Theses and Dissertations

Permanent URI for this collection

https://hdl.handle.net/10217/100425

Of special note are theses cited in James R. Meiman's Little South Poudre Watershed and Pingree Park Campus (Colorado State University, College of Forestry and Natural Resources, 1971).

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Open Access
Avian conservation and ecology in northern Vietnam
(Colorado State University. Libraries, 2009) Vu, Thinh Tien, author; Doherty, Paul F., Jr., advisor; Huyvaert, Kathryn, advisor
Due to the rapid rate of biodiversity loss in Vietnam conserving the avian biodiversity is a contemporary issue of concern and my dissertation was aimed at several issues focused on avian conservation. Recently, the number of non-native tree plantations has increased but the conservation potential of such plantations remains unknown. In Chapter 1, I estimated bird species richness to be highest in mature natural forest, lower in second-growth natural forest, and lowest in pine plantation. I suggest that natural forest types should receive priority for conservation in Vietnam. In Chapter 2, I compared bird movement over a paved road (6-8m wide) and within forest interior plots. The probabilities of approaching the playback for ground species at the road site were lower than those in the forest interior. The road seems to moderately affect the ability for ground-feeding bird species to cross gaps. Roads in the natural reserves should be designed to be as narrow as possible. In Chapter 3, to investigate the effects of logging on biodiversity, I modeled the recovery of avian communities following a variety of potential logging schemes. I found that, to conserve 80% of the species pool, logging schemes with either cycle length > 40 years or wood volume left after harvest > 55% should be implemented. Wildlife diseases are raising concerns with respect to human and domestic animal health, as well as the persistence of wildlife populations. Chapter 4 was aimed at characterizing the sample prevalence of avian malaria in wild land birds. The prevalence of avian malaria was 45.85%. However, higher parasite prevalence was observed in flocking species compared to solitary species and higher parasite prevalence was observed in adult birds compared to juvenile birds. In Chapter 5, I focused on surveillance for the presence of avian influenza virus nucleic acids and antibodies in wild land birds. Serum samples from four birds out of 197 birds sampled were antibody positive for the H5 subtype. Sample prevalence for avian influenza virus nucleic acids was 7.25%. This result suggests that attention should be given to land birds in AI surveillance and monitoring programs.
Open Access
Generalized mixed effects models for estimating demographic parameters with mark-resight data
(Colorado State University. Libraries, 2008) McClintock, Brett Thomas, author; White, Gary C., advisor
Mark-resight methods constitute a slightly different type of data than found in traditional mark-recapture, but they are in the same spirit of accounting for imperfect detection towards reliably estimating demographic parameters. Compared to mark-recapture, mark-resight can often be a less expensive and less invasive alternative in long-term population monitoring programs. However, the mark-resight estimators developed to date do not provide a flexible framework allowing the efficient use of covariates in modeling the detection process, information-theoretic model selection and multimodel inference, and the joint estimation of abundance and related demographic parameters. Here I develop a series of mark-relight models for the sampling conditions most often encountered in these studies that address this need for a more generalized framework. In Chapter 1, I introduce the the logit-normal mixed effects model (LNE) for estimating abundance when sampling is without replacement and the number of marked individuals in the population is known exactly. I compare the model to other mark-resight abundance estimators when applied to mainland New Zealand robin (Petroica australis) data recently collected in Eglinton Valley. Fiordland National Park. I also summarize its relative performance in simulation experiments. It can often be difficult to achieve sampling without replacement or to know the exact number of harked individuals in a population. In Chapter 2, I address these limitations of LNE by introducing the (zero-truncated) Poisson-log normal mixed effects abundance model, (Z)PNE. I demonstrate the use and advantages of (Z)PNE using black-tailed prairie dog (Cynomys ludovicianus) data recently collected in Colorado. I also investigate the expected relative performance of the model in simulation experiments. In Chapter 3, I extend (Z)PNE to a full-likelihood robust design model analogous to that used in mark-recapture for the simultaneous estimation of abundance, apparent survival, and transition probabilities between observable and unobservable states. I illustrate the use of the model with additional New Zealand robin data collected in Fiordland National Park, New Zealand. I also report on a series of simulation experiments evaluating the performance of the model under a variety of sampling conditions.
Open Access
Effects of groundwater withdrawal and drought on native fishes and their habitats in the Arikaree River, Colorado
(Colorado State University. Libraries, 2009) Falke, Jeffrey Arron, author; Fausch, Kurt D., advisor
Great Plains streams are harsh environments for fishes, and are increasingly degraded by human-caused impacts, including overuse of groundwater. Plains stream fishes are in decline, due in part to interactions between natural drought and anthropogenic stream drying. To address these issues, in a collaborative study we developed a model of groundwater and surface water that predicted fish habitat quantity within the Arikaree River basin in eastern Colorado into the future, based upon three scenarios of land and water use (e.g., irrigation pumping). We found that under the status quo of pumping, >50% of remaining refuge habitats in the wettest segment of river will be dry in 35 years, and will be isolated in a 1-km fragment along the river. Loss of critical habitats due to stream dewatering, and subsequent negative effects on native fishes, are not unique to eastern Colorado but are in fact widespread across the western Great Plains. Secondly, to set this research in context, I conducted a review of metapopulation and metacommunity research in the stream fish literature. Stream fish populations and communities are spatially structured at multiple scales, and easily fragmented. To date, this spatial structure has not been incorporated into stream fish population and community models. However, recent research in this area should improve our understanding of processes that regulate stream fish assemblages. Next, I developed a spawning phenology for Arikaree River fishes and found that cumulative growing season degree days had the strongest effect on hatching initiation. Occupancy by larvae of most species was related to local scale spawning habitat characteristics (e.g., habitat size and type). Among years, colonization and extinction rates for individual species differed in segments that were fed by groundwater, versus those that were not, and were influenced by climate variability among years. Last, I investigated when and where the threatened brassy minnow, Hybognathus hankinsoni, spawns, and what environmental factors influence growth and survival of this species within and among years. Interannual variability in climate, and the hydrologic context of segments along the riverscape, had a strong influence on habitat availability and recruitment of brassy minnow in the Arikaree River.
