Browsing by Subject "habitat"
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Item Early Migratory Behavior of Northern Fur Seal (Callorhinus ursinus) Pups from Bering Island, Russia(2012-07-16) Lee, Olivia AstilleroI examined the population trends of northern fur seals (Callorhinus ursinus) using an age-specific metapopulation model that allowed migration between rookeries. Mortality and birth rates were modified to simulate future population trends. I also examined the early migratory behavior and habitat associations of pups from Bering Island (BI), Russia. I instrumented 35 pups with Mk10-AL satellite tags and stomach temperature telemeters which provided diving, foraging and location data. I hypothesized that some aspects of pup behavior from the stable BI population differed from the behavior of pups from the unstable Pribilof Islands (PI). The population model revealed that emigration did not contribute significantly to the current PI population decline. However, large source populations contributed significantly to population growth in newly colonized rookeries. A stabilization of the PI population was predicted with a 10 to 20 percent reduction in both juvenile and adult female mortality rates. The diving behavior of pups showed a general progression towards longer and deeper dives as pups aged, particularly between 1600 ? 0400 (local time), that was similar to PI pup behavior. However, unlike pups from the PI, I found three main diving strategies among BI pups: 1) shallow daytime divers (mean depth = 3.56 m), 2) deep daytime divers (mean depth = 6.36 m) and 3) mixed divers (mean depth = 4.81 m). The foraging behavior of pups showed that most successful ingestion events occurred between 1600 ? 0400, with successful ingestion events lasting 25.36 plus/minus 27.37 min. There was no significant difference among the three strategies in the depth of successful foraging dives. I also examined the foraging search strategies in adult females and pups. Both pups and adults conducted Levy walks, although pups foraged in smaller patches (1 km scales). Using a logistic model to determine habitat associations, I found that pup locations were positively correlated with increasing chlorophyll a concentrations, distances from shore, and sea surface temperatures, and were negatively correlated with depth. There was no significant relationship between all pup locations and the regions (peripheries or centers) or types (cyclonic or anti-cyclonic) of eddies, but ingestion event locations were related to mesoscale eddy peripheries.Item Ecological Consequences of Landscape Fragmentation on the Lizard Community in the Mescalero-Monahans Shinnery Sands(2012-10-29) Leavitt, Daniel 1979-Landscape fragmentation poses a major threat to biodiversity world-wide. The goal of my dissertation research was to determine the effects of landscape fragmentation on a lizard community in the Mescalero-Monahans shinnery sands, New Mexico and the extent to which conservation efforts might protect biodiversity in this ecosystem. My research relied heavily on data collected from a large-scale spatially-replicated comparative study. The purpose of this study was to evaluate the impacts of landscape fragmentation as a result of oil and gas development on the dunes sagebrush lizard (Sceloporus arenicolus). Results from analysis of lizard community structure indicate that fragmented sites are less diverse than non-fragmented sites. In particular, two species are found in lower density and occupancy in the fragmented locations (Holbrookia maculata and Sceloporus arenicolus). Analysis of landscape configuration at the scale of a trapping grid indicated that sand dune blowout shape and size differed between fragmented and non-fragmented locations. Differences in landscape pattern were associated with reduced lizard diversity. Because of this association between lower diversity and altered landscape pattern, extensive alterations to landscape pattern may cause disassembly at the ecosystem level. The maintenance of existing landscape pattern may be important to the maintenance of diversity in this ecosystem. Evaluations of habitat use patterns of the lizards in this community demonstrate that a few species have narrow preferences for certain habitats. In particular, H. maculata, Phrynosoma cornutum, and S. arenicolus all demonstrated narrow habitat use patterns. Effect size of fragmentation for each species indicated that the same three species showed a large effect when comparing their average abundances between fragmented and non-fragmented locations. Thus species that are most likely to benefit or be harmed by landscape fragmentation are those with the most specific habitat requirements. Umbrella species represent one of many approaches to conservation using surrogate species. I used data on ants, beetles, small mammals, lizards, and endemic species to test the use of the dunes sagebrush lizard (Sceloporus arenicolus) as an umbrella for endemism and biodiversity of the Mescalero-Monahans shinnery sands ecosystem. I applied a comparative approach at three spatial scales to examine how conservation practices at different scales may affect biodiversity and endemism in this ecosystem. At the largest scale, the frequency of occurrence for endemic species