SCENE CHANGES: The Unmaking of Place

MARK TWAIN
The Celebrated Jumping Frog of Calaveras County

Smiley said all a frog wanted was education, and he could do 'most anything – and I believe him. Why, I've seen him set Dan'l Webster down here on this floor – Dan'l Webster was the name of the frog – and sing out, "Flies, Dan'l, flies!" and quicker'n you could wink he'd spring straight up and snake a fly off'n the counter there, and flop down on the floor ag'in as solid as a gob of mud, and fall to scratching the side of his head with his hind foot as indifferent as if he hadn't no idea he'd been doin' any more'n any frog might do. You never see a frog so modest and straightfor'ard as he was, for all he was so gifted.

— Mark Twain, "The Celebrated Jumping Frog of Calaveras County,"
from The Unabridged Mark Twain.
Philadelphia: Running Press, 1976

 

These images show a portion of Calaveras County, in the Sierra foothills east of Stockton, California. The left image was captured July 28, 1989; the right image is from July 19, 2009. The town that has grown so much in the intervening two decades is Copperopolis, with its golf resort in the lower center. Development in wetland areas requires much filling and consequent loss of wetland habitat. While this doesn't show up well in a visible light image, see below.

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In the Change Detection procedure known as Tasseled Cap, a formula is applied to the data to produce displays identified as Brightness, Greenness, and Wetness. Here they are shown in Red, Green, and Blue respectively. Brightness (Red) is greater in drier soils than wetter ones, so the image on the right, where wetlands have been filled in, is much redder. And wetlands typically combine water with vegetation (Blue and Green), producing the aquas and light greens that are prevalent in the earlier image but vanishing in the later one.

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Mark Twain's frog is understood to have been the California red-legged frog, the largest native frog west of the Continental Divide. This frog was common at that time to the wetland areas near Angels Camp, a fading gold mining camp in the Sierra foothills where the story takes place. Its habitat extended throughout California's Coast Range and Sierra foothills and around the northern end of the Central Valley, and on down into Baja California. Today it is largely limited to parts of the Coast Range. Although "Twain's frog" is a folk hero regularly evoked by boosters in Calaveras County, and although frog jumping contests are still a popular event at the annual county fair, the red-legged frog is extinct in the Central Valley and has vanished from 99% of its Sierra range.

The decline of the red-legged frog matches that of amphibians generally. Of the world's 6260 documented amphibian species, 2030 – nearly one-third – are threatened with extinction or have recently become extinct, and a significant proportion of the remaining species are likely to be so.¹ Entire communities of amphibians are facing ecological collapse.

Amphibians are especially vulnerable to environmental change. Since they live both on land and in water, they are exposed to habitat changes and contaminants in both places. Their skin is highly permeable and readily absorbs pollutants in the water. They are unprotected by hair or feathers. Their eggs, too, are vulnerable; they are not encased in hard shells, but in many cases are laid in soft masses that float on the surface of the water, attached to vegetation to keep them in place, until they hatch. A rampant fungal infection, chytridiomycosis, believed to have been spread by a South African frog widely used for pregnancy tests, is also devastating amphibian populations.²

In the case of the red-legged frog, a number of possible causes for its decline have been investigated, including habitat loss, predation by non-native species (especially the bullfrog), exposure to agricultural chemicals, and UV-B radiation. There is evidence that each of these has played a role. One study demonstrated a link between extinction sites and upwind farmland where pesticides were heavily used, especially in the Central Valley and the Sierra foothills; it also found a link with higher elevations where the increase in ultraviolet radiation is especially noticeable.³ Other studies have found similar results. But scientists broadly agree that the major culprit is habitat loss and fragmentation. Great swaths of wetland are being filled to enable the construction of homes, shopping malls, reservoirs, and roads, and the siting and approval of these developments have not always complied with the requirements of the Endangered Species Act (ESA).

The red-legged frog was formally listed as an endangered species under the ESA in 1996. Listing requires that critical habitat be defined and protected, and that a recovery plan be drawn up. It has been shown that species that have enjoyed critical habitat protection for two or more years are more than twice as likely to show increasing population numbers.⁴ Yet typically there is at best a considerable lag between the listing and the defining, protecting, and drawing up.

The process began well enough for the red-legged frog. In 2004 the U.S. Fish and Wildlife Service proposed to protect over 4 million acres of critical habitat for the animal, in keeping with scientific recommendations. But by 2006, due to a lawsuit by developers and pressure from Administration officials, this number had been revised to about 450,000 acres – one-tenth of what had been called for. And development projects went ahead accordingly.

In response to allegations of political corruption and another lawsuit, a new analysis resulted in the 2010 decision to protect about 1.6 million acres, 2764 of which are in Calaveras County, where previously there had been none.⁵

A separate lawsuit, which addressed approval by the Environmental Protection Agency of toxic pesticides in and near red-legged frog habitat, led to a 2013 settlement that will help protect the frogs from seven of the chemicals most toxic to amphibians.⁶ Given that the original list included 64 pesticides of concern, it remains to be seen if this will prove adequate.

In the meantime, a few years earlier, two children discovered a small population of red-legged frogs near a pond on their family's Calaveras County ranch, the first sighting in the county since 1969.⁷ The family has been working with biologists to find the best way to combine cattle ranching with protecting the frogs and their habitat. With this combination of enthusiasm and expertise, there may be cautious hope for this celebrated critter.