Chapter 7
Imperiled Amphibians and Reptiles

Amphibians and reptiles are collectively known by biologists as herpetofauna. At present, there are over 5,000 described amphibian species and over 6,000 reptiles. New species in both these groups are being discovered every day, particularly in remote tropical regions that are only now being explored.

Most of the herpetofauna native to the United States are found in wetlands and riparian habitat (the banks and immediate areas around waterbodies, such as streams). Biologists say that amphibians and reptiles play a crucial role in these ecosystems by controlling insects, processing dead organic matter into a form that is edible by smaller creatures, and providing an important link in the food chain.

Many herpetofauna species are under threat, primarily due to declines and degradation in their habitats in recent decades.

AMPHIBIANS

Amphibians are vertebrate animals in the taxonomic class Amphibia. They represent the most ancient group of terrestrial vertebrates. The earliest amphibians are known from fossils and date from the early Devonian era, some 400 million years ago. The three groups of amphibians that have survived to the present day are salamanders, frogs (and toads), and caecilians.

Salamanders belong to the orders Caudata or Urodela. They have moist smooth skin, slender bodies, four short legs, and long tails. This category includes the amphibians commonly known as newts (land-dwelling salamanders) and sirens (salamanders with lungs in addition to gills). The majority of salamanders are fairly small in size, most often six inches long or less. The Chinese and Japanese giant salamanders, which grow to be as large as five feet in length, are the largest of all amphibians. There are approximately 500 salamander species worldwide, and about 150 species in the United States.

Frogs and toads are in the order Anura. These amphibians do not have tails as adults. They have small bodies with two short front legs and two long hind legs. Their feet are webbed, and they are good jumpers and hoppers. True frogs belong to the family Ranidae, while true toads belong to the family Bufonidae. There are many other families in this order whose members are commonly described as tree frogs, tailed frogs, spadefoot toads, horned toads, clawed frogs, Surinam toads, narrow-mouth frogs, or poison dart toads. Many of the species go through a swimming tadpole stage before metamorphosing into an adult. However, in some species, eggs hatch directly as juvenile froglets, which are miniature versions of the adults. Tadpoles are most often herbivorous, although there are some carnivorous tadpoles, including cannibalistic species. Adults are carnivorous and catch prey with their sticky tongues. There are at least 5,000 known frog and toad species, but only about 100 of these species are found in the United States.

Caecilians belong to the orders Gymnophiona or Apoda and share a common ancestor with the other amphibians, but look much different. They are often mistaken for worms or snakes. They have long slender bodies with no limbs and are found primarily in the tropics. There are approximately 160 species of Caecilians worldwide, but none are native to the United States.

"Amphi-" means "both," and amphibians get their name from the fact that many species occupy both aquatic and terrestrial habitats. In particular, a large number of amphibian species undergo a dramatic change called metamorphosis, in which individuals move from an aquatic larval stage to a terrestrial adult stage. In many frog species, for example, aquatic, swimming tadpoles metamorphose into terrestrial jumping frogs. In the process, they lose their muscular swimming tails and acquire forelimbs and hind limbs. Many amphibian species occupy terrestrial habitats through most of the year, but migrate to ponds to breed. However, there are also species that are either entirely aquatic or entirely terrestrial. Whatever their habitat, amphibians generally require some moisture to survive. This is because amphibians pass some oxygen and other chemicals in and out of their body directly through their living skin, using processes that require water to function.

A large number of amphibian species are in serious decline due 1to factors such as habitat loss, pollution, and climate change. Amphibians are particularly vulnerable to pollution because their skin readily absorbs water and other substances from the environment. For this reason, amphibians are frequently considered biological indicator species, meaning that their presence, condition, and numbers are monitored as a gauge of the overall well-being of their habitat.

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 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.

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 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 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.

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.

WORLDWIDE THREATS TO AMPHIBIANS

At the end of the twentieth century, biologists uncovered growing evidence of a global decline in amphibian populations. AmphibiaWeb (http://amphibiaweb.org), a conservation organization that monitors amphibian species worldwide, reported in 2006 that more than 160 species have become extinct in recent decades and at least 2,400 other species are declining in population. Amphibian declines have been documented worldwide, though the degree of decline varies across regions. Areas that have been hardest hit include Central America and Australia. In the United States, amphibian declines have been concentrated in California, the Rocky Mountains, the Southwest, and Puerto Rico. Particularly disturbing is the loss of numerous populations within protected and relatively pristine wildlife refuges.

