Biological mimicry is a sophisticated evolutionary strategy where an organism evolves to look like another species or object to gain a survival advantage. This phenomenon involves at least three participants: the mimic, the model, and the receiver. The mimic imitates the signal, while the model is the species or object being copied. The receiver, typically a predator or prey, is the third party tricked by the resemblance, leading to a benefit for the mimic. Mimicry can be used to deter predators, lure prey, or establish a shared defense system.
Protective Deception
Protective deception, often called Batesian mimicry, involves an organism bluffing its way out of danger by impersonating a dangerous species. This occurs when a palatable, undefended species (the mimic) evolves a close visual or behavioral resemblance to an unpalatable or toxic model species. The strategy relies on the receiver, usually a predator, having had a negative experience with the genuine model and learning to avoid anything that looks similar.
A classic example is the relationship between the Viceroy butterfly (Limenitis archippus) and the Monarch butterfly (Danaus plexippus). The Monarch is the model, storing toxins from the milkweed it eats, making it distasteful to birds. The harmless Viceroy lacks these toxins but has evolved nearly identical orange and black wing patterns. A bird that eats a Monarch learns to avoid all butterflies with that coloration, thus protecting the Viceroy.
This defensive strategy is common among insects that copy stinging species. Many harmless hoverflies have evolved the yellow-and-black banding patterns of wasps and bees. These flies lack a stinger, but their resemblance is often sufficient to deter a potential predator that has previously been stung. In some cases, the mimicry is not perfect, such as the Spilomyia longicornis hoverfly, which lacks the wasp’s long antennae but waves its front legs to complete the illusion.
Shared Warning Signals
Müllerian mimicry involves multiple genuinely defended species sharing the same warning signal, creating a form of collective honesty. In this system, two or more unpalatable or toxic species share similar aposematic signals, such as bright coloration or distinct patterns. Since all participants are dangerous, they are both mimics and models for one another, benefiting mutually from the shared signal.
The shared signal acts like a common brand of danger, allowing predators to learn avoidance faster. A predator only needs to sample one individual from the shared group to recognize the signal and avoid all others with that appearance. This reduces the total number of individuals sacrificed across all species before the predator learns its lesson.
This convergence is notably observed in the tropical rainforests with Heliconius butterflies, where numerous toxic species share a variety of complex wing patterns, forming what ecologists call a mimicry ring. In the Americas, various species of venomous coral snakes also exhibit this pattern by sharing bright red, yellow, and black banding. The strong selection pressure for a clear warning signal drives the different species to look more alike in areas where they co-exist.
Mimicry for Hunting and Ambush
While many forms of mimicry are defensive, aggressive mimicry is an offensive strategy used to capture prey or access a host. In this system, a predator or parasite resembles a harmless third party to lure its target closer. Instead of deterring a receiver, the mimic attracts it by impersonating a food source, a potential mate, or a safe place.
A striking example is the deep-sea Anglerfish, which possesses a modified dorsal spine, called an esca, that hangs in front of its mouth. The esca often glows with bioluminescence and resembles a small, edible organism, like a shrimp or a tiny fish. When smaller fish are drawn in by the lure, the Anglerfish quickly engulfs them.
Another instance of deceptive predation is found in the female Photuris firefly. These predatory females mimic the specific light-flashing mating signals of females from other firefly genera, such as Photinus. Unsuspecting males, attracted by what they believe is a receptive mate, are instead captured and consumed by the Photuris female.
Mimicry Versus Camouflage
Although both mimicry and camouflage are adaptive strategies that involve visual appearance, they operate through fundamentally different mechanisms. Camouflage, also known as crypsis, is an adaptation where an animal blends into its general background or environment to avoid detection. This is primarily a two-party interaction designed to conceal the animal’s presence entirely.
Mimicry, by contrast, is a three-party interaction designed not to hide the organism, but to redirect the attention of a receiver. The mimic does not blend into the background but instead copies a specific model to convey a particular message, such as danger or safety. A stick insect that looks like a twig is a classic example of crypsis.
Conversely, a harmless snake displaying the banding of a venomous coral snake uses mimicry. The snake is intentionally visible, using the pattern of a dangerous model to trick a predator into avoidance. The difference lies in the specific target of the deception: the environment in camouflage, versus a specific model species in mimicry.