Behavioral differences among closely related species can result from adaptation via natural selection, and this is especially true of innately expressed behavior that shows evidence of complex design or function. A major goal of biologists is to understand how and why complex, adaptive behavior evolves. To this end, I investigated the evolution, ecology and genetics of innate burrowing differences in deer mice (genus Peromyscus). First, I show that several species of deer mice recapitulate their natural burrowing habits under laboratory conditions. When I compare these behaviors in a phylogenetic context, I find that burrowing is species-specific and the complex burrows of the oldfield mouse (P. polionotus) likely arose from simple behavior similar to that expressed by two closely related species. Second, I examine the influences of soil composition and genetics on the burrowing behavior of oldfield mice. Although burrow length variation is relatively constant in nature, burrow depth is negatively associated with the silt content of soils. To determine the genetic architecture of complex burrowing, I crossed the oldfield mouse and its sister species, the deer mouse (P. maniculatus), which builds a relatively simple burrow. My results suggest that complexity results from the integration of several component behaviors: the lengthening of entrance tunnels and the construction of an escape tunnel. Additionally, complex burrowing segregates as a dominant trait and I identify four quantitative trait loci that influence burrow variation--three affect tunnel length and a single locus influences escape tunnel construction. Last, I test whether Peromyscus burrow socially. Specifically, I measure burrows constructed by both pairs of mice and individuals across three Peromyscus species with different social systems. Only in the monogamous species (P. polionotus), which is also the only species that builds complex burrows, do pairs of mice coordinate their behavior to build longer burrows. This effect of pairing increases burrow length in same-sex pairs of unrelated individuals, but it is most pronounced in male-female pairs, suggesting that oldfield mice invest most heavily in burrows constructed for the purpose of reproduction.

No description available.

Thesis (M.S.)--University of Nevada, Reno, 1999. / Includes bibliographical references. Online version available on the World Wide Web.

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.

The golden mouse (Ochrotomys nuttalli), a state-threatened species in Illinois, is sympatric throughout most of its geographic range with the ubiquitous white-footed mouse (Peromyscus leucopus). The degree of interspecific competitive interaction between these species has been investigated by previous researchers, with often conflicting results. I live trapped and marked both species on two grids from 21 May 2008 through 8 May 2009. One grid was the control area; from the second grid I removed white-footed mice. Habitat on the grids was very similar for six measured habitat variables. My objectives were to document the extent of competition between the two species as indicated by a population density or behavioral response of golden mice to removal of white-footed mice on the experimental grid, and to determine if white-footed mouse presence or habitat variables affected the capture of golden mice. During 6,528 trap nights per grid, I captured a total of 22 individual O. nuttalli and 66 P. leucopus on the control grid, and 48 O. nuttalli and 202 P. leucopus on the removal grid. Compared to previous studies (Rose, 2008), the number of individual golden mice captured on my two sites (n = 70) was very large. Whereas I expected an increase in numbers and space use of golden mice upon removal of Peromyscus, the only statistically significant change was an apparent decrease in space use--there was no population density change. These results, which may indicate a lack of interspecific competition, are more likely the result of experimental design flaws, especially considering the following results. The likelihood of trapping a golden mouse at any given station on the control site was unaffected by any of the six habitat variables. White-footed mouse presence significantly decreased the likelihood of capturing golden mice on both sites. These results were the same for both elevated and ground traps. On the experimental site, golden mice changed from predominantly arboreal space use before Peromyscus removal to equal space use between arboreal and ground habitat after Peromyscusremoval. These results illustrate a spatially segregated habitat with competitively superior white-footed mice dominating the ground level microhabitat and golden mice staying predominantly in elevated microhabitat. My study, and others, demonstrate that golden mice in southern Illinois are likely habitat generalists (Morzillo et al., 2003), competitively inferior to Peromyscus(Feldhamer and Maycroft, 1992), and excluded from certain microhabitat; although it may be they actually prefer different microhabitats.

