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Effects of de-snaring on the demography and population dynamics of African lions
(Montana State University - Bozeman, College of Letters & Science, 2023) Banda, Kambwiri; Chairperson, Graduate Committee: Scott Creel
Lions and other African large carnivores are in decline, due in part to effects of illegal hunting with snares, which can reduce prey availability and directly kill or injure carnivores. It is difficult to effectively remove snares from large ecosystems by patrolling, but an additional approach to reduce effects on large carnivores is to monitor the population closely and de-snare individuals who are found in a snare or have broken free but still carry the wire (often with serious injury). The effectiveness of de-snaring programs to reduce impacts on large carnivores has not been directly tested. Here, we used long-term demographic data from 386 individually identified lions in the Luangwa Valley Ecosystem to test the effects on population growth (lambda) and population size (N) of a program to remove snares from injured lions and treat their wounds. Stochastic Leslie matrix projections for a period of five years showed that the population grew with the benefits of de-snaring but was expected to decline without de-snaring. Mean annual growth (lambda) was 1.037 (growth in 70% of years), closely matching observed changes in population size. Mean annual growth was 0.99 (with growth in 47% of years) for a model that assumed snared animals would have died if not treated, and 0.95 (with growth in 37% of years) for models that also accounted for super-additive effects via the death of dependent cubs and increased infanticide with increased male mortality. De-snaring requires intensive effort, but it can appreciably reduce the effect of snaring on lion population dynamics.
Reproductive and juvenile ecology of mountain whitefish in the upper Green River, Wyoming
(Montana State University - Bozeman, College of Letters & Science, 2022) Brown, Colter Davis; Chairperson, Graduate Committee: Christopher S. Guy
Mountain Whitefish Prosopium williamsoni are a salmonid native to the northern Rocky Mountains that has experienced declines in population abundance in rivers throughout Idaho, Colorado, Wyoming, and Montana. Problems with recruitment are suspected, but often the specific mechanisms causing population declines are unknown. Our approach to better understand the mechanisms that influence Mountain Whitefish population dynamics was to compare population characteristics between the Green River, Wyoming and the Madison River, Montana populations. Boyer et al. (2017a) conducted an extensive study on the movement and reproductive ecology of Mountain Whitefish in the Madison River, and we used this study as a template to make direct comparisons between the populations. Our primary research questions were 1) what is the age and length at first maturity, spawning periodicity, fecundity, and age structure of Mountain Whitefish, 2) what is the spatial and temporal distribution of Mountain Whitefish through their spawning period, and what influence do abiotic factors have on spawning and movement, and 3) what is the spatial distribution and habitat use of age-0 Mountain Whitefish? We collected otoliths and gonadal samples from 127 Mountain Whitefish in the Green River, implanted 100 fish with radio transmitters and tracked them from September 1 to early November in 2019 and 2020, determined spawning period and locations using egg mats, kick netting, and angling, and sampled age-0 Mountain Whitefish using a beach seine in slow-water habitats. The geographic separation and difference in hydrogeomorphic conditions between the systems allowed us to form generalizations about Mountain Whitefish in the Intermountain West. We found Mountain Whitefish in both systems mature between ages 2 and 4, primarily spawn annually, have a similar relative fecundity, spawning movements vary, males begin movement prior to females, and age-0 fish drift downstream of spawning locations and use slow-water silt-laden habitats after hatching. The main disparities between systems were that in the Green River water temperature was more suitable for embryo development, and age structure was more uniform and older. This research enhanced our understanding of Mountain Whitefish reproductive and juvenile ecology and provided evidence for factors that may influence recruitment of Mountain Whitefish.
