Documenting extinction in real time: Decline of the Houston toad on a primary recovery site

Abstract

The Houston toad Bufo (Anaxyrus) houstonensis is a federally endangered amphibian endemic to east central Texas and is primarily found in the Lost Pines ecoregion. In 2010, we became cautiously optimistic regarding the recovery of the species on the Griffith League Ranch, one of the toad’s primary recovery sites, after an unusually successful reproductive season. Subsequently, the extreme drought throughout Texas deepened, culminating in the fall 2011 high-severity wildfires throughout the Lost Pines ecoregion. After the drought and wildfires, we continued to intensively monitor Houston toads via anuran call surveys, drift fence arrays, and visual observations of reproduction. Our objective was to investigate the dynamics of the Houston toad population on the Griffith League Ranch during these dramatic impacts to its habitat and to discuss the potential for Houston toad recovery in the ecoregion. In summary, both a simulation model and our field monitoring data suggest the Houston toad population on the Griffith League Ranch is at critically low numbers and may be extirpated in the near future if human-mediated recovery strategies are not continued and refined. We do not discern any evidence to suggest the 2011 wildfires have had any direct detrimental impacts on subsequent Houston toad population dynamics. Still, high-resolution data will be needed in the future to quantify how the wildfires affected Houston toad viability over the medium and long term.