|Listed||October 13, 1970|
|Description||Brown, dark-spotted toad with a distinctive call.|
|Habitat||Permanent or seasonal wetlands.|
|Reproduction||Egg masses of between 500 and|
|Threats||Loss of wetlands, urbanization.|
The Houston toad is brown (occasionally reddish) with dark brown or black spots. Its back is covered with single or multiple fused warts. Females reach up to 3.2 in (8 cm) in length; males average slightly smaller. The Houston toad is similar to the dwarf American toad (Bufo americanus charlesmithi ) but displays larger crests behind the eye sockets. The toad's mating call is described as similar to the tinkling of a small bell.
The Houston toad uses rain pools, flooded fields, and natural or man-made ponds for breeding, which occurs at sporadic intervals. Females reach sexual maturity at about two years of age. Breeding begins in spring when the air temperature rises above 57°F (14°C). Masses of between 500 and 6,000 eggs are laid between mid-February and late June. For tadpoles to develop, pools must persist for at least 60 days. After breeding, the toad seeks refuge in leaf litter, under logs, or in burrows.
Houston toads are found in seasonal or permanent ponds but are restricted to sandy loams that are suitable for burrowing. Surrounding vegetation varies from mixed deciduous forest to open coastal prairie grasslands. When spring rains are below normal, ponds dry up prematurely, killing tadpoles before they can metamorphose.
Historically, the Houston toad ranged across the central coastal region of Texas. Population sites have been documented from Austin, Bastrop, Burleson, Colorado, Fort Bend, Harris, and Liberty counties.
The Houston toad is currently thought to survive near Austin in Bastrop County wetlands north of the Colorado River, in Burleson County south of Bryan (around Lake Woodrow), and in Harris County south of Hobby Airport. Several small, experimental populations were recently established in Colorado County.
The largest population is found in Bastrop County on state lands within Bastrop and Buescher state parks and an adjacent nature preserve. This population has increased in recent years and may number as many as 1,500 individuals. Low numbers of toads (probably under 50) still exist in Burleson County but often fail to breed because of insufficient water. The Houston toad has not been seen in Harris County since 1976 but may survive there. The toad's sporadic breeding pattern and secretive nature make it difficult to find new populations or even to relocate previously identified ones.
Drought in the 1950s sharply curtailed Houston toad numbers, and the subsequent expansion of the Austin and Houston metropolitan areas has permanently reduced the toad's habitat. Wetlands have been replaced with residential suburbs and related developments. In the mid-1960s, large tracts of forest in Bastrop County along the Colorado River were cleared for residential development and for recreational sites. Road construction and the laying of sewage lines significantly altered drainage patterns in the region, drying out many seasonal ponds. The University of Texas Environmental Science Park (Buescher Division) was established in 1971, comprising 720 acres (291 hectares) adjacent to Buescher State Park in Bastrop County. Much of this area is now maintained as a nature preserve and is managed to enhance the habitat needs of the Houston toad. In 1979, 1,400 acres (570 hectares) were added to this preserve, including land previously designated as Critical Habitat for the toad.
Conservation and Recovery
In the early 1980s, biologists implemented a propagation program at the Houston Zoo and subsequently released captive-bred toads at the Bastrop County Preserve and at the Attwater Prairie Chicken National Wildlife Refuge in Colorado County. Egg masses were also moved from Bastrop County to ponds in Colorado County in an attempt to expand the toad's distribution.
Hillis, D. M., et al. 1984. "Reproductive Ecology and Hybridization of the Endangered Houston Toad." Journal of Herpetology 18: 56-72.
U.S. Fish and Wildlife Service. 1984. "Houston Toad Recovery Plan." U.S. Fish and Wildlife Service, Albuquerque.