Scientists are concerned because a large number of amphibian species—particularly frogs—has become extinct over a very short period of time. Other species are either declining or showing high levels of gross deformities, such as extra limbs.

The golden toad, named for its unusual and striking orange color, is a prime example of the global amphibian decline. Over a three-year period, golden toads disappeared inexplicably from their only known habitat in the Monteverde Cloud Forest Reserve in Costa Rica. In 1987 herpetologists observed an apparently healthy golden toad population estimated at 1,500 adults along with a new generation of tadpoles. The following year, in 1988, there were only eleven toads. In 1989 only a single surviving toad was found. It was the last individual on record for the species (Britton Windeler, "The Extinction of the Golden Toad [Bufo periglenes]—Symptom of a Worldwide Crisis," 2005, http://jrscience.wcp.muohio.edu/fieldcourses05/PapersCostaRicaArticles/TheExtinctionoftheGoldenT.html).

Habitat Destruction

Recent amphibian declines appear to result from a combination of causes. Loss of habitat is a major factor in the decline of numerous amphibian species, as it is for many endangered species. The destruction of tropical forests and wetlands—ecosystems that are rich with amphibians—has done particular damage to populations. In the United States, deforestation is blamed for the loss or decline of salamander species in the Pacific Northwest and Appalachian hardwood forests. In addition, some amphibians have lost appropriate aquatic breeding habitats, particularly small bodies of water such as ponds. These aquatic habitats are often developed or filled in by humans, because they appear to be less biologically valuable than larger aquatic habitats.

Finally, habitat fragmentation may be particularly harmful to amphibian species that migrate during the breeding season. These species require not only that both breeding and nonbreeding habitats remain undisturbed, but also that there be intact habitat along migration routes.

Pollution

Pollution is a second major factor in global amphibian declines. Because amphibians absorb water directly through skin and into their bodies, they are particularly vulnerable to water pollution from pesticides or fertilizer runoff.

Furthermore, air pollution by substances such as chlorofluorocarbons (CFCs) has reduced the amount of protective ozone in the Earth's atmosphere. This has resulted in increased levels of ultraviolet (UV) radiation striking the Earth's surface. UV radiation has wavelengths of 290 to 400 nanometers (nm). Wavelengths between 290 and 315 nm are called UV-B radiation and are the most dangerous, because they can damage deoxyribonucleic acid (DNA) by producing chemicals called cyclobutane pyrimidine dimers. (See Figure 7.2.) Exposure to UV-B radiation causes genetic mutations that can prevent normal development or kill eggs. Increased UV-B levels particularly affect the many frog species whose eggs lack shells and float on the exposed surfaces of ponds. Tadpoles and adults are also at risk, because of their thin delicate skins.

Invasive Species

Many amphibian species have also been affected by the introduction of nonnative species that either compete with them or prey on them. These include fish, crayfish, and other amphibians. The bullfrog, the cane toad (a very large frog species), and the African clawed frog (a species often used in biological research) are some of the invasive species believed to have affected amphibian populations. In addition, introduced trout are blamed for the extinction of several species of harlequin frogs in Costa Rica. It is hypothesized that trout consume tadpoles. Similarly, introduced salmon have affected native frog populations in California.

Disease

Amphibian diseases caused variously by bacteria, viruses, and fungi have devastated certain populations. Of particular importance in recent years is the chytrid fungus. This fungus attacks skin, and was first identified in 1998 in diseased amphibians. There are often no symptoms initially, but eventually affected individuals begin to shed skin and die. The precise cause of death is not known, though damage to the skin can interfere with respiration. The chytrid fungus is believed to be responsible for the demise of numerous species in Australia and Panama. In 2000 it was also documented in populations of the Chiricahua leopard frog in Arizona and the boreal toad in the Rocky Mountains. Officials at the Klondike Gold Rush National Historic Park in Skag-way, Alaska, reported in May 2006 that five of nine western toads evaluated there during the summer of 2005 had tested positive for the fungus. The disease was being aggressively investigated as a cause of a decline in toad population in southern Alaska during recent years (http://www.nps.gov/applications/digest/printheadline.cfm?type=Announcements&id1/44457).

