• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 520
  • 33
  • 9
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 633
  • 633
  • 255
  • 247
  • 170
  • 147
  • 90
  • 82
  • 75
  • 72
  • 66
  • 65
  • 62
  • 56
  • 52
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Determining habitat suitability for the western gray squirrel and eastern gray squirrel in California| Predicting future ranges with Maxent and ArcGIS

Creley, Carly McKean 26 July 2016 (has links)
<p> The main goals of this study were to map the current distribution of the invasive eastern gray squirrel in California as of 2016, to project the potential future geographic range of the species, and to identify areas where the future range of the eastern gray squirrel is likely to overlap the range of the native western gray squirrel. Location data were obtained from museum specimens, wildlife rehabilitation centers, a roadkill database, and research-grade citizen observations. Ecological niche models were created with Maxent, while range and habitat suitability maps were produced with ArcGIS software. Populations of eastern gray squirrels are currently concentrated around Sacramento, the San Francisco Bay, Monterey, and Bellota. The highest priority areas for control and eradication are areas of western gray squirrel habitat near existing eastern gray squirrel populations, including both peninsulas of the San Francisco Bay, areas near Santa Cruz, Oakland, Santa Rosa, and the Monterey Peninsula.</p>
12

An economic measure of nonconsumptive wildlife values : implications for policy analysis

Richards, Merton T.(Merton Taylor),1939- January 1980 (has links)
In the last 200 years the importance of wild animals to man has taken two distinct forms: the use of creatures that provide 'game" for sport hunting, and the existence of value for the scientific or aesthetic appreciation of wildlife. Further, the relative strength of these two uses has shifted over time. It appears that a recent, significant growth in the number of people who hold high value for nongame uses of wildlife has taken place. The traditional emphasis of state wildlife management agencies has been on the production of game species in response to the overwhelming financial support from sportsmen. It is often argued that game management contributes to the welfare of nongame species. The reverse is also true, and sportsmen's interests could be served by a wildlife program giving greater weight to nongame activities. Through a modest redefinition of objectives the Arizona Game and Fish Department could effect a political alignment of game (consumptive) and nongame (monconsumptive) wildlife interests. This study is based on a federally funded research project in which the nonconsumptive uses and values of wildlife are being assessed. In particular, the purpose of this study is two-phased: to estimate the economic benefits to nonconsumptive wildlife users from viewing, studying, and photographing wild animals, and to relate these benefits to the political process in which the Arizona Game and Fish Department obtains its funding and political support. A modification of the travel-cost technique was used in this study to estimate economic benefits obtained by nonconsumptive wildlife users. Importantly, an explicit measure of the monetary value of travel time is empirically derived, providing improved benefit estimates. Visitors to seven wildlife viewing locations in Southeast Arizona responded to a mailed questionnaire at a rate of 86 per cent to provide a voluntary sample of more than 600 wildlife enthusiasts. An array of social and economic data were gathered for individuals and households. Respondents can be generally characterized as highly educated, affluent, middle aged, metropolitan residents. Using multiple regression analysis, demand functions were estimated for each household visiting three representative sites. Consumers' surplus values were then estimated for each site, incorporating an explicit measure of the value of travel time. These values compare favorably to consumers' surplus values estimated for hunting and fishing activities in Arizona. The results of the economic analysis performed in this study are primarily methodological. They are suggestive, however, of considerable political influence regarding wildlife management in Arizona. Importantly, a method exists for measuring the economic value or social welfare of the nonconsumptive use of wildlife. Such measures, widely assessed, could permit the comparison of economic values between consumptive and nonconsumptive wildlife uses and the evaluation of the associated change in consumer welfare resulting from alternative management activities. Based on the estimates of the number of people for whom nonconsumptive wildlife appreciation is important, there is reason to expect that significant political involvement in wildlife management issues will occur. These findings portend a major opportunity for the Arizona Game and Fish Depar went in terms of operational budgets and continued wildlife management authority in the state. Several recommendations are made to the Arizona Game and Fish Department, including improvement in their public image and greater political involvement with nonconsumptive wildlife interest groups.
13