The available data examining the influence of rotational grazing on rodent responses are limited. This study investigated how rotational livestock grazing practices influence small mammal rodent abundances and species diversity. We looked for evidence of variation in the occurrence and/or numbers of certain rodent species among three plant community types (grassland, shrubland, grass-shrub mix), managed with or without grazing. We used Sherman live traps over a total of eight trapping sessions. We totaled 486 trapnights for each of the six plant community and grazing management combinations. The three plant community types were identified by visual cover. Out of the eight different species we captured, only Peromyscus maniculatus (North American deermouse) and Reithrodontomys megalotis (western harvest mouse) had sufficient captures to be analyzed for differences in abundance. Using all eight species to calculate the Shannon’s diversity index for each plot, we found evidence that rodent species diversity is less in grassland habitats than in shrubland habitats or grassland/shrubland mixed habitats (p

The purpose of this study is to compare two populations of Peromyscus maniculatus gambelii from the same location, separated by about 80 years in an attempt to determine the degree of dissimilarity between them.

Successful translocation of a listed species into an area of previous occupation requires knowledge of the habitat needs. The presence of the necessary food items is critical to the successful establishment of a new population; this information is unknown for Peromyscus polionotus niveiventris, the southeastern beach mouse, a threatened subspecies on the east coast of Florida. I used fecal and stable isotope analysis to determine the diet of this subspecies at Cape Canaveral Air Force Station, Brevard County, Florida, between the autumn of 2003 and the spring of 2005. Six trapping grids were established, three in the dune/swale and three in the coastal scrub communities. Fecal and hair samples were collected and analyzed. The diet varied in the amount of 13C consumed between habitats and in the amount of both 15N and 13C consumed among grids within a habitat. There was no significant interaction between habitat and sex in the amount of either 15N or 13C consumed, and sexes also did not differ significantly. Fecal analysis uncovered the dominance in the diet of C3 plants. My data refuted the current belief, that the southeastern beach mouse prefers beach grass seeds of C4 plants, which were consumed but not in the frequency or quantity expected. I also analyzed the diet of Peromyscus gossypinus, the cotton mouse, and Sigmodon hispidus, the hispid cotton rat, using the two techniques. Both species consumed a combination of plant and arthropod material. Their diets varied between dune/swale and coastal scrub habitats. All three species' diets were significantly different, with Peromyscus polionotus niveiventris and Peromyscus gossypinus being the most similar. Both consume a greater proportion of arthropod material compared to the hispid cotton rat. Interspecific competition between the southeastern beach mouse and the cotton mouse may occur in times of limited resources.

Despite the extraordinary diversity of behavior across the animal kingdom, the genes and molecules that contribute to such natural diversity are largely unknown. In this thesis, I leverage the dramatic divergence in behavior between two closely related species of deer mice (genus Peromyscus) to investigate the genetic, cellular, and neuroendocrine basis of behavior. In chapter 2, I show that the monogamous oldfield mouse (Peromyscus polionotus subgriseus) has evolved a novel cell type in the adrenal gland that expresses the enzyme AKR1C18, which converts progesterone into 20α-hydroxyprogesterone (20α-OHP). I then demonstrate that 20α-OHP is more abundant in oldfield mice than in the closely-related promiscuous prairie deer mouse (P. maniculatus bairdii) and that it increases monogamous-typical parental behaviors when administered to both monogamous fathers. Using quantitative trait locus mapping in a cross between these species, I discover interspecific genetic variation that drives expression of the glycoprotein tenascin N and ultimately contributes to gain of adrenal AKR1C18 expression in oldfield mice. In chapter 3, I investigate the genetic architecture underlying the striking difference in exploratory behavior between prairie deer mice and oldfield mice. Through congenic fine-mapping, I identify a 15-Mb locus that strongly contributes to species differences in exploratory behavior. I then investigate the potential contributions of one of the 18 genes in the locus, Olfm4, which harbors cis-regulatory variants that drives its expression in the oldfield hypothalamus. Taken together, my research advances our understanding of the genetic and molecular causes that drive rapid behavioral divergence between species.