African wild dog demography in an ecosystem with reduced prey and dominant competitors
(Montana State University - Bozeman, College of Letters & Science, 2021) Goodheart, Benjamin Michael; Chairperson, Graduate Committee: Scott Creel; Scott Creel, Matthew S. Becker, Milan Vinks, Kambwiri Banda, Carolyn Sanguinetti, Paul Schuette, Elias Rosenblatt, Chase Dart, Anna Kusler, Kim Young-Overton, Xia Stevens, Alstone Mwanza and Chuma Simukonda were co-authors of the article, 'Low apex carnivore density does not release a subordinate competitor when driven by prey depletion' in the journal 'Biological conservation' which is contained within this thesis.
Conservation of competitively subordinate carnivores presents a difficult challenge because they are limited by dominant competitors. Prey depletion is one of the leading causes of large carnivore decline worldwide, but little is known about the net effect of prey depletion on subordinate carnivores when their dominant competitors are also reduced. African wild dogs are often limited by high densities of dominant competitors, particularly lions. We measured African wild dog density and survival, using mark-recapture models fit to 8 years of data from 425 known individuals in the Greater Kafue Ecosystem, Zambia. The GKE is affected by prey depletion, particularly of large herbivores, and thus the density of lions is significantly lower than ecologically comparable ecosystems. Counter to expectations from mesopredator release theory, wild dog density in GKE was far lower than comparable ecosystems with higher lion and prey density, though annual survival rates were comparable to large and stable populations. Average pack size was small and home range size was among the largest recorded. Our results show that low lion density did not competitively release the GKE wild dog population and we infer that the low density of wild dogs was a product of low prey density. Our results suggest that there is an optimal ratio of prey and competitors at which wild dogs achieve their highest densities. This finding has immediate implications for the conservation of the endangered African wild dog, and broad implications for the conservation of subordinate species affected by resource depletion and intraguild competition.
Vital rates, annual abundance, and movement of white sharks in the northeastern Pacific
(Montana State University - Bozeman, College of Letters & Science, 2020) Kanive, Paul Edward; Chairperson, Graduate Committee: Jay J. Rotella; Jay J. Rotella, Salvador J. Jorgensen, Taylor K. Chapple, James E. Hines, Scot D. Anderson, Barbara A. Block were co-authors of the article, 'Size-specific apparent survival rate estimates of white sharks using mark-recapture models' in the journal 'Canadian journal of fisheries and aquatic sciences' which is contained within this dissertation.; Jay J. Rotella, Taylor K. Chapple, Scot D. Anderson, Timothy White, Barbara A. Block and Salvador J. Jorgensen were co-authors of the article, 'Estimation of regional annual abundance and evidence for increasing numbers of white sharks off California' which is contained within this dissertation.; Jay J. Rotella, Taylor K. Chapple, Scot D. Anderson, Mauricio Hoyos-Padilla, Barbara A. Block, Salvador J. Jorgensen were co-authors of the article, 'Connectivity between the central California and Guadalupe Island white shark populations' which is contained within this dissertation.
Reliable estimates of populations' vital rates and abundance are fundamental requirements for making assessments and informed management decisions regarding any species. For large marine fish species whose movements are extensive throughout ocean basins, data for individuals are difficult to acquire. Without empirical data, large assumptions must be made about a species' vital rates (i.e. survival and fecundity) to make population assessments, which can potentially lead to erroneous results. Using mark-recapture and acoustic-telemetry data, I conducted analyses estimating vital rates, annual abundance, and coastal movement for white sharks (Carcharodon carcharias) off California, US. First, I used a novel approach to estimate size-specific annual apparent survival rates and to test for differences in survival between sexes after accounting for imperfect sex assignment. Our results provide little evidence for differences in sex-specific survival rates. However, I estimated the first size-specific annual apparent survival rates for sub-adult and adult white sharks. Second, I estimated annual abundance for four white shark demographic groups off the coast of California over an eight-year study period. The estimated total annual population of sub-adult and adult white sharks increased from 180 to 266 individuals during the study. Additionally, group-specific population growth rate point estimates were all > 1.00, which indicates that all groups had positive annual positive growth during the study period, although, uncertainty around those estimates were greater for sub-adults than adults and does not rule out other possibilities for population trajectories. Finally, through collaboration between Mexico and the US, I was able to analyze a comprehensive acoustic telemetry dataset that explored connectivity between two main aggregation sites that form the northeastern Pacific population of white sharks. I found that movement between the two regions was rare and more probable to be sub-adult sharks. These analyses underscore the value of collecting and analyzing empirical data to develop reliable estimates of vital rates for a top marine predator. The work also illustrates the ongoing need to cultivate international research collaboration to include data from both the US and Mexico to make accurate population inferences for the northeastern Pacific population of white sharks.
