The combined effect of habitat destruction, climate change, pollution, and chytrid cannot be addressed solely in the wild. Captive assurance populations have become the only hope for many species faced with imminent extinction and are an important component of an integrated conservation effort. AZA-accredited zoos and aquariums, with their demonstrated expertise in endangered species breeding programs, have been called upon to meet this conservation challenge. The Houston Zoo is involved in two primary amphibian projects:
In recent years, conservation biologists have drawn our attention to a worldwide decline in wild populations of frogs, toads, and salamanders - a phenomenon that has come to be called the Global Amphibian Crisis. While habitat loss is still considered the most serious threat to the majority of species, especially in the humid tropical forest regions of the world, a fungal disease known as chytrid has been identified as being exceptionally deadly to amphibians, while not seeming to affect other groups of vertebrates – fish, reptiles, birds and mammals.
One of the regions in which chytrid epidemics have erupted is Central America, first appearing in Costa Rica and heading south into Panama. Since it affects most amphibian species with which it comes in contact and also appears to persist in the environment, experts agree that the only hope of saving some of the more endangered, restricted-range species is to collect animals from remaining wild populations, establish captive breeding programs, and be prepared to conduct reintroduction projects in the future, should chytrid run its course or methods be found to eradicate the fungus without negatively impacting the environment.
In response to this need, the Houston Zoo has joined with a number of other AZA zoos and aquariums, academic institutions, and international conservation organizations to establish the El Valle Amphibian Conservation Center in central Panama. This new facility is still under construction, but already holds several hundred native Panamanian frogs, toads, and salamanders. The goal is to eventually maintain as many as 1,000 animals representing approximately 40 species. Captive breeding programs are being established for 17 high priority species Anotheca spinosa, Atelopus varius, A. zeteki, Centrolene ilex, Dendrobates vicentii, Eleutherodactylus bufoniformis, E. museosus, E. punctariolus, E. tabasarae, Gastrotheca cornuta, Hemiphractus fasciatus, Hyalinobatrachium vireovittatum, Hyla calypsa, H. colymba, H. fimbrimembra, H. palmeri, and Phyllomedusa lemur. Many of these have never bred in captivity before and very little is known about their life histories, so we stand to learn a great deal about tropical amphibian reproductive biology as a result of this project.
While one-half of the Center is devoted to quarantine, treatment and captive breeding efforts, the other half of the facility will be open to the public and exhibit two dozen or more native amphibian species. The exhibits will be presented to depict natural environments in Panama from the seashore to the mountain tops, and will also highlight the impacts of human activities on amphibian populations. The central exhibit will showcase the golden frog, a cultural icon and a national symbol for wildlife conservation in Panama.
The Houston toad (Bufo houstonensis) was the first amphibian granted protection under the U.S. Endangered Species Act. Critical habitat was designated in Bastrop and Burleson counties in 1978, in areas supporting the largest populations known at that time. Primary threats to this species’ survival are habitat modification and fragmentation, vehicular traffic, predation, and prolonged drought. To that list we may soon need to add chytridiomycosis, a fungal disease that is decimating Central American amphibian populations and has now been reported in wild populations of the Barton Creek salamander (Eurycea sosorum) in the Colorado River watershed.
Nearly 30 years ago, at the same time that the State of Texas acquired critical Houston toad habitat in Bastrop County adjacent to Buescher and Bastrop state parks, the Houston Zoo initiated a captive breeding program to help supplement remaining populations or establish new ones in protected areas. However, in spite of introducing 62 adults, 6,985 newly metamorphosed toads, and 401,384 eggs at 10 sites within the Attwater Prairie Chicken National Wildlife Refuge over a five-year period (1982-1986), it was not possible to establish a viable population at that site.
Historically, the Houston toad ranged across the state’s central coastal region, but disappeared from Harris and Fort Bend counties in the 1960s following an extended drought and Houston’s urban expansion. Although this species has been found in nine additional counties (Austin, Bastrop, Burleson, Colorado, Lavaca, Lee, Leon, Milam, and Robertson) as recently as the 1990s, several of these populations have not been detected since their discovery. In 2006, the species was heard calling only in Bastrop and Leon counties; in Leon only a single male was located. Bastrop County is the species’ final stronghold, but studies also suggest its population is in decline.
In the spring of 2007, the Houston Zoo received partial egg strands from the Bastrop County population collected by Texas State University. Houston Toads were brought into captivity for four reasons. The first is as a safe guard or “assurance population” against a catastrophic event that might cause the Houston Toad to go extinct in the wild. If this happens, Toads in captivity will serve as a source for individuals for reintroductions. The second reason is that in the 1984 USFWS Recovery Plan, a conservation stragegy recommended was the reintroduction of toads into appropriate habitat. It is hoped the captive toads will serve as a source for individuals who might be reintroduced into historical localities. The third reason is for head starting. Head starting is a process where high-mortality life stages (such as larval and juvenile in amphibians) are protected and released after they had reached a certain size or life stage. This technique has proved helpful in the recovery of other endangered species. The fourth and final reason is research. Toads can be very difficult to find in the wild, even during the breeding season. With toads in captivity we can study various aspects of their natural history and biology, such as activity temperatures, burrowing abilities, and substrate preferences that are very difficult to study in the wild. The eggs hatched and about 1,500 toads completed metamorphosis. We performed three releases in 2007 (May, July, and September) and another in April 2008. About 1,200 toads were released in total and we look forward to seeing the results of this work in the coming years. The remaining toads were kept at the zoo to start the formation of our assurance colony.
|
Search |
Houston Web Design | Houston Social Media |
Powered by Tendenci® |
Privacy
The Houston Zoo is a registered 501(c)(3) organization.
