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
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.

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