increased though no other patterns emerged because S. arenicolus was present at all sites and there were no relationships between relative abundances of S. arenicolus and the other taxonomic groups. At the smallest scale, both beetle species richness, diversity, and endemic species richness were higher in the presence of S. arenicolus. To protect biodiversity in this ecosystem, conservation efforts should focus on protection at the scale of the species distribution rather than on the small-scale placement of individual well pads.Item Environmental predictors of bottlenose dolphins distribution and core feeding densities in Galveston Bay, Texas(Texas A&M University, 2006-08-16) Moreno, Maria Paula TeixeiraCoastal dolphins are often exposed to habitat degradation and direct interactions with humans. Major factors that influence dolphin distribution, critical for conservation concerns, are still poorly understood even for the bottlenose dolphin, the best-studied cetacean. To establish the environmental conditions that best predict occurrence of bottlenose dolphins and high feeding densities in Galveston Bay, I conducted a total of 367 boat surveys in five locations of the estuary, totaling 3,814.77 km of search effort. I counted groups of dolphins and measured surface water temperature, salinity, turbidity, total number of boats, shrimp vessels, and number of seabirds. Using geospatial tools, these data -- along with location, distance to the Gulf of Mexico and water depth -- were analyzed on a 500- m resolution grid. Temporal factors at daily and seasonal scales were also examined. Occurrence was modeled using a Generalized Additive Model and core feeding densities (i.e., feeding densities above 2 SD of the mean) were modeled with a Generalized Linear Model. A total of 1,802 dolphins in 262 groups were detected, 56.87% of which were feeding. I found that all factors except warm/cold seasons and turbidity were useful to predict dolphin distribution, which was related non-linearly to most predictors. Fewer variables were relevant in predicting core feeding densities. These were, in decreasing order of relevance, distance to the Gulf of Mexico, surface water temperature, depth, number of boats, and warm/cold seasons. Feeding was highly clustered and the main core areas, less than approximately 3 km2 wide, were stable across time of day and season. The majority of the occurrences (86.2%) and feeding groups (94%) were situated in two bay locations - Galveston Ship Channel (GSC) and Bolivar Roads (BRD) - that amounted to only one- fifth of the surveyed area. Compared to conditions in GSC and BRD when no dolphins were sighted, feeding cores weredeeper and more seabirds were observed. This fine-scale study of bottlenose dolphin distribution may contribute to a better understanding of habitat requirements for coastal dolphins. It also may provide information needed to minimize potential negative impacts to this population caused by human activities.Item Evaluation of the Landowner Incentive Program in Texas: 1997-2007(2012-02-14) Knipps, AnnaThe Landowner Incentive Program (LIP) was developed by the Texas Parks and Wildlife Department in 1997 in response to controversy and conflict between wildlife conservation agencies and landowners. The incentive was meant to encourage voluntary enhancement or establishment of habitat for rare species in the state, by providing technical assistance and a 75% cost-share. To evaluate the program in its first decade of existence, I gathered feedback from stakeholders via interviews, a mail survey, and case studies of LIP projects that focused on the black-capped vireo. The stakeholders I identified as administrators of the program, field personnel who acted as liaisons between administrators and landowners, and the landowners themselves. I used a qualitative theme analysis for interviews and open-ended survey responses to capture salient topics from the various perspectives. I analyzed closed-ended mail survey responses with descriptive statistics and ANOVA. For the case studies, I conducted vireo and habitat surveys and report the results with descriptive statistics or anecdotes. Stakeholders were generally pleased with the program in its first decade regarding rare species habitat improvements. Most of the 126 projects were completed and resulted in an increase of habitat for a variety of species across the state. The funding sources changed over the decade, bringing with them new directives, but in general LIP investments benefitted rare and declining species, whether listed under the ESA or not. Relations between landowners and conservation agencies also seemed to be improved in some cases and to be created in others. Every program has its difficulties to work through as it evolves, and LIP is no exception. The first 7 years of the program were state-administered and encountered a variety of modifications due to personnel changes and differing opinions on program priorities. In 2002, LIP became a national program, requiring Texas to compete for funds, and also federal clearance requirements that caused many administrative delays. My recommendations for program improvement included improved monitoring of project outcome, immediate evaluation of participants, increased communication and