The Houston toad is “toad-ally” Texan!
The Houston toad (Bufo [Anaxyrus] houstonensis) was first identified in the 1950s by amateur herpetologist, John Wottring, who was the first to suspect the unique nighttime call of a toad he had detected in south Houston belonged to an undescribed species. Based on its geographic distribution and skeletal morphology, the “Wottring toad” was officially named Bufo houstonensis in 1953 (Sanders, 1953). Unfortunately, only 20 years after its initial discovery, the population crashed. In 1973, the Houston toad became the first amphibian to be added to the endangered species list. Today it is estimated that only 300 remain in the wild.
The Houston toad is a habitat specialist, which means the species requires very specific environmental conditions in order to live in an area. Because the Houston toad aestivates almost year-round (aestivation is similar to hibernation, except an animal has a lowered metabolic state during hot and dry conditions rather than in cold conditions), it needs areas of deep sand so it can easily dig into the soil. The Houston toad also appears to prefer forested areas that also have Loblolly pine trees, Post Oak trees, or a mix of these hardwoods (Brown 1971). In the springtime, adult Houston toads seek out shallow ponds and temporary water sources for breeding (see photo below of perfect Houston toad springtime habitat!)
Where are they found?
Historically, twelve eastern-central Texas counties have supported Houston toads. These counties include: Austin, Bastrop, Burleson, Colorado, Fort Bend, Harris, Lavaca, Lee, Leon, Liberty, Milam, and Robertson counties. The toad population in many of these counties has significantly declined over the years. In fact, Houston toads are considered extinct in Harris, Fort Bend, and Liberty counties. Only a few individuals have been detected in Colorado, Lavaca, Austin, and Leon counties over the past several years. Toads that weathered the fire in Bastrop and a recently re-discovered population in Robertson may represent the last populations of Houston toads remaining in the state.
Breeding and life history
The Houston toad breeding season occurs between late January to mid-May. Breeding usually starts after the first heavy rains of the year and when nighttime temperatures do not fall below 50F. Houston toads use both permanent and ephemeral (temporary) bodies of water as sites for breeding. Houston toads are explosive breeders, meaning that the males and females come to the breeding pond all at once for short periods of time during the season.
Male Houston toads have a bright, blue throat sack that inflates as they call. The call, a distinct, high-pitched trill, generally lasts from about 20-30 seconds.Historically, hundreds of Houston toads could be found at once around a single pond. Today, even hearing one or two calling during the breeding season is rare. A recording of a male Houston toad calling at the Houston Zoo is below:
Female Houston toads can lay from 2,000 – 6,000 eggs at a time. The clutch of eggs is called a “strand,” which refers to the shape of the egg mass. Toad eggs look like “beads on a string” unlike a frog eggs, which are often laid in a round ball.
Houston toad eggs generally hatch within a 48-hour period and the tadpoles will live in the pond from ~2.5 to 7 weeks, depending on food resources and the water temperature. After the final stages of metamorphosis occur, tiny, emergent toads will leave the water in search of food. Juveniles will remain around the edge of the water source for ~ 2 weeks, and then start to disperse towards upland, forested habitat using drainages.
Rapid and widespread urbanization in the last half of the 20th century has led to the destruction and fragmentation of the Houston toad’s habitat, which is hypothesized to be the leading reason behind the toad’s decline. Conversion of land to agriculture, roads, housing developments, golf courses, and shopping centers have destroyed the wooded and wetland areas that the toad needs for survival. Additional threats also includes pollution, invasive species, consumption by domestic cats and dogs, and fire ants.
Natural disasters take their toll
Bastrop State Park, once considered the largest, contiguous, piece of state-protected Houston toad habitat supporting one of the last healthy breeding populations of Houston toads, suffered a catastrophic wildfire in the fall of 2011. The Bastrop-Complex wildfire destroyed ~40% of this critical area and it will be decades before the park will be restored.
Hope for the future?
Determined not to let the Houston toad go extinct, several organizations including U.S. Fish and Wildlife Service (USFWS), Texas Parks and Wildlife (TPWD), Texas State University (TSU), and the Houston Zoo, Inc. have joined together to protect this species. USFWS and TPWD help to manage protected lands and assist private landowners in the restoration and protection of critical toad habitat. Researchers at TSU are seeking to understand the fire’s effect on the wild Houston toad population, and to learn more about the toad’s basic biology so the best decisions can be made to protect it. The Houston Zoo’s captive assurance program serves as an ark and also as a breeding facility for the species. Between 2014-2015, the zoo released 400,000+ Houston toad eggs back into the wild.
Private landowners: We need your help!!
Much of the remaining habitat suitable for the Houston toad is found on private lands; therefore, the future of the species remains in the hands of individual Texans. Property owners in Bastrop county interested in making a positive impact on this species are encouraged to contact either USFWS or TPWD to see if funds are available for habitat restoration. Additional information about property management for the Houston toad can be found under the “Resources” tab. The success of the Houston toad conservation program will inevitably rely on individual Texans who want to support this native in need!
Citations and More Reading:
Allen CR, Epperson DM, Garmestani AS. 2004. Red imported fire ant impacts on wildlife: a decade of research. American Midland Naturalist 152:88–103.
Brown LE, Mesrobian A. 2005. Houston toads and Texas politics. Pages 150–160 in Lannoo M, editor. Amphibian declines: the conservation status of United States species. Ewing, New Jersey: University of California Press.
Jacobson, N.L. 1989. Breeding dynamics of the Houston Toad. Southwestern Naturalist 34:374–380.
Sanders, O. 1953. A new species of toad, with a discussion of morphology of the bufonid skull. Herpetologica 9:25-47.
Gaston, M., J. R. Dixon, and M. R. J. Forstner. 2001. Geographic distribution: Bufo houstonensis. Herpetological Review 32:187-188.
Dixon, J. R. 2000. Amphibians and reptiles of Texas, 2nd edition. Texas A & M University Press, College Station, Texas, USA.
Morrison, L.W. 2002. Long-term impacts of an arthropod community invasion by the imported fire ant, Solenopsis invicta . Ecology 83:2337–2345.
Freed, P.S, Neitman, K. 1988. Notes on predation on the endangered Houston toad, Bufo houstonensis. Texas Journal of Science 40:454–456.
U.S. Fish and Wildlife Service. 1984. Houston toad recovery plan. Albuquerque, New Mexico: U.S. Fish and Wildlife Service. Available: http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=D004
Vandewege, M.W., Swannack, T.M., Greuter, K.L., Brown, D.J., and Forstner, M.R.J. 2013. Breeding site fidelity and terrestrial movement of an endangered amphibian, the Houston toad (Bufo houstonensis). Herpetological Conservation and Biol. 8: 435-446