College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item ANTHROPOGENIC INFLUENCES ON BOTTOM-UP AND TOP-DOWN REGULATION OF ANIMAL DISTRIBUTIONS, POPULATIONS, AND BEHAVIORS IN URBAN ENVIRONMENTS(2024) Herrera, Daniel Joseph; Gallo, Travis; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Animal populations are simultaneously governed by both bottom-up (e.g., habitat availability) and top-down (e.g., predation) regulation. While ecologists historically sought to differentiate the roles of bottom-up and top-down regulation on ecosystems, the two are not so easily defined in urban ecosystems due to the immense influence humans have on ecological processes in cities. In Chapter One, I present this argument from a philosophical perspective and comment on how this philosophy has shaped my worldview. In Chapter Two, I examine the legacy of historical park planning on urban bird assemblages using archived municipal maps and historical bird data. My analysis found a positive correlation between percent park area and both species richness and functional richness of birds. Additionally, I found the effect size of park area was larger than the effect of certain life history traits thought to facilitate urban exploitation. These results indicate that landscape features and life history traits are equally responsible for the success of synurbic species. Chapter Three explores the effect of urbanization on animal behavior by analyzing anti-predator behavior of white-tailed deer (Odocoileus virginianus) in relation to ambient light, noise, and human activity. Despite negligible predation risk in my study area, deer expressed higher vigilance behavior in dark and noisy conditions, and increased their foraging group size during noisy conditions. These results suggest that anti-predator behaviors are a response to the perception of predation risk rather than a response to the actual presence of predators. Although predation of deer is rare in urban ecosystems, predation of smaller wildlife species by mesopredators, such as non-native domestic cats (Felis catus) is common. Chapter Four examines the potential for predation and zoonotic disease transmission between cats and eight native mammals by estimating the spatial and temporal overlap between species. I found that cat distribution was largely driven by anthropogenic features, whereas native wildlife was generally deterred by anthropogenic features and instead occupied forested areas. I also found that cats, as a species, were active on the landscape during the full 24-hour cycle. As a result, while spatial overlap between cats and wildlife varied across the study area, temporal overlap was possible anywhere cats and wildlife co-occurred. Chapter Five expands on Chapter Four and investigates predation directly by using observations of cats carrying prey documented by motion-activated cameras. I found that predation by cats was higher in areas where supplemental cat food was prevalent, but declined near forested areas. Additionally, my results indicate that cats within 250 meters of a forest edge predominantly preyed on native wildlife, whereas cats generally preyed on non-native rats (Rattus norvegicus) when greater than 250 meters from a forest edge. Each chapter provides applied recommendations to the management and conservation of urban wildlife, but together, my work demonstrates the entanglement of bottom-up, top-down, and anthropogenic forces in urban ecosystems. In light of these findings, I advocate for a more nuanced understanding of ecosystem regulation through a socio-ecological lens.Item THE EFFECTS OF HISTORICAL AND CURRENT LAND USE ON THE HABITAT USE AND COMMUNITIES OF URBAN WILDLIFE IN THE WASHINGTON, D.C. METROPOLITAN AREA(2024) Collins, Merri Kathleen; Gallo, Travis; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding past legacies of urban land use is important to identify ecological processes and inform best management practices for wildlife-friendly cities in the future. My first dissertation chapter is an overview of my personal research philosophy and how it relates to this dissertation. The second chapter is a systematic literature review that addresses the state of global urban wildlife research. Urban wildlife research is predominantly conducted in North America, Europe, and Australia by academic researchers, and less so in the Global South. The third chapter explores how a gregarious species, the Eastern wild turkey (Meleagris gallopavo silvestris) once extant from the Washinton, D.C. landscape, is making a comeback. Wild turkey had a higher probability of occupying sites further from roads and at lower elevations. The fourth and concluding chapter looks at historic neighborhood valuation in Washington, D.C. to identify any legacy effects of racist and discriminatory urban planning on mammal communities. While I did not find any relationship, I did find similar mammal communities across the city regardless of neighborhood categorization and I derive management implications from this information.Item LEVERAGING FINE-SCALE GEOSPATIAL DATA TO ADVANCE BIODIVERSITY SENSITIVE URBAN PLANNING, WILDLIFE MANAGEMENT, AND GREEN CORRIDOR DESIGN: APPLICATION TO THE DISTRICT OF COLUMBIA(2023) Spivy, Annette Leah; Mullinax, Jennifer; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Typically, urban wildlife communities are made up of generalist species