The world of reptiles and amphibians abounds with unique defense mechanisms. Defenses fall into four categories: Camouflage A toad mimics dead leaves. Morphology (shape and structure) An anole displays a bright dewlap. Behavior A hog-nosed snake plays dead. Chemical defenses An arrow-poison frog advertises its toxicity. Most animals use a combination of two or three, or even all four, of these defense strategies. Photos © Greg Neise

by Carol Flynn Camouflage Camouflage, a means of blending into the natural surroundings, is used by many if not most herps. Examples include a partially submerged crocodile that resembles a floating log; a common green iguana sitting in a tree; a dappled brown-and-purple gecko blending in with the changing rocky desert lighting. Perhaps the most unique examples of color camouflage are the lizards that can change color to various shades of greens, yellows, browns, and grays in response to environmental, physiological, and psychological conditions. The African chameleons are very adept at this, as are anoles, iguanoids from the southeastern United States. The changes in color result from the expansion and movement of pigment in the animal's skin cells and are caused by hormonal secretions, nervous system activity, or a combination of both. Besides color, shape can help with camouflage. There are several types of leaf-tailed geckos whose flattened bodies and leaf-shaped tails blend almost perfectly with the bark of the Madagascar forest trees. Morphology Shape brings us to a discussion of morphological defenses-specific body structures and shapes that provide the animal with an advantage. The structures are often used in tandem with certain behaviors for full advantage. For example, when disturbed, the leaf-tailed gecko exposes its shockingly bright red mouth and tongue to appear frightening and to startle the potential predator. A certain salamander that lives in the higher elevations of the Sierra Nevada tucks itself into a ball and rolls away downhill from predators. Some lizards-iguanas, geckos-possess a trait termed "autonomy" where the tail breaks off at certain vertebrae, leaving the attacker holding a wiggling stump while the important part of the lizard escapes. Making the body bigger, or at least making it appear to be bigger, is a frequently used defense. Tomato frogs will inflate their bodies until they are grossly distorted. Many lizards have a dewlap, which is a sac of skin at the throat, that they puff up. The desert-dwelling chuckwalla seeks shelter in rock crevices, inflating its body so that it cannot be pulled out by a hungry predator. Basilisks, in the iguana family, have a dewlap for display, but also have special fringes of skin on the long toes of their hind legs that allow them to run across the water's surface to escape predators that cannot move as fast by swimming. There are "flying" lizards. The genus Draco features several species that have well-developed flaps of skin (the tympanum) attached across the rib cage that allow the animal to glide through the rainforest. Actually, almost all herps have structures for defense-frogs have powerful back legs for jumping away; many herps are covered by tough scales or leathery skin; many have long tails to lash as weapons; some of the biggest and sharpest teeth belong to reptiles. Sheer size protects alligators, crocodiles, and Komodo dragons. Some lizards, snakes, and amphibians have horns and various growths to look intimidating. And turtles and tortoises carry their own bunkers around with them in the form of their shells. Behavior The same is true for behavioral defenses. Most herps are capable of making defensive noises (hissing, barking) and movements (lunging, biting). Escaping is a behavior common to all. The rattlesnake's only use for its rattle is as a defensive warning to scare away other creatures. Gaping bright mouths, displaying dewlaps, rolling away, and running on water are all behaviors. One unique example of defensive behavior is the hognose snake. If camouflage and aggressive displays don't work, the hognose snake will flop over on its back and play dead, hoping the predator will go away because it didn't kill the hognose itself. No matter how many times the snake is righted, it continues to flop over and act dead until it is no longer being bothered and can crawl away safely. Another interesting behavior is shown by some species of horned lizards that squirt blood from their orbital sinuses as an antipredator display. Chemical defenses While there are examples of chemical defenses in mammals, birds, fish, and invertebrates, when it comes to sheer deadliness, reptiles and amphibians win Nature's prize. Monitors, especially Komodo dragons, have saliva so chock full of deadly bacteria that even if an animal sustains only a small bite, it is likely to die from a bacterial superinfection. Some herps produce chemical toxins in their bodies. Two lizards in the New World, the Gila monster and the Mexican beaded lizard, have grooved teeth through which venom flows into the wound. All