Why are some animals, for example frogs, snakes and butterflies, brightly colored for self-defense, and what is aposematism in this context?
Mechanisms for defense against predators take many forms. A common adaptation is camouflage, where the animal avoids being eaten by its predator by blending in with the background, adapting a specific color or shape. The leaf insect takes on the shape and color of a leaf. It even sways as it walks, to resemble a leaf swaying in the wind. The dead leaf butterfly (Kalima inachus), when the wings are folded, it looks like a dried leaf.
Sometimes animals follow the opposite tactic to avoid being eaten by predators. Rather than disappearing into the background, they aggressively advertise themselves through color or shape that they are not worth eating. The brightly colored animal may be poisonous, taste bad, smell foul or have spines, or just be too aggressive. If the prey sees that it makes no sense to eat them, they leave them alone.
This tactic is called aposematism, and the animal that pursues it is aposematic. The word aposematic is derived from the Greek (“apo” means “way”, and “sematic” means “sign”).
Aposematism works best when members of the prey are together in large numbers. A few members are eaten by the predator, which then realizes they are not worthy of the food and the rest are left alone. The most common colors are red, yellow, black and white.
There are many examples of aposematics. Of these, the ladybug and tiger moth are bitter to eat. The poison dart frog has poisonous glands that can cause pain and the skunk has a foul odor.
There are also animals that are not really poisonous or otherwise unpleasant, but have bright colors that may lead the predator to believe that they are not good to eat: for example the hornet moth, which resembles the yellow-coated wasp. The predator is fooled into thinking that the moth will sting it and so it leaves the moth alone.
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SOURCE – www.thehindu.com