Year of the Frog
Why Year of the Frog?
Frogs are going extinct. So are toads, salamanders, newts, and the intriguingly unusual caecilians. In fact, the World Conservation Union (IUCN) estimates that at least one-third of known amphibian species are threatened with extinction. While the major culprit has historically been habitat loss and degradation, many of the declines and extinctions previously referred to as "enigmatic" are now being attributed to the rapidly dispersing infectious disease chytridiomycosis ("chytrid"). This fungus is causing population and species extinctions at an alarming rate. Can you imagine if we were about to lose one-third of the world's mammals?
Chytridiomycosis ("chytrid")
The disease known as chytridiomycosis, results when a chytridiomycete fungus called Batrachochytrium dendrobatidis ("chytrid") attacks keratin in the skin tissue of amphibians. Many researchers believe that this infectious fungus inhibits the frog’s ability to respire and osmoregulate, eventually killing the frog. Chytrid has been implicated in amphibian declines in the Americas, Caribbean, and Australia and its range continues to grow.
Chytrid is not the only cause of amphibian decline, but is a likely explanation for unexplained declines in high-altitude, protected regions and may hasten the collapse of populations weakened by other threats such as habitat destruction, climate change, and water and air pollution.
Our own little Project
Houston Toad Head-starting Program
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 Austin, Texas.
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, Fort Bend and Liberty 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 suggest its population is in decline.
In the spring of this year, the Houston Zoo received egg strands from the Bastrop County population. These will be hatched and the tadpoles raised to the juvenile stage in preparation for a return to nature. The Zoo has the capacity to produce up to 10,000 young toads for this head-starting program, but also plans to hold back a significant number of adult pairs for continued breeding purposes. Reintroduction efforts could begin as early as the fall of 2007, based on recommendations from Texas State University, Texas Parks and Wildlife Department, and the US Fish and Wildlife Service. The first attempts will be made in areas where the Houston toad has been absent for close to three decades.
Frogs are going extinct. So are toads, salamanders, newts, and the intriguingly unusual caecilians. In fact, the World Conservation Union (IUCN) estimates that at least one-third of known amphibian species are threatened with extinction. While the major culprit has historically been habitat loss and degradation, many of the declines and extinctions previously referred to as "enigmatic" are now being attributed to the rapidly dispersing infectious disease chytridiomycosis ("chytrid"). This fungus is causing population and species extinctions at an alarming rate. Can you imagine if we were about to lose one-third of the world's mammals?
Chytridiomycosis ("chytrid")
The disease known as chytridiomycosis, results when a chytridiomycete fungus called Batrachochytrium dendrobatidis ("chytrid") attacks keratin in the skin tissue of amphibians. Many researchers believe that this infectious fungus inhibits the frog’s ability to respire and osmoregulate, eventually killing the frog. Chytrid has been implicated in amphibian declines in the Americas, Caribbean, and Australia and its range continues to grow.
Chytrid is not the only cause of amphibian decline, but is a likely explanation for unexplained declines in high-altitude, protected regions and may hasten the collapse of populations weakened by other threats such as habitat destruction, climate change, and water and air pollution.
Our own little Project
Houston Toad Head-starting Program
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 Austin, Texas.
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, Fort Bend and Liberty 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 suggest its population is in decline.
In the spring of this year, the Houston Zoo received egg strands from the Bastrop County population. These will be hatched and the tadpoles raised to the juvenile stage in preparation for a return to nature. The Zoo has the capacity to produce up to 10,000 young toads for this head-starting program, but also plans to hold back a significant number of adult pairs for continued breeding purposes. Reintroduction efforts could begin as early as the fall of 2007, based on recommendations from Texas State University, Texas Parks and Wildlife Department, and the US Fish and Wildlife Service. The first attempts will be made in areas where the Houston toad has been absent for close to three decades.