Geology topics

W. David Walter

Publications and source records attributed to W. David Walter.

54 records · Page 3Linked to original sources

USGS2018

Heterogeneity of a landscape influences size of home range in a North American cervid

In the northeastern United States, chronic wasting disease has recently been detected in white-tailed deer ( Odocoileus virginianus ) populations, and understanding the relationship between landscape configuration and home range may improve disease surveillance and containment efforts. The objectives of our study were to compare size of home range for deer occupying a continuum of forested landscapes and to investigate relationships between size of home range and measures of landscape configuration. We used a movement-based kernel density estimator to estimate home range at five spatial scales among deer across study areas. We developed 7 linear regression models that used measures of the configuration of the forested landscape to explain size of home range. We observed differences in size of home range between sexes among areas that differed based on landscape configuration. We documented size of home range changed with various metrics that identifying connectivity of forested patches. Generally, size of home range increased with an increasing proportion of homogenous forest. Our results suggest that deer in our region occupy a landscape at hierarchically-nested scales that is controlled by the connectivity of the forested landscape across local or broad geographical regions.

Pennsylvania↗

USGS2018

Incorporating detection probability to estimate pheasant density

ndices of abundance, such as point counts, commonly are used to monitor trends in bird populations. In some circumstances, however, an index of abundance provides insufficient information for making management decisions and accurate density estimates are necessary. Wild ring-necked pheasants ( Phasianus colchicus ) were translocated to 10 study areas in Pennsylvania from 2007 to 2014 with the goal of establishing female densities of 3.86 pheasants/km 2 . We developed a population density estimator that used 3-minute crowing counts adjusted for probability of detection to estimate male pheasant density and flushing surveys to estimate the female:male ratio. To account for detection probability, we estimated the probability a pheasant was available to be detected by monitoring crowing frequency of male pheasants fitted with radio-transmitters and the probability an observer was able to detect a crowing pheasant at distances from 0 to 0.93 km. We found the probability a pheasant crowed during 3 minutes decreased linearly over our survey period from 0.66 in mid-April to 0.46 by the end of May. At the farthest distance we were able to accurately detect a crowing pheasant. We estimated the probability of detecting a pheasant at 0.80 km to be 0.019 ± 0.005 (SE), which means that we could not assume any fixed distance beyond which crowing birds could not be detected. Therefore, we replaced the probability of detection in the standard distance sampling estimator with the effective area of detection. The estimation of the effective area of detection is robust to choice of radius of the point and did not require observers to estimate the distance to crowing pheasants. We estimated the female:male ratio to be 1.02:1, despite the ratio of released pheasants being 4.46:1. Only 1 study area achieved the female density goal ( = 4.16); the maximum density at all other study areas was <2 females/km 2 . The estimator we developed incorporated multiple detection probabilities to provide density estimates and simplified the crowing count protocol by eliminating the need for observers to estimate their distance from a detected bird, which makes the estimator useful for estimation of population abundance when explicit population density objectives must be evaluated.

Pennsylvania↗

USGS2018

Chronic wasting disease—Status, science, and management support by the U.S. Geological Survey

The U.S. Geological Survey (USGS) investigates chronic wasting disease (CWD) at multiple science centers and cooperative research units across the Nation and supports the management of CWD through science-based strategies. CWD research conducted by USGS scientists has three strategies: (1) to understand the biology, ecology, and causes and distribution of CWD; (2) to assess and predict the spread and persistence of CWD in wildlife and the environment; and (3) to develop tools for early detection, diagnosis, surveillance, and control of CWD.

Open-File Report↗

USGS2017

Influence of precipitation and crop germination on resource selection by mule deer (Odocoileus hemionus) in southwest Colorado

Mule deer ( Odocoileus hemionus ) populations in the western United States provide many benefits to local economies but can also cause considerable damage to agriculture, particularly damage to lucrative crops. Limited information exists to understand resource selection of mule deer in response to annual variation in crop rotation and climatic conditions. We tested the hypothesis that mule deer select certain crops, and in particular sunflower, based on annual climatic variability. Our objective was to use movements, estimates of home range, and resource selection analysis to identify resources selected by mule deer. We used annually-derived crop-specific datasets along with Global Positioning System collars to monitor 14 mule deer in an agricultural area near public lands in southwestern Colorado, USA. We estimated home ranges for two winter seasons that ranged between 7.68 and 9.88 km 2 , and for two summer seasons that ranged between 5.51 and 6.24 km 2 . Mule deer selected areas closer to forest and alfalfa for most periods during 2012, but selected areas closer to sunflower in a majority of periods during 2013. Considerable annual variation in climate patterns and precipitation levels appeared to influence selection by mule deer because of variability in crop rotation and success of germination of specific crops.

