Houston Toad (Anaxyrus houstonensis)
The Anaxyrus houstonensis, more commonly known as the Houston Toad, is just one of the species of interest considered endangered in the Brazos River basin.
The Houston Toad has been listed as Federally Endangered by the U.S. Fish and Wildlife Service since 1970. This species is impacted by habitat loss and fragmentation due to man-made factors, including wetland alteration, urbanization, historically poor cattle grazing practices, fire suppression, forest clear-cutting, and pollution. The species’ population has also had an impact due to being killed by cars during breeding migration.
Meanwhile, natural factors affecting the decline of the Houston Toad include drought and the proliferation of the red fire ant in Texas.
The Houston Toad is currently found in only nine of 13 historically populated counties in Texas: Austin, Bastrop, Burleson, Colorado, Lavaca, Lee, Leon, Milam, and Robertson.
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The Houston Toad primarily lives on land. However, during its tadpole stage, its life is aquatic. As adults though, these toads prefer forested areas consisting of pine and oak with deep sandy soils. Land-use change poses a severe threat because forest canopy is considered a major component of their habitat. The habitat of their largest population, found in Bastrop County, was severely impacted by the wildfires in September 2011.
The Houston Toad lays eggs in ponds or other pooled water sources that persist for 30 days or longer. The eggs are laid in strings in the water, fertilized by the males, then hatch into tadpoles. They grow and metamorphose into the adult stage, growing up to 3.5 inches long in seven weeks. These toadlets will remain near their hatching grounds for up to 13 weeks before migrating to the adult habitats.
Males make a 20-30-second-long shrill call to draw females to the edge of a water source for breeding. Males call from December to June, and most breeding takes place from January to May. Females travel in groups to respond to the male calls, and this is when they are most vulnerable to being killed by cars on the road. Because most of the breeding occurs over a short period of time, Houston Toads are considered explosive breeders.
Photo courtesy of Paul Crump
Ongoing Research/Conservation Efforts
The Houston Zoo maintains a 1,200-foot facility for research and captive breeding of egg strands to be released into the wild. Research continues on the life, history and habitat requirements to determine the best management practices to assist in aiding in recovery. Efforts to engage landowners in the recovery process include Habitat Conservation Plans and the Houston Toad Safe Harbor Agreement. Guidelines for Houston Toad habitat management are posted on the USFWS website here. Researchers at Texas State University are developing auditory detection methods of Houston Toads for use in observer-free presence/absence recognition from a sound recording, according to the Fish and Wildlife Management.
For more information on the Houston Toad, go to:
- MacLaren, A.R., McCracken, S.F., and Forstner, M.R.J. 2018. Development, validation, and application of automated detection tools for rare and endangered Anuran vocalizations. Journal of Fish and Wildlife Management 9(1):144-154.
Read more about the other endangered species of interest here.