally, we used white-tailed deer ( Odocoileus virginianus ) densities to identify areas where success of elk restoration may be hampered due to meningeal worm ( Parelaphostrongylus tenuis ) transmission. By combining results of the 3 spatial data layers (i.e., habitat model, elk–human conflict model, deer density), our model indicated that restoration sites located in west-central and north-central Arkansas were most favorable for reintroduction.

Arkansas↗

USGS2011

Nest success of grassland sparrows on reclaimed surface mines

Grasslands resulting from surface mine reclamation support grassland songbird populations in several midwestern and eastern states in the United States, especially where reclaimed mines are large (>1,000ha). However, most reclaimed surface mines in Pennsylvania are small (<200ha), and nest success is unknown. We evaluated nest success of grasshopper (Ammodramus savannarum), Henslow's (A. henslowii), and Savannah sparrows (Passerculus sandwichensis) on 4 reclaimed surface mines (50-180ha) in western Pennsylvania, USA from 2006 to 2007. Overall nest success based on mean covariate values was 0.435 (95% CI = 0.376-0.504) for grasshopper sparrows, 0.396 (95% CI = 0.295-0.533) for Henslow's sparrows, and 0.158 (95% CI = 0.063-0.392) for Savannah sparrows. These estimates of nest success are comparable to those on larger reclaimed mines and other habitats. Grasshopper and Henslow's sparrow nests that were well concealed were less likely to fail than highly visible nests (??visible = -0.028, CI = -0.051 to -0.005 for grasshopper sparrows; ??visible = -0.063, CI = -0.112 to -0.014 for Henslow's sparrows), and nests in areas with surrounding deep litter were more likely to fail than nests in areas with shallow litter (??litterD = -0.145, CI = -0.335 to 0.045 for grasshopper sparrows; ??litterD = -0.676, CI = -1.187 to -0.116 for Henslow's sparrows). Savannah sparrow nests in areas with high visual obstruction by vegetation were less likely to fail than nests in areas with sparse and short vegetation (??VisOb = 0.048, CI = 0.006-0.091). Daily probability of survival for grasshopper sparrow nests was greatest early and late in the breeding season, and Savannah sparrow nest survival followed a decreasing linear trend. Nest survival of Henslow's sparrows was greater on warm days (??temp = 0.197, CI = 0.014-0.379), whereas for Savannah sparrows nest survival decreased on warm days and on days with rain, but for Savannah sparrows confidence intervals of weather effects included zero (??temp = -0.098, CI = -0.246 to 0.050; ??rain = 3.13, CI = -14.19 to 20.45). We suggest that small reclaimed surface mine grasslands can provide valuable nesting habitat and could be important to the conservation of grassland bird populations. Because nest success can increase in the latter part of the nesting season, agricultural disturbances or management activities in mid- to late summer could adversely affect reproductive success. ?? 2011 The Wildlife Society.

Journal of Wildlife Management↗

USGS1999

Bat activity in thinned, unthinned, and old-growth forests in western Oregon

Many aspects of the influences of forest management activities on bats (Chiroptera) in the Pacific Northwest are poorly known. We compared thinned and unthinned forest stands of the same age and old-growth forest stands to determine potential differences in structure and amount of use by bats. We hypothesized that activity levels of bats would differ in stands differing in structure as a result of management history and that activity of bats would be similar in stands of similar structure. We used automated ultrasonic detectors (Anabat II) to record calls of bats in 50-100-year-old thinned and unthinned stands, and in old-growth (a?Y200 yr old) stands in the Oregon Coast Range during the summers of 1994 and 1995. Our median index of bat activity was higher in old-growth than in unthinned stands and higher in thinned than in unthinned stands. We were not able to detect a significant difference between the index of median bat activity for old-growth and thinned stands. More than 90% of identifiable passes were identified as calls from Myotis species. The 3 stand types we examined differed in certain structural characteristics such as density and size of trees, and amount of overstory and understory cover. We concluded that the structural changes caused by thinning may benefit bats by creating habitat structure in young stands that bats are able to use more effectively.

Journal of Wildlife Management↗