Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item 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.Item Feeding ecology and food-web interactions of the fish assemblage in the upper Missouri River and lower Yellowstone River with an emphasis on pallid sturgeon conservation(Montana State University - Bozeman, College of Letters & Science, 2018) Dutton, Adeline Jean; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy was a co-author of the article, 'Diet overlap and gape size of pallid sturgeon and shovelnose sturgeon in the Missouri River and Yellowstone River' submitted to the journal 'Journal of applied ichthyology' which is contained within this thesis.; Christopher S. Guy and Eric A. Scholl were co-authors of the article, 'Quantitative food-web linkages among primary, secondary, and tertiary consumers in the upper Missouri River and lower Yellowstone River' submitted to the journal 'Journal of freshwater ecology' which is contained within this thesis.A conservation propagation program started in the late 1990s for the endangered Pallid Sturgeon Scaphirhynchus albus because the species was not recruiting in the Missouri River. Stocking has been successful and several studies have suggested that the survival of stocked Pallid Sturgeon in the upper Missouri River is relatively high. Stocking of hatchery-origin Pallid Sturgeon may have created an uncharacteristic population structure, which could lead to intraspecific and interspecific competition between juvenile Pallid Sturgeon, Shovelnose Sturgeon, and other fish species in the Missouri and Yellowstone rivers. The purpose of this study was to describe the diets of Pallid Sturgeon and Shovelnose Sturgeon, determine if gape size differed between species, and assess diets of many secondary and tertiary consumers to describe the food web of the upper Missouri and lower Yellowstone rivers. Pianka's index of diet overlap was highest in segments near Fort Peck Dam in the Missouri River. Diet overlap was low in the Missouri River below the confluence with the Yellowstone River and in the Yellowstone River. Gape size was slightly different between Pallid Sturgeon and Shovelnose Sturgeon suggesting it was not the mechanism for the shift to piscivory in Pallid Sturgeon. Chironomidae were the most abundant primary consumer in the upper Missouri River and lower Yellowstone River. Hydropsychidae were not abundant in either river system, but were frequently consumed by Goldeye, Channel Catfish, Shovelnose Sturgeon, and Stonecat in the Missouri River and Shovelnose Sturgeon in the Yellowstone River. Emerald Shiner were the most abundant secondary consumer in both rivers and the most frequently consumed secondary consumer by Pallid Sturgeon, in the Missouri River. In addition, Pallid Sturgeon in the Missouri River consumed Channel Catfish, Shovelnose Sturgeon, and either Sicklefin Chub or Sturgeon Chub. In the Yellowstone River, Pallid Sturgeon consumed Channel Catfish, Scaphirhynchus spp., and Stonecat. These results provide a foundation into key linkages among predators and prey to better understand the effects of stocking Pallid Sturgeon in the upper Missouri River and lower Yellowstone River.Item Risky business: dealing with risk in a predator - prey community(Montana State University - Bozeman, College of Letters & Science, 2017) Droge, Egil Dag; Chairperson, Graduate Committee: Scott Creel; Scott Creel, Matthew S. Becker and Jassiel M'soka were co-authors of the article, 'Spatial and temporal avoidance of risk within a large carnivore guild - predator avoidance by predators' in the journal 'Ecology and evolution' which is contained within this thesis.; Scott Creel, Matthew S. Becker and Jassiel M'soka were co-authors of the article, 'Measuring the 'landscape of fear': risky times and risky places interact to affect the response of prey' in the journal 'Ecology and evolution' which is contained within this thesis.; Scott Creel, Matthew S. Becker, David A. Christianson and Fred G.R. Watson were co-authors of the article, 'Response of wildebeest (Connochaetes taurinus) movements to spatial variation in long term risks from a complete predator guild' which is contained within this thesis.The Liuwa ecosystem has several ecological properties that affect interactions among large predators, with lions and hyaenas as dominant species and African wild dog and cheetah as subordinate species, and between predator and prey. First, the vegetation structure is highly uniform and typified by open grasslands with good visibility over long distances. Secondly the prey community is heavily dominated by wildebeest, with much lower numbers of zebra, oribi and other species. These characteristics combined with GPS data on a fine spatial scale, and a large observational dataset on both predators and prey enabled us to focus on several little-studied questions about the effects of predation risk in the wild. Interspecific competition between predators can be a strongly limiting force for subordinate predators like cheetahs and African wild dogs. Both species use niche partitioning to reduce the risk of dangerous interactions in different ways that appear to have ramifications for coexistence. Wild dogs showed more dietary and temporal overlap with dominant competitors while cheetahs combine divergence in diet, temporal avoidance and reactive local spatial avoidance to coexist with lions and hyenas in areas of high prey density, even in open habitats. These results provide new insight into the conditions under which partitioning may not allow for coexistence of African wild dog, while it does for cheetah, with dominant predators making wild dogs more prone to competitive exclusion (local extirpation), particularly in open, uniform ecosystems with simple prey communities. Focusing on predator-prey relationships the overall the conclusion is that the assessment of risk by animals is a very fine-tuned process. Our results confirm that both the risky places hypothesis (LT risk) and the risky times hypothesis (ST risk) are important, leading to both reactive and proactive