Hares and skylarks as indicators of environmentally sensitive farming on the South Downs

Wakeham-Dawson, Andrew January 1994 (has links)
No description available.
14

Investigating the effects of noise pollution from energy development on the bat community in the Piceance Basin

Warner, Katherine Anne 01 September 2016 (has links)
<p> Throughout the United States, and globally, there has been recent interest in large-scale monitoring of bats, driven largely by the many threats that bats currently face such as climate change, white nose syndrome, habitat loss, and wind energy development. Additionally, many human activities generate sensory disturbances including anthropogenic light and noise pollution that have been shown to affect habitat use and foraging efficiency in bats and other wildlife. My research took place in the Piceance Basin of northwestern Colorado, where there has been considerable development of natural gas resources in recent years. During the drilling phase for natural gas, drill rigs run continuously for weeks to months at each well development site. In addition to the physical disturbance and increased human presence at the well pad, drill rigs are brightly lit, and also emit high amplitude anthropogenic noise. The light and noise from active drill rigs can travel many miles from the source, far beyond areas where wildlife habitat has been physically disturbed. The goal of my research was to isolate noise from the other associated forms of disturbance, and investigate what, if any, effects drilling noise is having on the bat community. </p><p> My dissertation is comprised of three stand-alone chapters, as follows. In Chapter 1, I test two different strategies for deploying bat detectors to determine which strategy yields higher detection and species identification rates. In Chapters 2 and 3, I present the results of noise playback experiments. Chapter 2 compares bat activity levels at control sites, and at treatment sites where noise was added experimentally. In Chapter 3, I monitor bat activity patterns both during and after a noise playback experiment to determine how rapidly activity levels recover post-exposure. A brief summary of each chapter follows. </p><p> In Chapter 1, I focus on the methods for recording bat echolocation calls, and identifying free-flying bats in the field. Unlike capture techniques, current acoustical methods for bat monitoring do not provide information about unique individuals, age, sex, or reproductive status. What acoustical monitoring can provide is information about bat activity levels, habitat use, and species identification in some cases, without interfering with bat movement, foraging, or other activities. The commercially available technology for recording bat echolocation calls has rapidly advanced, and there are many ultrasound detector&ndash;recorder systems (hereafter, &lsquo;bat detectors&rsquo;) available with a wide range of recoding options. Due to rapid attenuation of ultrasound signals, one of the challenges to acoustical monitoring is the relatively limited recording range of bat detectors. To increase this range, I took advantage of a bat detector that had the ability to record on two channels (in stereo). By attaching microphone extension cables, I was able to increase the distance between the left and right channel microphones, thereby increasing the acoustical sampling space. When this data collection effort took place, the SM2BAT+ detector from Wildlife Acoustics, Inc. was the only commercially available bat detector that had the two-channel recording capability. I deployed two identical bat detectors at each study site, and compared the recordings made using the stereo option to recordings made from a single channel. </p><p> In general, the stereo setup outperformed the single-channel systems. With the stereo microphones separated by approximately 10 m, the bat detectors that recorded in stereo produced 2.7 times more recordings overall. The increased number of recordings resulted in a higher number of calls that could be identified to species. The benefit of the stereo setup was not equal for all species. With the stereo microphones only about 10 m apart, there was some overlap between the calls that were identified on the left and right channels. The highest rate of overlap (19.5%) was in big brown bats (<i>Eptesicus fuscus </i>). Rates of overlap for species in the Myotis genus were all less than 5%, and none of the recordings of pallid bats (<i>Antrozous pallidus </i>) were identified on both channels for the same bat-pass-event. The stereo option is a promising way to increase the number of bat recordings, which may be a particularly useful when surveying for rare species. </p><p> In Chapter 2, I used a noise playback experiment