Prey species in the animal kingdom have evolved remarkable adaptations to survive against predators. Many involve deception, such as mimicry, where one species resembles another. Batesian mimicry is a compelling example, allowing a harmless organism to gain protection by imitating a more dangerous counterpart.
How Batesian Mimicry Works
Batesian mimicry functions through a deceptive three-party interaction involving a harmless “mimic,” a dangerous or unpalatable “model,” and a “predator” that is fooled by the resemblance. The model species possesses a defense, such as toxicity, a foul taste, or venom, often advertised through bright, conspicuous warning coloration known as aposematism. Predators that attempt to consume these models learn to associate their warning signals with an unpleasant experience, leading them to avoid such prey in the future.
The mimic species, lacking the model’s defenses, evolves to imitate these warning signals through similar colors, patterns, or behaviors. By resembling the dangerous model, the mimic benefits from the predator’s learned avoidance. This strategy allows the mimic to deter predators without expending the energy required to develop its own defenses. This deception relies on the predator’s prior negative experiences with the genuine model.
Illustrative Cases of Batesian Mimicry
Numerous examples of Batesian mimicry exist across various animal groups. A common instance involves hoverflies (family Syrphidae) mimicking bees and wasps. Many hoverfly species display the black and yellow banding patterns of stinging Hymenoptera, though they are harmless and lack stingers. Predators, having learned to avoid the painful sting of bees and wasps, often steer clear of these hoverflies.
Another example is the mimicry of venomous coral snakes (genus Micrurus) by non-venomous king snakes (genus Lampropeltis). Coral snakes are highly venomous, exhibiting distinct patterns of red, yellow, and black bands. Harmless king snakes, such as the scarlet kingsnake (Lampropeltis elapsoides), have evolved similar banding patterns, causing predators to mistake them for dangerous coral snakes and avoid them. The robber fly Mallophora bomboides also mimics its bumblebee model, Bombus pensylvanicus, which is noxious to predators due to its sting.
Why Batesian Mimicry Evolves
Batesian mimicry evolves through natural selection, favoring mimics that closely resemble their models. Predators act as the selective force; mimics that resemble the unpalatable model are less likely to be attacked, increasing their chances of survival and reproduction. Over generations, these advantageous traits become more prevalent in the mimic population.
For Batesian mimicry to be effective, the model species needs to be more abundant than the mimic. If mimics become too numerous, predators may encounter them more frequently, leading to positive experiences with the palatable mimic and a breakdown of the warning signal. This dynamic pressures the mimic to maintain a less common presence relative to its model. The predator’s ability to learn and remember the association between the model’s appearance and its unpalatability is also fundamental for the mimicry to succeed.
Distinguishing Batesian Mimicry
Batesian mimicry is contrasted with other forms of mimicry, particularly Müllerian mimicry, due to their distinct mechanisms. In Batesian mimicry, a harmless species gains protection by imitating a harmful one. This means only the model possesses a true defense, and the mimic benefits from this defense without having one itself.
In contrast, Müllerian mimicry involves two or more species, all genuinely dangerous or unpalatable, evolving to resemble each other. This shared warning signal provides a mutual benefit, as predators learn to avoid the common pattern more quickly, reinforcing the deterrent for all species. Unlike Batesian mimicry, where the mimic essentially “bluffs,” Müllerian mimicry represents an honest signal shared among multiple defended species.