Stepping Up Recovery for the Houston Toad
Najvar, Paige A., Endangered Species Bulletin
Hidden beneath the sandy soils of the ecologically unique "Lost Pines" region of central Texas resides one of the state's most imperiled species. The Houston toad (Bufo houstonensis) is a small, greenish-brown, speckled amphibian that can be distinguished from other toads by the high-pitched, trill-sounding call that males emit during breeding choruses each spring. It depends on the forests of loblolly pine (Pinus taeda) and various hardwood trees it inhabits for migrating, hibernating, and feeding. Ephemeral water sources serve as breeding sites.
In 1970, the Fish and Wildlife Service listed the Houston toad as an endangered species, in large part because of landscape fragmentation and destruction caused by urban development and agricultural conversion. Given its status as a rare and naturally restricted species, the Houston toad has long been known to be particularly vulnerable to anthropogenic changes in its habitat. After decades of habitat loss, intensive, range-wide survey efforts led by Texas State University in the past few years detected the species in only six counties.
One of the largest remaining Houston toad populations occurs within Bastrop State Park in Bastrop County, Texas. In the other five counties, breeding choruses have been few, and the number of males heard calling during any given chorusing event have ranged from only 5 to 20. In fact, only about 100 males were heard chorusing outside of Bastrop State Park during the 2008 breeding season. This indicates a substantial decline in the Houston toad's status since the last range-wide surveys conducted by Texas Parks and Wildlife Department in the late 1980s and early 1990s. Given ongoing habitat loss throughout its range, recent Texas drought conditions, and dwindling populations, we now fear this species could face extinction in the wild within the next several years unless intensive recovery efforts are undertaken.
We are working with Texas State University and the Houston Zoo to ward against extinction of the Houston toad through headstarting. This practice involves easing individuals of an imperiled species through the most vulnerable stages of their life-cycle (i.e., eggs, tadpoles, and juveniles), when many would die naturally or be eaten by predators.
Although it is a new concept for Houston toad recovery, headstarting has proven to be a successful management tool for other species, such as the Chiricahua leopard frog (Lithobates chiricahuensis) and some sea turtle species. The Houston toad has an enormous reproductive potential, with the greatest mortality in the early stages of its life cycle. We believe headstarting may be an effective way to increase the number of Houston toads that successfully develop into adult toads and reproduce. …