to isolate noise from other forms of anthropogenic disturbance, and monitored the bat activity level response. I recorded the sounds of an active drill rig, and played these recordings at treatment sites. I measured sound pressure levels at the drill site, and estimated the sound pressure levels at the noise playback sites. Using outdoor speakers, I was unable to project the drill rig noise at the same amplitude of an actual rig, but I was able to significantly elevate the sound levels at treatment sites. The noise levels at treatment sites roughly corresponded to noise levels that can be experienced approximately 100 m from a drill rig. This distance from a drill rig is typically beyond the well pad, in habitat that is not physically disturbed. There is widespread recognition that noise, light, and other sensory disturbances can affect the behavior and physiology of wildlife. The goal of the experiment was to determine if noise alone impacted the activity levels of bats, after being separated from the other forms of disturbance at a drilling site. I projected noise at treatment sites that were not already developed, and paired these treatment sites with control sites with no added noise. I conducted this experiment in 2013 and 2014, and present the results from 20 sites each year (10 control-treatment pairs annually). </p><p> Both years, there was an overall decrease in bat activity at treatment sites, when compared to control sites. In 2013, 8 of the 10 treatment sites had lower estimated bat activity levels. In 2014, all 10 treatment sites had lower estimated activity levels, although for some control-treatment pairs there was overlap in the credible intervals. Multiple species showed signs of reduced activity at treatment sites. For both years, <i>M. ciliolabrum </i> and <i>L. cinarius</i> had reduced activity levels at treatment sites. The response of other species was more idiosyncratic, with reduced activity in one field season, and inconclusive or no response during the other year. The species that did respond to the noise treatment have very different life histories, making it difficult to generalize about how any given species may respond to noise. </p><p> Chapter 3 focuses on bat activity level trends over time during a two period cross-over experiment. The classic two-period crossover experiment consists of two treatments (i.e., treatments &lsquo;A&rsquo; and &lsquo;B&rsquo;), where each site is exposed to both treatments, and the order of the treatments is randomly assigned. For this study, &lsquo;A&rsquo; refers to no added noise, and &lsquo;B&rsquo; refers to a noise treatment consisting of the projected recording of drilling noise. A total of 12 sites were randomly assigned to the A:B sequence, and 13 sites were assigned to the B:A sequence. I acoustically monitored bat activity throughout the experiment, with particular interest in understanding the activity level dynamics post-exposure to the noise treatment. Most studies that investigate the impacts of noise on wildlife have focused on the response to noise during a noise treatment period, or noise event. Only a handful of previous studies have addressed the post-exposure period after noise ends. In these studies, noise treatments or events were relatively short in duration (a few minutes), and the corresponding recovery period was monitored over a similarly brief timeframe. My study differs in both the duration of the noise treatment (continuous noise over six days/nights), and in the duration of the post-exposure monitoring period (also six days/nights). I focused on the response of four bat species, <i>Myotis ciliolabrum, Myotis evotis, Lasiurus cinareus,</i> and <i>Taderida brasiliensis.</i> </p><p> Of the four focal species, <i>M. evotis</i> showed no substantial response to the noise treatment. The responses of <i>M. ciliolabrum</i> and <i>T. brasiliensis</i> were somewhat challenging to interpret. The overall activity levels of these species were lower during the treatment period in the A:B sequence, but they also had declining activity levels throughout the pre-exposure period. The activity patterns of <i>L. cinareus</i> provided the most convincing evidence of noise avoidance. Furthermore, <i> L. cinareus</i> activity levels did not show signs of recovery after the noise treatment ended in the B:A sequence. This suggests that after the six-day post-exposure period, there were still lingering effects of noise on <i>L. cinareus</i> activity levels. This study provides evidence that the effects of noise can linger for multiple days post-exposure. Future wildlife studies that assess periods of post-exposure could contribute meaningfully to this area of research, and aid in the development of conservation and mitigation efforts.</p>
15