Global Warming

Global warming is blamed for destroying unique habitats such as cloud forests (forests containing large amounts of water mists) in tropical regions, resulting in the loss of some amphibian species.

Quirin Schiermeier in "The Costs of Global Warming" (Nature, January 26, 2006) reported that global warming was also aggravating infectious diseases in the frog populations of Central and South America. The scientists found that warmer temperatures were associated with increased cloud cover over tropical mountain areas. These conditions were conducive to increased growth of the deadly chytrid fungus.

Human Collection

Many amphibian species are vigorously hunted for food, the pet trade, or as medical research specimens.

Amphibian Deformities

Amphibian deformities (see Figure 7.3) first hit the spotlight in 1995, when middle-school students discovered large numbers of deformed frogs in a pond in Minnesota. By 2000 scientists had documented malformed frogs in forty-four states and fifty-seven species. According to FrogWeb, an online service of the National Biological Information Infrastructure (http://frogweb. nbii.gov/index.html), rates of deformity as high as 60% have been documented in some local populations.

The high incidence of amphibian deformities in U.S. species appears to have multiple causes, as no single hypothesis accounts for all the different types of deformities seen. The most common deformities include missing hind limbs and toes, missing feet, misshapen feet, missing eyes, deformed front legs, and extra legs. Some of these malformations are believed to be related to a parasitic trematode, or flatworm, which in experiments causes the development of additional limbs. Aquatic trematodes have increased in number due to human activity, via a complicated chain of events. First, fertilizer runoff increases nutrient levels in ponds, allowing more algae to grow. An increase in algae results in a larger population of algae-eating snails, and snails host juvenile parasitic trematodes. Trematodes move on to frogs when they mature, forming cysts in the vicinity of developing frog legs. Chemical pollution and UV radiation may account for some of the other observed deformities.

The U.S. Geological Survey (USGS) set up a system whereby members of the public can report observations of deformed amphibians. The North American Reporting Center for Amphibian Malformations (NARCAM) is managed by the USGS National Biological Information Infrastructure and the University of Georgia's Savannah River Ecology Lab. Reports can be submitted online at the Web site http://frogweb.nbii.gov/narcam/.

REPTILES

Reptiles belong to the class Reptilia. Although they may appear similar, reptiles differ from amphibians in that their skin is cornified—that is, made of dead cells. All reptiles obtain oxygen from the air using lungs. Most reptiles lay shelled eggs, although some species, particularly lizards and snakes, give birth to live young. Approximately 8,000 species of reptiles have been described. These include turtles, snakes, lizards, and crocodilians. Birds are also technically reptiles (birds and crocodiles are actually close relatives), but have historically been treated separately.

There are four taxonomic orders of reptiles:

• Squamata—More than 7,500 species of lizards, anoles, iguanas, gila monsters, monitors, skinks, geckos, chameleons, snakes (including asps, boas, pythons, and vipers), racerunners, whiptails, and amphisbaenians (worm lizards)
• Testudines—Approximately 300 species of turtles, terrapins, and tortoises
• Crocodilia—Around twenty-four species, including alligators, caimans, crocodiles, and gavials (gharials)
• Rhynchocephalia—Two species of tuataras found only in New Zealand

There are approximately 2,400 species of snakes and 3,800 species of lizards. Together, they represent the largest group of reptiles. Most lizards are carnivorous, although there are some herbivorous species as well, including the iguanas. Snakes are elongate reptiles that have lost their limbs during the course of evolution. All species are carnivorous. Most snakes are adapted to eating relatively large prey items, and have highly mobile jaws that allow them to swallow large prey. In some species, the jaw can be unhinged to accommodate prey. Several groups of snakes are also characterized by a poisonous venom which they use to kill prey.