Colorado, Utah↗

USGS2017

CWDPRNP: A tool for cervid prion sequence analysis in program R

Chronic wasting disease is a fatal, neurological disease caused by an infectious prion protein, which affects economically and ecologically important members of the family Cervidae. Single nucleotide polymorphisms within the prion protein gene have been linked to differential susceptibility to the disease in many species. Wildlife managers are seeking to determine the frequencies of disease-associated alleles and genotypes and delineate spatial genetic patterns. The CWDPRNP package, implemented in program R, provides a unified framework for analyzing prion protein gene variability and spatial structure.

Bioinformatics↗

USGS2016

Evaluating a strategy to deliver vaccine to white-tailed deer at a landscape level

Effective delivery of vaccines and other pharmaceuticals to wildlife populations is needed when zoonotic diseases pose a risk to public health and natural resources or have considerable economic consequences. The objective of our study was to develop a bait-distribution strategy for potential delivery of oral bovine tuberculosis (bTB) vaccine to white-tailed deer ( Odocoileus virginianus ) where deer are reservoirs for the disease. During 17 February and 2 March 2011, we created a grid of experimental bait stations ( n  = 64) on Sandhill Wildlife Management Area, Wisconsin, USA, to assess station densities needed to attract and deliver placebo baits to free-ranging white-tailed deer and look for associations among deer density, number of bait stations per deer, and bait consumption. We placed 1 L of commercially available alfalfa cubes at bait stations 652 m apart, and monitored stations with motion-activated cameras for 5 days to document visitation and consumption by deer and nontarget species. Deer discovered 38% of all bait stations within 37 hr, on average (SE = 3.91 hr), and consumed variable amounts of bait at each station. Deer were documented in 94% of all photographs of wildlife at bait stations. We found no correlation between bait consumption and deer density or the number of bait stations per deer. We provide the first information on use of baits by free-ranging deer and nontarget wildlife to eventually vaccinate deer against bTB at a landscape level. The results of this study can further the development of strategies in delivery of pharmaceuticals to free-ranging white-tailed deer.

Wildlife Society Bulletin↗

USGS2016

Effects of repeated simulated removal activities on feral swine movements and space use

Abundance and distribution of feral swine ( Sus scrofa ) in the USA have increased dramatically during the last 30 years. Effective measures are needed to control and eradicate feral swine populations without displacing animals over wider areas. Our objective was to investigate effects of repeated simulated removal activities on feral swine movements and space use. We analyzed location data from 21 feral swine that we fitted with Global Positioning System harnesses in southern MO, USA. Various removal activities were applied over time to eight feral swine before lethal removal, including trapped-and-released, chased with dogs, chased with hunter, and chased with helicopter. We found that core space-use areas were reduced following the first removal activity, whereas overall space-use areas and diurnal movement distances increased following the second removal activity. Mean geographic centroid shifts did not differ between pre- and post-periods for either the first or second removal activities. Our information on feral swine movements and space use precipitated by human removal activities, such as hunting, trapping, and chasing with dogs, helps fill a knowledge void and will aid wildlife managers. Strategies to optimize management are needed to reduce feral swine populations while preventing enlarged home ranges and displacing individuals, which could lead to increased disease transmission risk and human-feral swine conflict in adjacent areas.

European Journal of Wildlife Research↗

USGS2016

Antemortem detection of chronic wasting disease prions in nasal brush collections and rectal biopsies from white-tailed deer by real time quaking-induced conversion

Chronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, was first documented nearly 50 years ago in Colorado and Wyoming and has since spread to cervids in 23 states, two Canadian provinces, and the Republic of Korea. The expansion of this disease makes the development of sensitive diagnostic assays and antemortem sampling techniques crucial for the mitigation of its spread; this is especially true in cases of relocation/reintroduction of farmed or free-ranging deer and elk or surveillance studies of private or protected herds, where depopulation is contraindicated. This study sought to evaluate the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay by using recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens and nasal brush samples collected antemortem from farmed white-tailed deer ( n = 409). Antemortem findings were then compared to results from ante- and postmortem samples (RAMALT, brainstem, and medial retropharyngeal lymph nodes) evaluated by using the current gold standard in vitro assay, immunohistochemistry (IHC) analysis. We hypothesized that the sensitivity of RT-QuIC would be comparable to IHC analysis in antemortem tissues and would correlate with both the genotype and the stage of clinical disease. Our results showed that RAMALT testing by RT-QuIC assay had the highest sensitivity (69.8%) compared to that of postmortem testing, with a specificity of >93.9%. These data suggest that RT-QuIC, like IHC analysis, is an effective assay for detection of PrP CWD in rectal biopsy specimens and other antemortem samples and, with further research to identify more sensitive tissues, bodily fluids, or experimental conditions, has potential for large-scale and rapid automated testing for CWD diagnosis.

