Biological mimicry is a fascinating evolutionary adaptation where one species, the mimic, evolves to resemble another organism, the model, or an inanimate object. This resemblance is not accidental; it is driven by natural selection to deceive a third party, the signal receiver, which is often a predator, prey, or potential mate. The resulting deception provides a significant survival or reproductive advantage for the mimic species.
Setting the Scene: Mimicry Versus Camouflage
Mimicry is frequently confused with camouflage, but they represent distinct survival strategies in nature. Camouflage, or crypsis, involves an organism blending into its background to avoid detection entirely, such as a chameleon changing color to match a leaf or a polar bear blending with snow.
Mimicry, conversely, relies on being detected but then being mistaken for something else. The mimic is generally conspicuous and relies on the receiver misidentifying it as the model species, which is typically dangerous or unpalatable. For example, a non-toxic hoverfly is easily seen, but its yellow and black stripes cause a bird to mistake it for a stinging wasp. While a stick insect uses camouflage to disappear against a twig, the hoverfly uses mimicry to advertise a false identity.
Mimicry for Survival: Defensive Strategies
Defensive mimicry involves strategies aimed at avoiding predation. These systems rely on the predator’s ability to learn and remember warning signals, such as bright colors or distinct patterns, known as aposematism. Defensive mimicry is broadly categorized into two major types: Batesian and Müllerian.
Batesian Mimicry
Batesian mimicry is a form of bluff, where a palatable, harmless species (the mimic) copies the warning signals of an unpalatable, defended species (the model). This deception works because the predator has learned through a negative experience to avoid the model, and it now avoids the mimic as well. The mimic essentially parasitizes the protective reputation of the model without incurring the energetic cost of producing toxins or defenses.
The Viceroy butterfly, an edible species, closely resembles the toxic Monarch butterfly. Predators avoid both species after tasting the noxious Monarch, providing protection for the Viceroy. Similarly, non-venomous Kingsnakes possess the red, yellow, and black banding pattern of the highly venomous Coral Snake, deterring potential attackers. The success of this strategy depends on the model being more abundant than the mimic, ensuring predators continue to associate the warning signal with a bad meal.
Müllerian Mimicry
Müllerian mimicry involves two or more unpalatable or toxic species evolving to resemble each other, often sharing the same warning coloration. This mutual resemblance benefits all species involved because it consolidates the learning experience for predators.
This reduces the total number of individuals that must be sacrificed across all species before the predator learns its lesson. The shared black and yellow stripes of many stinging bees and wasps are a prime example, where a negative encounter with one species leads to the avoidance of all similar-looking species.
Mimicry for Acquisition: Offensive and Reproductive Roles
Mimicry is also employed by organisms to acquire resources, such as food or mates. This is known as aggressive mimicry, where the deception benefits the mimic by allowing it to get closer to a potential meal or host. The mimic resembles something harmless or even attractive to the prey.
The Anglerfish uses a form of aggressive mimicry, where a modified fin spine acts as a bioluminescent lure, resembling a small, attractive prey item. When smaller fish are drawn in by the deceptive lure, the Anglerfish is able to quickly consume them. Another example is the female Photuris firefly, which mimics the flash mating signals of another firefly species, Photinus, to attract and then eat the unsuspecting males.
Automimicry
Automimicry is a specialized type of mimicry where one part of an organism’s body resembles another part of the same organism. Some hairstreak butterflies have small tails and eyespots on the edge of their hindwings that resemble a false head and antennae. When attacked, predators are directed to strike the less vulnerable part of the wing instead of the actual head, allowing the butterfly to escape a fatal injury.