that are adept at utilizing human resources. However, many wildlife species struggle in the face of extensive urbanization and would benefit from increased conservation of urban green space, increased urban landscape connectivity, and proactive wildlife population management strategies. Unfortunately, maintaining and/or increasing the availability of quality habitat for biodiversity conservation in urban areas can be challenging as these conservation efforts are often influenced by the decreasing availability of critical resources and the challenges in allocating those resources among competing socioeconomic and environmental needs. Therefore, to improve the management and conservation of urban wildlife, accurate measurements of potential trade-offs between the environmental, economic, and social goals and management actions of a city’s sustainable development plan are needed. Until now, much of the effort in wildlife habitat modeling and biodiversity mapping has been across large geographic areas or broad spatial scales. Those efforts have provided valuable insights into overall biodiversity patterns, identifying key hotspots, and understanding large-scale ecological processes. However, in urban environments, the dynamics of wildlife, habitat availability, and ecosystem services operate differently than in natural or rural landscapes. As urbanization continues to expand, there is a growing need to focus on fine-scale factors to address specific conservation challenges in urban systems. This research seeks to address some of these challenges and demonstrates how new and traditional species-relevant geospatial datasets can be leveraged in urban planning and design to drive local-scale conservation decisions that put biodiversity in the forefront. This work links long-term, multi-taxon, wildlife survey data and high-resolution land use and land cover datasets (1m) to determine where high-quality, well-connected habitats exist, or could most easily be justified and acquired, within the District of Columbia. This work also evaluates the spatial patterns of ecosystem service provisions across the urban landscape to identify “win-win” areas for conservation or restoration that will benefit both biodiversity and human wellbeing. Finally, the work evaluates a local translocation effort of the vulnerable eastern box turtle (Terrapene carolina carolina) to inform mitigation strategies when a sudden loss of habitat in an urban environment is inevitable. This research is particularly relevant to wildlife managers and urban planners in highly urbanized areas, where large parcels of land with suitable habitat are minimal and municipal environmental departments are often under-resourced. Local policymakers interested in incentivizing conservation efforts to meet state or national goals can use this information for strategic urban conservation initiatives.Item EVALUATING RELATIONSHIPS BETWEEN BATS AND LANDSCAPE CHARACTERISTICS IN A WHITE-NOSE SYNDROME POSITIVE REGION: DOES URBANIZATION PLAY AN IMPORTANT ROLE?(2021) Browne, Shannon P.; Mullinax, Jennifer M.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)White-nose Syndrome (WNS) is a cascading disease process, initiated by a skin fungus, killing most cave bat populations across North America. WNS severity differs with the ecology of both the pathogen and the bat species host. This study aimed to identify the habitat features most related to cave bat species by surveying cave bats and habitat features across the urban-rural gradient in Maryland. Our understanding of cave bat ecology in Maryland has changed recently due to technological advancements, though prominent gaps still exist in the urbanized Piedmont and Coastal Plain provinces. As such, a novel urban definition was created to allow research sites to well represent each level of the gradient, and sites were surveyed in random order during four seasons from 2015 to 2017. We found unique results when analyzing predator-prey correlations at weekly scales as well as nightly generalized linear mixed models (GLMM) of habitat usage. At both temporal scales, big brown (Eptesicus fuscus) and tri-colored bat (Perimyotis subflavus) activity were higher at urban than suburban sites. While analyzing predatory-prey correlations at the weekly level, big brown bat activity was highly related to their preferred prey counts at urban sites, while tri-colored bat activity correlated to their preferred prey counts at rural sites. Tri-colored bat activity also occurred at sites during seasons that supported less activity by big brown bats. When analyzing habitat features at the nightly level using GLMMs, in suburbia, big brown bat activity appeared most related to their preferred prey and taller trees. Meanwhile, tri-colored bat activity still held a strong relationship with prey at rural sites across multiple seasons. Big brown bats may select suburbia for roosting and foraging while tri-colored bats may select rural settings for foraging. Interestingly, prey were most abundant at rural sites, indicating rural settings may support higher habitat quality along the gradient. Possible reasons for the seemingly spatial and temporal partitioning by these two species included differing resource availability and some form of niche partitioning. Repeated acoustic surveys and telemetry studies across spatial and temporal scales are recommended