Climate-fire-vegetation dynamics in the Greater Yellowstone Ecosystem: recent trends and future projections in a changing climate
(Montana State University - Bozeman, College of Letters & Science, 2020) Emmett, Kristen Dawn; Co-chairs, Graduate Committee: Benjamin Poulter and David Roberts; Katherine M. Renwick and Benjamin Poulter were co-authors of the article, 'Disdentangling climate and disturbance effects on regional vegetation greening trends' in the journal 'Ecosystems' which is contained within this dissertation.; Katherine M. Renwick and Benjamin Poulter were co-authors of the article, 'Adapting a dynamic vegetation model for regional biomass, plant biogeography, and fire modeling in the western U.S.: evaluating LPJ-GUESSLMFIRECF' submitted to the journal 'Ecological modelling' which is contained within this dissertation.; Benjamin Poulter was a co-author of the article, 'Processed-based modeling approaches for climate-vegetation-fire feedbacks in the Greater Yellowstone Ecosystem' which is contained within this dissertation.
Climate change threatens to change forested ecosystems and wildfire characteristics across the globe. For the Greater Yellowstone Ecosystem (GYE), under future warming temperatures, wildfire activity is expected to increase and the suitable habitat for many dominant tree species is expected to shrink. Previous studies predict large high severity fires to occur more frequently, potentially so frequent that forests are unable to grow old enough to produce seeds and self-regenerate. Studies of suitable climate spaces show that previously habitable areas may become too warm or dry to support common GYE trees. The first goal of this dissertation was to use vegetation images from satellites to detect recent changes in forest productivity in the GYE, and then determine the relative importance of recent climate and disturbance observations in explaining these changes. We found that areas with detected increases in plant growth, or 'greening' trends, were associated with forested areas regenerating after wildfire. Detected decreases in plant growth, or 'browning' trends, were associated with areas that had recently burned. Historically dry areas with recent increases in precipitation were associated with greening trends. Warming of 0-2 °C was associated with greening trends, while greater increases in temperature (>2 °C) were correlated with browning trends. The key take-away is although forests in the GYE are usually considered temperature limited, changes in precipitation may be more important than previously thought. The second goal of this dissertation was to adapt a global vegetation computer model for regional applications to simulate forests and wildfire dynamics, ultimately to run simulations under future climate conditions to predict how forest extent and composition may change. Life history characteristics and climate limitations were aquired for the dominant GYE plant types to dictate their establishment, growth, competition, and mortality in the new model. Before running future simulations, it is required to evaluate how well the model represents current conditions. Adding new equations that calculate the initiation, spread, and effects of crown fires was required to reproduce recent vegetation abundance, distribution of plant types, and fire activity in the GYE. Methods, expected results, and implications of running future simulations are described in Chapter 4.
Distribution, phenology, growth, and overwinter mortality of age-0 smallmouth bass in the Yellowstone River, with implications for upstream range expansion
(Montana State University - Bozeman, College of Letters & Science, 2020) Voss, Nicholas Sheridan; Chairperson, Graduate Committee: Alexander V. Zale; Robert Al-Chokhachy, Adam J. Sepulveda, Christine E. Verhille, Michael P. Ruggles and Alexander V. Zale were co-authors of the article, 'Distribution, phenology, growth, and overwinter mortality of age-0 smallmouth bass in the Yellowstone River, with implications for upstream range expansion' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.