Journal of Clinical Microbiology↗

USGS2016

Seeded amplification of chronic wasting disease prions in nasal brushings and recto-anal mucosal associated lymphoid tissues from elk by real time quaking-induced conversion

Chronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, was first documented nearly 50 years ago in Colorado and Wyoming and has since been detected across North America and the Republic of Korea. The expansion of this disease makes the development of sensitive diagnostic assays and antemortem sampling techniques crucial for the mitigation of its spread; this is especially true in cases of relocation/reintroduction or prevalence studies of large or protected herds, where depopulation may be contraindicated. This study evaluated the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay of recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens and nasal brushings collected antemortem. These findings were compared to results of immunohistochemistry (IHC) analysis of ante- and postmortem samples. RAMALT samples were collected from populations of farmed and free-ranging Rocky Mountain elk ( Cervus elaphus nelsoni ; n = 323), and nasal brush samples were collected from a subpopulation of these animals ( n = 205). We hypothesized that the sensitivity of RT-QuIC would be comparable to that of IHC analysis of RAMALT and would correspond to that of IHC analysis of postmortem tissues. We found RAMALT sensitivity (77.3%) to be highly correlative between RT-QuIC and IHC analysis. Sensitivity was lower when testing nasal brushings (34%), though both RAMALT and nasal brush test sensitivities were dependent on both the PRNP genotype and disease progression determined by the obex score. These data suggest that RT-QuIC, like IHC analysis, is a relatively sensitive assay for detection of CWD prions in RAMALT biopsy specimens and, with further investigation, has potential for large-scale and rapid automated testing of antemortem samples for CWD.

Journal of Clinical Microbiology↗

USGS2016

Winter and summer home ranges of American White Pelicans (Pelecanus erythrorhynchos) captured at loafing sites in the southeastern United States

Satellite telemetry was used to investigate summer and winter home ranges for resident and migrant American White Pelicans ( Pelecanus erythrorhynchos ) captured in the southeastern United States between 2002 and 2007. Home range utilization distributions were calculated using 50% and 95% kernel density estimators with the plug-in bandwidth selector. Mean summer home ranges (95%) varied from 177 to 4,710 km 2 and mean winter home ranges (95%) ranged from 185 to 916 km 2 . Mean 50% and 95% home ranges of adult American White Pelicans during summer tended to be larger than those during winter, whereas mean 50% and 95% home ranges of immature pelicans during summer tended to be smaller than those during winter. Home ranges for all American White Pelicans encompassed the latitude range of 24°–55° N, including wintering, stop over, and nesting habitat. These data provide baseline movement and home range data for future studies of American White Pelican ecology.

Alabama, Arkansas, Louisiana, Mississippi↗

USGS2015

Habitat influences distribution of chronic wasting disease in white-tailed deer

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy that was first detected in 1967 in a captive research facility in Colorado. In the northeastern United States, CWD was first confirmed in white-tailed deer ( Odocoileus virginianus ) in 2005. Because CWD is a new and emerging disease with a spatial distribution that had yet to be assessed in the Northeast, we examined demographic, environmental, and spatial effects to determine how each related to this spatial distribution. The objectives of our study were to identify environmental and spatial effects that best described the spatial distribution of CWD in free-ranging white-tailed deer and identify areas that support deer that are at risk for CWD infection in the Northeast. We used Bayesian hierarchical modeling that incorporated demographic covariates, such as sex and age, along with environmental covariates, which included elevation, slope, riparian corridor, percent clay, and 3 landscapes (i.e., developed, forested, open). The model with the most support contained landscape covariates and spatial effects that represented clustering of CWD in adjacent grid cells. Forested landscapes had the strongest relationship with the distribution of CWD, with increased risk of CWD occurring in areas that had lesser amounts of forest. Our results will assist resource managers in understanding the spatial distribution of CWD within the study area, and in surrounding areas where CWD has yet to be found. Efficiency of disease surveillance and containment efforts can be improved by allocating resources used for surveillance in areas with deer populations that are at greatest risk for infection.