Many reptiles are in serious decline. Numerous species are endangered due to habitat loss or degradation. In addition, humans hunt reptile species for their skins, shells, or meat. Global climate change has affected some reptile species, particularly turtles, in ominous ways—this is because in some reptiles, ambient temperatures determine whether males or females are produced. Even a small increase in temperature can result in few or no males being born. Natural disasters, such as hurricanes, can also affect reptiles by killing the animals or damaging their habitats. In July 2005 an estimated 84,000 eggs laid by green and loggerhead sea turtles in Mexico's Yucatan peninsula were washed away during Hurricane Emily. According to a report by Eloise Quintanilla in Christian Science Monitor, only one nest survived the storm at Akumal beach, representing about 700 eggs, of which 80% were expected to hatch ("Hurricane Emily Takes Toll on Sea Turtles," July 22, 2005).

THREATENED AND ENDANGERED REPTILES

As of March 2006 there were thirty-seven U.S. reptiles listed as threatened or endangered under the ESA, as shown in Table 7.4. Most of the species (twenty-two) are threatened, while fourteen species are endangered. One species, the green sea turtle, has dual status, because it has two separate populations in the United States.

With the exception of the sea turtles, many of the other imperiled reptiles are geographically clustered as follows: California (six species), Puerto Rico (six species), and Florida (four species). Sea turtles spend most of their lives at sea, only coming onto land to nest and lay young. Because there are many potential nesting sites along the U.S. coasts, the sea turtles are listed in numerous states.

Here is a breakdown of imperiled U.S. reptiles by taxonomic order:

• Squamata—twenty-one species
• Testudines—fourteen species (six sea turtles, two tortoises [land-dwelling turtles], and six other turtle species)
• Crocodilia—two species

According to the U.S. Fish and Wildlife Service, nearly $41.6 million was spent under the Endangered Species Act during fiscal year 2004 on threatened and endangered reptiles. Sea turtle species accounted for the vast majority of the expenditures. The ten entities with the highest expenditures are shown in Table 7.5.

Imperiled Sea Turtles in the United States

Sea (or marine) turtles are excellent swimmers and spend nearly their entire lives in water. They feed on a wide array of food items, including mollusks, vegetation, and crustaceans. Some sea turtles are migratory, swimming thousands of miles between feeding and nesting areas. Individuals are exposed to a variety of both natural and human threats. As a result, only an estimated one in 10,000 sea turtles survives to adulthood.

There are seven species of sea turtles that exist worldwide. One species, the flatback turtle, occurs near Australia. The other six species spend part or all of their lives in U.S. territorial waters. The green sea turtle, hawksbill sea turtle, leatherback sea turtle, and loggerhead sea turtle also nest on U.S. lands. (See Figure 7.4.) The Kemp's ridley sea turtle and olive ridley sea turtle nest in other countries.

Imperiled sea turtles fall under the jurisdiction of the U.S. Fish and Wildlife Service while they are on U.S. land, and under the jurisdiction of the Fisheries Service while they are at sea.

Information on the distribution of each imperiled sea turtle species is provided below:

• Green sea turtles—found in U.S. waters around Hawaii, U.S. Virgin Islands, Puerto Rico, along the mainland coast from Texas to Massachusetts and from Southern California to Alaska. Key feeding grounds are in Florida coastal waters. Primary nesting sites are the Florida east coast, U.S. Virgin Islands, Puerto Rico, and a remote atoll in Hawaii.
• Hawksbill sea turtles—found in U.S. waters primarily around Hawaii, U.S. Virgin Islands, Puerto Rico, and along the Gulf and southeast Florida coasts. Key nesting sites are in Puerto Rico, the U.S. Virgin Islands, Hawaii, and the southeast coast and keys of Florida.
• Kemp's ridley sea turtles—found in U.S. waters along the Gulf Coast and New England coast. Primary nesting sites are in Mexico and Texas along the Gulf coast.
• Leatherback sea turtles—found in U.S. waters around Hawaii, U.S. Virgin Islands, Puerto Rico, and along the entire Atlantic Coast. Major nesting locations are in the U.S. Virgin Islands and Georgia.
• Loggerhead sea turtles—found in U.S. waters along the entire Atlantic and Pacific coasts. Primary nesting sites occur on the Gulf and east coast of Florida and in Georgia, South Carolina, and North Carolina.
• Olive ridley sea turtles—found occasionally in southwestern U.S. waters. Major nesting sites are in Mexico along the Pacific coast and in other tropical locations.