frogs and toads produce chemical toxins in their skins, but most of the poisons are not very potent. In Central and South America, however, there are species of tiny frogs that are the deadliest animals in the world. These are, of course, the poison dart or poison arrow frogs, so-called because for centuries natives have applied the toxins extracted from the frogs' skin to the tips of their hunting implements; the toxins remain effective for more than a year. Actually, only 55 of 135 recognized species of poison arrow frogs are deadly toxic. These frogs flaunt neon colors and vividly contrasting markings that warn predators to stay away (this is called "aposematic coloration"). Researchers at the National Institutes of Health have identified nearly 300 compounds secreted by these frogs. They're in a class of chemicals called "alkaloids," which also includes cocaine, morphine, and curares. These compounds work on the muscle and nervous systems. How the frogs actually produce the toxins in their bodies is unknown. Wild frogs gradually lose their toxicity when captured, and captive offspring are not toxic, leading researchers to believe that the animals' natural diet, which can't be replicated in captivity, plays a role in toxin production. Probably more than any other herp "scare," the thought of a venomous snake captures the human imagination. Unlike poison arrow frogs, venomous snakes do not lose their toxicity in captivity. Snake venoms are very complex mixtures of proteins, enzymes, minerals, and other substances. Traditionally categorized as hemotoxic, cardiotoxic, and/or neurotoxic, it now appears that most snake venoms consist of a mixture of all three types of toxins. A snake's biting apparatus consists of muscles, venom glands, ducts, and fangs. Fangs that are lost grow back. Snakes produce venom as a means to kill prey; they generally don't waste it as a defense mechanism. Venomous snakes have superb camouflage. If disturbed, usually snakes will try to escape, followed by threats and often bites in which venom is not released. In the U.S., about 20 of the 120 species of snakes are venomous. These are mainly the pit vipers, which include rattlesnakes and copperheads, and the coral snakes. The Mojave rattlesnake, which ranges from California to Mexico, is the deadliest North American pit viper. Its less potent cousins, the cottonmouths, copperheads, timber rattlers, and pygmy rattlesnakes, can be found in Illinois. The Gaboon viper of Africa, the largest of the true (Old World) vipers, holds the record for the longest fangs (two inches) and can deliver a large amount of extremely toxic venom very deeply. Cobras are also fascinating examples of snakes with morphological and behavioral defenses (hoods, posturing) as well as chemical defenses. The spitting, or black-necked, cobra can shoot venom from its hypodermic fangs up to six feet away. Some nonvenomous snakes have an interesting defense-color and marking patterns that mimic those of venomous snakes. One example are Africa's false coral snakes. In southern Europe, the viperine grass snake resembles the death adder, but is actually harmless. It is interesting to note that the venoms secreted by frogs and snakes are being studied for potential medicinal uses. Parental care One last defense adaptation needs to be mentioned-defending one's eggs and young. Reptiles and amphibians are generally thought to practice little parental care, but actually more examples of parenting behavior are being observed. Alligators and crocodiles have long been observed guarding their nests, helping their young hatch, transporting their young to water, and guarding them. Some snakes will use their accumulated body heat to incubate their eggs while guarding their nests. The male Darwin frog takes his tadpoles into his mouth, where the young complete their development in his vocal sac and hop out of his mouth as froglets. In some species of poison arrow frogs, the female guards her batch of eggs. When the tadpoles hatch, she gives them rides on her back one by one into the forest canopy to deposit them in little pools of water cupped in the leaves of certain plants. Every few days she returns to tend her scattered brood by laying unfertilized eggs in the little pools. The eggs are rich in nutrients and nourish the tadpole until it has grown large enough to find food on its own. Also, at this stage, the tadpoles have not yet developed toxins and are easy marks for predators such as crabs. The mother frog's scattering, guarding, and feeding of her young are a defense mechanism to ensure that at least some will survive. Just imagine-these examples are just a few of the fascinating defense mechanisms of reptiles and amphibians! Sources Animal Kingdom magazine Aquaticus magazine (published by the John G. Shedd Aquarium) Basic Book of Amphibians International Wildlife magazine Lizards in the Terrarium National Geographic magazine Natural History magazine Publications of the Chicago Herpetological Society Reptiles Wildlife Conservation magazine Zoobooks ZooLife magazine