Journal of Wildlife Management↗

USGS2015

Is there a single best estimator? selection of home range estimators using area- under- the-curve

Background Global positioning system (GPS) technology for monitoring home range and movements of wildlife has resulted in prohibitively large sample sizes of locations for traditional estimators of home range. We used area-under-the-curve to explore the fit of 8 estimators of home range to data collected with both GPS and concurrent very high frequency (VHF) technology on a terrestrial mammal, the Florida panther Puma concolor coryi , to evaluate recently developed and traditional estimators. Results Area-under-the-curve was the highest for Florida panthers equipped with Global Positioning System (GPS) technology compared to VHF technology. For our study animal, estimators of home range that incorporated a temporal component to estimation performed better than traditional first- and second-generation estimators. Conclusions Comparisons of fit of home range contours with locations collected would suggest that use of VHF technology is not as accurate as GPS technology to estimate size of home range for large mammals. Estimators of home range collected with GPS technology performed better than those estimated with VHF technology regardless of estimator used. Furthermore, estimators that incorporate a temporal component (third-generation estimators) appeared to be the most reliable regardless of whether kernel-based or Brownian bridge-based algorithms were used and in comparison to first- and second-generation estimators. We defined third-generation estimators of home range as any estimator that incorporates time, space, animal-specific parameters, and habitat. Such estimators would include movement-based kernel density, Brownian bridge movement models, and dynamic Brownian bridge movement models among others that have yet to be evaluated.

Florida↗

USGS2014

Surveillance and monitoring of white-tailed deer for chronic wasting disease in the northeastern United States

Chronic wasting disease (CWD) is a prion disease that affects both wild and captive cervid populations. In the past 45 y, CWD has spread from northern Colorado to all bordering states, as well as the midwestern United States (Midwest) and northeastern United States (Northeast), Canada, and South Korea. Because CWD is a relatively new issue for wildlife management agencies in the Northeast, we surveyed a representative (e.g., cervid biologist, wildlife veterinarian) from 14 states to gain a better understanding of state-specific surveillance measures. Between 2002 and 2012, New York (37,093) and Pennsylvania (35,324) tested the greatest number of harvested white-tailed deer Odocoileus virginianus in the Northeast. Additionally, the 14 states surveyed have tested 121,730 harvested deer, or approximately 15,216/y, since CWD was first detected in 2005. The most common tissues used by agencies in the Northeast for testing were retropharyngeal lymph nodes, which have been determined to be the most reliable in detecting CWD in cervids. Understanding CWD surveillance efforts at a regional scale can help to provide guidance for the development of new surveillance plans or the improvement of existing ones. Furthermore, collaborations among state and regional agencies in the Northeast may attempt to identify deficiencies in surveillance by state or subregion.

Connecticut, Delaware, Maine, Maryland, Massachuse↗

USGS2014

Linking bovine tuberculosis on cattle farms to white-tailed deer and environmental variables using Bayesian hierarchical analysis

Bovine tuberculosis is a bacterial disease caused by Mycobacterium bovis in livestock and wildlife with hosts that include Eurasian badgers ( Meles meles ), brushtail possum ( Trichosurus vulpecula ), and white-tailed deer ( Odocoileus virginianus ). Risk-assessment efforts in Michigan have been initiated on farms to minimize interactions of cattle with wildlife hosts but research on M. bovis on cattle farms has not investigated the spatial context of disease epidemiology. To incorporate spatially explicit data, initial likelihood of infection probabilities for cattle farms tested for M. bovis , prevalence of M. bovis in white-tailed deer, deer density, and environmental variables for each farm were modeled in a Bayesian hierarchical framework. We used geo-referenced locations of 762 cattle farms that have been tested for M. bovis , white-tailed deer prevalence, and several environmental variables that may lead to long-term survival and viability of M. bovis on farms and surrounding habitats (i.e., soil type, habitat type). Bayesian hierarchical analyses identified deer prevalence and proportion of sandy soil within our sampling grid as the most supported model. Analysis of cattle farms tested for M. bovis identified that for every 1% increase in sandy soil resulted in an increase in odds of infection by 4%. Our analysis revealed that the influence of prevalence of M. bovis in white-tailed deer was still a concern even after considerable efforts to prevent cattle interactions with white-tailed deer through on-farm mitigation and reduction in the deer population. Cattle farms test positive for M. bovis annually in our study area suggesting that the potential for an environmental source either on farms or in the surrounding landscape may contributing to new or re-infections with M. bovis . Our research provides an initial assessment of potential environmental factors that could be incorporated into additional modeling efforts as more knowledge of deer herd factors and cattle farm prevalence is documented.

