Frogs Forever?
Under threat in the wild, saving frogs will be the focus of an exciting new Aquarium exhibit and conservation effort.
by Rob Howatson
Mimic Poison Frog (Dendrobates imitator) Photo: Ron Holt, Courtesy Atlanta Botanical Garden, Amphibian Ark. |
For more than 360 million years, amphibians have not only survived but also flourished around the world. These creatures have been so amazingly well-adapted and resilient that they even survived the cataclysm that wiped out the dinosaurs all those eons ago – but that may be about to change.
In the past decade some 165 species of frogs have become extinct. In fact, one-third to one-half of the world’s 6,000 known amphibian species could vanish in our lifetime, resulting in the single largest mass extinction since the disappearance of the dinosaurs. It’s a global crisis that has sparked the Vancouver Aquarium to take action.
This spring, the Aquarium will open a fascinating new exhibit that will train the spotlight on the plight of the world’s frogs. The exhibit is part of a global initiative to save frogs launched by Amphibian Ark (a coalition of three leading conservation groups working to ensure the global survival of amphibians in nature), which has declared 2008 The Year of the Frog. The goal of the campaign is to raise awareness about the vulnerability of amphibians and to rescue at least 500 of the most threatened species. The frogs will be protected in zoos and aquariums until, hopefully, the threats to the wild populations can be controlled and the animals can be released back into nature. The Aquarium is participating on both fronts, with a public exhibit and its own behind-the-scenes frog conservation programs.
Multiple threats to frogs
Dennis Thoney, the Aquarium’s director of facility operations and animal management and the man who will be overseeing the Aquarium’s new frog exhibit, paints a dark picture of the current extinction crisis facing the world’s frogs: “Frog habitat is being lost all over the planet as forests are clear cut and wetlands drained.
Red-eyed Tree Frog (Agalychnis callidryas) Photo: Ron Holt, Courtesy Atlanta Botanical Garden, Amphibian Ark. |
“Climate change, disease, pollution and pesticides are also taking a nasty toll on amphibians, and in parts of the world where frogs are a popular menu item, they are often overharvested in the wild,” adds Thoney. “But the most pressing challenge for B.C. frogs has been the introduction of invasive species.”
The spread of invasive species is hard to control in such a highly connected world. Frogs may be intentionally introduced into a region, as the cane toads were in Australia in 1935, or may arrive as stowaways in cargo shipments. Sometimes it is not the immigrant species that are the biggest threat to indigenous frogs, but rather the diseases they carry.
The most ominous case in point is chytrid fungus. In the 1940s, clawed frogs (Xenopus spp.) were exported from their native South Africa in huge numbers to be used in human pregnancy testing (much as rabbits once were), as well as kept for pets and studied in laboratories around the world. No one at the time realized that these animals were asymptomatic carriers of a fungal disease that is fatal to many amphibians. When clawed frogs inevitably escaped and established themselves in new territories, chytrid spread, decimating other frog populations.
The fungus makes it difficult for the frogs to use their pores, quickly causing them to die of dehydration. Currently, it is sweeping through Japan, affecting the Japanese giant salamander, which, with a maximum length of 1.5 metres (5 feet), is the world’s second-largest salamander. Chytrid has also nearly wiped out the mountain chicken frog on the Caribbean island of Dominica, and has largely silenced the mountain yellow-legged frog’s rasping bark in Yosemite National Park.
“As for B.C., we know that the fungus is here,” says Vancouver Aquarium president Dr. John Nightingale. “Chytrid seems to spread more slowly in our colder climate, but low temperatures won’t stop it from affecting, for example, the already endangered leopard frog population in this province. Give the fungus another five years and it could spread and ravage the relatively healthy concentrations of leopard frogs elsewhere in Canada.”
B.C. is home to many species of frogs, including the coastal tailed frog (Ascaphus truei), boreal chorus frog (Pseudacris maculata) and Columbia spotted frog (Rana luteiventris). Many B.C. frog species are considered endangered to some degree. Most of them also live at the limit of their species’ northernmost range, which means life for a B.C. frog is tenuous at best.
“Introduce a couple of large, predatory frog varieties, such as the bullfrog and the green frog,” says Thoney, “and they are going to overrun the ponds, which is what has happened locally.”
Bullfrogs, which were introduced to British Columbia early in the 20th century by people who originally planned to farm them for food (the bullfrogs’ meaty legs were considered a potential culinary delicacy), are now found in the Lower Mainland, the southern half of Vancouver Island and Lasqueti Island.