Open Access
Cold summer stream temperatures reduce recruitment of native cutthroat trout populations
(Colorado State University. Libraries, 2007) Coleman, Mark Anthony, author; Fausch, Kurt D., advisor
Translocation is a key strategy for conserving subspecies of native cutthroat trout Oncorhynchus clarkii, which have declined markedly throughout their native ranges in North America. Previous research showed that translocation success in high-elevation southern Rocky Mountain streams was more likely in warmer streams, and suggested that cold temperatures could limit juvenile trout recruitment and explain translocation failures. However, the effects of cold temperature on recruitment had not been previously investigated. I studied these effects using an integrated laboratory and field approach. In the lab, age-0 Colorado River cutthroat trout O. c. pleuriticus were subjected to one of three natural temperature regimes during two years, which averaged 7°C, 8.5°C and 10.0°C during the warmest summer month. From hatching to swimup, mean survival was high during both years, ranging from 97% (warm regime) to 85% (cold). After swimup, warm regime fry had much greater survival and grew more than 60% larger, on average, than cold regime fry by the onset of winter in the 2003 experiment. The pattern of lower survival in colder temperature regimes held through mid-winter, with 76% survival (warm regime), 62% (intermediate), and 29% (cold). Likewise, during the 2004 experiment, survival to early winter ranged from 44% (warm regime) to 10% (cold). Most mortality in all treatments occurred during a recruitment bottleneck encompassing a 4- to 6-week period following swimup. A response surface analysis of percent dry weight data indicated that the energy content of fry at swimup was lower in colder regimes, and declined during the recruitment bottleneck in all regimes. In the field, I monitored temperatures and conducted surveys to estimate densities of age-0 fry at peak emergence in six headwater streams that varied in thermal characteristics. Density and growth increased with Celsius degree days during the growing season. My results indicate a strong recruitment bottleneck after swimup, when temperature-related energy deficits probably cause significant mortality. Fisheries managers in the southern Rocky Mountains may increase translocation success of native cutthroat trout by selecting sites with ≥800-900 degree days during the growing season, and fry grow to ≥30-35 mm by the end of the growing season.
Open Access
Bayesian analysis of age-at-harvest data with focus on wildlife monitoring programs
(Colorado State University. Libraries, 2007) Conn, Paul Bayne, author; White, Gary C., advisor
State and federal agencies often collect hunter harvest data at check stations. When age- and sex-classes can be determined at the time of harvest, such data provide a wealth of information about population structure. For instance, such summaries are used extensively in quantitative fisheries stock assessment. However, statistically defensible approaches for using age-at-harvest data to monitor terrestrial wildlife populations have not appeared until quite recently, and are deficient in several respects. The primary focus of this dissertation is on developing better methods for analyzing wildlife age-at-harvest data, and on applying these methods to real and hypothetical populations. Chapter one starts by developing statistical methods necessary for fitting population dynamics models to age-at-harvest data. As an example, I analyze marking and harvest records from female black bears (Ursus americanus) in Pennsylvania. In chapter two, I describe numerical implementation issues, as well as results from several extensive rounds of simulation testing. I show that Markov chains will typically need to be quite long to accurately summarize the posterior distribution of model parameters. Nonetheless, estimators are shown to display little bias, to have satisfactory credible interval coverage, and to have a high degree of precision. I show that abundance estimators are quite robust to aging errors, although using data from marked animals twice may lead to overstated measures of precision. In chapter three, I conduct a power analysis to determine if it would be feasible to monitor black bear in Colorado with age-at-harvest and radio telemetry data. My focus in this chapter is on detecting and estimating population trend for varying levels of effort. I show that five year studies are typically too short for all anticipated levels of marking effort, but that ten year studies can yield meaningful estimates of population trend. In chapter four, I address methods that can be used to correct age-at-harvest data for misclassification errors. When the aging criterion is inexact, it is possible to correct for errors if additional information is available on error rates. I illustrate proposed methodology with a black bear dataset from Pennsylvania.
Open Access
Effect of enhanced nutrition during winter on the Uncompahgre Plateau mule deer population
(Colorado State University. Libraries, 2007) Bishop, Chad Jeffrey, author; White, Gary C., advisor
Mule deer (Odocoileus hemionus) populations declined across much of the West during the 1990s, prompting state wildlife agencies to explore mule deer limiting factors. The greatest concern of agencies and sportsmen was whether declining habitat quality, predation, or both were responsible for the observed declines. In Colorado, the Uncompahgre Plateau mule deer population received the most attention because of a steep population decline from the 1980s through the late 1990s. Biologists hypothesized that poor quality of the pinyon (Pirns edulis) and juniper (Juniperus osteosperma) winter range was the primary cause of the observed decline. In contrast, many of the Colorado Division of Wildlife’s (CDOW) constituents hypothesized that high predation rates were keeping the mule deer herd below nutritional carrying capacity. These hypotheses represented very different paradigms of population limitation. Perhaps more importantly, the competing views suggested that CDOW should pursue one of two very different management strategies: 1) implement habitat improvements in the pinyon-juniper winter range, or 2) implement efforts to reduce predator populations, particularly coyote (Canis latrans) populations. Information was needed to guide the decision process. I therefore evaluated the effect of enhanced nutrition during winter on the Uncompahgre deer population as a way to evaluate the importance of habitat quality versus that of predation.
Open Access
Seasonal trophic niche dynamics of mottled sculpin and juvenile brown trout in a regulated Rocky Mountain river
(Colorado State University. Libraries, 2023) Platis, Nitsa, author; Kanno, Yoichiro, advisor; Johnson, Brett, advisor; Kampf, Stephanie, committee member
In temperate ecosystems, resource availability fluctuates seasonally due to changes in environmental conditions and productivity throughout the year. Intra- and inter-specific trophic niche overlap under resource limitation is a measure of competitive interactions and influences species coexistence and community dynamics, but patterns of this overlap are highly variable among regions and communities. In this study, we analyzed stomach content samples and stable isotope signatures to evaluate seasonal trophic niche dynamics of mottled sculpin Cottus bairdii (80-130 mm total length) and juvenile brown trout Salmo trutta (80-200 mm) in the Blue River, Colorado, USA, where aquatic production varies seasonally and has been reduced due to upstream dams. Prey biomass (i.e., benthic macroinvertebrates) peaked in spring and declined through summer and autumn. Stomach content and stable isotope analysis results revealed diet composition of mottled sculpin and brown trout shifted seasonally in response to changes in resource availability. In autumn, both species exhibited the highest frequency of empty stomachs and expanded population trophic niches due to increased inter-individual diet variation despite decreased individual trophic niche breadth. Interspecific trophic niche overlap was relatively high across all seasons, but the lowest degree of overlap occurred in autumn of both years. Isotopic analysis revealed similar trends of wider isotopic niches and reduced overlap in autumn compared to spring. Taken together, our data indicate that seasonal variation impacts individual and population-level trophic niche dynamics, as well as interspecific niche overlap between mottled sculpin and juvenile brown trout. These two species occur sympatrically in many coldwater streams throughout North America, and our findings indicate trophic segregation under resource limitation may serve as a mechanism that facilitates their coexistence.
