Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 20-25). Also available in electronic format on the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 154-164). Also available via the Internet.

Research on the chronic effects of toxic chemicals on individuals, populations, communities, and ecosystems is imperative to regulate pollutants and preserve threatened species and habitats. I designed a two-pronged study to investigate the effects of heavy metal contaminants on small mammal populations, communities and body condition. To compare population and community metrics, I conducted a year-long mark-and-release study from over 5,400 trap nights on a contaminated and reference site within Crab Orchard National Wildlife Refuge, a Superfund site. During the second phase, I compared contaminant residues to body condition in 29 white-footed mice (Peromyscus leucopus) and 21 southern short-tailed shrews (Blarina carolinensis) from the Refuge and from three reference sites. Body weight, age structure, trapping success or species diversity did not differ between sites. Mice from the contaminated site were more abundant with lower reproduction (as number of juveniles per adult female). Cadmium in both livers and kidneys of mice and shrews was significantly greater on the contaminated site. Elevated renal cadmium in mice (96 ± 79 mg/kg dry weight) and shrews (242 ± 166 mg/kg dry weight) from the contaminated site could likely impair physiologic functions with long-term effects. For white-footed mice, increasing renal copper, lead, and nickel were good predictors of low ash, water, and protein but did not correlate significantly with crude lipid content. In shrews, however, metals either showed no relationship or, in the case of renal cadmium and copper were positively related to body condition as increased protein content. Simply comparing animals from reference versus contaminated sites provided few insights into overall community structure or population dynamics of white-footed mice. While metals explained as much as 40% of body condition (ash) in mice, findings in both species are counter-intuitive or refute predictions. Future studies should include manipulative field experiments that pair higher-resolution, biologic responses such as histologic and biomarker assays with population and community dynamics.

Similarities between golden mice (Ochrotomys nuttalli) and white-footed mice (Peromyscus leucopus) have been well-studied in both field and laboratory settings. Often sympatric, these species share similar habitat, as well as other resources, yet previous researchers have found little evidence for interspecific competition. Niche partitioning may reduce direct competition through specialization of resource use. Although the golden mouse is considered a resource specialist, it is likely that the degree of habitat specialization differs by locality, and thus, the degree of interspecific competition with similar species is variable. To determine the extent to which microhabitat use differs between golden mice and white-footed mice, I measured 16 and 15 microhabitat variables during the leaf-on and leaf-off seasons, respectively, in Jackson County, Illinois. Trapping took place on 3 grids from March 2010 to September 2011. The ratio of individual golden mice (n = 74) to white-footed mice (n = 85) was unusually high during this study. Microhabitat use models were constructed for both species during both seasons using logistic regression by comparing microhabitat at trapping stations where each species was captured vs. stations without captures. Few variables described habitat occupied by golden mice. Overall, dense vegetation up to 2.0 m was most important for golden mice and ground-level structures such as logs were most important for white-footed mice. Captures and noncaptures were predicted with a high degree of accuracy by logistic regression (81.5-90.3%). Discriminant function analysis was used to identify which microhabitat variables optimally discriminated between habitat used by golden mice, white-footed mice, and neither species. More variables discriminated between species during the leaf-on season than the leaf-off season although discriminating variables during leaf-off were more important overall. Habitat where either species was captured was combined and compared against habitat where no mice were captured; microhabitat used by mice was statistically distinct within the study area. Captures and noncaptures were classified correctly more than would be expected by chance by discriminant function analysis but moderate classification success values indicated microhabitat differences between species were subtle. Microhabitat and elevated trap use varied between seasons for both species, but neither species used ground or elevated traps more than expected during the leaf-on season. Spatial segregation was more apparent during the leaf-off season when golden mice used elevated traps more than expected and white-footed mice used ground traps more than expected. Overall results suggest that golden mice exhibited a great deal of plasticity in microhabitat use seasonally, and are more habitat generalists than previous literature would suggest. Although some spatial segregation was apparent between golden mice and white-footed mice, there was no evidence for avoidance between species, which implies a lack of interference competition. It is likely that other life-history factors (such as metabolic rate, nest building, or sociality) in combination with microhabitat and vertical partitioning allow coexistence between these species rather than microhabitat segregation alone.

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Thesis (Ph. D.)--Miami University, Dept. of Zoology, 2004. / Title from second page of PDF document. Document formatted into pages; contains [3], iii, 138 p. : ill. Includes bibliographical references (p.121-138).

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 198-229).

Golden mice (Ochrotomys nuttalli) are generally an elusive and rare species throughout their geographic range in the southeastern United States. They are considered to be habitat specialists that prefer dense understory consisting of shrubs and vines. Golden mice are less vagile, and likely disperse shorter distances than other sympatric species such as the white-footed mouse (Peromyscus leucopus). Conversely, white-footed mice are considered habitat generalists that inhabit a variety of habitat types, are more vagile, and disperse farther than golden mice. Because of this it is likely that golden mice have a lower genetic diversity and are more genetically subdivided than white-footed mice. In southern Illinois, golden mice are on the periphery of their range, which is one of the reasons they are on the state-threatened list in Illinois. It has been hypothesized that populations on the periphery of a species range will have more population structure and lower genetic diversity than populations in the core of the range. Tissue samples for golden mice and white-footed mice were collected from 24 sites throughout southern Illinois and 24 sites throughout the golden mouse core range. I analyzed 13 and 10 microsatellite markers as well as 594 and 624 base pairs of the mitochondrial control region for golden mice and white-footed mice, respectively, to characterize and compare the genetic diversity and population structure of both species. Overall haplotype diversity (0.76) and nucleotide diversity (0.20%) was lower in golden mice compared to white footed mice (0.99 and 1.97%). Results of an AMOVA using the mitochondrial control region revealed more subdivision among the 3 populations of golden mice (Φst = 0.099, P < 0.001) than among the 3 populations of white-footed mice (Φst = 0.058, P < 0.001). Microsatellite loci showed a similar trend with overall FST values of 0.027 (P < 0.001) for golden mice and 0.004 (P = 0.137) for white-footed mice. I intended to compare golden mouse individuals from southern Illinois and the core of the range, but too few individuals were collected from the core. More samples need to be collected throughout the core of the range to better understand the population genetics of golden mice in the core of the range compared to the periphery.

Island isolation can cause changes in body size, cranial characteristics, and genetic variation in mammals. We use geometric morphometrics to test skull and mandible shape and size change across three species of endemic Cozumel Island rodents in order to test the “island rule” of larger size in isolated rodents. We also sequenced the D-Loop and cytochrome b region of the mitochondrial genome and tested for differences in genetic variation between island and mainland groups, as well as population structure and gene flow in order to assess the effect of island isolation on these three rodents. We found that the three species of rodents showed varying degrees of size and shape differences from island to mainland with some species varying considerably and others not at all. The genetic results were similar with some species exhibiting potential founder effects, while others showed little differentiation between the island and mainland. We conclude that evolution on islands is highly conditional on the history, community composition, and biology of the colonizing species.