Ecotourism| Conserving biocultural diversity and contributing to sustainable development

Gould, Elizabeth A. 30 December 2016 (has links)
<p> This thesis looks at how ecotourists can become aware of biocultural diversity (the intersection of biological and cultural diversity) and help contribute to sustainable development, which considers the needs of both present and future generations. The thesis will address the ecotourism industry and how people who travel with companies that cater to ecotourists can contribute to biocultural diversity and sustainable development. It will utilize a sustainable development framework and a critical theory approach for considering biological and cultural perspectives including human rights and social justice, the contribution of traditional knowledge, community involvement, and the effects of human impact and globalization. The primary audience of my research is people who travel the globe in search of the earth&rsquo;s natural wonders. I highlight issues related to minimizing environmental impact, respecting local cultures, building environmental awareness, and providing direct financial benefits for conservation. My central research question is: <i>How can travelers help to preserve the environment, be sensitive to local cultures, and contribute to a sustainable future?</i> I ask: <i>By understanding the distinct correlation between biological and cultural diversity, how can we utilize both traditional (and local) knowledge combined with scientific knowledge to help sustain and preserve our natural ecosystems?</i></p><p> I conclude with findings that point to the need for shared community authority, management, and decision making; mutual benefits; recognition of the rights, values, norms, power structures, and dynamics of local populations; respect for belief systems as well as traditional and local ecological knowledge; and the importance of contextual adaptation.</p>
16

Nesting preferences of the light-footed Ridgway's rail in two Southern California wetlands

Barton, Michelle L. 13 August 2016 (has links)
<p> Survival of the endangered Light-footed Ridgway&rsquo;s Rail (Rallus obsoletus levipes) depends on marsh conservation and restoration efforts that supply suitable nesting habitat. Previous research indicates that rails preferentially nest in low marsh areas with tall, dense Spartina foliosa (Pacific cordgrass). While canopy architecture (e.g. height and density) is important, additional microhabitat and landscape-level metrics may be involved in nest-site selection. This project characterized microhabitat parameters (e.g. vegetation and food availability) and landscape-level parameters (e.g. spatial configuration) for 40 nests and 40 non-nest sites in two California wetlands, Upper Newport Bay and the Tijuana Slough, to identify habitat features that predict reproductive success. Assessment of the microhabitat and landscape-level parameters suggests that vegetation structure (e.g. height, stem density) is important, but that invertebrate density and composition, tidal connectivity, and elevation are also important to Light-footed Ridgway&rsquo;s Rail nesting.</p>
17

Factors influencing nest survival of white-tipped doves in the lower Rio Grande Valley, Texas

Giese, Jordan Clarence 03 March 2017 (has links)
<p> The white-tipped dove (<i>Leptotila verreauxi</i>) is a sedentary, secretive columbid that ranges from Argentina to the Lower Rio Grande Valley (LRGV) of south Texas. Since its designation as a game species in 1984, little research has been dedicated to the species&rsquo; reproductive ecology. My objectives were to (1) identify predators of white-tipped dove eggs and nestling, (2) determine how the predator community differs among land cover types, (3) examine the impact of vegetation and landscape variation in both citrus and woodland land cover types on nest survival, (4) examine the impact of temporal variation on nest survival, (5) provide information on general nest ecology that is currently lacking, (6) investigate movements of doves and examine feasibility of tracking and recapture using a GPS/VHF transmitters pilot study. During the summers of 2015 and 2016, I conducted nest searches in citrus and woodland sites in Hidalgo County, Texas. I placed real-time, infrared emitting camera systems on a subset of nests to monitor predation. I also trapped, banded, and placed backpack transmitters on doves in Estero Llano Grande State Park (ELGSP) In the 2 years, I located 63 dove nests, 34 in citrus and 29 in woodland. I placed camera systems on 33 nests and identified 9 species of nest predator. Green jays (<i>Cyanocorax incas</i>) were our most common nest predator, accounting for 10 of 28 predation events. Other predators were crested caracara (<i>Caracara cheriway</i>), Harris&rsquo;s hawk (<i>Parabuteo unicinctus</i>), great-tailed grackle (<i>Quisicalus mexicanus</i>), tawny crazy ant (<i> Nylanderia fulva</i>), rat (<i>Rattus</i> spp.), opossum (<i> Didelphis virginiana</i>), house cat (<i>Felis catus</i>), and Texas indigo snake (<i>Drymarchon melanurus erebennus</i>). Based on AIC candidate model selection, I identified nest stage as the best predictor of daily nest survival rate across both land cover types. By separating land covers for a second step to model selection, I identified different environmental variables as predictors of daily survival rate in each land cover type. In the woodland site, my null model was most important, indicating that no measured variables were important for predicting nest survival. In citrus, canopy cover was the top model. In citrus, a diverse predator community due to heavy human disturbance may have increased the importance of canopy cover and other concealment variables for nest survival. The different predator communities they encounter in the two land cover types that they nest in prioritize much different environmental conditions for nest survival.</p>
18

