Microscopic examination of the tracheal dimensions of normal Florida mice (Peromyscus floridanus) and cotton mice (P. gossypinus) showed no significant differences between the two species, but external examination showed the tracheal length of the Florida mouse to be longer than that of the cotton mouse. Microscopic examination of the intrapulmonary apparatus (bronchioles, alveolar ducts, atria, and alveoli) of normal Florida and cotton mice showed no significant differences in measurements between the two species. Cotton mice were exposed to exhaust gases produced by the burning of solid rocket motor (SRM) fuel. Mice exposed once for a duration of 10 min demonstrated an LD50 of 52 to 56 ppm HCl/g body weight and an LD50 of 169 to 173 mg Al2O3/m3/g body weight. These LD50 values suggested that SRM exhaust components may have a synergistic lethal effect when compared to the effects of individual components of the exhaust. Cotton mice exposed to the exhaust exhibited external signs of respiratory distress and dyspnea. Those mice that received lethal exposures showed internal signs of early inflammatory reactions. However, the most likely cause of death was a sudden shift in blood pH.

Climatic and geographic events such as glaciations, island formation, river formation, and urbanization strongly affect habitat specialist species. By contrast, it is traditionally assumed that these events have little effect on habitat generalists but few studies have tested this assumption. In this study I sought to identify the effects of historic and contemporary biogeographic events on the genetic structure of a habitat generalist, the cotton mouse (Peromyscus gossypinus). This species is distributed throughout the southeastern United States, a region that has experienced dramatic geographic changes associated with both historic Pleistocene glacial cycles, as well as contemporary anthropogenic forces. In analyzing the genetic structuring in this species I took a telescopic approach, beginning with the patterns of variation throughout the species range from a phylogenetic standpoint. Using mitochondrial sequence data I identified three reciprocally monophyletic clades of the cotton mouse, a southeastern, northeaster, and western clade. Among these clades I identified eight distinct subspecies, four of which had previously not been identified using morphological characters. Of the four previously identified subspecies, this study resulted in a restructuring of the range of all except the Key Largo cotton mouse, which is restricted to northern Key Largo Florida. Secondly, I employed phylogeographic methods to examine the genetic patterns of the cotton mouse in a geographic context. Phylogeographic breaks in the cotton mouse are largely consistent with those observed in other taxa distributed throughout the southeastern United States. Geographic structuring in this species shows deep patterns associated with glacial maxima and minima of the Pleistocene period. Many of these patterns are maintained by contemporary geographic barriers to gene flow. Thirdly, I identified geographic structuring of genetic variation at a regional and local level. This structuring is partially due to the cotton mouse’s limited dispersal ability but is strengthened and reinforced by naturally occurring contemporary barriers to gene flow and contemporary anthropogenic forces which serve to limit dispersal in this species. Finally, I determined that urbanization has a dramatic negative effect on gene flow and genetic variation in this species on a local scale. Over a twenty year period populations in urban areas experienced a marked decrease in genetic variation while populations in non-urban areas experienced an increase in variation. During this time period, gene flow was effectively cut off among populations that had previously been panmictic. This study demonstrates that small mammal habitat generalists can be affected by both historic and contemporary climatic and geographic events at multiple geographic scales. These effects range from large scale geographic structuring throughout the species’ range to fine scale structuring associated with contemporary anthropogenic forces.

The perception of increased predation risk by nocturnal mice and other small mammals has been shown to reduce activity levels, particularly in foraging effort. Various cues of predation risk have been used in previous studies, but few have assessed the potential interactions between different types of cues. I conducted field, laboratory, and enclosure experiments using predator scents, artificial light, and microhabitat variables to determine the effects of direct and indirect cues of predation risk on foraging behavior in wild nocturnal mice. Experimental foraging trays served as artificial resource patches, and giving-up densities were measured in order to test for foraging persistence in patches exposed to cues of predation risk. Cotton mice (Peromyscus gossypinus) were used in laboratory and enclosure trials, and were the most common mice present at the sites used for field trials. Although previous foraging studies have used other Peromyscus species, this species has not been tested, but ranges over densely populated areas of the United States where artificial light could potentially affect its behavior. In outdoor and laboratory enclosures, cotton mice showed no aversive response to bobcat urine, cloths rubbed on cats, or snake sheds, but did exhibit avoidance of cat fur and artificial light. In the field experiment, mice showed a strong preference for covered microhabitats, but did not avoid bobcat urine or artificial light. Foraging in artificial resource patches also increased throughout the duration of the field experiment, possibly coinciding with a reduction in naturally-available forage. Mice in this population appear to use cover as their primary means of avoiding detection or capture by predators, though they do avoid artificial light and at least one fur-derived odor when their available options for escape are reduced.

No description available.