Joe Elbert's Zoo Tales

In this occasional Page Three feature, photographer Joe Elbert uses a camera to show you inside Washington's National Zoo. You can see his videos at http://washingtonpost.com/zootales.

They slither mysteriously from a dark hiding place in the rocks. Their scales catch the light. They open their large mouths to bare lethal-looking teeth. Crocodiles, snakes, lizards and turtles can frighten and fascinate.

Unlike many of the National Zoo's other animals, most of the 70 species of reptiles and amphibians found in the Reptile Discovery Center live indoors year-round. Birds and mammals -- including humans -- are endothermic, meaning their bodies can maintain a constant temperature despite changes in the temperature of their surroundings. Reptiles and amphibians, on the other hand, are ectothermic: They regulate their body temperature through changes in behavior, such as finding shade or basking in the sun.

Crocodiles have been around since the time of the dinosaurs. But now, because of hunting and the loss of wetland habitats, nearly all species of crocodile are in danger of extinction. The National Zoo participates in the Cuban Crocodile Species Survival Plan, a cooperative breeding and conservation program among North American zoos.

Reptiles and amphibians eat a wide variety of food. Snakes, for instance, are carnivores; frogs and salamanders are insectivores; and some turtles and lizards are herbivores. At the National Zoo, carnivorous reptiles are fed rats, mice or rabbits. Insectivores and omnivores are given crickets, cockroaches, fruit flies and earthworms. The herbivores are fed a "salad" mixture of vegetables and leafy greens.

Banded or blotched, colorful or dull, snakeskin can warn predators or serve as camouflage. It is the first defense against trauma and disease. Snakeskin also plays a part in movement. Belly scales catch on irregular ground surfaces and create enough traction for snakes to pull forward.

All snakes are carnivorous, but how they capture and kill their prey varies by species. Many of the world's 3,000 snake species kill their prey by constriction; others do so with venom. Still others, such as garter and water snakes, eat their prey alive.

Snake venom is a cocktail of toxic proteins, produced in special glands and delivered through enlarged teeth, or fangs. Some venom kills by clotting blood or destroying tissue. Other venom paralyzes the heart or stops an animal's breathing.