cooperation among various agencies who work with landowners, and dedicated staff to assist all other stakeholders in the LIP process.Item Habitat associations of cavity-nesting owls in the Sierra Nevada(2009-05-15) Groce, Julie ElizabethSeveral species of small, cavity-nesting owls occur in the Sierra Nevada, including in areas impacted by human activities. The owls typically use standing dead trees (snags) for nest sites. Although descriptive studies exist regarding habitats associations around nest and roost sites, few studies have examined habitat associations at larger spatial scales or relative to certain snag characteristics (e.g., density, decay class). To improve our understanding of the habitat associations of these owls, I compared habitat characteristics at 2 spatial scales around areas of owl detection and non-detection. I also examined distances between conspecifics and heterospecifics to determine if clustering of conspecifics or avoidance of predators occurred. I conducted owl broadcast surveys and snag sampling during the spring and summer of 2006 and 2007 in the Lake Tahoe Basin of central Sierra Nevada. I measured additional habitat variables (e.g., vegetation cover, distance to roadways) from pre-existing geographical information system layers. I used stepwise logistic regression to ascertain which variables were influential in predicting owl occurrence. The northern saw-whet owl (Aegolius acadicus) was the only species detected in sufficient numbers for statistical analysis, with a detection probability of 0.25. I detected saw-whets in a wide range of conditions and it appeared that few factors influenced their distribution in the basin. Areas dominated by white fir, however, were correlated with the absence of saw-whets at both the macrohabitat and microhabitat scales. White fir-dominated areas tend to occur on the west side of the basin and it is possible white fir was acting as a proxy for other factors not measured in this study, such as microclimate conditions or prey availability. I was also more likely to find a saw-whet within 1000 m of another saw-whet than within 1000 m of a non-use point, indicating clustering of conspecifics in the basin. While it appears saw-whet needs are being met in the basin, restoration projects are ongoing to decrease both the number of snags and relative abundance of white fir. Continued monitoring of the species is essential to understand potential effects of restoration activities. Suggestions are provided for appropriate timing and effort of future surveys.Item Habitat selection and movement patterns of cattle and white-tailed deer in a temperate savanna(Texas A&M University, 2005-11-01) Depew, Jarrod JasonThis study investigated the use of high resolution satellite imagery in research involving habitat selection, and movement patterns of white-tailed deer and cattle in a semi-arid landscape. Vegetation classification was developed based on Ikonos satellite imagery that was then used to define habitat selection and characterize movement paths of deer and cattle to allow a better understanding of these 2 species. Pasture attributes were also measured to determine animal distribution throughout the study area in relation to roads, fences, water location, and supplemental feeders. Three cattle and 3 free ranging white-tailed deer were used during 3 trials to test seasonal differences in habitat selection and spatial distribution across the pasture. Ikonos satellite imagery was classified to a final classification accuracy of 83.6%. Seven vegetation classes were defined in the classification with 1 class of bare ground/ herbaceous that represents interspaces between shrub vegetation. Classification accuracy was obtained using a ?? meter buffer to all ground control points increasing the accuracy from 71.29%. All physical pasture attributes were significant to animal distributions in the study area when compared to the random distribution. Roads and water location were most important to cattle during the spring and summer. White tailed deer use of the pasture was more dependent on vegetation characteristics than physical attributes. Both cattle and deer selected habitat patches with a proportionately large percentage of bare-ground/interspaces (>40%). Deer were predominately found in areas containing higher percentages of shrub species, while cattle were found in areas containing a mixture of larger tree species in addition to shrub complexes. Travel velocity and path tortuosity were measured to determine effects of vegetation attributes on animal movements. Both cattle and deer followed fairly linear paths (Fractal Dimension<1.2). Factors contributing to path tortuosity included mean patch size, number patches, and patch fractal dimension. Travel velocity was also measured and compared to vegetation association attributes. Travel velocity was significantly different between seasons for white-tailed deer however cattle and deer comparisons were not significant across the 3 trials. Number of patches, patch fractal dimension, mean patch size, and patch area were significant in the travel velocity model.Item Habitat use by the golden-cheeked warbler in Texas(2009-05-15) Newnam, John CalvinUnderstanding species-habitat relationships is fundamental to the conservation of