Open Access
Provisioning and nest success of an aerial insectivore at a high elevation breeding site
(Colorado State University. Libraries, 2023) Simons, Victoria F., author; Horton, Kyle G., advisor; Doherty, Paul F., Jr., committee member; Ruegg, Kristen C., committee member
Tree Swallows (Tachycineta bicolor) are a model organism in ornithology. However, few studies have been conducted in the western portion of their breeding range, particularly at high elevation. High elevation habitats, like Colorado State University's Mountain Campus, are impacted by climate change. Tree Swallows in these ecosystems face threats due to recent population declines and climate-related changes. These challenges could impact the species' survival in these areas, and for my Master's thesis I investigated two aspects of provisioning behavior, namely weather conditions and insect abundance. My first chapter focused on how daily weather conditions influenced female Tree Swallow's rates of nest visitation and food provisioning. Using radio-frequency identification technology, I compared visitation rates to hourly weather conditions. I found that poor weather, including cooler temperatures and precipitation events, was negatively correlated with the number of visits made to the nest, which subsequently influenced the growth and development of nestlings. In Chapter 2, I addressed the question of how weather affected food availability. Tree Swallows rely on flying insects as their main food source, and inclement weather is known to decrease insect availability in the airspace. To investigate if lowered female provisioning effort matched periods of food unavailability, I deployed a mobile radar unit – the BirdScan MR1 – to quantify insect abundance. I then compared insect activity to nest visitation rates and found that females made significantly more visits to their nestlings when insects were more abundant. Additionally, I found that insect activity was significantly influenced by weather conditions, demonstrating that weather may be used as a proxy for insect abundance at sites where direct monitoring of insects is not possible. Put together, the results of my first and second chapters deepen our understanding of how female Tree Swallows navigate the complexities of aerial conditions – both biotic and abiotic – to forage and provision for their growing nestlings in an ever-changing high elevation environment. As the effects of climate change become more pronounced, high elevation habitats are likely to undergo rapid changes. Consequently, insight into the relationship between weather and food availability becomes increasingly important.
Open Access
Influence of abiotic and biotic factors on the response of benthic macroinvertebrates to metals
(Colorado State University. Libraries, 1995) Kiffney, Peter Michael, author; Clements, Will, advisor; Fausch, Kurt D., committee member; Kondratieff, Boris C., committee member; Chapman, Phillip, committee member
Stream ecologists are well aware that chemical, biological, and physical characteristics of lotic systems vary spatially and temporally. With this in mind, I designed a series of experiments and field studies to examine the role of spatial variation in stream benthic macroinvertebrate communities in response to metals. Specifically, I tested the hypothesis that stream invertebrate communities from pristine streams of different size and altitude varied in their response to metals. To evaluate how metals affected biotic interactions, I manipulated invertebrate density, predation intensity, and metals in stream microcosms. Using stream invertebrate communities, I also designed an experiment and field survey to identify reliable bioindicators of metal contamination in western streams. Results from microcosm experiments and field studies showed that benthic invertebrate populations from high-altitude streams were more sensitive to the effects of metals than invertebrate populations from low-altitude streams. For example, Baetis sp. and Rhithrogena hageni from Little Beaver Creek (LBC), Colorado, (high-altitude stream) were significantly more sensitive to zinc than the same species from the South Fork of the Poudre River (SFP) (low-altitude stream) in stream microcosms. Results from field surveys showed that densities of most groups of aquatic insects (e.g., Ephemeroptera, Plecoptera, Trichoptera) were lower at high-altitude metal contaminated streams than those same groups at low-altitude streams. Other factors, such as variation in water temperature or nutrient concentrations between high- and low-altitude streams, could be lll responsible for these differences. However, because invertebrate responses were similar under controlled and field conditions, I hypothesize that differences in abundances between reference and contaminated locations was a result of metals. To determine if body size contributed to the variation in sensitivity of insects to metals, size measurements were made on species collected from LBC (high-altitude) and SFP (low-altitude). Measurements were also made on species from control and metal-treated stream microcosm. Most species were smaller at LBC (high-altitude stream) than the same species from SFP (low-altitude stream). For example, the mayfly Baetis tricaudatus and the caddisfly Arctopsyche grandis were significantly larger at SFP than LBC. In addition, insect body size was larger in metal-dosed microcosms than in controls. Brachycentrus sp., B. tricaudatus, R. hageni, Eohemerella infrequens, and P. badia were significantly larger in metal-treated microcosms than in controls. Logistic regression indicated survival in metal-dosed microcosms was less for small individuals than for larger individuals of the same species. These results suggest that some insect species from high-altitude streams were smaller than those from low-altitude streams, and that survival was greater for larger lifestages. Thus the variation in response of macroinvertebrates between different altitude streams observed in earlier studies may be due to differences in body size. The effects of low levels of metals (half the chronic levels of Cd, Cu, and Zn) on some species varied in relation to invertebrate density (low and high density) and invertebrate predation (no predators added and predators added). The abundance of Hydropsyche sp. was significantly lower in metal-dosed, high density treatments than in control, high density treatments. Moreover, the effects of an invertebrate predator (Hesperoperla pacifica) on Hydropsyche sp. was significantly greater in metal-dosed microcosms than in controls. These results suggest that metals interact with biotic factors to influence stream invertebrate community structure, and that effects occurred at metal concentrations lower than chronic criteria value. Toxicity experiments in stream microcosms showed that the abundance and species richness of aquatic insects were significantly reduced at 1x, 5x and 10x the United States Environmental Protection Agency chronic levels of cadmium, copper, and zinc (1x=1.1, 5.0, and 110 μg/L Cd, Cu, and Zn, respectively). Mayflies were the most sensitive group, as the abundance of Baetis sp. and Rithrogena hageni were significantly reduced in the Ix treatment. The response of Drunella grandis was size dependent, as small lifestages were significantly more sensitive than large lifestages. Stoneflies were also affected, but their response was more variable with abundances of some species (Pteronarcella badia) being reduced in the Ix treatment, whereas other species were unaffected (Sweltsa sp.). Heptageniid mayflies were consistently less abundant downstream of sources of metal contamination in the Arkansas and Eagle rivers, whereas the response of other measures were more variable. For instance, species richness and total density were greater at a metal-contaminated site on the Arkansas River compared with an upstream reference site. Therefore, results from this experiment and field survey suggest that changes in abundance of heptageniid mayflies may provide a reliable indicator of metal-contamination in western streams.