Non-native fish introductions are a leading threat to freshwater biodiversity, and accurate assessments of future impact are often hindered by the challenge of anticipating future range expansion. Successful introductions of non-native Smallmouth Bass Micropterus dolomieu have occurred globally and often exhibit secondary spread to upstream habitat. This has occurred in the Yellowstone River, Montana (USA). Observations of adults in socio-economically valuable trout habitat have highlighted a need to better understand the controls on the upstream distribution of Smallmouth Bass in this system, particularly the influence of cold upstream climates on first-year growth and size-selective overwinter mortality (a potential life history bottleneck at northern latitudes). We documented the phenology, growth, and survival of age-0 Smallmouth Bass in relation to water temperature between the uppermost distribution of adults, and downstream regions where they are abundant. Successful reproduction (i.e., age-0 presence) was rare or absent throughout the uppermost 150 km of the upstream distribution of adults, suggesting that something currently prevents or discourages successful reproduction farther upstream. Surprisingly, the mean late-autumn body size of age-0 Smallmouth Bass did not differ significantly among the uppermost 200 km of their distribution, despite upstream declines in ambient water temperature. Although water temperature was a key attribute affecting age-0 growth, upstream shifts towards earlier hatching mediated the expected negative effect of colder upstream climates. Furthermore, surveys of overwinter survivors and simulations of age-0 starvation mortality indicated that age-0 individuals at the upstream extent of their distribution successfully recruited to the age-1 year-class in four consecutive years. Taken together, our results suggest that Smallmouth Bass have not yet reached the thermal limit of their upstream distribution, and that first-year growth, survival, and consequent spread by this non-native predator are probably driven by the complex interactions of spawn timing and ambient thermal and hydrologic regimes in the Yellowstone River.
Is habitat constraining bighorn sheep distribution and restoration: a case study in the Greater Yellowstone Ecosystem
(Montana State University - Bozeman, College of Letters & Science, 2019) Lula, Ethan Shawn; Chairperson, Graduate Committee: Robert A. Garrott
Rocky Mountain Bighorn Sheep (Ovis canadensis) restoration continues to be a challenge throughout western North America despite nearly a century of efforts dedicated to the species' recovery. A persistent problem for restoration is populations failing to expand into surrounding areas of habitat even during years of population growth. While populations can be constrained by several environmental factors and behavioral tendencies, we contend habitat availability is not the primary limiting factor. This study incorporated GPS data from bighorn sheep within the Taylor-Hilgard population in the Madison Mountain Range, located in the northwestern extent of the Greater Yellowstone Ecosystem (GYE), to develop summer and winter resource selection function (RSF) habitat models. The objective of this study was to evaluate a hypothesis that habitat was not the primary factor limiting distributions of bighorn sheep within the Madison Range by developing biologically-plausible RSF models and using covariates expected to influence selection. Multiple functional forms and spatial grains for covariates were considered and sets of summer and winter resource selection models compared using AIC subscript c. Results indicated that bighorn sheep resource selection was grain dependent, with bighorn sheep generally selecting covariates at the larger 500 m and 1,000 m spatial grains. Summer selection was characterized by rugged terrain, steep slopes, reduced canopy cover, southwestern aspects and ridgelines. Winter selection was characterized by low elevations, southwestern aspects, steep slopes, reduced canopy cover, ridgelines, high summer NDVI amplitude, and areas close to steep terrain (slopes > or = 45°). Predicted winter habitat occurred in a non-contiguous distribution primarily along low-elevation, southwest-facing aspects within the Madison Valley, and predicted summer habitat was concentrated along high elevation ridgelines. Model results were successfully validated using independent GPS data. Potential abundance for the Madison Range was estimated by linking the winter RSF to population estimates for the Taylor Hilgard and results suggested that the Range may be capable of supporting 2 to 4 times the number of bighorn sheep currently estimated. Study results supported the hypothesis that habitat was not the primary factor limiting extant bighorn sheep populations, suggesting that broader distributions within the Range are possible if novel restoration strategies are considered.
