The Houston toad is a seriously endangered species that was not discovered until the 1940s and was assigned to the endangered list in 1970. Scientists estimate that the total population of Houston toads ranges between 3,000 and 4,000. Loss of suitable habitat, drought, and the increase of roads and traffic may lead to the extinction of this toad unless conservation efforts are successful.
The greatest concentration of Houston toads is in the south, especially in Texas. Without a specific type of habitat, the Houston toad is unable to reproduce. They require still waters or those that gently flow, such as what is found in wetlands environments. The soil must be very sandy and loose enough to permit burrowing.
Burrowing is essential to the Houston toad as it must hibernate during cold winter months. It also burrows to escape summer’s heat, especially in drought conditions. The habitat must include a water source that persists for at least a month so that the toad eggs will develop into tadpoles and the tadpoles into land-ready toads.
Mating can occur any time during the first half of the year. Adult Houston toads call one another to mate by trilling back and forth as they move toward one another. Humid days and warm nights inspire the toads out of hibernation. They will not emerge unless mating conditions are right. This means that most mating occurs during February or March, depending upon the weather.
A number of predators contribute to the threat to the Houston toad. Carnivorous fish, snakes, and some birds will consume these toads as well as eggs and tadpoles. Egg-laying in temporary water holes that evaporate over time provides some protection from these predators. Flooded river banks, saturated fields, and other damp areas are the toad’s best bet.
Five days is required for the eggs to hatch into tadpoles. In warm water, a toadlet is able to leave water and survive in as little as 15 days. If the water is colder, it can take as long as three months to mature. This is another reason why temporary, shallow water holes offer toads the best breeding environment. Shallow water is usually warmer than deep or flowing water.
The Houston toad has evolved to blend into the surrounding habitat. Its skin is bumpy and colored in muted brown or gray tones. The toadlets are a mere half of an inch (1.26 cm) in length.