Open Access
Implications of movement behavior responses of both Asian and African elephants in changing landscapes of the 21st century
(Colorado State University. Libraries, 2023) Chan, Aung Nyein, author; Wittemyer, George, advisor; Leimgruber, Peter, committee member; Noon, Barry, committee member; Aldridge, Cameron, committee member
An organism moves to fulfil its most fundamental survival and reproductive needs. Studying movement behavior can provide insights into both inter- and intra-specific interactions, how a species interacts with its environment and accesses resources, species distribution, etc. Given human presence affects mammalian movement across the globe, animal movement studies are increasingly important to assess and understand the impacts of humans on wildlife. Movement behavior response to human presence is particularly relevant and important to understand in the 21st century since global human population is projected to reach 9.7 billion by the year 2050. The unprecedented level of human presence and associated land use changes will impact all living organisms on the planet, particularly megaherbivores such as Asian and African elephants which have some of the largest space use requirements among terrestrial mammals. My dissertation research focuses on studying and understanding the movement behavior responses of Asian and African elephants to human-related landscape changes. The Asian elephant (Elephas maximus) which is currently listed as endangered under the IUCN red list of threatened species. The population status of the species is unclear but declining. The species is facing habitat loss and fragmentation due to agricultural expansion, heightened human-elephant conflicts related to human encroachment in previous wilderness areas, and illegal killings, including but not limited to, poaching for skin, ivory, and meat. The largest remaining tracts of wildland (i.e., habitat suitable for wild elephant to exist) among the current extant range countries/states occurs in the country of Myanmar. However, the struggling economy and unstable political climate put unusual amount of stress on the remaining elephant populations across the country. Asian elephant numbers are declining across much of their range in Myanmar, driven largely by serious threats from land use change resulting in habitat loss and fragmentation. To effectively manage and conserve the remaining populations of endangered elephants in the country, it is crucial to understand their movement behavior across the country's agricultural gradient. Chapter 1 provided baseline information on elephant spatial requirements and the factors affecting them in Myanmar. This information is important for advancing future land-use planning that considers space-use requirements for elephants. Failing to do so may further endanger already declining elephant populations in Myanmar and across the species' range. We used autocorrelated kernel density estimator (AKDE) based on a continuous-time movement modeling (ctmm) framework to estimate dry season (26 ranges from 22 different individuals), wet season (12 ranges from 10 different individuals), and annual range sizes (8 individuals), and reported the 95%, 50% AKDE, and 95% Minimum Convex Polygon (MCP) range sizes. We assessed how landscape characteristics influenced range size based on a broad array of 48 landscape metrics characterizing aspects of vegetation, water, and human features and their juxtaposition in the study areas. To identify the most relevant landscape metrics and simplify our candidate set of informative metrics, we relied on exploratory factor analysis and Spearman's rank correlation coefficients. Based on this analysis we adopted a final set of metrics into our regression analysis. In a multiple regression framework, we developed candidate models to explain the variation in AKDE dry season range sizes based on the previously identified, salient metrics of landscape composition. Our objectives were to (1) estimate the sizes of dry, wet, and annual ranges of wild elephants in Myanmar; and quantify the relationship between dry season (the period when human-elephant interactions are the most likely to occur) range size and configurations of agriculture and natural vegetation within the range, and (2) evaluate how percentage of agriculture within dry core range (50% AKDE range) of elephants relates to their daily distance traveled. Elephant dry season ranges were highly variable, averaging 792.0 km2 and 184.2 km2 for the 95% and 50% AKDE home ranges, respectively. We found both the shape and spatial configuration of agriculture and natural vegetation patches within an individual elephant's range play a significant role in determining the size of its range. We also found that elephants are moving more (larger energy expenditure) in ranges with higher percentages of agricultural area. Chapter 2 reveals how elephants interact with agriculture and other important environmental variables such as natural vegetation, roads, and water, etc. Habitat loss and fragmentation due to accelerated agriculture expansion is a major threat to existing wildlife populations across Asia. Although it had been shown that Asian elephant space use was correlated with the level of fragmentation on the landscape in Chapter 1, the mechanism underlying this process is not well documented and can serve to help focus conservation efforts. We analyzed selection behavior of wild elephants across three study sites with different levels of agriculture use patterns in Myanmar, assessing the impact of structure in the agriculture- wildlands interface on habitat selection by elephants. Given elephants exhibit heterogeneous spatial behavior, we fitted two types of selection models to gain insight into the diversity of strategies employed at the local- and home-range scale. We used variance partitioning analysis to quantify the explanatory contribution of individual, study site, and sex. We found that the variation in the resource selection behavior was mainly due to individual differences, and the level of agriculture present in an individual's range was the most influential to its selection behavior. Gaining a deeper understanding of habitat selection behavior by elephants across the changing landscapes of Asia can help inform management decisions and conservation actions. As the military coup in 2021 in Myanmar affected my ability to continue working in Myanmar, we decided to transition into assessing the connectivity between Etosha National Park and an adjacent Kunene multi-use conservancies area in Namibia for African elephant (Loxodonta africana) as Chapter 3. This region is of particular importance in African elephant conservation since the population is doing relatively well in the area and could serve as one of the remaining strongholds for the species. The loss of habitat and fragmentation of landscapes could lead to declines in wildlife populations, highlighting the need to identify and preserve critical habitats. Connectivity between populations plays a crucial role in mitigating the risks faced by small populations and ensuring their long-term persistence. As a result, the identification of corridors has become a key objective in wildlife conservation. Various methods have been developed to identify high connectivity locations, including resistance surface modeling and empirical-based approaches using GPS tracking data. We used GPS telemetry data from 66 elephants to empirically quantify connectivity using a graph-theoretic approach and assessed landscape features influencing connectivity. We applied the 'movescape' approach to define and locate different types of corridors and examined how landscape features differed across these corridors. Our results revealed strong variation in connectivity across the landscape, with