Imperiled Amphibians and Reptiles - Threatened And Endangered Species Of Amphibians

As of March 2006 there were twenty-one U.S. amphibian species listed as threatened or endangered under the Endangered Species Act (ESA). (See Table 7.1.) The list contains eleven species of salamander and ten species of frogs and toads (including the golden coqui and the guajón, which are Puerto Rican frogs). Most of the listed species are endangered and nearly all have recovery plans in place. Geographically the list is dominated by western states, where thirteen of the imperiled species are found, primarily in California or Texas.

The U.S. Fish and Wildlife Service (FWS) reports that $8.4 million was spent under the ESA during fiscal year 2004 on amphibian species. The ten species with the highest expenditures are shown in Table 7.2.

Imperiled Salamanders in the United States

Of the eleven salamanders listed in Table 7.1, only four species are found outside the western states. The primary ranges of all species are as follows:

• Texas—Barton Springs, San Marcos, and Texas blind salamanders (See Figure 7.1.)
• California—California tiger, Desert slender, and Santa Cruz long-toed salamanders
• Arizona—Sonora tiger salamander
• Alabama—Red Hills salamander
• Virginia—Shenandoah salamander
• West Virginia—Cheat Mountain salamander

The Flatwoods salamander is found in the coastal plain areas of Florida, Georgia, and South Carolina.

Some endangered salamanders, including many cave species, have highly restricted habitats. The Barton Springs salamander is only found in and around spring-fed pools TABLE 7.2 The ten listed amphibian entities with the highest expenditures under the Endangered Species Act, fiscal year 2004 Adapted from "Table 1. Reported FY 2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)in Zilker Park in Austin, Texas. The species was first listed as endangered in 1997. Urban development has contributed to degradation of the local groundwater that feeds the spring. In addition, flows from the spring have decreased due to increasing human use of groundwater from the aquifer. Finally, the Barton Springs salamander has been the subject of contentious debate between conservationists and those who wish to expand development around the area of the pools.

TABLE 7.2
The ten listed amphibian entities with the highest expenditures under the Endangered Species Act, fiscal year 2004
Ranking	Common name	Listing*	Expenditure
*E = endangered, T = threatened.
SOURCE: Adapted from "Table 1. Reported FY 2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)
1	Barton Springs salamander	E	$1,884,500
2	California red-legged frog	T	$1,576,949
3	California tiger salamander	T	$1,261,128
4	Arroyo (= arroyo southwestern) toad	E	$1,062,719
5	Mississippi gopher frog (wherever found west of Mobile and Tombigbee Rivers in AL, MS, and LA)	E	$ 589,700
6	Chiricahua leopard frog	T	$ 519,850
7	Flatwoods salamander	T	$ 461,610
8	Wyoming toad	E	$ 241,267
9	Mountain yellow-legged frog	E	$ 220,977
10	Houston toad	E	$ 187,040

In 2005 the U.S. Fish and Wildlife Service published a final recovery plan for the Barton Springs salamander and began a five-year review of its listing status.

Imperiled Frogs and Toads in the United States

The ten species of imperiled frogs and toads found in the United States are geographically diverse. Their habitats are located in the West, Southeast, and Puerto Rico. California is home to the California red-legged frog, the arroyo toad, and the mountain yellow-legged frog (which also lives in Nevada). Arizona and New Mexico provide habitat for the Chiricahua leopard frog. The Houston toad and Wyoming toad are found in Texas and Wyoming, respectively.

The Mississippi gopher frog is native to the south-eastern United States. Three imperiled amphibians are found in Puerto Rico—the golden coqui, guajón, and Puerto Rican crested toad.

CALIFORNIA RED-LEGGED FROG

The California red-legged frog is the largest native frog in the western United States. The frog was made famous by Mark FIGURE 7.1 The Texas blind salamander lives in underground caves and has only vestigial eyes, found below the skin. (U.S. Fish and Wildlife Service.)Twain's short story "The Celebrated Jumping Frog of Calaveras County," which was published in 1865. The species experienced a significant decline during the mid-twentieth century. According to Environmental Defense (http://www.environmentaldefense.org/documents/3733_Species_CA%20Frog.pdf), by 1960 California red-legged frogs had disappeared altogether from the state's Central Valley, probably due to the loss of most of their habitat. In 1996 the species was listed as threatened under the Endangered Species Act.

California red-legged frogs require riverside habitats covered by vegetation and close to deep-water pools. They are extremely sensitive to habitat disturbance and water pollution—tadpoles are particularly sensitive to varying oxygen levels and siltation (mud and other natural impurities) during metamorphosis. The frogs require three to four years to reach maturity and have a normal life span of eight to ten years.

Water reservoir construction and agricultural or residential development are the primary factors in the decline of this species. Biologists have shown that California red-legged frogs generally disappear from habitats within five years of a reservoir or water diversion project. The removal of vegetation associated with flood control, combined with the use of herbicides and restructuring of landscapes, further degrade remaining habitat. Finally, nonnative species have also attacked red-legged frog populations. These include alien fish predators as well as such competing species as bullfrogs.

