Mimicry is an evolved resemblance where one organism, the mimic, takes on characteristics of another or its surroundings. This adaptation provides a survival advantage, allowing species to avoid danger or secure food. The resemblance can involve appearance, sounds, behaviors, or smells, aiming to deceive a third party, often a predator or prey. Natural selection drives this phenomenon, passing beneficial resemblances through generations.
Understanding Mimicry: Diverse Strategies
Mimicry manifests in several distinct forms, each serving a specific ecological purpose. Batesian mimicry occurs when a harmless species evolves to resemble a dangerous or unpalatable one. This strategy allows the edible mimic to deter predators by appearing harmful, despite lacking the model’s actual defenses. For instance, a harmless insect might mimic a stinging wasp’s warning coloration.
Müllerian mimicry involves two or more unpalatable or dangerous species resembling each other. Both the mimic and model benefit mutually, as predators learn to avoid a shared warning signal more quickly. This reinforces avoidance behavior for all species involved, meaning fewer individuals are sacrificed to teach predators about their unpalatability.
Aggressive mimicry is a strategy where a predator or parasite mimics something harmless or attractive to lure its prey or host. This allows the mimic to approach its target undetected. The resemblance can be to the prey itself, a potential mate, or an environmental feature that attracts the prey.
Self-mimicry, also known as automimicry, is a specialized form where an animal mimics another part of its own body. This tactic often misdirects predators, leading them to attack a less vulnerable body part. It can also involve one part of the body resembling a more dangerous or important part, such as false eyespots on wings.
Animal Masters of Mimicry
Many animals exhibit remarkable mimetic abilities for survival and hunting.
In Batesian mimicry, the harmless hoverfly (family Syrphidae) often mimics the striped patterns of stinging bees and wasps. Though palatable to predators, these flies gain protection because predators avoid them, associating their appearance with the painful sting of their models. This visual deception allows hoverflies to avoid being eaten by insectivorous birds and other predators.
A classic example of Müllerian mimicry involves the Monarch butterfly and the Viceroy butterfly. The Monarch is unpalatable to birds due to toxins acquired from its milkweed diet. The Viceroy, also unpalatable, resembles the Monarch, making this a case of Müllerian mimicry where both species benefit from sharing a warning signal. Predators quickly learn to avoid both species after a single unpleasant experience.
Aggressive mimicry is skillfully employed by animals like the Alligator Snapping Turtle. This freshwater turtle lies motionless on the riverbed with its mouth open, wiggling a worm-shaped appendage on its tongue. Fish are lured by this seemingly harmless bait, swimming close enough to be rapidly captured by the turtle’s powerful jaws. Another striking example is the Mimic Octopus, which can impersonate a wide array of marine animals, including venomous lionfish, sea snakes, or flatfish, to avoid predators or approach unsuspecting prey. It can even mimic a crab to lure other crabs as mates before preying on them.
The False Cleanerfish (Aspidontus taeniatus) is another aggressive mimic, closely resembling the Bluestreak Cleaner Wrasse (Labroides dimidiatus). The Cleaner Wrasse provides a valuable service by removing parasites from larger fish at “cleaning stations” on coral reefs. The False Cleanerfish mimics the wrasse’s appearance and distinctive “dance” to approach unsuspecting fish, but instead bites off pieces of fin or skin. This deception allows it to feed on the tissues of its unsuspecting clients.
In the terrestrial environment, the non-venomous Scarlet Kingsnake exhibits Batesian mimicry by closely resembling the highly venomous Coral Snake. The distinct red, black, and yellow banding patterns of the Coral Snake warn predators of its toxicity. By adopting similar warning coloration, the Kingsnake deters predators that have learned to avoid the dangerous Coral Snake. While the exact band order can differentiate them, the resemblance is often sufficient to provide protection.
Self-mimicry is well-illustrated by the Owl butterfly, which possesses large, circular eyespots on its wings. These eyespots strikingly resemble the eyes of larger predators, such as owls. When threatened, the butterfly flashes these spots, startling or intimidating potential predators and giving the butterfly a chance to escape. This visual trick directs attacks away from the butterfly’s vulnerable body.
The Evolutionary Drive for Mimicry
Mimicry is an outcome of natural selection, a process where organisms better suited to their environment tend to survive and reproduce more successfully. The survival advantage conferred by mimicry, whether avoiding predators, catching prey, or attracting mates, drives the evolution of these resemblances over generations. Mimicry results from random genetic mutations that lead to beneficial resemblances, which are then passed on.
The interaction between mimics, their models, and the “dupes” (the animals being deceived) creates dynamic evolutionary pressure. In Batesian mimicry, predators learn to avoid a mimic due to its resemblance to a harmful model. This learning process exerts strong selective pressure on the mimic to maintain its deceptive appearance.
This interplay can lead to an evolutionary “arms race” between species. If mimics become too numerous or perfect, the model’s warning signal might be diluted, potentially leading the model to evolve new differentiating traits. Conversely, mimics constantly face selection to improve their resemblance to remain effective. This continuous back-and-forth shapes the intricate nature of mimetic relationships.
How Mimicry Works: Sensory and Genetic Basis
Mimicry relies on the sensory perception of the “dupe” or receiver, such as a predator, prey, or host. For visual mimics, like butterflies or snakes, effectiveness hinges on how well their colors, patterns, and shapes are perceived. Predators often learn to associate visual signals, like warning coloration, with negative experiences, leading them to avoid anything that resembles those signals. This learning process is key to mimicry’s success.
Beyond visual cues, mimicry can involve other senses, including acoustic, chemical, tactile, or electrical signals. For example, some insects mimic dangerous species’ sounds to deter predators, while certain orchids mimic female insects’ scent to attract male pollinators. The mimic’s deception depends on exploiting pre-existing biases or learned associations within the receiver’s sensory processing.
The development of mimetic traits is rooted in an organism’s genetics. Specific genes control the production of pigments and the formation of patterns that create the resemblance. Research, particularly in butterflies like Heliconius, has identified genes such as optix and WntA that influence color and pattern development. Different genetic pathways can lead to similar mimetic appearances.
Environmental factors also shape the expression and effectiveness of mimicry. Pressures like predation drive the selection of advantageous mimetic traits. Factors such as diet, temperature, and humidity can influence the development and expression of these traits, ensuring the mimicry remains convincing in its ecological context.