paths of high connectivity near water sources between the study areas. We found that factors related to water sources and human presence primarily influenced connectivity. The findings of this study provide valuable insights into the connectivity patterns and landscape features influencing connectivity for African elephants in northwestern Namibia. We discussed this findings in the context of future conservation management scenarios. Finally, Chapter 4 assessed the current knowledge on population status of Asian elephants across all 13 range countries or states. We conducted a literature search on Google Scholar using keywords, "Asian elephants", "Population size", "Abundance", and "Density". We found 26 articles and 9 governmental and non-governmental reports from 2000 to 2022 to evaluate the extent of population assessments using statistically robust methods. Our findings indicate that only 4.39% of the current known distribution of Asian elephants had been assessed using robust sampling and statistical approaches. Out of the 13 range states, only 7 had conducted assessments, with only 3 countries performing robust population assessments in the last 5 years. We highlight the urgent need for more comprehensive and up-to-date studies to accurately estimate the population size of Asian elephants. We recommend investing in spatial capture- recapture approaches using fecal-DNA and photographic capture-recapture methods where feasible to improve abundance estimation. The results of this review emphasize the critical role of accurate population knowledge for effective conservation and management actions for endangered species like the Asian elephant. This dissertation provides critical pieces of information regarding movement ecology and conservation of both Asian elephant and African elephant. We present analyses on space use requirements, resource selection behavior and the quantification of sources of variation in the movement behavior for Asian elephant in Myanmar. Chapter 1 and chapter 2 were the first two studies to assess movement behavior in Myanmar using empirical data. Since identifying and conserving corridors is one of the key objectives for African elephant's conservation, chapter 3 provides crucial information for managers on the ground in Etosha National Park and surrounding areas. Finally, we highlighted the research gap in Asian elephant conservation by reviewing studies and reports on population status across the species' range.
Open Access
Breeding waterfowl productivity in a flood-irrigated agricultural landscape
(Colorado State University. Libraries, 2023) Setash, Casey M., author; Koons, David N., advisor; Pejchar, Liba, committee member; Gammonley, James H., committee member; Sueltenfuss, Jeremy P., committee member
Similar to agricultural production, the sustainable management of waterfowl populations across the western United States inherently depends on limited water availability. Both endeavors are increasingly challenged by municipal demands for water, drought, and changes in the seasonality of precipitation. Healthy wetlands for wildlife can be sustained in conjunction with the needs of agricultural producers on working lands, but the multifaceted importance of water management is rarely quantified. Information pertaining to the multiple benefits of water management practices might bring to light the larger societal importance of sound water management. This may allow natural resource managers to allocate resources more efficiently and effectively by directing them towards the practices with demonstrated advantages for both wildlife and agricultural producers. The North Platte Basin in north-central Colorado (hereafter North Park) is a model system to evaluate benefits and trade-offs of hydrological manipulations that benefit both agricultural producers and fish and wildlife. Not only are waterfowl and water management already being conducted by federal and state agencies and NGOs like Ducks Unlimited, but North Park is also representative of many working lands throughout the Intermountain West. Agricultural producers in North Park flood irrigate rather than using center-pivot irrigation, which strongly affects on hydrological regimes, water tables, wetlands, and stream flows. Flood irrigation more closely resembles natural stream and river flood regimes and is thought to be more beneficial for wildlife, water table recharge, and evaporative cooling of return flow water. As water resources become diverted for urban municipal uses and the increasing frequency of drought reduces water availability in the semi-arid West, it is believed that the North Platte Basin may begin to play a significant role in the production of waterfowl on a statewide or even a flyway scale. As private land becomes an increasingly important component of waterfowl habitat and water resources become limiting, a strong foundational knowledge regarding how flood-irrigated systems impact wetland-dependent species will therefore be imperative to properly manage waterfowl populations in coordination with agricultural production. We first sought to evaluate the efficacy of flood-irrigated agricultural lands as nesting habitat for breeding waterfowl in the context of land-use intensity. The debate over the best agricultural practices for biological conservation typically focuses on land sharing and land sparing production strategies. One end of the spectrum posits that high-intensity agriculture and the smaller footprint associated with it allows for other land parcels to be spared for biodiversity and therefore provides more suitable habitat, whereas others argue that agricultural lands should be cultivated at a low intensity and interspersed with wildlife habitat, therefore sharing the land with wildlife. We evaluated the demographic consequences of land-sharing and land-sparing practices on breeding bird nest site selection and nest survival, focusing specifically on waterfowl in a flood-irrigated hay agricultural system. We specifically assessed the habitat features related to both shared and spared lands driving nest site selection at two scales and how those same features scaled up to impact nest survival. Nests were located disproportionately closer to uncut irrigated meadows and farther from harvested hay meadows relative to available points, but closer to irrigation ditches. Nests closer to irrigation ditches, uncut irrigated meadows, and open water also experienced higher nest survival. This system is representative of many agricultural systems around the globe and illustrates the ways agricultural practices can shape habitat selection have reproductive consequences for wildlife. After evaluating the importance of wetlands associated with flood irrigation for nesting, we focused our efforts on elucidating their contributions as foraging habitat. Food availability varies considerably over space and time in wetland systems, and consumers must be able to track those changes during energetically-expensive events like breeding. Resource tracking has been studied frequently among herbivores, but rarely receives attention among consumers of macroinvertebrates. We evaluated the change in resource energy density across habitat types and time, and the ability of waterfowl to track macroinvertebrate resources across wetland types and over the course of the breeding season in a high-elevation, flood-irrigated system. We also assessed whether the density of energy resulting from macroinvertebrates explained more of the variation in waterfowl abundance across habitats, or whether the consistency (i.e., temporal evenness) of the resource played a larger role using a pseudo-R2 metric. Energy density varied widely across wetland types, but was highest in basin wetlands (i.e., ponds) and was higher in wetlands with higher temperatures, specific