In Praise of Amphibians
Frogs have been around since the Jurassic era, when they hopped and croaked during the age of dinosaurs. They currently exist on every continent except Antarctica, having adapted to environments ranging from tropical rainforests to deserts to tundra. Some can endure extreme cold: Gray tree frogs can survive in temperatures as low as 20 degrees below zero Fahrenheit by producing an antifreeze agent, glycerol, in their bloodstream. If frozen in ice, they will simply hop away when the ice melts.1
But this evolutionary success story has taken an alarming turn, as frog populations have diminished dramatically around the globe.2
In 2004, the Global Amphibian Assessment, spearheaded by the International Union for Conservation of Nature (IUCN), found fully one-third of the planet’s roughly 6,000 kinds of amphibians at risk of extinction. Amphibians include frogs, toads, salamanders, newts, and caecilians; and frogs comprise two-thirds of all amphibian animals.
Large predators such as the Mexican gray wolf and the snow leopard are endangered, but frogs are just as crucial to the balance of their ecosystems, and have roles as both predators and prey. “Who could resist the red-eyed tree frog, poster child for the rain forest,” asks Jeffrey Masson. To raise awareness about the amphibian extinction crisis, the IUCN and other scientific and research institutions have named 2008 the “Year of the Frog.”
What causes the decline of amphibians? Frogs face a variety of threats: habitat loss, pollution, global warming, human appetite for their legs, and the lethal chytrid fungus (Batrachochytrium dendrobatidis).3 Humans are responsible for most or all of these threats, possibly even including the spread of the chytrid fungus, which is currently untreatable.4
The chytrid fungus was discovered a decade ago. African clawed frogs (apparently carriers of the fungus, but resistant to it) have been shipped around the world for laboratory testing as well as the pet food industry for decades. This may have been responsible for spreading the disease.5 The spread of amphibian chytrid may also be exacerbated by global warming.6
The Last Golden Toad
Amphibians such as frogs and toads (toads are really a kind of frog, explains Jeffrey Moussaieff Masson) 7 have revealed ingenious and myriad survival mechanisms, but the challenges they face now are both pervasive and abrupt. According to Tim Flannery’s book The Weather Makers, the golden toad of Costa Rica “was the first documented victim of global warming.” The golden toads were indigenous to the Monteverde Cloud Forest.
These toads, only discovered in 1966, lived on the upper slopes of a mountain in the cloud forest. Field researcher Marty Crump saw the extinction process first-hand. During the late 1980s, as climate change caused the area to become drier, the cloud moved higher. The wet breeding season became shorter, and the pools with tadpoles dried up quickly.
In 1987, the end was near, as only 27 tadpoles survived for a week before the pools dried up. The following year, Crump observed a solitary male during mating season. In May 1989, she again observed a single male, about 10 feet from where a male stood last season — likely the same one. That lonely toad was the last one seen.8
The Year of the Frog is alerting people to the threats facing amphibians, so people will increase their efforts to stem habitat destruction and pollution and to mitigate climate change. A commitment to vegan living can help reduce the tons of frogs caught each day and sent to the world’s restaurants; more fundamentally, cooking without meat, eggs, or dairy products is a highly effective way each of us can reduce greenhouse gas emissions. If each of us would go vegan, we’d spare the planet’s atmosphere a ton and a half of greenhouse gas each year.9
As scientists Andy Dobson of Princeton and Andrew R. Blaustein of Oregon State University wrote in the journal Nature, “The frogs are sending an alarm call to all concerned about the future of biodiversity and the need to protect the greatest of all open-access resources — the atmosphere.”10
Astonishing Variety of Survival Strategies
Frogs can be found in the searing heat of the Southwest desert as well as in the humid rain forests. Joseph Wood Krutch, in his book The Desert Year, marvels at the flora and fauna of the Sonoran desert that “manage to survive on a quantity of water which would soon bring death to those of any other climate.” Couch’s spadefoot toads hibernate underground for most of the year, only to emerge to mate during the brief and undependable rainy season. On a warm summer night after the second rain, Krutch heard the spadefoot toads make “the whole desert…suddenly vocal.”11 The toads reproduce in temporary rain pools, and the tadpoles must mature quickly to survive. They can metamorphose into froglets in as quickly as nine days.12
I encountered a Colorado River toad, also known as a Sonoran Desert toad, in Paradise Valley, Arizona. My rescued dog Ross proudly entered the house with an enormous toad hanging from both sides of his mouth. The toad was successfully dislodged, apparently unharmed, and released. But a few minutes later Ross’s breathing became labored, and he starting barking and running into doors. Lucky a vet was near. A Colorado River toad’s glands secrete a poison that can kill a full-grown dog.13 The large toads also secrete psychoactive substances, causing hallucinations.14 Some people, unfortunately, have found the hallucinatory effects of these substances enticing.
