Soil and vegetative associations of heteromyid rodents in Central and South Texas with comments on trapping techniques
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Heteromyid rodents occur in arid and semiarid lands in western North America, and are primarily granivorous. Heteromyids often form guilds because of a shared food source. These guilds often are found in habitats with sandy soils and vegetation that offers both open areas and dense shrub cover. In this study, I investigated soil and vegetative associations for heteromyid communities at the landscape and microhabitat scales in Central and South Texas. I utilized captures as a proxy for abundance. As a minor objective, I investigated the capture success of Dipodomys compactus, the most trap-shy heteromyid species included in this study, for one season of trapping. I placed traps in each representative treatment (a combination of both land cover and soil type) on consecutive nights for three seasons on two study sites (Guadalupe County and Jim Hogg County). I assessed microhabitat parameters, including herbaceous cover of grasses and forbs, bare ground, leaf litter, and densiometer readings within each treatment for all seasons on both sites. For the landscape level analyses, I conducted a chi-square goodness of fit test to determine if captures of Chaetodipus hispidus, Dipodomys compactus, and Perognathus merriami differed per treatment. I conducted a simple linear regression model for each microhabitat parameter per species per site. Overall capture success for the Guadalupe County study site for all heteromyids within all seasons for 2,816 trap nights was 2.06% and overall capture success for the Jim Hogg study site for all heteromyids within all seasons for 2,646 trap nights was 19.16%. For the landscape level analyses, capture was significantly different per treatment for each species on both study sites. For the microhabitat analyses on the Jim Hogg County study site, herbaceous cover and bare ground were significant predictors of occurrence of C. hispidus with a positive trend observed for herbaceous cover (β = 0.1259, R2 = 0.1516, P = 0.0276), and a negative trend observed for bare ground (β = -0.2156, R2 = 0.2477, P = 0.0038). No other microhabitat parameters were deemed significant for the other species on either site. For the paired trap study, extra-large (10.16x11.43x38.1 cm) folding H.B. Sherman traps had the highest probability of capture success for D. compactus. I determined that selection for or avoidance of certain land cover and soil types on the landscape scale could suggest potential habitat partitioning by heteromyid species. If a treatment was neither selected for nor avoided, then that indicates that a heteromyid species occurred as expected within that treatment, based on the overall availability of the particular land cover category and soil type. Microhabitat parameters were not important predictors of occurrence on the Guadalupe County study site, perhaps because of a homogeneous landscape, when compared with the Jim Hogg County study site, which offers more heterogeneity for heteromyid species.