Conservation priorities are increasingly important in the face of modern human activities. Anthropogenic activities such as deforestation, pollution, and climate change have negative impacts on all vertebrates. In chapter 1, I examine whether there are relationships among density dependence, population size variability, and extinction risk in mammals to see whether these parameters are indicative of population health. Also included were analyses of how body mass and age to maturity affect those three measures. On a smaller, more local scale, I asked questions regarding biodiversity of small mammals in a highly fragmented environment, the tallgrass prairie. In chapter 2, I examined how cattle grazing impacts small mammal biodiversity in the Sheyenne National Grassland on a short term, season-long scale. By understanding the interaction of large herbivores, vegetation height, and small mammals, appropriate measures can be taken to conserve this rare habitat properly, without sacrificing biodiversity.