Thousands of miles away, in Central and South America, poison dart frogs have similarly evolved toxic skin secretions. The frogs are often spectacularly colored —bright blues, green and black, gold, or yellow and black — which sends a warning to potential predators: Don’t eat me. They vary in toxicity — the frogs may kill their victims or paralyze them or simply leave a bad taste in their mouths. The golden poison frog may be the most poisonous animal on the planet: A single frog contains enough toxins to kill some 20,000 mice or 10 humans. Some frogs mimic the vivid colors of dart poison frogs without having any toxins but still scaring off would-be predators.15
But once again, we humans have exploited these amphibians by using their toxins, in this case for hunting still other animals. An indigenous people of Colombia, the Emberá Chocó, rub their blowgun darts along the backs of these small frogs to make their darts poisonous.16
Frogs have survived for 200 million years. So even as they face a large number of threats, there is cause for some optimism. But as the Year of the Frog campaign reminds us, it is our duty to be vigilant and to do what we can to save all amphibian species from the oblivion of the golden toad.
- 1. Jeffrey Moussaieff Masson, Altruistic Armadillos, Zenlike Zebras (Ballantine Books, 2006), at 117.
- 2. An overview of frogs and their interactions within their biocommunities is provided online by the American Museum of Natural History. “Frogs: A Chorus of Colors”; available: http://www.amnh.org/exhibitions/frogs/ (last visited 28 Apr. 2008).
- 3. Jane E. Brody, “Increasingly in Decline, Frogs Face a Deadly Fungus”—The New York Times (29 Jun. 2004).
- 4. Recent research has suggested, however, that a bacterium can ward off amphibian chytrid. “Bacteria Show Promise in Fending off Global Amphibian Killer,” Physorg.com (23 May 2007), available: http://www.physorg.com/news99134333.html (last visited 28 Apr. 2008).
- 5. Amphibian Ark press release, “Amphibian Crisis, Amphibian Ark and the 2008 Year of the Frog Campaign.”
- 6. Andrew C. Revkin, “Frog Killer Is Linked to Global Warming”—The New York Times (12 Jan. 2006).
- 7. Altruistic Armadillos, Zenlike Zebras at 116.
- 8. Tim Flannery, The Weather Makers (Grove Press, 2005) at 116-17.
- 9. This was shown by geophysics professors Pamela Martin and Gidon Eshel. See University of Chicago press release, “ Study: Vegan Diets Healthier for Planet, People Than Meat Diets” (13 Apr. 2006).
- 10. “Frog Killer Is Linked to Global Warming” (see above).
- 11. Joseph Wood Krutch, The Desert Year ( University of Arizona Press).
- 12. The Arizona-Sonora Desert Museum, “Couch’s Spadefoot”; available: http://www.desertmuseum.org/books/nhsd_spadefoot.php (last visited 28 Apr. 2008).
- 13. Steven J. Phillips, Patricia Wentworth Comus, eds., A Natural History of the Sonoran Desert ( University of California Press, 2000), at 537.
- 14. The Arizona-Sonora Desert Museum, “Sonoran Desert Toad”; available: http://www.desertmuseum.org/books/nhsd_desert_toad.php; and
Wildlife Conservation Society, “Colorado River Toad Factsheet”; available: ( http://www.wcs.org/7490/factsheetarchive/factsheet-rivertoad (both last visited 28 Apr. 2008).
- 15. American Museum of Natural History. “Frogs: A Chorus of Colors” (see above).
- 16. The Encyclopedia of Earth, “ Biological Diversity in Tumbes-Chocó-Magdalena”; available: http://www.eoearth.org/article/Biological_diversity_in_Tumbes-Choc%C3%B3-Magdalena (last visited 28 Apr. 2008).