Big Day for Endangered Houston Toads

09/28/2009

"Headstarted" Houston toads released back into the wild Copyright (c) 2009 Houston Zoo/Rachel Rommel

Last Monday was a big day for young Houston toads (Bufo houstonensis) – a federally endangered species with fewer than 300 remaining in the wild. Biologists released 140 of the toads into the same pond in Bastrop State Park where they were collected as eggs in February. They had been “head-started” at the Houston Zoo to help them avoid predation during the stages and ages in which they’re most vulnerable. The released toads had grown to a couple inches in length, so they will be much better able to ward off predators. When released from their containers, they hopped gingerly on the pine straw carpeting the forest - the place that will now be their wild habitat home.

“What we are doing is a proven strategy when survivorship of the juveniles is low and the wild populations have crashed,” says Texas State University biology professor Michael Forstner who has worked with the species for many years. The process is called head-starting or population supplementation, and after test runs starting in 2007, they were ready to try this out on a bigger scale. “We monitor the species in the wild, detect eggs after breeding, collect half of that egg strand and raise it in captivity away from predators.  Boom, there’s a big jump in juvenile survivorship, allowing us to then release those to enhance the wild populations, but at the very same pond that they were originally laid as eggs.”

Houston toads have been much more sensitive to habitat loss and urban and agricultural development than their relative, the Gulf Coast toad, which remains very abundant even around big cities. Houston toads, on the other hand, have steadily declined from their heyday when they ranged throughout eastern Texas’ post oak savannah and western piney woods habitat. They prefer sandy soils because their burrowing skills aren’t so great, but sandy soils have a patchy distribution in east-central Texas. The remaining suitable habitat is fragmented by roads, cities, and agriculture, making it almost impossible for the species to recover naturally.

The widespread use of chemicals such as DDT in the 1950s through 1970s may have contributed to their decline, and other chemicals remain on land and water today that may impact the frogs. Converting ephemeral wetlands to more permanent ponds increases their competition with other frogs and toads for breeding habitat. Red imported fire ants, introduced from South America in the 1940s, have also caused problems for the toads since they can eat the toadlets alive. Fire ants can also devastate the local arthropod community, eliminating many of the insects that Houston toads eat.

With so few remaining in the wild, scientists went into “triage” mode, trying desperately to save the species. They collected around 600 eggs from a pond in Bastrop State Park, and reared them in a quarantine facility in the Houston Zoo to increase their chances at survival. Under normal conditions in the wild, less than ten percent of eggs and tadpoles would escape predation by aquatic creatures, ranging from dragonfly larvae to other frogs. Once the tadpoles metamorphose into tiny toadlets they have a much better chance at survival but they’re still not home free.  The zoo kept the toads until they were several months old, so they had grown a bit larger and could better escape predation by raccoons, snakes and birds.

Beyond head-starting the toads, several people are working hard to restore habitat, including conservation biologists from Texas Parks & Wildlife Department, Environmental Defense Fund, and the Capitol Area Boy Scouts of America. “Simultaneously, the same group of collaborators is pushing hard on ecosystem restoration,” says Forstner. This involves enhanced connectivity, decreased fire suppression and reinstalling a natural regime of fire, [creating] ephemeral ponds, and minimizing invasive species.” In the first use of the U.S. Fish & Wildlife Service's Safe Harbor agreement for an amphibian in Texas, rancher Bob Long made habitat improvements to help the beleaguered toads (see video for more info), and more than twenty adult male toads have since been spotted there. Individuals like Long may ultimately be the toad’s only chance for full recovery, since 95% of Texas land is privately owned.

Comments

[kimosabe]

Simultaneously, the same group of collaborators is pushing hard on ecosystem restoration,” says Forstner. This involves enhanced connectivity, decreased fire suppression and reinstalling a natural regime of fire, [creating] ephemeral ponds, and minimizing invasive species.”
Does this mean what I think it means?
Are you telling me the fire was intentional by the environmentalist?