A recovery plan for the California red-legged frog was published by the U.S. Fish and Wildlife Service in Recovery Plan for the California Red-legged Frog (Rana aurora draytonii) (2002, http://ecos.fws.gov/docs/recovery_plans/2002/020528.pdf). It calls for eliminating threats in current habitats, restoring damaged habitats, and reintroducing populations into the historic range of the species. The U.S. National Park Service helped to preserve one current frog habitat by altering water flow in the Piru Creek connection between Lake Piru and Pyramid Lake, located in the Los Angeles and Los Padres National Forests about sixty miles northwest of Los Angeles. This also benefited another threatened species, the arroyo southwestern toad.

The FWS has taken measures to preserve habitat in the foothills of the Sierra Nevada, in the central coastal mountains near San Francisco, along the Pacific coast near Los Angeles, and in the Tehachapi Mountains. Protected frog habitats have also been established in Marin and Sonoma counties.

GUAJÓN

The guajón is a cave-dwelling species endemic to Puerto Rico. It grows to be about three inches long and is primarily brown, but sometimes has yellow markings. The frog has very large protruding eyes that are rimmed in white, giving it an unusual appearance that some observers consider spooky. Because of its appearance, it has been nicknamed the "demon of Puerto Rico."

Its decline has resulted largely from introductions of alien species such as mongooses, rats, and cats, all of which eat unhatched guajón eggs. In addition the species has experienced habitat loss from garbage dumping in caves and deforestation for agriculture, roads, and dams. Deforestation also creates the potential for future environmental disasters such as flash floods, which drown adult frogs and destroy nests. Encroaching agriculture causes pollution from fertilizer runoff. Finally, the guajón, is frequently killed by superstitious local residents who believe the mere sight of the animal can bring disaster.

Foreign Amphibians in Danger

As of March 2006 there were nine foreign amphibian species listed as threatened or endangered under the Endangered Species Act. (See Table 7.3.) This includes seven frog and toad species and two salamander species.

The World Conservation Union (IUCN) reported in its 2004 Red List of Threatened Species that 1,770 amphibian species are threatened. This represents nearly one-third of all described amphibian species, the highest percentage for any group of animals.

GIANT SALAMANDERS

There are two species of giant salamanders, the Chinese giant salamander and the Japanese giant salamander. These are by far the largest living amphibian species, reaching lengths of up to five feet. Both are listed under the ESA and are highly endangered. Giant salamanders are aquatic, and have folded and wrinkled skin that allows them to absorb oxygen from their watery habitats. The Chinese giant salamander is found in fast mountain streams in western China. Despite TABLE 7.3 Foreign endangered and threatened amphibian species, March 2006 Adapted from "Foreign Listed Species Report as of 03/06/2006," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, March 6, 2006, http://ecos.fws.gov/tess_public/servlet/gov.doi.tess_public.servlets.ForeignListing?listings=0#A (accessed March 6, 2006)official protection, the species is endangered partly because of hunting for food or medicine. The Chinese giant salamander is also harmed by loss of habitat and aquatic pollution. Its close relative, the Japanese giant salamander, is also endangered and protected. This species inhabits cold, fast mountain streams in northern Kyushu Island and western Honshu in Japan. Japanese giant salamanders have been successfully bred in captivity.

TABLE 7.3
Foreign endangered and threatened amphibian species, March 2006
Status*	Species name
*E = endangered, T = threatened.
SOURCE: Adapted from "Foreign Listed Species Report as of 03/06/2006," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, March 6, 2006, http://ecos.fws.gov/tess_public/servlet/gov.doi.tess_public.servlets.ForeignListing?listings=0#A (accessed March 6, 2006)
T	Frog, Goliath (Conraua goliath)
E	Frog, Israel painted (Discoglossus nigriventer)
E	Frog, Panamanian golden (Atelopus varius zeteki)
E	Frog, Stephen Island (Leiopelma hamiltoni)
E	Salamander, Chinese giant (Andrias davidianus (= davidianus d.))
E	Salamander, Japanese giant (Andrias japonicus (= davidianus j.))
E	Toad, Cameroon (Bufo superciliaris)
E	Toad, Monte Verde golden (Bufo periglenes)
E	Toads, African viviparous (Nectophrynoides spp.)

GASTRIC-BROODING FROGS

There are two species of gastric-brooding frogs, both found in Australia. Gastric-brooding frogs are described as timid and are often found hiding under rocks in water. These species were only discovered in the 1970s, and, unfortunately, became extinct only a decade after their discovery. Gastric-brooding frogs get their name from their unusual reproductive strategy—females brood their young in their stomachs. During brooding, the mother does not eat and does not produce stomach acids. The gestation period lasts about eight weeks, and as many as thirty tadpoles may be in the brood. Juveniles eventually emerge as miniature froglets from the mother's mouth. Although it is not certain what led to the extinction of gastric-brooding frogs, one hypothesis is that populations were killed off by the chytrid fungus, which is also responsible for the decline of other frog species.

CAECILIANS

Very little is known about most species of caecilians. Some species are aquatic, but most of these elusive animals are underground burrowers that are difficult to locate and to study. Caecilians generally have very poor eyesight because of their underground habitat—some have no eyes at all or are nearly blind. Because so little is known about this group, it is difficult for environmentalists to assess the level of endangerment of these animals. The loss of tropical habitats worldwide suggests that many caecilians are likely imperiled.