THREATS TO NESTING TURTLES

Sea turtles bury their eggs in nests on sandy beaches. The building of beachfront resorts and homes has destroyed a large proportion of nesting habitat. Artificial lighting associated with coastal development also poses a problem—lights discourage females from nesting and also cause hatchlings to become disoriented and wander inland instead of out to sea. Finally, beach nourishment—the human practice of rebuilding eroded beach soil—creates unusually compacted sand on which turtles are unable to nest.

SHRIMP-NET CASUALTIES

Shrimp trawling is recognized as one of the most deadly human activities for sea turtles in the Gulf of Mexico and the Caribbean. During the late 1970s the National Marine Fisheries Service began developing turtle excluder devices (TEDs), which allow sea turtles to escape from shrimp nets. By the early 1980s the agency had developed a TED (see Figure 7.5) estimated to exclude 97% of turtles from shrimp nets, while allowing no shrimp to escape. At that time the NMFS estimated that shrimp trawling killed more than 12,000 sea turtles annually. Despite the proven effectiveness of TEDs and their relatively low cost, use of the devices was bitterly opposed by most shrimpers and the southeastern states in which they were based. The regulatory and legal history of TED usage is described in a chronology compiled by the South Carolina Department of Natural Resources at http://www.dnr.sc.gov/seaturtle/teds.htm.

The chronology reports that during the early 1980s the NMFS asked for voluntary use of the devices by the shrimping industry, but this request was widely ignored. By 1986 less than 2% of the U.S. shrimp fleet was using TEDs. In 1987 federal regulations were published requiring TED usage in certain fisheries during specified seasons. The regulations were challenged in court by the states of North Carolina and Louisiana and by shrimp industry groups. Numerous lawsuits and administrative problems delayed federal enforcement of TED usage until July 20, 1989. Enforcement implementation set off a two-day revolt among Gulf Coast shrimpers. They reportedly "blockaded harbors, impeded navigation, and engaged in other forms of violence to protest against the TED regulations." On July 24, 1989, the federal government backed down, issuing a forty-five-day reprieve in TED enforcement while other options for turtle protection were considered. The next day a coalition of environmental groups sued the federal government for failing to enforce the TED regulations and eventually won their case. By 1991 year-round TED use was required for U.S. shrimpers.

On November 21, 1989, Public Law 101-162, Section 609 was enacted in the United States banning the import of shrimp from countries that use harvesting methods deemed harmful to sea turtles. The law was challenged by India, Malaysia, Pakistan, and Thailand as violating commerce agreements under the World Trade Organization (WTO). In 1998 a WTO commission found that the United States was not implementing the law consistently with all countries. In return the United States agreed to change its implementation procedures and offer technical assistance to those countries that requested it.

Each year by May 1 the U.S. Department of State issues a list of nations certified to import shrimp into the United States. Certification is based, in part, on the results of inspections conducted by the Department of State and the National Marine Fisheries Service. On April 28, 2006, the Department of State released a list of thirty-eight nations and one economy (Hong Kong) certified for shrimp imports under Section 609. Certification means that the shrimp were obtained using TEDs, from cold-water regions not populated by sea turtles, from aqua-culture (shrimp farming), or by specialized techniques that do not endanger sea turtles. Shrimp imports are allowed from non-certified countries on a shipment-by-shipment basis if the respective governments can show that the shrimp were harvested in a manner not harmful to sea turtles (http://georgetown.usembassy.gov/guyana/pr_shrimp_08may2006.html).

KEMP'S RIDLEY TURTLE

Kemp's ridley turtle is the smallest sea turtle, with individuals measuring about three feet in length and weighing less than 100 pounds. Kemp's ridley is also the most endangered of the sea turtle species. It has two major nesting sites—Rancho Nuevo, Mexico (the primary nesting location) and the Texas Gulf Coast.

The decline of the Kemp's ridley sea turtle is due primarily to human activities such as egg collecting, fishing for juveniles and adults, and killing of adults for meat or other products. In addition, the turtles have historically been subject to high levels of incidental take by shrimp trawlers. They are also affected by pollution from oil wells, and by floating debris in the Gulf of Mexico, which can choke or entangle turtles. Now under strict protection, the population appears to be in the earliest stages of recovery. In 2001 the Texas Parks and Wildlife Department (TPWD) enacted restrictions on shrimp trawling within Gulf waters near nesting sea turtle populations. In May 2006 the TPWD reported that more than two dozen Kemp's ridley nests had been found along the Texas coast, most at Padre Island National Seashore. Further, the TPWD indicated that nesting activity in Texas is increasing each year and characterized the outlook for the turtles as "mostly good" (http://www.tpwd.state.tx.us/newsmedia/releases/?req=20060508e).

