Herpetology is the scientific study of amphibians and reptiles. The term "herpetology" is derived from the Greek and refers to the study of creeping things. Birds and mammals, for the most part, have legs that lift their bodies above the surface of the ground. Amphibians (class Amphibia) and reptiles (class Reptilia), with the exception of crocodiles and lizards, generally have legs inadequate to elevate their bellies above the terrain, thus they creep.
Both Amphibia and Reptilia are within the phylum Chordata, which also includes several classes of fishes, reptiles, birds and mammals. Amphibia include the anurans, which are frogs and toads; the urodeles, which include salamanders and sirens; and the gymnophioma, which are peculiar worm-like legless caecilians. Larval amphibians (tadpoles) respire with gills whereas adults breathe with lungs. Amphibian skin is ordinarily scaleless. Reptilia includes lizards, snakes, turtles, and crocodiles. They have scaly skin and respire with lungs. Extinct reptiles are of great scientific and popular interest and include dinosaurs, pterosaurs, and ichthyosaurs.
Some scientists are both herpetologists and ecologists. They study habitat, food, population movements, reproductive strategies, life expectancy, causes of death, and a myriad of other ecological problems. Their studies have significance not only to survival of the animals that they study but also to humans. Amphibians and reptiles manage their metabolism of xenobiotic (foreign to the body) toxic substances in much the same way as humans do, by metabolic change in the liver and other organs that permits rapid excretion. It becomes a notable concern when amphibians and/or reptiles cannot survive in an altered environment. Amphibians in a number of countries have been reported to be found in diminishing numbers and many are anatomically abnormal. Because of their similarity in managing toxic substances, whatever is causing the population perturbations and anomalous anatomy in the lower creatures may be of equal concern to humans.
The studies of amphibians and reptiles relating to pathology and medicine is less well known than similar studies with higher organisms. Herpes viruses are now recognized as being microbial agents related to animal and human cancer. Burkitt's lymphoma and Kaposi's sarcoma are two human cancers with an established link with herpes viruses. The first cancer of any type known to be causally associated with a herpes virus was the Lucké renal adenocarcinoma of the leopard frog, Rana pipiens. Virologists working with the frog cancer can perform a multiplicity of experiments with the herpes virus and frog cancer. The frog experiments would be very difficult to perform on other animals, and would be precluded for ethical reasons from human experimentation.
The feasibility of vertebrate cloning was first demonstrated in the frog, R. pipiens, in Philadelphia in 1952, and later in the South African clawed toad, Xenopus laevis, in England in 1958. Prior to the frog experiments, it was generally thought that cloning was a "fan tastical" dream. Cloning has since been achieved with sheep, cows, and other mammals.
As economic resources, turtle meat and crocodile (raised on farms for that purpose) hides have a significant role in the Louisiana economy. Further, many amphibians and reptiles are collected for scientific study. Only rodents exceed in number frogs used for biomedical research.