Herpetology deals with what are called the cold-blooded tetrapods, that is, those land vertebrates which are ectothermic (deriving their body temperature from their environment) rather than endothermic (deriving their body heat from an independent, internal source). Studies in this field also relate to snakes (the cold-blooded reptiles lacking limbs). This distinction applies to most (though not quite all) living tetrapods, but may break down somewhat in regard to extinct reptilian creatures such as dinosaurs, about whose body metabolism we know frustratingly little and the sea turtles which seem to have some degree of endothermy owing to their large size. (See the article on Bob Bakker for more information about the warm-blooded dinosaur theory.)
The two taxonomic classes dealt with in herpetology, reptiles and amphibians, share “cold-bloodedness” but otherwise have surprisingly little else in common. Typically, amphibians have a permeable skin that assists in the exchange of gases and respiration, have a three-chambered heart, and are often bound to water for at least some part of their life, if only the laying of eggs or birth of young. Their skins have many glands and are often toxic. Reptiles, by contrast, have a dry watertight skin, usually protected by scales, that normally has few if any glands. The reptilian heart is a three-chambered one (four-chambered in the case of crocodilians), and living reptilians usually if not always lay eggs or give birth on land; even marine turtles which only come ashore for this purpose. Again, extinct creatures may have exhibited some differences. A number of reptile species, most notably some of the snake species, undergo live birth in which development is completely internal.
Herpetology offers benefits to humanity in the study of the role of amphibians and reptiles in global ecology, in particular in the role of amphibians as long-range ecological warning devices (their decline worldwide is the subject of much study) and the use of the toxins of some amphibians and venoms of some snakes in human medicine. Currently, some snake venom has been used to create anti-coagulants that work to treat stroke victims and heart attack cases.
People with an avid interest in herpetology and who keep different reptiles or amphibians, often refer to them selves as “herpers”.