The Desert Tortoise

The desert tortoise (see Figure 7.6) was listed in 1990 as threatened in most of its range in the Mojave and Sonoran Deserts in California, Arizona, Nevada, and Utah. Decline of this species has resulted from collection by humans, predation of young turtles by ravens, off-road vehicles, invasive plant species, and habitat destruction due to development for agriculture, mining, and livestock grazing. Livestock grazing is particularly harmful to tortoises because it results in competition for food, as well as the trampling of young tortoises, eggs, or tortoise burrows. Invasive plant species have caused declines in the native plants that serve as food for tortoises. Off-road vehicles destroy vegetation and sometimes hit tortoises.

Desert tortoise populations are constrained by the fact that females do not reproduce until they are fifteen to twenty years of age (individuals can live eighty to 100 years), and by small clutch sizes, with only three to fourteen eggs per clutch. Juvenile mortality is also extremely high, with only 2% to 3% surviving to adulthood. About half this mortality is due to predation by ravens, whose populations in the desert tortoise's habitat have increased with increasing urbanization of desert areas—human garbage provides food for ravens and power lines provide perches.

Protected habitat for the desert tortoise includes areas within Joshua Tree National Park and Lake Mead National Recreation Area in Nevada and Arizona. There is also a desert tortoise research natural area on a Bureau of Land Management habitat in California. A habitat conservation plan for the area around Las Vegas requires developers to pay fees for tortoise conservation.

Snakes and Lizards

SAN FRANCISCO GARTER SNAKE

The San Francisco garter snake is one of the most endangered reptiles in the United States. It was one of the first species to be listed under the Endangered Species Act. The decline of this species can be attributed primarily to habitat loss resulting from urbanization. Most of the snake's habitat was lost when the Skyline Ponds, located along Skyline Boulevard south of San Francisco County along the San Andreas Fault, were drained in 1966 for development. In addition, the building of the San Francisco International Airport and the Bay Area Rapid Transit regional commuter network destroyed additional snake habitat. Pollution and illegal collection have also contributed to the species' decline. Most San Francisco garter snakes today inhabit areas in San Mateo County, south of San Francisco. The species lives close to streams or ponds and feeds mainly on frogs, including Pacific tree frogs, small bullfrogs, and California red-legged frogs, which are also endangered.

LAKE ERIE WATERSNAKE

The Lake Erie watersnake inhabits portions of the Ohio mainland, as well as several small islands in Lake Erie. Its population has declined due primarily to habitat loss and human persecution, among other factors. The Lake Erie watersnake is now extinct on three islands that it previously inhabited. The species was listed as threatened in 1999, and a recovery plan was completed by the U.S. Fish and Wildlife Service in September 2003.

MONITO GECKO

The endangered Monito gecko is a small lizard less than two inches long. This species exists only on the thirty-eight-acre Monito Island off the Puerto Rican coast. Endangerment of the Monito gecko has resulted from human activity and habitat destruction. After World War II the U.S. military used Monito Island as a site for bombing exercises, causing large-scale habitat destruction. The military also introduced predatory rats, which eat gecko eggs. In 1982 the FWS observed only twenty-four Monito geckos on Monito Island. In 1985 Monito Island was designated critical habitat for the species. The Commonwealth of Puerto Rico is now managing the island for the gecko and as a refuge for seabirds; unauthorized human visitation is prohibited.

ORNED LIZARDS (HORNY TOADS)

Horned lizards are native to the deserts of North America. There are fourteen species of horned lizards. All species have flat, broad torsos and spiny scales and feed largely on ants. Although all horned lizards are reptiles, they are often referred to as horny toads because they bear some resemblance to toads in size and shape.

The Texas horned lizard was once abundant in the state of Texas and was designated the official state reptile in 1992. It has declined largely as a result of pesticide pollution, the spread of invasive fire ants across the state, and habitat loss. It is protected by state law in Texas.

