Ecology of small mammals in the northern Chihuahuan Desert

Fort Bliss Military Base, located in Dona Aiia and Otero counties, New Mexico and El Paso County, Texas, is within the northern limits of the Chihuahuan Desert. A small mammal survey was conducted biannually from Spring 1997 to Fall 1998 on twelve vegetatively distinct habitats. Each habitat contained two duplicate grids constructed with census and assessments lines as a modification of O'Farrell's method (1977) and sampled using Sherman live-traps. Sampling generally occurred on two periods of three consecutive nights (one for census lines and one for assessment lines) for a total of 35,136 trap nights.

The data obtained from this project (number of captures, traps of capture, species, etc.) will be used to determine the status of rodent communities within the twelve habitats. Analyses utilizing the obtained data include: relative abundance of each species; species diversity per habitat and season; species composition per habitat (rodent community assemblages); rodent density per habitat (number of captured individuals/hectare); survivability of each species (proportion of individuals recaptured at a given time); and movement of each species (mean squared deviations from the centroid of activity).

During the study, 2,091 individuals (19 species) were captured. Diversity was highest in the sandy arroyo scrub habitat (Simpson's = 0.8859) and lowest in the coppice dune habitat (Simpson's = 0.4120). On the basis of species composition, all grassland habitats grouped together with a bootstrap support value of 58% and the acacia hillside and sand) an'oyo scrub habitats clustered with a value of 85%. Rodent density was highest in the swale habitat (39.16 individuals/ha) and lowest in the coppice dune habitat (9.95 individuals/ha). Heteromyids displayed the greatest longevity with six species surviving through the 18-month study period. Onychomys leucogaster had the highest average movement (4.59 mean squared deviations-MSD) and Sigmodon hispidus had the lowest average movement (2.43 MSD).

Results from this study provide baseline information concerning small mammals of the Chihuahuan Desert. In addition, these data provide military personnel with the necessary information to make decisions concerning the possible impact of military activity on small mammal communities.