Michigan↗

USGS2011

Soil clay content underlies prion infection odds

Environmental factors—especially soil properties—have been suggested as potentially important in the transmission of infectious prion diseases. Because binding to montmorillonite (an aluminosilicate clay mineral) or clay-enriched soils had been shown to enhance experimental prion transmissibility, we hypothesized that prion transmission among mule deer might also be enhanced in ranges with relatively high soil clay content. In this study, we report apparent influences of soil clay content on the odds of prion infection in free-ranging deer. Analysis of data from prion-infected deer herds in northern Colorado, USA, revealed that a 1% increase in the clay-sized particle content in soils within the approximate home range of an individual deer increased its odds of infection by up to 8.9%. Our findings suggest that soil clay content and related environmental properties deserve greater attention in assessing risks of prion disease outbreaks and prospects for their control in both natural and production settings.

Colorado↗

USGS2009

Dietary response of sympatric deer to fire using stable isotope analysis of liver tissue

Carbon (?? 13 C) and nitrogen (?? 15 N) isotopes in biological samples from large herbivores identify photosynthetic pathways (C 3 vs. C 4 ) of plants they consumed and can elucidate potential nutritional characteristics of dietary selection. Because large herbivores consume a diversity of forage types, ?? 13 C and ?? 15 N in their tissue can index ingested and assimilated diets through time. We assessed ?? 13 C and ?? 15 N in metabolically active liver tissue of sympatric mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) to identify dietary disparity resulting from use of burned and unburned areas in a largely forested landscape. Interspecific variation in dietary disparity of deer was documented 2-3 years post-fire in response to lag-time effects of vegetative response to burning and seasonal (i.e., summer, winter) differences in forage type. Liver ?? 13 C for mule deer were lower during winter and higher during summer 2 years post-fire on burned habitat compared to unburned habitat suggesting different forages were consumed by mule deer in response to fire. Liver ?? 15 N for both species were higher on burned than unburned habitat during winter and summer suggesting deer consumed more nutritious forage on burned habitat during both seasons 2 and 3 years post-fire. Unlike traditional methods of dietary assessment that do not measure uptake of carbon and nitrogen from dietary components, analyses of stable isotopes in liver or similar tissue elucidated ?? 13 C and ?? 15 N assimilation from seasonal dietary components and resulting differences in the foraging ecology of sympatric species in response to fire.

Wildlife Biology in Practice↗

USGS2006

Response of Rocky Mountain elk (Cervus elaphus) to wind-power development

Wind-power development is occurring throughout North America, but its effects on mammals are largely unexplored. Our objective was to determine response (i.e., home-range, diet quality) of Rocky Mountain elk (Cervus elaphus) to wind-power development in southwestern Oklahoma. Ten elk were radiocollared in an area of wind-power development on 31 March 2003 and were relocated bi-weekly through March 2005. Wind-power construction was initiated on 1 June 2003 and was completed by December 2003 with 45 active turbines. The largest composite home range sizes (>80 km2) occurred April-June and September, regardless of the status of wind-power facility development. The smallest home range sizes (<50 km2) typically occurred in October-February when elk aggregated to forage on winter wheat. No elk left the study site during the study and elk freely crossed the gravel roads used to access the wind-power facility. Carbon and nitrogen isotopes and percent nitrogen in feces suggested that wind-power development did not affect nutrition of elk during construction. Although disturbance and loss of some grassland habitat was apparent, elk were not adversely affected by wind-power development as determined by home range and dietary quality.

American Midland Naturalist↗

USGS2005

Efficacy of immobilizing free-ranging elk with Telazol® and xylazine hydrochloride using transmitter-equipped darts

From January 1999 to April 2002, 14 free-ranging elk were darted with a mixture of Telazol ® reconstituted with xylazine hydrochloride (HCl) in a forested habitat in southwestern Oklahoma and north-central Arkansas. Elk were darted from ground blinds, tree stands, or a vehicle at distances of 14–46 m and were recovered 37–274 m from the dart site. Elk were located using radiotelemetry with 3-cc disposable Pneu-dart ® transmitter darts. Mean±SD dose of Telazol ® and xylazine HCl was 590±192 mg/ml and 276±153 mg/ml, respectively, and mean time to standing after injection of reversal agent was 27 min (range: 1–65 min). The combination of Telazol ® and xylazine HCl successfully immobilized free-ranging elk, and transmitter-equipped darts permitted successful location of sedated elk by two people in areas of dense forest cover. The dose required to sedate elk appeared to vary depending on physiology and behavior, but no drug-induced mortality occurred despite the wide variance in the doses administered. We recommend 500 mg Telazol ® reconstituted with 300 mg xylazine HCl as an initial dose for a ≥200 kg elk. If needed to achieve full sedation, up to 3 additional ml of the mixture may be administered without adverse effects.

Journal of Wildlife Diseases↗