Houston Toad Recovery Benefits from New Techniques and Strong Partnerships
Blueprint
ASSESS
In 1970, the Houston Toad was the first amphibian to appear in the United States Endangered Species Act and was listed as endangered. They have been classified as Endangered on the IUCN Red List of Threatened Species since 1986. Continued habitat losses alongside severe droughts and wildfires threaten this species. Habitat fragmentation has also restricted the movement of individuals between areas that reduces overall genetic diversity and leads to the decline of isolated local populations. Range-wide surveys and research conducted by biologists from Texas State University sponsored by the Texas Parks and Wildlife Department showed a severe decline of the toad population from 2000 to 2007. These data strongly suggested that the Houston Toad would be extirpated from the largest known population in the near future unless steps were taken to protect its existing habitat and to increase the number of Houston Toads in the wild.
PLAN
The first Houston Toad Recovery Plan was drafted in 1984 with the two main goals of identifying all remaining populations and restoring populations in the historic range. After the dire results of surveys ending in 2007, local stakeholders moved forward with the active stewardship envisioned by this document. In 2007, the Houston Zoo stepped up their resources with the intent to establish a captive assurance colony, and a propagation, headstart, and toadlet release programme. However, wildfires resulting from a decade of severe drought devastated the release zones and reversed the positive gains from the zoo’s headstarting programme. The toad was on the brink of extinction.
At the annual Houston Toad recovery team meeting in 2013, the representatives decided to implement a new strategy whereby the zoo would devote its efforts to maximizing the number of eggs produced for release, rather than the more time-intensive production of toadlets. Egg strands would be placed in the wild at the origin ponds to attempt to restore the toad population to pre-decline levels.
ACT
Since 2013, the assurance colony has expanded to include the Fort Worth Zoo and Dallas Zoos. From 2014 to 2021, the total number of eggs released increased from roughly 150,000 to 1,000,000 annually as husbandry methodology was refined. In 2019, the USFWS San Marcos Aquatic Resources Centre joined the reproductive efforts, producing and releasing 10,000 eggs during their first breeding season in 2020. Combined, the assurance colony consists of approximately 1,000 adult Houston Toads. At the release sites, mesh exclosures around each egg strand protect eggs and tadpoles from predators and mimic the natural pattern of explosive breeding. To date, over 6.3 million eggs, juveniles, and tadpoles have been released.
Initial education outreach efforts focussed on incentivizing private landowners to maintain toad habitat as part of the 2008 Bastrop County Habitat Conservation Plan. Building on this action, Texas Parks and Wildlife created a Houston Toad Safe Harbour Agreement program that certified its first landowner in late 2017.
Results
New reintroduction techniques have changed the recovery paradigm and the program has seen dramatically increased egg production. Research among partner institutions, including several veterinary colleges, developed assisted reproductive techniques such as hormone treatments, biobanking, and in vitro fertilization to optimize genetic diversity and successful egg development. Before the eggs hatched, egg strands were transported to release sites, which has shown higher survivability than transporting tadpoles or toadlets. This method is also more cost- and time-effective than raising toads to juvenile stages.
The wild population is on the road to recovery. Adult toad detections have increased and large multi-male choruses are being heard for the first time since 2006. In 2021, over 450 males were heard calling at the release sites and 42 wild egg strands were found. In addition, juvenile toads are expanding their range and have been found as much as 2.5 miles from the release sites.
A revision to the Houston Toad Recovery Plan was officially posted by the United States Fish and Wildlife Service in May 2021 for public comment.
Visual & Audio References
©Houston Zoo
Collaborations
Major
Partners
Houston Zoo
Fort Worth Zoo
Dallas Zoo
Texas State University
United States Fish and Wildlife Service
Texas Parks and Wildlife Department
Additional
Contributors
Capital Area Council of Boy Scouts of America; Private landowners in the area; Lost Pines Habitat Conservation Plan participants; University of Georgia; Mississippi State University; Texas A&M University
Additional Resources
Content Updated as of 8/27/2020