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Will frogs survive? Inside the National Aquarium

By Nicole Angeli | March 25, 2009

If you were one of the spring 2009 general biology lab students at Hopkins to make it to the National Aquarium in Baltimore, you would have been lucky to catch a glimpse of one of the most famous frogs currently bred in captivity. In Hidden Life, the six resident golden Panamanian frogs (Atelopus zeteki) are the top of their food chain.

The public can look for the black on yellow dalmatian spots distinctive of the species, and with luck, pass the exhibit immediately after the morning feeding when the froggy individuals come out of hiding to stalk crickets.

Hidden Life is an offshoot of the Aquarium's Tropical Rainforest exhibit, a two-story glass pyramid of natural light and screeching birds. Its eight habitats line a darkened hallway just outside the main Rainforest exhibit and re-create the environments that are crucial for a frog to live its entire life history.

What the public doesn't see is behind the scenes, where three on-staff herpetologists tend a much larger colony of golden Panamanian frogs than are on exhibit.

Frogs will occasionally rotate between the colony room and the habitat cases in the front room for public view because of the species' publicity.

Breeding programs are the last hope of the Panamanian golden frog, which declined in numbers so quickly that in less than 10 years since the discovery of the frog, it is now presumed extinct from the wild.

It was last recorded in the wild on camera by the BBC for the popular David Attenborough wildlife videos in 2007. The world-wide conservation community responded to the declines early, with an action plan of amphibian collection and distribution.

Through the coordination of the World Association of Zoos and Aquariums and two IUCN sub-groups, the Conservation Breeding Specialist and Amphibian Specialist groups, a program called Amphibian Ark was formed to regulate the distribution of the species.

The golden Panamanian frog has been touted as a paragon of conservation biology because of the wild success attained in establishing breeding programs in almost a dozen zoos across North America through Amphibian Ark.

The huge numbers of collected frogs resulted in a resident colony split between two Baltimore institutions: the Maryland Zoo in Baltimore and several transfers that make up the current collection at the National Aquarium in Baltimore.

A reason that zoos are the chosen venue for captive breeding of the golden Panamanian frogs is that zoological parks have the resources to combine conservation with public awareness of the larger issue of amphibian decline. The golden Panamanian frog is a case study for how multiple environmental and pandemic stressors will eventually eliminate a species.

Golden Panamanian frogs face multiple stresses, but according to the International Union for Conservation of Nature and Natural Resources (IUCN), chytridiomycosis is likely their main threat.

The disease is caused by a pathogenic chytrid fungus (Batrachochytrium dendrobatidis). Chytrid, the short name used when referring to the disease, attacks the sensitive epithelial cells of amphibians and causes gross deformities and eventual systemic death.

Tadpoles may present with deformed mouthparts, while adults may present with no symptoms or what in humans would be "psychological" symptoms: sluggishness, inability to feed and apparent lack of concern with protective cover. These factors often kill the frogs indirectly: Any frog sitting in the open is a welcome dinner to monkeys in the Amazon or birds in the Costa Rican cloud forests.

In conjunction with recorded threats of deforestation and overexploitation to benefit the pet trade, it is likely that captive frogs will no longer be viable in native settings. These habitats may have completely disappeared, so conservationists would be introducing frogs into new ranges which may be infected or share space with overbearing predation. The pet trade is currently profitable for indigenous communities, especially in Asia.

The IUCN has issued a color-coded map of amphibian decline causation that exclusively points to the pet trade as the major cause of amphibian decline in Asia, a continent that was chytrid-free until 2008. While conservationists are talking about how breeding will help to sustain the species, the real challenge to longevity is controlling chytrid.

Without simple eradication measures, the fungus will wipe out entire populations of reintroduced rare amphibians, thus unlikely to benefit the species. Rather than propagate a species, a reintroduction will result in mass casualty events.

Ways to control the disease are currently being explored. One way to denature the DNA of the fungus is with sprays of low saline concentration. A researcher in California bathes the frogs in a series of warm baths to kill the fungus on its skin, with the hope that when released it will be stonger and more resistant to reinfection.

The United States Fish and Wildlife Service has found that in populations affected by chytrid, perhaps 10 percent to 40 percent of frogs will carry the disease. A more complex bath method used by captive poison dart frog breeders is a series of immersions in a low concentration anti-fungal solution, which was developed at the Smithsonian Institute Department of Pathology by Donald K. Nichols.

Frighteningly, 50 percent of amphibians in a population are found to perish within the first year of initial contact with chytrid, found by Karen Lips, a foremost herpetologist in the research of the chytrid disease. Exhibits and captive breeding can only postpone the most drastic consequence: the complete extinction of amphibians.

Conservation International estimated that 32 percent of amphibians were on a trajectory towards extinction in 2004; that number has increased in the past five years to 40 percent of all amphibians. Exhibits at zoos may be the last place we can see frogs within 50 years without an effective natural extermination of chytrid. It has already happened with the golden Panamanian frog.

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