Spatiotemporal patterns of resource use and density of American black bears on Yellowstone's northern range
(Montana State University - Bozeman, College of Letters & Science, 2020) Bowersock, Nathaniel Roth; Chairperson, Graduate Committee: Andrea Litt; Andrea R. Litt, Kerry A. Gunther, Jay J. Rotella, Jerod A. Merkle and Frank T. van Manen were co-authors of the article, 'Influence of resource waves on American black bears during Spring in the northern range of Yellowstone National Park' which is contained within this thesis.; Andrea R. Litt, Kerry A. Gunther, Michael A. Sawaya, Jay J. Rotella and Frank T. van Manen were co-authors of the article, 'Factors associated with varying density of black bears on Yellowstone National Park's northern range' which is contained within this thesis.
The availability of resources, such as food and cover, can directly influence the movement and distribution of wildlife populations. The abundance and seasonal timing of many resources have changed in Yellowstone National Park (YNP), which has influenced populations of American black bears (Ursus americanus), an opportunistic omnivore. Previous studies have focused on how changes in resources have influenced black bears in the central and southern regions of YNP, however little work has focused on black bears in the northern part of the park. In 2017-2018, we used GPS collars and non-invasive genetic sampling to understand resource selection and variation in densities of black bears on the Northern Range. We sought to 1) assess whether black bears were following seasonal pulses of resources (resource waves) in the spring, such as the green wave and elk (Cervus canadensis) calving wave and 2) evaluate how densities of black bears varied based on landscape features, generating a baseline abundance estimate to help track changes in the population over time. We found evidence that black bears followed the green wave, prioritizing forage quality over quantity when selecting patches of green vegetation in early spring. However, black bears were less likely to select areas near historical elk calving grounds, suggesting that consumption of neonates is more opportunistic. Densities of black bears varied among vegetation communities, with the highest densities in forested communities dominated by Douglas fir. Our study provides the first baseline density estimates for black bears on the Northern Range, with an average density of 12.8 bears/100km 2 (95% CI = 9.4 - 17.5), which is higher than other regions in YNP. Availability of high-quality resources may allow for higher densities of black bears, with potential ramifications for other wildlife populations on the Northern Range. Information about resource selection and variation in estimated densities could be used to guide management decisions to continue to reduce human-bear conflicts and provide safe wildlife viewing experiences for the growing number of visitors to YNP.
Understanding the present and past climate-fire-vegetation dynamics of southern South America (40 - 45°S)
(Montana State University - Bozeman, College of Letters & Science, 2020) Ogunkoya, Ayodele Gilbert; Chairperson, Graduate Committee: Benjamin Poulter; David Roberts (co-chair); Jed O. Kaplan, Cathy Whitlock, William Nanavati, Benjamin Poulter and David Roberts were co-authors of the article, 'Drivers of modeled forest cover change in southern South America are linked to climate and CO^2' which is contained within this thesis.; Jed O. Kaplan, Cathy Whitlock, William Nanavati, Benjamin Poulter, David Roberts and Steve Hostetler were co-authors of the article, 'Climate drivers of late-glacial to postgalacial forest cover along the eastern Andes of Northern Patagonia (lat. 40 - 45°S)' which is contained within this thesis.
