Fire Ants in Houston Toad Habitat: Annual Activity and Responses to Canopy Cover and Fire

The red imported fire ant Solenopsis invicta (RIFA) is an invasive species found throughout the southern and southeastern United States. Since its introduction, RIFA has been shown to negatively affect a wide range of native vertebrate and invertebrate species. The purposes of this study were to delineate the annual RIFA activity pattern, investigate the association between overstory canopy cover and RIFA captures, and evaluate the effects of low-intensity prescribed fire around pond edges on RIFA in the Lost Pines ecoregion of Texas, a region that provides habitat for most of the remaining endangered Houston toads Bufo houstonensis. We found that annual RIFA activity followed a quadratic curve, with above-average activity between May and October. We found an inverse relationship between mean percentage of canopy cover near pond edges and mean number of RIFA captured. We found that low-intensity prescribed burning had no significant influence on RIFA captures during our study period. However, strong spatial and temporal capture variability was apparent, and thus a strong impact would have been necessary to detect an effect. Although this study provides evidence that should decrease concerns that wildlife managers, conservation biologists, and landowners in the Lost Pines ecoregion may have about exacerbating RIFA abundance when using fire as an ecosystem management tool, we recommend additional work be conducted using a greater sample size, greater sampling effort, and longer study duration. We found that RIFA activity was highest during the time frame in which juvenile Houston toads emerge from ponds. Thus, RIFA control may be a useful Houston toad recovery tool where breeding ponds are not within dense canopy habitats.