“Our biologists and curators used to see red-legged frogs right in Stanley Park,” says Thoney. “Now when they do sampling, all they find is bullfrog tadpoles.”
Canaries in the coal mine
Photo: Gerry Marantelli, Amphibian Ark |
Panamanian Golden Frog (Atelopus zeteki)Chytrid, habitat loss, climate change and the many toxicants that humans dump on nature have created a “perfect storm” so deadly for frogs and so worrying for herpetologists (those who study reptiles and amphibians) that it should concern everyone says Dr. Jeffrey Bonner, president of the St. Louis Zoo and chairman of Amphibian Ark.
“Amphibians are excellent bio-indicators,” says Bonner. “Like a canary in a coal mine, they can give early warning signals regarding changes to an ecosystem.”
Bonner explains that frogs live in such close contact with the earth, and take in so much through their skin, that they are highly sensitive to environmental perturbations. These can be climatic in nature, but more importantly they can involve contaminants in the environment.
Changes in the environment can have a profound impact on amphibians – and by extension on humans as well. One case in point involves Missouri populations of hellbenders, which are the largest species of salamander native to North America. Bonner says these amphibians have stopped reproducing, with the males presenting poor sperm counts. Alarmingly, on average, rural Missouri men have lower sperm counts than other American males.
“This to me says that there could be a connection and that a little alert has been issued – one that says that if the amphibians in our streams are not faring well and the humans are not faring well, then maybe there is the same root cause,” cautions Bonner. “Maybe we should examine what we are dumping down our drains.”
Amphibians not only signal medical threats to humans, says Bonner, but they may also provide cures. He describes the unusual reproduction system of the gastric brooding frog – how the female swallows her fertilized eggs and the young mature inside the stomach. To give birth, the parent simply opens her mouth and out pop perfectly formed little frogs.
“What pharmaceutical company would not want to fill its Petri dish with the hormone or peptide that these tadpoles use to shut down mom’s digestive tract?” asks Bonner. “That substance could have held the cure for human obesity. I say ‘could have’ because the chytrid fungus obliterated the brooders in Australia in 1981.”
Fortunately, there are other surviving frogs that hold tantalizing possibilities in the fight against human diseases.
“We recently tested 14 different species and found that four of them produce a substance that inhibits the transmission of AIDS,” says Bonner. In light of such discoveries, the $50 million that Amphibian Ark requires for its rescue project does not seem like much to save 500 frog species. And the Vancouver Aquarium’s participation becomes all the more vital.
Aquarium conservation program
To support Amphibian Ark’s Year of the Frog, the Aquarium is opening a major new exhibit of amphibians this spring, consisting of more than 23 species from around the world.
Photo: Ron Holt, Courtesy Atlanta Botanical Garden, Amphibian Ark. |
“The exhibit will be in the Lower Pacific Canada Gallery and include information about the crisis extinction and how people can help stem the losses,” says Thoney.
“In the coming year, the Aquarium will also implement direct action frog conservation programs for the public,” he adds (the programs are currently in development).
The Aquarium will continue its ongoing efforts to bolster the declining population of the Oregon spotted frog, which is now found in only three small sites in Canada – all of them in the Fraser Valley.
“We do that through a head-start program,” explains Thoney. “Eggs are collected from the ponds and raised in captivity to an age where they have at least a fighting chance to elude predators such as bullfrogs. Then we release them back into the wild.”
The Aquarium will use its new rooftop greenhouse facility as the breeding centre for its Oregon spotted frog conservation program.
The Aquarium will also participate in researching the tailed frog, a three-centimetre-long (one-inch), voiceless creature with a long lifespan (15 to 20 years) and a stubby tail (which is a copulatory organ). These reclusive frogs can be found under rocks in mountain streams along B.C.’s mainland coast, where their survival status has been designated a “special concern,” and in the southernmost Kootenay region, where they are “endangered.”
As the first truly global campaign in the history of the zoo and aquarium community, Amphibian Ark will undoubtedly encounter some rough seas. It took decades for the “save the whales” campaign to receive broad public support. Frogs simply do not have that kind of time.
Nightingale, though, feels there is hope: “The rapid movement by municipalities in the Lower Mainland to stop the use of pesticides and herbicides is a positive step for amphibians. There will be more insects for them to eat and the frogs won’t be poisoned by them.”
And there is another ace up the sleeve of Amphibian Ark supporters. Call it the “Kermit Factor.”
“Amphibian exhibitions always strike a chord with the public,” says Thoney. “People love looking at frogs. The animals are so unusual, and come in so many different colours and shapes. They are almost like pieces of living art.”
Hopefully future generations will not find this art confined to museums.