Modern predators : the science, sovereignty, and sentiment of wildlife conservation in Zambia.

Godfrey, Elizabeth 03 March 2014 (has links)
This dissertation presents the suspicions and tensions encountered during ethnographic fieldwork with (what I call) the Predator Project Zambezi (PPZ), a WWF-funded research and conservation organization based in Zambia. It extrapolates the broader contexts of this uneasiness and situates it within global conservation discourses. The distrust that manifests between the wildlife authorities in Zambia, the residents of rural areas, and PPZ epitomizes postcolonial contentions over state sovereignty and the continued hegemony of Euro-American environmental ideologies. Moreover, the objective perspective that is claimed by PPZ as a scientific organization is challenged through analysis of its daily epistemic contradictions. In this ethnography, I show how the priorities of conservation institutions as communicated through PPZ ultimately work to arrest the post-colonies in a continuous state of catching up to the eco-modern condition that is ascribed to the global North.
19

Spatial and Temporal Patterns of Genetic Variation in Scarlet Macaws: Implications for Population Management in La Selva Maya, Central America

Schmidt, Kari January 2013 (has links)
Advances in technology and molecular methodologies now provide an unprecedented view into the complex realm of natural populations by elucidating the degree and distribution of genetic variation, historical and contemporary processes driving differentiation, and individual behavior patterns. These critical biological parameters create a framework to enhance wildlife management initiatives, as illustrated here through the implementation of a model approach for the systematic genetic assessment of a group of scarlet macaws Ara macao under threat in La Selva Maya, a tri-national system of protected areas in Mexico, Guatemala, and Belize. A total of 2172 base pairs across four mitochondrial data partitions were employed to test the current hypothesis of subspecific diversification. Phylogenetic reconstruction uncovered two phylogeographic units exhibiting distinct and complex evolutionary histories, emphasizing the importance of Central American populations to intraspecific diversity. Focusing on A. m. cyanoptera, mitochondrial control region sequences of 850 base pairs were examined within a hierarchical context to investigate patterns of genetic substructure at varying spatial scales and extent of molecular variation, including potential temporal shifts in response to anthropogenic pressures. Population-level statistical tests detected evidence of recently restricted gene flow among nest sites in La Selva Maya, a stark contrast to the historical state of panmixia across the region; although overall levels of genetic variation remain high, a decrease in diversity was noted among modern samples originating in the Chiquibul Forest Reserve, Belize. Multilocus genotypes based on eight microsatellite markers were combined with haplotypic data to evaluate whether focal nest sites in the Maya Biosphere Reserve, Guatemala represent distinct genetic clusters. Results from population genetic analyses argue against the presence of site fidelity at fine geographic scales. Examination of pairwise relative relatedness indices supports the observation of genetic connectivity across local breeding areas, while also revealing important insights into recent demographic trends, movement patterns, and breeding behaviors. In summary, this work demonstrates the continuity of biological and ecological influences across individual, local, regional, and continental scales, thus creating an empirical framework to refine population management goals and prioritize mitigation strategies in order to maximize conservation outcomes and foster long-term survival of wild scarlet macaws in La Selva Maya.
20

Wildlife habitat conservation policy in Canada the role of international agreements for policy development /

Statham, Kimberley A. January 1999 (has links)
Thesis (M.E.S.)--York University, 1999. Graduate Programme in Environmental Studies. / Typescript. Includes bibliographical references (leaves 78-84). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ44669.

Page generated in 0.1537 seconds