conductivity, and lower dissolved oxygen. Both breeding pair abundance and duckling abundance were positively associated with energy density and resource consistency (R2 = 0.06 for pair abundance and 0.31 for duckling abundance), but energy density explained more of the variation in both waterfowl responses (R2 = 0.77 for pair abundance and 0.58 for duckling abundance). These results have the potential to not only elucidate mechanisms of habitat selection among waterfowl, but also indicate where and when water resources should be allocated as climate conditions become increasingly arid. The technological tools we used initially to evaluate waterfowl use of flood-irrigated habitats (i.e., Global Positioning System [GPS] tags) have become a common tool in ecological studies of animal behavior and demography despite previous research indicating negative impacts on vital rates across a variety of taxa. We therefore focused next on evaluating the impacts of GPS tags on our focal waterfowl species and others across the life-history spectrum. Researchers face tradeoffs when deciding whether they are an appropriate tool because GPS tags may impact vital rates, but they provide detailed data on movements and behavior that often cannot be obtained in other ways. Using band recovery data from hunter harvests, we evaluated the strength of effects induced by GPS tags on annual mortality of adult females across 13 waterfowl species, and whether species with a slower life-history strategy might be more resilient to GPS tag effects than their fast-lived counterparts. Hazard ratios, indicating the risk of death for individuals wearing GPS tags compared to those wearing only metal bands, ranged from 0.92 - 4.38 and the mean difference in survival between marker types across species was 0.31, but these results are averaged across the study period. The magnitude of tag effects remained constant across life-history tempo, indicating that slower-lived species were not able to buffer the effect of wearing GPS tags. When scaling effect sizes up to a currency of fitness, slower-lived species exhibited a similar handicap of wearing GPS tags compared to species with a faster life-history strategy, and the effects were notable. Our results highlight that even small impacts to important vital rates can affect inference pertaining to survival and mortality as well as fitness from birds affixed with GPS tags. The results of this study revealed considerable survival effects across species, although time trends illustrated decreasing effect sizes for most species over time. Results emphasize the importance of testing for such effects in future research as technology advances. Finally, we used components of each previous chapter to characterize the population of breeding ducks in this system and the demographic consequences of environmental conditions. Waterfowl populations in the Intermountain West rely upon water availability and are not as frequently studied as populations within North American core breeding areas like the Prairie Pothole Region. Different species experience different environmental conditions during peak nest initiation depending on their breeding phenology, especially in variable environments like those associated with high-elevation systems. We fit species-specific integrated population models to evaluate the demographic drivers of mallard and gadwall populations breeding in a high-elevation intermountain basin in Colorado representative of many Intermountain West habitats from 2018-2022. Each species initiated nests at opposite ends of the phenological spectrum, allowing us to assess the effects of environmental conditions on demography. Both mallard and gadwall annual after-hatch-year (AHY) female survival probabilities were comparable to estimates from other regions (hatch-year [HY] mallards = 0.48 [SD = 0.09] to 0.53 [SD = 0.07], AHY mallards = 0.53 [SD = 0.07] to 0.57 [SD = 0.05], HY gadwall = 0.44 [SD = 0.13] to 0.52 [SD = 0.14], AHY gadwall = 0.56 [SD = 0.11] to 0. 66 [SD = 0.12]). Annual recruitment, a metric of the number of females produced per breeding pair, was similar among gadwall (0.62 [SD = 0.80] to 1.04 [SD = 1.04]) and mallards (0.40 [SD = 0.48] to 1.59 [SD = 0.95]), but realized population growth rate (λ) did not vary as much for gadwall (0.93 [SD = 0.56] to 1.21 [SD = 0.59]) as it did for mallards (0.76 [SD = 0.24] to 1.55 [SD = 0.24]). Recruitment of both species exhibited quadratic relationships with spring growing degree days, indicating recruitment was higher during springs with intermediate temperatures, and spring snow-water equivalent metrics in the surrounding mountains positively impacted HY and AHY mallard survival in addition to HY gadwall survival. The results of this study emphasize the need for continued monitoring of waterfowl outside of traditional survey areas and provide insight into water management strategies to target important vital rates as climate and land use change.
Open Access
Forest elephants modulate their behavior to adapt to sounds of danger
(Colorado State University. Libraries, 2023) Verahrami, Anahita K., author; Bombaci, Sara, advisor; Blanchard, Nathaniel, committee member; Wittemyer, George, committee member
The African forest elephant (Loxodonta cyclotis) plays a critical role in upholding the structure and function of the Congo Basin, the world's second largest tropical forest which crucially contributes to global carbon sequestration. Research has demonstrated an 86% decline in forest elephant population numbers between 1990-2021, largely because of hunting for ivory. Due to the species' cryptic nature in their dense rainforest habitat, little is known on how they respond to human disturbances such as gun hunting. The studies that have been completed reveal that forest elephants may respond to disturbance by demonstrating changes in their abundance, distribution, and nocturnal activity. Changes in forest elephant distribution and activity not only have ramifications for the species' activity budgets, which when affected, may influence their foraging and reproductive behaviors and success, but may also impact the species' interspecific interactions with vegetation in certain areas, affecting forest growth and function. However, little is known on how a key population of this critically endangered species in the northern Republic of Congo is responding to disturbance such as hunting in the region. Using acoustic detection models in combination with a landscape-scale acoustic monitoring effort in and around Nouabalé-Ndoki National Park, Republic of Congo, I assess how forest elephant vocal activity is being influenced by gun hunting. Using these data, I examine (1) how forest elephant vocal activity changes across an eight-day period and (2) if forest elephants are shifting to more nighttime vocal activity following a gun hunting event. Results show that, on average, forest elephants are present and vocal at sites without gun events 53% of the time, but at sites with gun events, this value drops to 43%. Results also indicate that this change in activity following a gun hunting event is sustained over the eight-day period examined and does not vary from day-to-day. Results from the analysis exploring how the proportion of nighttime calling activity changes in response to gun hunting show that number of gunshots is an important predictor of nighttime vocal activity. Specifically, as the number of gunshots increase, there is a dramatic increase in the proportion of nighttime calling activity. Understanding the degree at which forest elephants are affected by gun hunting provides a convincing argument to focus limited conservation resources on developing more effective strategies to reduce indirect impacts from hunting on this critically endangered and ecologically important species.
