Surface Density and Nocturnal Activity in a West Texas Assemblage of Scorpions

Abstract

Scorpions are potentially ecologically important in arid habitats, but the ability to assess this is limited by the lack of basic population- and community-level data for scorpion assemblages. We describe several such measures gathered over 16 months from a site in western Texas. Eight species occurred at this site, of which 3 (Centruroides vittatus, Vaejovis waueri, and Diplocentrus) composed >98% of all individuals. Centruroides vittatus was numerically dominant in most months. Despite this, species diversity and evenness were high when compared to other scorpion assemblages. Nocturnal activity was strongly dominated by C. vittatus, which accounted for >90% of all individuals. Surface density and biomass of C. vittatus and V waueri varied significantly among months, being highest in the spring and fall, while density and biomass of Diplocentrus were more constant. We found little evidence that temperature influenced density patterns, but nocturnal activity and species diversity and evenness increased with increasing temperature. Both population-and community-level density and biomass were substantially lower (usually by 1 to 2 orders of magnitude) than in other arid-zone scorpion assemblages. This suggests that the ecological importance of scorpions varies, probably dependent upon habitat type and the ecology of the individual species in the community.