Diversity of Small Mammals and Herpetofauna
at Black Gap Wildlife Management Area, Brewster County, Texas
by Lisa L. Green and Louis A. Harveson
 Baseline surveys with standardized methods are required for analysis of populations between regions or over time at same location. This analysis can aid land managers to determine changes in community structure due to management practices or natural occurrences.
This study established standard methodologies for surveying and inventorying small mammals and herpetofauna populations at Black Gap Wildlife Management Area. Trapping was conducted March-October 1999 and July 2001 at 20 pre-established transects on five range sites.
In 4,800 trap nights, 287 small mammals representing 15 species were captured, and 655 captures of 28 herpetofauna species were trapped in 560 array nights. Total trap success for small mammals was 5.98% and was highest (10.42%) in March-April.
The most dominant species by percent captures were Perognathus flavus/merriami (28.57%), Dipodomys merriami (18.82%), Peromyscus eremicus (18.47%) and Chaetodipus nelsoni (14.6%). Overall trap success for herpetofauna was 116.96% and highest in July 2001 (161.25%).
Gastrophryne olivacea was the most dominant species and represented 41.37% of all captures. Cnemidophorus inornatus represented 16.18% and C. tigris represented 10.99%.
Gravelly Desert Grassland had greater species richness than the Gravelly Desert Shrub range site for herpetofauna, and species richness was the only community parameter (P = 0.0070, F = 3.11, df = 6) that varied significantly across trap sessions. Expected species richness was 23 for small mammals and 60 for herpetofauna.
This study found lower species richness than other studies in the region, which may be due to an underrepresentation of some of the more dominant ranges sites found at Black Gap WMA.
Cooperative funding for this project was provided by Texas Parks and Wildlife Department and Sul Ross State University.
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Sul Ross State University