Open Access
The bighorn sheep of Battlement Mesa - a low elevation population
(Colorado State University. Libraries, 1991) Cunningham, Mary Louise, author; Bailey, James A., advisor; Alldredge, A. William, committee member; Lehner, Philip N., committee member
I studied bighorn sheep on Battlement Mesa, Colorado, from 12/88 to 7/90, to determine present and past herd status and distribution, so that 1) management options are clarified and 2) future management activities may be evaluated. I studied the herd by tracking 1 radio-collared ewe and obtaining visual observations and by systematically sampling study area units for sheep, sheep sign, potential competitors, potential predators and sheep carcasses. I recorded water sources that were encountered. I developed an historic perspective of the herd by searching agency files and local newspapers and interviewing local residents. The herd numbered up to 200-250 animals in the early 1900s and declined to an estimated 50 animals by 1970. Minimum herd sizes during 1989 and 1990 were 23 and 26, including lambs, respectively. Since 1961, the herd has abandoned approximately 56 km2 of historic range in the Mamm Peaks area. The herd decline corresponded with probable vegetation changes on Battlement Mesa, intensive livestock grazing through the 1950s, reports of poaching and an increasing elk herd. Sheep remained on the western portion of the range during winter and spring, 1989. Ewe/juvenile groups migrated to Anderson and Durant Gulches between 5/15-7/15/89 for lambing. Rams were more dispersed and in groups of 1-3, except during the rutting season. Ewe/juvenile group size ranged from 1-13. During dry months, (7/89, 8/89, 6/90) sheep concentrated in Anderson and Durant Gulches where a free-flowing spring and a seep were located. Bighorn sheep on Battlement Mesa appear limited by dense mountain shrub stands which separate all productive meadows from escape terrain and cover historic migration routes. A significantly greater use of the shale slope habitat contributed most to rejecting the null hypothesis that sheep use habitat types in proportion to their availabilities on Battlement Mesa. Sheep remained on shale slopes most (75% of all observations) of the time, using scattered grasses, forbs and shrubs for forage and seeps for water. Intensive and long term habitat management for bighorn sheep on Battlement Mesa is required. I suggest a 4-phase management program to improve existing range and later to reestablish and maintain historic migration corridors to productive historic summer range. Without management to improve existing conditions, this small, unique herd will remain static or decline.
Open Access
Demographic consequences of agricultural practices on a long-lived avian predator
(Colorado State University. Libraries, 2022) Vennum, Christopher Ryan, author; Koons, David N., advisor; Pejchar, Liba, committee member; Kendall, Bill, committee member; Boone, Randall, committee member
To view the abstract, please see the full text of the document.
Open Access
Triploid walleye: a new frontier for nonnative predator management in the West
(Colorado State University. Libraries, 2022) Farrell, Collin J., author; Johnson, Brett, advisor; Myrick, Christopher, advisor; Hansen, Adam, committee member; Angeloni, Lisa, committee member
To view the abstract, please see the full text of the document.
Open Access
An experimental test of intra- and inter-specific competition between invasive western mosquitofish (Gambusia affinis) and native plains topminnow (Fundulus Sciadicus)
(Colorado State University. Libraries, 2022) Lewis, Samuel, author; Kanno, Yoichiro, advisor; Salerno, Jonathan D., committee member; Sanderson, John S., committee member; Preston, Daniel L., committee member
1. Invasive species are a major threat to freshwater conservation. Species coexistence in invaded habitats depends on the relative strength of intra- versus inter-specific competition, where inter-specific competition from invasive species to native species is often stronger than intra-specific competition, jeopardizing their coexistence.2. In this study, I conducted a laboratory experiment to test for the relative competitive strength between native plains topminnow (Fundulus Sciadicus) and invasive western mosquitofish (Gambusia affinis) at 16, 22, and 28 °C. Data were analyzed using the isodar theory, which assumes that animals are ideally distributed to maximize their fitness and thus their distributions measure the quality and quantity of habitat patches. This was supplemented by behavioral observations of intra- and inter-specific competition. 3. Contrary to my predictions, I did not find evidence that competition was asymmetrical from the invasive mosquitofish to the native plains topminnow. Instead, more individuals occupied their shared preferred habitat (a slow-moving pool) in sympatry compared to allopatry, and the isodar analysis demonstrated that intra-specific competition was significantly stronger than inter-specific competition at all temperature levels. This analysis of habitat selection was corroborated by behavioral observations that aggression was most frequent between plains topminnow in sympatry. 4. This study indicates that aggression might not always be the key mechanism of invasion, even for one of the most successful aquatic invasive species widely known for their aggressive behavior. In mosquitofish, other ecological traits such as fast reproductive cycle and tolerance to a wide range of environmental conditions might be responsible for their invasion success globally. This suggests that mosquitofish may not be a driver in native species declines, but rather an opportunistic invader in degrading ecosystems.