The forest-steppe boundary that runs north-to-south along the eastern Andes is particularly dynamic over millennial time scales. Yet the relative role of long-term climate change and fire is poorly understood. In this study, I analyze the potential in using a process-based model in predicting species distribution, and the role fire and climate played in shaping the vegetation and treeline dynamics of Northern Patagonia (lat. 40 - 45 ° S). Paleoecological data, e.g., pollen, has been extensively used to study the relationship between climate and vegetation but has a low spatial resolution to distinguished between climate-fire-vegetation dynamics. Process-based model thus offers a transparent and robust method of incorporating a varying degree of complexity to understand fire behavior and fire-vegetation dynamics. Recently, LPJ-GUESS was parameterized to simulate major regional plant functional type (PFTs) and tree species distributions in this region. The model is able to predict regional species distribution across spatial scales by coupling establishment, growth, and mortality processes. Predicting spatial and temporal scale species distribution cannot be achieved without having the right climate and soil data, the climate data used was downscaled from 50 km to 1 km resolution using Worldclim climate data ( ~ 1 km) as the reference data. LPJ-GUESS model produced regional species distribution with fair to very good agreement with observation. The optimization of bioclimatic parameters and drought tolerance that is related to root depth, adaptability of plant to seasonal drought, and movement of nutrients consistently improved the accuracy of regional prediction of the species range. The model predicted that the vegetation distribution of present-day is mainly determined by climate and CO 2 rather than fire., while forest productivity responds strongly to elevated CO 2. However, based on the employed statistical methods of Canonical Correspondence Analysis (CCA) and Random Forest machine learning, combined with simulation results using paleoclimate. Results show that an increase in winter temperature drives the postglacial species distribution while changes in precipitation control radial growth and seedling establishment in the upper and lower treeline. These findings emphasize the importance of combining paleoecological methods with modeling to disentangle coarse-scale climate drivers from local influences.
Biophysical gradients and performance of whitebark pine plantings in the Greater Yellowstone Ecosystem
(Montana State University - Bozeman, College of Letters & Science, 2019) Laufenberg, David Anton; Chairperson, Graduate Committee: Andrew J. Hansen
The efficacy of planting efforts for species of conservation interest is important for ecosystem managers. Planting efforts represent an opportunity to conserve and manage species during a population crisis. Although federal agencies have been planting whitebark pine (WBP) in the Greater Yellowstone Ecosystem (GYE) for three decades, these efforts have been met with varying success. In this study, we use a combination of field sampling and remote sensing approaches in order to investigate local biophysical gradients as explanatory variables for WBP performance in GYE planting units. Present-day field sampling affords an opportunity to evaluate WBP performance relative to earlier planting and monitoring records. We used remotely-sensed temperature and precipitation alongside field measurements of elevation, aspect, slope, shading, and soils to utilize an adapted Thornthwaite-type water balance model to explain individual growth rates and site density change ratios (essentially survival and natural recruitment). We found that planting sites varied greatly in their biophysical characteristics and WBP performance. Five of twenty-nine sites had higher present-day density than at date of planting, therefore indicating some amount of natural regeneration occurring within those sites since time of planting. These sites were often higher in elevation, not south or southwest facing, and had soils that could hold moisture later in the season and for longer periods following precipitation events. Sites that experienced reductions in the density of WBP were often lower in elevation, with poorer soils, and facing south or southwest. They therefore experience greater potential evapotranspiration, and also greater water deficit when water demands are not being met. Notably, our two response variables, individual growth rate and site density change ratio represent short and long-term performance variables respectively. Although our results suggest that individual growth rates are likely more often limited by energy than water demands, the site density change ratio associated with this late to mature, long-lived species is likely a better benchmark for success. If they make it to maturity, trees planted this season will not begin to produce cones until the end of this century or the beginning of the next. Therefore, they must overcome forecasted periods of greater water stress in the coming decades and centuries. We strongly recommend planting efforts that seek to reduce the effects of increased drought stress by planting at sites with soils of greater water holding capacities (non-rhyolitic), planting on northerly and easterly aspects, and utilizing microsites particularly when planting at sites with potentially higher water stress. We also detected a negative relationship between the density of local competitors and WBP performance, but only at higher densities. Ecosystem managers will continue to plant WBP in the GYE for years to come, and this research helps to inform and identify high quality habitat during a period of changing climate and high GYE WBP mortality rates.

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