Reptile and Amphibian Defense Systems
Frogs, salamanders, snakes, and other herps are often small and live on the ground or in the water. Because of these characteristics, they are vulnerable to being preyed on by all kinds of carnivorous animals. In order to avoid being eaten, herps use a variety of strategies and protective mechanisms.
As a first line of defense, most herps try to avoid being seen by their predators. Many are nocturnal and use the cover of darkness to avoid notice. During the day, most herps tend to remain hidden beneath dead leaves, rocks, and logs, or in underground burrows.
Herps also avoid confrontation through camouflage. Using a variety of grays, greens, and browns, these animals can blend remarkably well into the background of their natural environment. It is amazing how difficult it is to see a smooth greensnake that is moving through the grass!
Countershading is an interesting form of camouflage for herps that live in the water. Many turtles, frogs, and salamanders have light colors on their bellies and dark colors on their backs. This color pattern makes them less visible to aquatic predators that see them against a light sky. Birds and other predators hunting from above also have a hard time spotting them against the dark water. Even some of the larger predators, such as snapping turtles and alligators, have countershading, perhaps to be less visible when stalking their prey.
A lot of species use spots, stripes, and blotches to break up the outline of their bodies when viewed against leaves or soil. The distinctive "x" on the back of the spring peeper is an example of a mark that allows this frog to virtually disappear when on the ground or perched on a blade of grass. Unlike animals that use camouflage, the colors of these animals do not necessarily blend with the background. In fact, many times the markings are quite bright and even gaudy. The eyes of the predator, however, are tricked into thinking the shape they are seeing is not an animal.
Some herps do not avoid or hide from predators, but instead frighten them off by displaying warning signs. For example, toads and newts have glands in their skin that produce toxins. In order for this toxicity to protect an animal from being eaten, the predators must be reminded that they are about to eat something that will make them sick. A common method of alerting a predator is by being very brightly colored. This explains why the young newts, or efts, that we see walking around the forest are bright orange and yellow. Their color is a vivid advertisement of their toxicity. Other common examples of this aposematic, or warning, coloration are the brightly banded, venomous coralsnakes and the very decorative, poison dart frogs of Central America.
Interestingly, a herp truly may be poisonous or it may be just bluffing. Some harmless herps have adapted their appearance to mimic that of a more poisonous relative. In this way, they take advantage of markings that bring back unpleasant memories for predators. Such mimicry may protect the brightly colored, red-backed salamander from would-be predators, even though it is not toxic like the similarly colored eastern newt. Some snakes also mimic their poisonous relatives as a means of defense. The nonpoisonous scarlet kingsnake looks remarkably like the venomous coralsnake, both of which are found in the same region.
Finally, many herps scare off potential predators with threatening postures or behaviors. Snapping turtles, when encountered on land, can be very aggressive, snapping their jaws and lunging. Probably the most notorious warning among herps is the very d a nearby rattlesnake is enough to make most animals halt in their tracks and mistinctive and chilling sound of a rattlesnake's tail. The mere suggestion ofake a hasty retreat. Some snakes will rise up as if poised to strike an attacker. This act also has the advantage of making them appear larger and perhaps more threatening.
The hog-nosed snake, a common resident of the coastal plain, uses a complicated set of behaviors when it is attacked. It first elevates its head and spreads out the skin of its neck in an effort to look bigger and more threatening. If this doesn't scare off a predator, the hog-nosed snake begins to writhe upside down. It then regurgitates a foul smelling liquid and finally becomes rigid. It holds this position for several minutes, until the predator becomes disinterested and moves off.This background information can be used with the lesson plans Mimics Survive and Reptile and Amphibian Defense Strategies.
Excerpted from Hands-On Herpetology.
Provided by the National Science Teachers Association.
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