to aid bats in greatest need during WNS.Item Understanding Conservationists' Perspectives Concerning the Ethical Dilemmas Associated with Declines in African Vulture Populations(2018) Yee, Natalie; Harrell, Reginal M; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Several African vulture populations are declining due to anthropogenic causes. This research explored viewpoints of conservationists to identify ethical dilemmas and extrapolate potential solutions that balance the needs of African vultures and the welfare of impacted societies. The methodology consisted of two parts: A Q-Methodology activity and a semi-structured interview. The Q-Methodology activity used statements in a ranked system to discover what the participants prioritized. The semi-structured interview allowed for an in-depth understanding as to why the respondents ranked the statements as they did. These steps addressed not only what the subjects believed, but why they believed it, a key element in uncovering the ethical standpoints of the respondents. One major finding demonstrated that overall, participants held a deontological (duty-driven) viewpoint that fuels them to pursue conservation work. Exploring views of conservationists familiar with the African vulture declines is the first step to creating ethical policies to save the vultures.Item BIOLOGY AND MANAGEMENT OF REPRODUCTION IN CAPTIVE CRANES(2017) Brown, Megan Elizabeth; Keefer, Carol L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There are 15 species of cranes found throughout the world, 11 of which are listed as vulnerable or endangered. All 15 species are currently managed in captivity; however, with increased threats to wild crane habitats and populations, ex situ management becomes increasingly critical as a hedge against extinction. Reproduction and the production of offspring is required to ensure self-sustaining populations managed in ex situ conservation breeding programs. However, current reproductive success of the endangered whooping crane (Grus americana), as well as other species, maintained ex situ is suboptimal and hinders population sustainability and reintroduction goals. The objectives of this dissertation were to 1) develop a cryopreservation protocol for crane semen to improve genetic management in endangered cranes, 2) investigated seasonal hormone patterns and measured the impact of captive environment on hormone production and reproductive behaviors, and 3) retrospectively examine the effect of bird as well as management variables on egg fertility in whooping cranes. The findings demonstrated that 1) sperm of both whooping and white-naped crane performed better following cryopreservation when dimethyl-sulfoxide is utilized as a cryoprotectant, 2) seasonal fluctuations occur in hormone production in both sexes, while addition of a water feature to captive enclosures stimulated reproduction in females, and 3) female specific variables had the greatest influence on probability of egg fertility. Overall findings will help whooping crane management Continued research into the mechanisms controlling sperm sensitivity to cryo-damage, egg production, and fertilization are necessary to mitigate reproductive problems in captive crane species.Item SECRETIVE MARSHBIRDS OF URBAN WETLANDS IN THE WASHINGTON, DC METROPOLITAN AREA(2016) Nielson, Patrice; Bowerman, William; Baldwin, Andrew; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Secretive marshbirds are in decline across their range and are species of greatest conservation need in state Wildlife Action Plans. However, their secretive nature means there is relatively sparse information available on their ecology. There is demand for this information in the Washington, DC area for updating conservation plans and guiding wetland restoration. Rapid Wetland Assessment Methods are often used to monitor success of restoration but it is unknown how well they indicate marshbird habitat. Using the Standardized North American Marshbird Monitoring Protocol, I surveyed 51 points in 25 marshes in the DC area in 2013 – 2015. I also collected data on marsh area, buffer width, vegetation/water interspersion, vegetation characteristics, flooding, and invertebrates. At each bird survey point I assessed wetland quality using the Floristic Quality Assessment Index (FQAI) and California Rapid Wetland Assessment (CRAM) methods. I used Program Presence to model detection and occupancy probabilities of secretive marshbirds as a function of habitat variables. I found king rails (Rallus elegans) at five survey sites and least bittern (Ixobrychus exilis) at thirteen survey sites. Secretive marshbirds were using both restored and natural marshes, marshes with and without invasive plant species, and marshes with a variety of dominant vegetation species. King rail occupancy was positively correlated with plant diversity and invertebrate abundance and weakly negatively correlated with persistent vegetation. Least bittern occupancy was strongly negatively correlated woody vegetation and invertebrate abundance and weakly positively correlated with persistent vegetation. Species-specific models provided a better fit for the data than generic marshbird models. A comparison model based on important habitat variables in other regions was a very poor fit for the data in all sets of models tested. FQAI was a better indicator of secretive