The Houston toad, Anaxyrus houstonensis, is a unique amphibian species native to the pine and oak forests of southeastern Texas. Discovered in the late 1940s and formally named in 1953, it was among the first amphibians listed as federally endangered. This unassuming toad, once found across a broader range, now faces significant challenges to its survival, making its story a compelling example of ongoing conservation efforts. Its continued existence is closely tied to specific environmental conditions, highlighting the interconnectedness of species and their habitats.
Identifying the Houston Toad
The Houston toad has distinct physical characteristics. Adults typically measure between 2 to 3.5 inches in length, with females generally being larger than males. Their coloration varies, often appearing light brown, gray, or purplish-gray, sometimes with green patches, providing effective camouflage. A pale underside, frequently marked with small, dark spots, further aids in blending in with the environment.
A distinguishing feature is prominent L-shaped cranial crests between its eyes. While subtle, these crests help differentiate it from other toad species. Males are known for their unique mating call: a long, high-pitched trill lasting 20 to 30 seconds. This call, emitted from December through June, with peak activity between January and May, is a primary way researchers detect the toad’s presence in the wild.
Habitat and Causes of Decline
The Houston toad requires specific habitat, primarily pine and oak savannahs with loose, deep sandy soils for burrowing. They also depend on shallow, temporary water sources (ephemeral ponds) for breeding, as these pools must persist for 30 to 60 days for tadpole development. Historically, its range included the Houston metropolitan area, but rapid urbanization and agricultural conversion have severely reduced its habitat, eliminating populations from Harris County by 1975. The largest remaining population now resides predominantly in Bastrop County, Texas.
Its decline is largely attributed to habitat loss and fragmentation from human activities. Urban development and conversion of forested lands to agricultural pastures have diminished wooded and wetland areas. Prolonged drought also poses a threat, causing breeding ponds to dry prematurely and leading to the loss of eggs and tadpoles. Furthermore, the introduction and spread of non-native red imported fire ants (Solenopsis invicta) have negatively impacted toad populations by preying on young toadlets emerging from breeding ponds and potentially reducing their food sources.
Conservation and Recovery Efforts
Efforts are underway to prevent the Houston toad’s extinction and promote its recovery. Captive breeding programs, notably at the Houston Zoo, play a central role. The Houston Zoo maintains a specialized facility for breeding and head-starting toads, releasing millions of eggs and toadlets into suitable wild habitats. This approach helps overcome early life stage vulnerabilities by protecting them during their most fragile period.
Habitat restoration projects also focus on managing land to create and maintain suitable environments. This includes prescribed burns to restore native bunchgrass communities in pine and post oak savannahs, and selective tree thinning to optimize canopy cover. Public-private partnerships, such as the Houston Toad Safe Harbor Agreement, encourage non-federal landowners to voluntarily manage their properties to benefit the toad, contributing to broader recovery goals. These collaborative actions provide a framework for improving the toad’s status and the ecosystems it depends upon.