Imperiled Amphibians and Reptiles - 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).