Appearances can be deceptive, so the saying goes. This is perhaps most accurate when applied to the animal kingdom, where cloak and dagger tactics can be the key to survival. Everywhere you look, there are examples of species that are trying to imitate others and avoid predation using the simple art of deceit. Although, mimicry in the natural world can be far more complex than you might imagine.
Broadly speaking, there are two types of mimicry utilised by animals – Batesian mimicry and Müllerian mimicry. Müllerian mimicry is where two species with a defence mechanism in their arsenals, such as a sting or a foul taste, evolve very similar warning signals1. A prime example is that of bees and wasps – both stinging insects who have evolutionarily converged to develop the same black-and-yellow warning stripes. Both animals benefit from this form of mimicry because predators learn to associate the colour combination with danger. The larger the number of species that develop the same warning signals, the more effective the deterrent becomes.
But Müllerian mimics are not strictly deceiving their predators. If anything, they provide other animals with honest cues about potential danger, with both predators and mimic benefiting from the interaction. The mimics avoid being eaten, while the predators avoid possible injury or a mouthful of distasteful food. The concept is named after the German naturalist Fritz Müller, who proposed the idea in 1878 while studying butterflies in Brazil. Müllerian mimicry can be found in various species, including poison dart frogs and some bird species23. It does not just work by visual cues either, with many snakes developing similar auditory warnings such as hissing or tail-rattling.
However, with Müllerian mimics receiving a selective advantage thanks to their exploits, it is no surprise that other species try to get in on the action. For example, many types of hoverfly have evolved to develop strikingly similar colourations and patterns to those of bees and wasps. But while bees and wasps can both inflict stings, hoverflies are entirely harmless. By mimicking dangerous insects, hoverflies pull off the perfect act, deceiving predators into thinking they are harmful and therefore avoiding being eaten. This is Batesian mimicry – the sneaky, alternative form of imitation.
Batesian mimicry primarily comes in visual cues, with the milk snake being one of the most famous examples. Milk snakes are characterised by having a banded pattern of red, yellow and black stripes. Another snake that boasts the same colours (just in a different order) is the coral snake. But while coral snakes can kill a human within hours of a venomous bite, milk snakes are completely harmless. Batesian mimicry was first documented in 1862 by Henry Walter Bates. Like Fritz Müller, Henry Bates also dedicated much of his time to studying Brazilian butterflies, which undoubtedly are the masters of this deceitful art.
At first glance, it may seem like Batesian mimics have the perfect strategy. They can deter predators without even having to spend the resources needed to maintain any actual weapons. However, in doing so, Batesian mimics are treading a very fine biological line. You see, the relationship between mimics and predators is delicately balanced and relies on trust. The higher the abundance of ‘fake mimics’, the more likely predators will stop believing the warning signals displayed to them simply. When this happens, the entire relationship can fall apart, with the phoney Batesian mimics having to suffer the shame of being eaten on a large scale.
For example, a study of coral snake mimics in the south-eastern United States found that predators only avoided the harmless look-alikes in areas inhabited by the deadly coral snakes. In regions where coral snakes weren’t found, the deception was far less effective, with the harmless look-alikes being preyed on regularly. The study, published in the journal Nature, therefore uncovered an example of frequency-dependent Batesian mimicry4. The relative abundance of the mimicking species impacts how readily other animals believe the deception.
So as is often the case with visual charades, it can be hard to pull off an effective imitation. However, for the species that can strike the right balance, it is an incredibly effective tool for survival, allowing them to hide right under the noses of potential predators.
Sherratt, T.N., 2008. The evolution of Müllerian mimicry. Naturwissenschaften, 95(8), p.681. ↩
Pfennig, D.W., Harcombe, W.R. and Pfennig, K.S., 2001. Frequency-dependent Batesian mimicry. Nature, 410(6826), pp.323-323. ↩