marshbird presence than CRAM, but neither method had very good predictive ability or goodness of fit. These results underscore the importance of having species- and region-specific models for effective conservation. Based on these findings, decreasing woody vegetation and managing for a variety of co-dominant species to avoid monocultures would improve habitat for marshbirds. Rapid Assessment Method scores should be interpreted with caution when applied to marshbird habitat conservation.Item Estimating Population Trends in American Woodcock (Scolopax Minor) Using Population Reconstruction Models(2016) West, Brent Hopkins; Bowerman, William W; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The American woodcock (Scolopax minor) population index in North America has declined 0.9% a year since 1968 prompting managers to identify priority information and management needs for the species (Sauer et al 2008). Managers identified a need for a population model that better informs on the status of American woodcock populations (Case et al. 2010). Population reconstruction techniques use long-term age-at-harvest data and harvest effort to estimate abundances with error estimates. Four new models were successfully developed using survey data (1999 to 2013). The optimal model estimates sex specific harvest probability for adult females at 0.148 (SE = 0.017) and all other age-sex cohorts at 0.082 (SE = 0.008) for the most current year 2013. The model estimated a yearly survival rate of 0.528 (SE = 0.008). Total abundance ranged from 5,206,000 woodcock in 2007 to 6,075,800 woodcock in 1999. This study represents the first population estimates of woodcock populations.Item Changing Course: Repurposing Golf Landscapes for Wildlife Habitat and Recreation(2015) Yoder, Nicholas William; Sullivan, Jack; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)More than 1,400 golf facilities in the United States have closed permanently since 2001, part of a natural supply correction, as well as a reflection of the fluctuating interest in the game. Through their design, golf courses inherently preserve a singular form of open, green space. In their most dynamic form, they are culturally integral landscapes with vibrant ecosystems that provide wildlife habitat. They represent some of the largest ‘undeveloped’ spaces in United States’ cities. Each golf course closing represents a single patch of many that, with sound design, could be woven together through a common purpose, like a landscape quilt. Through a site-specific analysis, the resulting design proposal for Wakefield Wildlife Reservation is a new type of landscape for the city of Westminster, MD, serving as an example for future projects. It will provide valuable habitat and dynamic recreational space, while expressing site and regional history.Item Population Declines and Genetic Variation: Effects of Serial Bottlenecks(2015) Callicrate, Taylor Eilers; Song, Jiuzhou; Fleischer, Robert C; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Islands foster unique biodiversity, yet also present biogeographic limitations that impose increased risk for population extinction through demographic and genetic constraints and decreased probability of surviving a catastrophe. Of particular interest, especially with regard to endangered species, is the genetic response of insular species to severe population declines or translocations. Both types of events, considered population bottlenecks, are expected to reduce genetic variation, and correspondingly, adaptive potential. For these reasons, it is important to understand how bottlenecks interact with insular population dynamics to affect genetic diversity. I used a combination of a laboratory model experiment and population genetics study of an in situ bottleneck in an endangered species to investigate how quantitative and molecular genetic variation are affected during bottlenecks. I used a laboratory animal model (red flour beetle, Tribolium castaneum) to compare how quantitative genetic variation is affected if a serial bottleneck occurs in a novel versus familiar environment. The experiment was designed to model a founder event or translocation to a new island with a novel environment. I found that phenotypic and additive variance for a quantitative trait were larger following a bottleneck occurring in the novel environment, suggesting that the novel environment could improve adaptive potential in bottlenecked populations. Next, I used molecular genetic markers to assess variation and signatures of selection in the Laysan finch (Telespiza cantans), a Hawaiian honeycreeper endemic to a small Northwestern Hawaiian island. Laysan finches experienced a major bottleneck on Laysan in the early 20th century, followed by a translocation and series of founder events as populations were established on the islets of Pearl and Hermes Reef (PHR) in the 1960s – 70s. I found that, contrary to expectation, bottlenecked Laysan finch populations did not show declines in genetic variation and were not differentiated as a result of genetic drift. These results are potentially caused by insular demographic dynamics. I identified loci with extreme differentiation between modern populations, potentially indicating genomic signals of selection. These regions could be important for adaptation to the novel environment on PHR and are candidates for future study.