In addition to habitat loss, California coastal horned lizards have been negatively affected by the proliferation of tiny black and dark brown Argentine ants, which have displaced the larger native ants on which the horned lizards depend for much of their food. Because the smaller, faster Argentine ants are more difficult to catch, coastal horned lizards from the Mexican border up to Los Angeles have experienced a sharp decline, according to a 2002 study by researchers at the University of California, San Diego (http://ucsdnews.ucsd.edu/newsrel/science/mclizard.htm).

CROCODILIANS

Crocodilians play a crucial role in their habitats. They control fish populations and also dig water holes, which are important to many species in times of drought. The disappearance of alligators and crocodiles has a profound effect on the biological communities these animals occupy. There are two imperiled crocodilian species in the United States—the American alligator and the American crocodile. They are very similar in appearance with only slight differences. The crocodile has a narrower, more pointed snout and an indentation in its upper jaw that allows a tooth to be seen when its mouth is closed.

The American alligator has a unique history under the Endangered Species Act. It was on the first list of endangered species published in 1967. During the 1970s and 1980s populations of the species in many states rebounded in abundance and could have been delisted. Instead they were reclassified as threatened. This measure was taken, in part, because federal officials acknowledged a certain amount of "public hostility" toward the creatures and feared that delisting would open the populations to excessive hunting. Also, it was feared that the American alligator was so similar in appearance to the highly endangered American crocodile that delisting the alligator might lead to accidental "taking" of the crocodile species. By 1987 the alligator was considered fully recovered in the United States. As of March 2006 the alligator is listed as threatened due to similarity of appearance to other crocodilians throughout its entire range.

The American crocodile is another success story of the Endangered Species Act. When the species was originally listed as endangered in 1975, less than 300 individuals existed. Over the next three decades the species thrived and expanded its nesting range to new locations on the east and west coasts of Florida. In March 2005 the U.S. Fish and Wildlife Service proposed downlisting the species in Florida to threatened. At that time the agency estimated there were 500 to 1,000 American crocodiles in the state and that the population was increasing. The FWS also announced plans to conduct a five-year status review of the American crocodile.

Threatened and Endangered Foreign Reptile Species

As of March 2006 there were eighty-three foreign reptile species listed under the ESA. (See Table 7.6.) The list is dominated by squamata (lizard and snake species) with thirty-six species, followed by the turtles (twenty-three species), crocodilians (twenty-two species), and tuataras (two species).

The Word Conservation Union's 2004 Red List of Threatened Species (2004, http://www.redlist.org/) reports that 304 reptile species are threatened. This represents nearly two-thirds of the 499 reptile species evaluated, but only 4% of all described species (8,163).

LIZARDS AND TURTLES

Monitor lizards are among the largest lizard species in existence. The Komodo dragon, native to only a few islands in Indonesia, is the world's largest lizard. It reaches lengths of as much as ten feet and weighs as much as 300 pounds. Despite the fact that the Komodo dragon is protected under Appendix I of the Convention on International Trade in Endangered Species (CITES) treaty, one of the greatest threats to this species is illegal trade. The price on delivery is approximately $30,000 for one Komodo dragon specimen.

Gray's monitor lizard, a species found in forested low mountain habitats of the Philippine Islands, is also prized in illegal trade. Gray's monitor is also protected under CITES Appendix I. Many turtles are highly imperiled, particularly in Asia, where they are hunted for both food and medicine.

CROCODILIANS

Illegal trade poses one of the greatest threats to crocodilians, despite CITES restrictions. Conservation efforts include enforcement of trade restrictions and habitat restoration. Captive breeding programs are also underway for several species.

The Chinese alligator is one of many species listed in CITES Appendix I. Unfortunately, this species is among those most prized by collectors, commanding a black market price of as much as $15,000. The false gavial, a crocodilian that grows to thirteen feet in length and is native to Indonesia, sells for an estimated $5,000 per specimen. Like the Chinese alligator, the false gavial is protected under CITES Appendix I.

TUATARAS

The two-foot long, lizard-like tuatara is sometimes called a living fossil, being the sole existing representative of a once diverse group, the Sphenodontia, which coexisted with dinosaurs. Tuataras are native to New Zealand and the Cook Strait. Like many other reptiles, tuataras are valued by collectors. They are protected by CITES under Appendix I.