responses. Critically, these effects do not act independently in their effects on the strength of antipredator responses. This interaction presents challenges for the design of research on risk effects. An effect of ST risk could be masked by unmeasured variation in LT risk (or vice versa), and an effect of ST risk might be caused by unmeasured variation in LT risk (or vice versa).Item Spotted hyaena survival and density in a lion depleted ecosystem : the effects of competition between large carnivores in African savannahs(Montana State University - Bozeman, College of Letters & Science, 2015) M'soka, Jassiel Lawrence Juma; Chairperson, Graduate Committee: Scott Creel; Scott Creel, Mathew S. Becker and James Murdoch were co-authors of the article, 'Ecological and anthropogenic effects on the density of migratory and resident ungulates in a human-inhabited protected area' submitted to the journal 'African journal of ecology ' which is contained within this thesis.; Scott Creel, Mathew S. Becker and Egil Droge were co-authors of the article, 'Spotted hyaena survival and density in a lion depleted ecosystem: the effects of competition between large carnivores in African savannahs' which is contained within this thesis.Competition is considered an important factor for large carnivore population dynamics, but the manner in which interspecific competition impacts these species are not well understood. This lack of knowledge is due to the ongoing declines of large carnivores, the loss of intact large carnivore guilds, the complexity of competitive relationships and how they can be impacted by ecological and anthropogenic factors. In light of rapid declines of carnivore populations across the globe, understanding how interspecific competition limits large carnivores is an important component for the management and conservation of these species. Using data from 233 individuals in five clans and capture-recapture robust design models we estimated the survival and density of spotted hyaena in 5 clans in the Liuwa Plain, where their main competitor, the African lion was reduced to a single individual. We tested for the effects of settlements, prey density, competition with lions and hyaena clan size on the mean hyaena survival. The average population size during the duration of study was 151.2 + or = 5.9(SE) individuals. Population size fluctuated through time with the seasonal fluctuations of the main prey species, the blue wildebeest. Mean annual survival across all age classes was 0.93 (95%CI: 0.39 - 0.99). We found no detectable effects of variation in hyaena clan size, prey density, local variation in utilization by lions, or proximity to people on survival. We also estimated the densities of wildebeest, oribi and zebra, the main prey species for the carnivores in the system using distance sampling methods. We tested for the effects of variables in three classes: environmental (year, season, vegetation, grass height, burn, water presence), predation risk (hyaena density), and anthropogenic (distance to park boundary and settlements). Densities ranged from 6.2 - 60.8 individuals km superscript -2 for wildebeest, 1.1-14.5 individuals km superscript -2 for oribi, and 1.8-8.1 individuals km superscript -2 for zebra. Results reveal resource partitioning among ungulate species and indicate that predation risk and proximity to humans affect ungulate distributions with implications for managing migrations in the Greater Liuwa Ecosystem. They suggest that the maintenance of native prey populations allows coexistence between humans and large carnivores in Liuwa Plain National Park.Item Development of occupancy surveys for mountain ungulates(Montana State University - Bozeman, College of Letters & Science, 2013) O'Reilly, Megan; Chairperson, Graduate Committee: Robert A. GarrottBighorn sheep (Ovis canadensis canadensis) and mountain goats (Oreamnos americanus) overlap in broad food and habitat requirements. In places where mountain goats are non-native there are concerns over potential competition between the two species. The southern Gallatin Mountain range, within and adjacent to the northwest boundary of Yellowstone National Park has both native bighorn sheep and non-native mountain goats. Existing observations of both species for this area vary in spatial precision and there are no records of where observers looked for animals but did not detect them. To gain a better understanding of the relationship between bighorn sheep and mountain goats and their habitat, it is necessary to understand resource selection and the extent of overlap in resource use at fine spatial and temporal scales. I used logistic regression to relate existing presence-only bighorn sheep and mountain goat data for this area to landscape features I expected would be important to both species. Using resulting coefficient estimates, I constructed a relative habitat suitability map and used it to define four survey regions within the study area. The crew of four spent 113 observer days afield and hiked 210 miles recording occupancy data for both mountain ungulates within these four survey regions. Observers surveyed 6,603 100 x 100 meter grid cells, with 15 groups of bighorn sheep and 34 groups of mountain goats observed during surveys. Because there were more mountain goat observations available, I used only mountain goat data to conduct formal occupancy analyses. Mountain goat occupancy was positively associated with ruggedness at the 100 meter scale and there was an important interaction between distance to escape terrain and tree cover at the 500 meter scale. As the distance to escape terrain increased mountain goats were less likely to occupy treed areas. The ruggedness index used in my presence-only modeling effort was based on the rate of change in slope. By using a ruggedness index which included changes in slope and aspect I improved model performance. This research demonstrates the feasibility of conducting occupancy surveys in mountainous terrain and provides interesting biological insights regarding mountain goats and their habitat.