a species. This is especially important when the species is considered endangered. The Golden-cheeked Warbler is a habitat specialist that breeds only in oak-juniper woodlands (considered a climax forest) of central Texas. The warbler was listed as endangered under the federal Endangered Species Act primarily because of habitat loss and fragmentation. Conservation measures include the preservation of existing habitat and attempts to manage and enhance areas that once supported the warbler to return to the climax oak-juniper woodlands. My objectives were (1) to quantify the vegetation structure and species composition by vegetation volume of occupied warbler habitat across the breeding range in Texas and (2) to quantify the habitat use by the warbler in categories of behavior, substrate, height, and tree species. Instantaneous, focal animal behavioral observations were collected for three breeding seasons at six sites across the range of the warbler. Warbler behavior and microhabitat use were compared to availability of vegetation volume by height class and tree species. I found that Goldencheeked Warbler habitat varied by vegetation volume, canopy height and tree species among all sites. The warbler preferred twigs and foliage and the upper two height classes of the habitat structure for all behaviors. Tree species use did not match availability at any sites. The one consistent species result was the warbler used Ashe juniper significantly less than it occurred at all sites. Other major species were used disproportionately to the species occurrence at each site. Some tree species were used more often than they occur in the habitat while others species were used less than they occur in the habitat. Preferences for height class and tree species use were not significantly influenced by vegetation volume. Some other factor not measured such as prey availability may be the cause. Because warbler habitat characteristics and use vary across the range, any efforts to manipulate vegetation to become habitat must consider regional characteristics of Golden-cheeked warbler habitat.Item Mycorrhizal Associations, Life History, and Habitat Characteristics of the Endangered Terrestrial Orchid Spiranthes parksii Correll and Sympatric Congener Spiranthes cernua: Implications for Conservation(2013-12-10) Ariza, Martha CSpiranthes parksii Correll is a federally listed endangered terrestrial orchid endemic of Texas. The species exhibit a very limited geographic distribution and most remaining populations are threatened by habitat loss and fragmentation. Development of in situ and ex situ conservation strategies is fundamental for the protection and re-introduction of the species in their natural habitat. In this dissertation the life history, symbiotic mycorrhizal fungal associations, and habitat characteristics of S. parksii and sympatric congener Spiranthes cernua were investigated by the use of in situ, and ex situ methods. The central research objective was to investigate the orchid-fungal relationship and its distribution in natural habitats and to provide critical information for conservation of the species. Population dynamics and reproductive phenology of both species were studied from 2007 to 2013. Demographic parameters, cost of reproduction, and response to environmental conditions were analyzed. Results indicate that probability of flowering is strongly influenced by vegetative size and environmental conditions in the year preceding a flowering event. Reproductive effort resulted in a decrease in plant size, reducing the probability of flowering subsequently. Environmental conditions explained ?70% of the annual variation in the proportion of flowering plants and inflorescence characteristics. Mycorrhizal fungi associations and belowground phenology of both species were studied for three growing seasons. Data suggest that both species form generalist mycorrhizal associations with fungi tentatively classified, as Epulorrhiza sp., and Ceratobasidium sp. Both orchids sustain mycorrhizal colonization throughout their life cycle. However, seasonal changes in mycorrhization reveled a distinctive annual cycle of infection and digestion of fungal hyphae. Seed viability, in situ germination, seedling development, and mycorrhization were examined in situ by using orchid seed baits. Results suggest that S. parksii seeds are short-lived and germination is constrained by rapid reduction in seed viability, prevailing environmental conditions, and distribution of compatible mycorrhizal fungi. Data indicates a small optimal window for recruitment restricted to the first spring after dispersal. Microhabitat characteristics of S. parksii were compared to microsites of sympatric S. cernua, historical S. parksii microsites and vacant microsites currently not supporting either orchid. Vegetation, edaphic, and environmental parameters were evaluated. The study found that microsites currently occupied by S. parksii differ significantly from other types in canopy cover, leaf litter, herbaceous cover, and soil pH. Furthermore, woody encroachment may significantly affect the availability of suitable microsites not only as a result of altered light environments, but also due to changes in community composition, microclimatic, and edaphic conditions.