Browsing by Subject "rodent"

Now showing 1 - 3 of 3
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    Ecology And Chemistry Of Small Mammals And The Implications For Understanding Their Paleoecology And Environments
    (2015-07) Haveles, Andrew
    Fundamental goals of paleoecologists and modern ecologists is to understand the evolutionary and ecological patterns in modern and ancient biodiversity. Diet is one ecological trait species may evolve or vary to exploit food resources and increase their fitness. Stable isotope analysis is one method used to infer diet and is transferable between modern and fossil populations. Stable isotope analysis has not been commonly applied to small mammals, mostly because of sampling limitations. Here, three studies focus on furthering our understanding of small mammal ecology and serve as a baseline comparison for interpreting similar data from the fossil record. Chapter 1 illustrates that small mammals varied their diets independently and indicate granivores focused on C4 derived resources, generalists consumed resources readily available, and an invertivore focused on invertebrates. Results indicate that intermediate ?13C values between C3 and C4 resources are likely from integrating multiple resources through direct consumption and invertivory. Therefore, interpreting ?13C values from consumers in the fossil record must be interpreted with caution. Chapters 2 and 3 include a ?13C dataset that expands to the regional scale and assess how rodent partition C3 and C4 resources as C4 biomass on the landscape varies. Small mammals mostly rely on C3 derived resources, but there are some spatial and ecological tendencies with granivores incorporating the most C4 derived resources and varied with C4 biomass. Climate variables explained some variance in C4 consumption for some species, while other species' diets were not explained by climate. Seasonality metrics were the best predictors of C4 consumption and ?13C values in rodent hairs were more positive during peak C4 growing seasons. Chapter 4 estimates temperature and precipitation using the area extant species' geographic ranges overlap today and then applied to ancient faunas where the same species co-occur. Temperature and precipitation estimates for Pleistocene-Holocene localities reflect the general warming during this transition and interpolated temperature and precipitation for climate intervals illustrate deviating spatial gradients through time. The culmination of work presented here greatly improves our understanding of small mammal ecology and sets s baseline for testing modes of evolution and ecology in the fossil record.
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    Effects of environmental factors on pathogen exposure and transmission in wild rodent populations
    (2023-08) Mistrick, Janine
    Anthropogenic land-use change is altering ecosystems across the globe and has been implicated as a major factor increasing the spillover of zoonotic diseases from wildlife into human populations. Wild rodents are of particular importance for spillover as they host the largest diversity of zoonotic pathogens of any mammalian order. Moreover, rodent hosts of zoonotic pathogens have been found to increase in abundance in anthropogenic landscapes. In my dissertation, I investigate the effects of environmental factors related to anthropogenic land-use change on pathogen prevalence and transmission in wild rodent populations. Using an observational field study across landscape and habitat types, I broadly investigate the effects of anthropogenic development on the prevalence of zoonotic bacterial pathogens in wild Peromyscus mice (Chapter 1). I then turn to finer spatial scales to consider how spatial overlap can be used to approximate transmission in wildlife populations (Chapter 2). Using wild bank voles (Clethrionomys glareolus) as a model system, I leverage a replicated, experimental field study to quantify the effects of food supplementation and helminth macroparasite removal on vole space use and spatial overlap to approximate transmission opportunities (Chapter 3). Finally, I test how spatial overlap predicts infection of an endemic viral pathogen and examine whether the relationship between spatial overlap and infection is influenced by food abundance and macroparasite infection (Chapter 4). My research indicates that agricultural development may increase the prevalence of zoonotic bacterial pathogens in wild rodents. Further, I show that environmental factors alter the space use of wild rodents and that both environmental conditions and host traits are important to predict how spatial overlap affects transmission of an endemic pathogen. As such, my dissertation research has contributed empirical evidence that shows how environmental conditions alter zoonotic pathogen prevalence and transmission in wild rodent populations. This represents an important step forward in our ability to quantify the effects of anthropogenic land-use change on disease dynamics in wildlife, advancing our ability to understand and predict transmission dynamics and control spillover potential from wildlife into human populations.
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    From Soil to Squirrel: The Legacy of Lead Pollution & Its Effects on Urban Wildlife Behavior
    (2024-04-18) Schulz, Rachel K; Devitz, Amy-Charlotte; Snell-Rood, Emilie C
    Urbanization increasingly threatens wildlife through the introduction of novel threats and pollution. Animals can use behavior to adapt to urban environments and urban pollutants drive changes in behavior, leading to populations of urban wildlife with some behaviors that are distinct from rural populations. Lead (Pb) pollution is ubiquitous in urban areas, but there can be significant local variation in soil lead levels. In this study, I examined the relationship between soil lead, hair lead, docility, and aggressive and social behavior in eastern gray squirrels (Sciurus carolinensis) and eastern chipmunks (Tamias striatus) in Minneapolis and Saint Paul, Minnesota. Docility was measured through a struggle test and aggressive and social responses were measured in a mirror image stimulation trial. Soil lead and hair lead were significantly positively correlated in gray squirrels and chipmunks, and there was no difference in hair lead based on species or sex. Chipmunks had significantly longer struggle times than gray squirrels, but struggle time did not vary based on hair lead or sex. Only six of 235 animals displayed aggression in the mirror image stimulation trial, and frequency of contacting the mirror in a nonaggressive way was not correlated with hair lead, species, or sex. These results provide correlational evidence of lead transfer from soils to gray squirrels and chipmunks, though the magnitude of lead accumulation does not seem to depend on the distinct life histories of these two species. At the levels currently present in these urban environments, lead does not affect aggressive or social behavior in gray squirrels or chipmunks. Future studies should examine aggression through direct observation rather than a mirror image stimulation trial to better quantify aggression in these species that have low territorial aggression.