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The art of mimicry: what creatures do to survive…

In nature, the struggle for survival is a daily battle, especially if you are smaller or slower than your possible predators. And this is why many have developed very sophisticated camouflage techniques to protect themselves from the perils of nature. The kind of camouflage depends on the animal’s physiology and behaviour, on the type of predator and on the environment in which the animal lives and hunts for food. Natural selection also plays a part: the way in which creatures camouflage themselves is genetically determined, so that each new generation will succeed in camouflaging itself more efficiently. Succeeding in blending into the environment is a kind of deception that provides benefits. One of the most commonly found forms of camouflage is cryptic behaviour. This can be divided into two types: homomorphism and homochromism . In the first case, the creature mimics the shape of inanimate objects in the surrounding environment. One of the most sophisticated examples found in nature is that of the orchid mantis (Hymenopus coronatus ), an authentic prodigy of mimicry. Its legs become similar to petals and its thorax shows brownish lengthwise streaks like those found on orchids. Its head takes the form of the reproductive apparatus of a flower. Thus it appears to be part of the orchid and in this way it succeeds not only in hiding from its predators, but also in trapping its own food. It waits motionless until fly near the flower to suck its nectar and at that point immobilises its prey with its powerful spiked legs.

Homomorphic mimecry Hymenopus coronatus. Source: animalesmascotas.com

In the second case, on the contrary, the creature changes its colour to mimic that of a substrate, making itself almost unrecognisable. An example is the “mossy leaf-tailed” ( sikorae ), a species found only in Madagascar. It is mostly active at night, when it hunts for small insects, while during the day, to avoid being disturbed, it can flatten itself to the extent that it blends in with the bark of the trees where it rests.

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Homochromic mimecry Uroplatus sikorae. Source: flickr.com

The mimetic signals of some individuals, rather than camouflaging them, sometimes show a wish to appear. Why is that? To protect themselves. Very bright colouring (yellow, red, purple and blue on a black or white background) are often associated with the ability to secrete and/or inject more or less poisonous chemical substances so that they become unpalatable to the predator. In fact, predators who when younger have had negative experiences when “tasting” such strange, colourful prey, will be able to associate bright colours with a sensation of disgust and will avoid preying again on creatures with those specific colour characteristics. This phenomenon is called aposematism , and in nature this strategy is imitated by various individuals belonging to the same mimicry ring. Imitation of colour combinations between phylogenetically distant poisonous species is known as Mullerian mimicry . It involves “agreeing” the colouring to be exhibited to show that they are really disgusting or dangerous. Both species share the benefits deriving from similar colouring. Two small frogs, Dendrobates leucomelas and Mantella madagascariensis , distinguished by black and yellow spots and both poisonous, are an example of Mullerian mimicry. Predators will avoid all frogs with colouring similar to those they have tasted. This means that the number of frogs sacrificed will be subdivided statistically amongst species in the same mimicry ring with a resulting decrease in losses of individuals in each single species.

Mullerian mimicry. A: Mantella madagascariensis. B: Dendrobates leucomelas. Source: news.mongabay.com

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Batesian mimicry on the contrary means imitation of an aposematic species that is unpalatable by a palatable species which, to increase its chances of survival, deceives a shared predator. Therefore, having colours similar to an aposematic species allows the harmless species to appear to belong to another species and discourage predators. In Indonesia, in fact, juvenile forms of Acanthurus pyroferus are born with colouring similar to that of the small angelfish, Centropyge vroliki . Centropyge angel fish do not produce poisons, but probably accumulate repellent substances by feeding on sponges and tunicates, poisonous creatures, in turn becoming unpalatable to predators, which avoid them. Therefore, predators will avoid eating not only angelfish, but also the juvenile forms of Acanthurus fish, since both have the same colouring.

Batesian mimicry. A: Canthrus pyroferus. B: Centropyge flavissimus. Source: scubaportal.it

The various camouflage strategies used by many species to survive also combine with each other, establishing very important but at the same very delicate balances. All this is due to natural selection allowing creatures to survive the eternal battle between prey and predators.

By Francesca Scannone