Open Access
Rites of passage: determining the efficacy of different fish passage designs along the northern Colorado Front Range
(Colorado State University. Libraries, 2022) Jones, Rachel, author; Myrick, Christopher, advisor; Kanno, Yoichiro, committee member; Wohl, Ellen, committee member
As historical instream barriers continue to be used and new man-made structures have the potential to further fragment river habitat, eastern Colorado fish communities face mounting challenges to survive in abbreviated river segments. Instream barriers are myriad in shape (dams, diversions, culverts, grade control, etc.) and serve a wide variety of economic and social necessities, often preventing their removal. In an attempt to restore longitudinal connectivity at instream barriers, fish passage structures of various types have recently been installed across the northern Colorado Front Range where rivers transition from high gradient mountain streams to low gradient eastern plains streams (often referred to as the transition zone). These structures are often designed with small-bodied native Plains fish species in mind. Frequently, little to no post-installation monitoring is performed for these fishways, so little is known of their comparative success. The goal of this study was to assess the passage success of the resident fish fauna at different passage structures to better understand how structure type and design affect efforts to restore connectivity. The study used long-term monitoring and short-term enclosure studies with stationary PIT tag antenna arrays that recorded movements of a free-ranging community of PIT-tagged fishes. A cast concrete rock ramp on the Cache La Poudre River and a grouted boulder wingwall bypass passage structure on the St. Vrain River were continuously monitored for nearly two years, offering insights into passage success, differences in functionality between the fishways, and the variable movement patterns of the local fish communities. Successful fishway passage was observed at both sites by numerous species over a variety of conditions, with the rock ramp passing 71% of tagged species with an overall passage rate of 55% for individuals, and the wingwall bypass passing 61% of tagged species at an overall individual passage rate of 62%. The long-term monitoring study is described in Chapter 1 of this thesis. Short-term enclosure experiments were used to evaluate both fish passage success at a given passage and to evaluate the method's capability to provide a rapid initial assessment of fishway performance. These trials added an additional pool-and-weir style passage to the two sites used in the long-term monitoring component of the study. Similar to the long-term monitoring study, the rock ramp and wingwall bypass structures both allowed passage of a majority of species, 63% and 70%, respectively, tested during the enclosure study producing overall passage rates of 49% and 64%, respectively. Conversely, fish passage at the pool-and-weir structure was largely non-existent (passage rate of 17%), suggesting it is not a satisfactory alternative for systems where the goal is to provide passage for non-jumping native fish species. The results from this study are described in detail in Chapter 2. Given the differing effects of design features and slopes on passage success for the types tested, this project suggests that future fish passage projects in these systems consider rock ramp-style structures, with specific attention to low gradients and nature-like designs where possible. In addition, long-term monitoring should be considered paramount for post-installation monitoring as it provided the greatest insight into fish passage performance. Many species, not constrained by limited time and conditions, demonstrated higher rates of passage. Greater detail of movement patterns and preferences throughout time was also obtained. However, the short-term enclosure trial process, with some refinements, can provide a valuable initial assessment of fishway functionality following construction.
Open Access
Detection and transmission of Renibacterium salmoninarum in Colorado inland trout
(Colorado State University. Libraries, 2022) Riepe, Tawni Brooks, author; Winkelman, Dana, advisor; Fetherman, Eric, committee member; Huyvaert, Kate, committee member; Webb, Colleen, committee member
To view the abstract, please see the full text of the document.
Open Access
How does rock-ramp fishway surface texture affect the passage success of small-bodied Great Plains fishes?
(Colorado State University. Libraries, 2021) Brittain, Cole, author; Myrick, Christopher A., advisor; Kanno, Yoichiro, committee member; Angeloni, Lisa, committee member
The waterways of the North American Great Plains have experienced extensive fragmentation from instream structures and intermittency caused by excessive dewatering. The modifications to these waterways include numerous barriers that prevent the upstream movement of fish. State and federal resource management agencies have turned to fish passage structures to restore connectivity. However, the passage efficiency of current structures may be limited for native small-bodied fish species by a lack of information on how fish swimming behavior and performance are affected by the key fishway design parameters of slope, length, and texture. Recent research has provided more information on fishway slope and length, and identified texture of the surface between the larger roughness elements as an area needing more investigation. We evaluated the effects of four surface textures (smooth; 1 – 2 mm diameter coarse sand; 6 – 10 mm diameter pea gravel, and; 19 – 31 mm diameter small cobble) on the passage success of three native small-bodied fish species, Arkansas Darter (Etheostoma cragini), Flathead Chub (Platygobio gracilis), and Stonecat (Noturus flavus) using a 6.1-m long experimental rock ramp fishway set at a 6% slope. Our results demonstrated that passage success for the Arkansas Darter increased from 0% on the smooth substrate to 32.2% for the small cobble substrate. A similar pattern was observed for the Stonecats, with an increase in passage success from 31.1% on the smooth substrate to 86.7% on the small cobble substrate. Flathead Chub passage success was independent of substrate treatment and exceeded 90% in all cases. Our study suggests that the use of more highly textured substrates is a viable option for increasing the passage success of small-bodied fishes that otherwise do not perform well on rock ramp fishways.
Open Access
Effects of invasive species on native herpetofauna and pond communities in urban environments
(Colorado State University. Libraries, 2022) Crone, Erin Renee, author; Preston, Daniel L., advisor; Angeloni, Lisa, committee member; Bailey, Larissa, committee member; Herrick, Bradley, committee member
Urban environments can provide high quality habitat for native species, yet these environments are also prone to species invasions via numerous introduction pathways. Invasive species may affect communities through multiple mechanisms including ecosystem engineering, predator-prey interactions, and resource competition, so isolating individual effects can be challenging. Further, urban environments commonly host multiple invasive species, which may interact with one another and amplify effects on native species. Despite their potential effects, however, the roles of invasive species in urban communities are often poorly understood. For example, the city of Madison, Wisconsin, USA is home to multiple invasive species, including jumping worms (Amynthas spp.), goldfish (Carassius auratus), and Chinese mystery snails (Cipangopaludina (=Bellamya) chinensis), but little is known about the community effects of these species. Jumping worms are non-native invasive earthworms that may act as ecosystem engineers in leaf litter habitat and potentially provide an abundant novel prey resource to native predators. Invasive goldfish and mystery snails have been widely introduced through aquarium trading and are known to co-occur in urban ponds. In the first study, we used a mesocosm experiment, laboratory feeding trials, and nonlethal stomach contents surveys to assess effects of invasive jumping worms on microhabitat and trophic interactions of native herpetofauna predators. We found that jumping worms reduced leaf litter biomass but did not influence soil conditions or survival of American toad (Anaxyrus americanus) metamorphs. Our results revealed that jumping worms are viable prey for native herpetofauna, especially common garter snakes (Thamnophis sirtalis), but may be challenging to capture due to defensive behaviors. In the second study, we used a mesocosm experiment to test for facilitative or antagonistic interactions between goldfish and mystery snails, and to examine individual and combined effects of goldfish and mystery snails in urban pond communities. We found evidence that goldfish facilitate invasive mystery snails, and that goldfish drive shifts in community composition and food web structure through trophic cascades. Comparatively, mystery snails had limited effects in the experimental community. Overall, our studies emphasize the diversity of roles invasive species can play in communities as ecosystem engineers, prey, predators, or competitors, and that their effects on native species are dependent on these roles. Broadly, our findings highlight the value of understanding invasive species effects in urban environments to direct management and support native species conservation.