Thursday

18


May , 2017
Mimicry comes easy to animals
14:46 pm

Maneka Sanjay Gandhi


Mimicry, by changing form, shape and colour on the spot, is unique to animals. Imagine if you went into a Chinese, or African, neighbourhood and had to defend yourself by looking Chinese or African. Or if you had to change your colour to black or white or polka dotted? Or become shorter, fatter, change the shape of your nose, increase the number of arms. We can’t do a single thing at will even if our lives depend on it.

But animals and insects do it easily. They change their forms to look like species that predators avoid. They smell differently, they change their shapes and colours to blend in with the background, or with their prey, or look like blobs of inanimate matter. They have learnt to eat without being eaten.

The mock viper (P. pulverulentus) of Asia is a mild harmless snake. It looks like a viperwith a triangular head, but the viper is a dangerous snake. The only difference is that the mock viper has round pupils. True vipers’ pupils are vertical slits. The Mock Viper knows it is harmless but is so clever that, when threatened, it squeezes the shape of its pupils to look like the slits of a true pit viper and then, in the panic this causes, it flees.

Appearing dangerous is the first defence. Another snake in this region, the Malayan bridle snake, mimics a venomous snake, called the Malayan krait, not just in its coloration, but by hiding its head under its coils when threatened.

The Milk snake (L. triangulum) is harmless but changes itself gradually to develop bands like the venomous Coral snake. Is this mimicry or a coincidence? Definitely deliberate mimicry, because it happens only in those regions where the milk snake and coral snake are found together. In other regions, the milk snake doesn’t look anything like the coral snake. Likewise, the harmless Scarlet King Snake is born with white bands. But young snakes start developing the colouring of the coral snakes with the yellow, apricot, or tangerine coloured banding.

The hognosed snake pretends to be dead and gives off a rotting smell. But before that it mimics a rattlesnake, raising its head as if about to strike and making a rattling sound.

It’s not just defence, animals that hunt need to be clever too. Either they adopt amazing disguises or they fool their prey into believing they are harmless while they get close to them.

The Green Lacewing larva feeds on woolly alder aphids who are protected by ants. So it plucks the white waxy wool from an aphid’s back, attaches it to its own and fools the ants into believing it is part of their flock. Once inside the circle, it eats the aphids.

The Zone tailed Hawk feeds on live animals, but it mimics the flight of a vulture who is a carrion eater. Small animals are deceived by the gliding flight, and vulture like outline, and are then snatched up.

The Cleaner Wrasse fish is harmless and its function is to eat the parasites on larger fish. They stand in line to be attended to. The Sabre Tooth Blennnyhas black and blue markings like the Cleaner and loiters at cleaning stations, imitating the Wrasse’s swimming pattern. It comes close to large fish and bites a chunk out of them before darting away.

The Dusky Dottyback is a small 3 inch harmless looking fish which lives in our Indo pacific coral reefs. It ranges in colour from pink to grey,but can change into any colour – green, yellow brown - to match its prey. It tricks baby fish of larger species into thinking it is one of them. Then it eats them. Its favourite prey are baby damselfish. This unique talent allows the dottyback to easily approach juvenile damselfish without detection and, by the time one group has alerted itself, it moves to new groups of fish and new colours.

The Cheilinus wrasse is a carnivorous fish of the coral reef. It changes its colour to mimic harmless plant eating fish, like goatfish or parrotfish, and swims in their schools until it gets close to its prey. But different wrasses use the power of mimicry to do different things. The Potters wrasse mimics the Potters Angel — a larger, more spiny, harder to catch fish.

The slender Trumpet fish swims vertically in the soft coral branches and changes its colour to match its background. It is almost invisible to the small animals that it hunts.

The Marine flatworm increases its size to look like a sea slug, which is avoided by aquatic predators because it emits a poisonous and malodorous substance.

The Bushveld Lizard (E. lugubris) in Southern Africa mimics notorious and noxious ‘oogpister’ beetles when young. While the adults blend with the red-tan colours of the Kalahari semi-desert, the lizard juveniles are jet-black and white and move with stiff, jerky movements and arched backs. Predators avoid the threat of the pungent, acidic fluid sprayed by these beetles when threatened.

Metalmark moths (Brenthia) are hunted by jumping spiders. So they make themselves look like the spiders that hunt them. How does a moth with wings mimic an arachnid with eight legs? When a metalmark is confronted by the spider, it arranges its wings to mimic the spider's pose, looking like a bigger, meaner, spider.

Capturing other insects becomes easier for ant-mimicking spiders who align six of their legs to look like ant legs and the extra pair to look like the antennae of a six-legged insect. Passing for a non-threatening ant allows them to get within easy striking distance of their prey.

Before butterflies rise to dazzle the world with their beauty they have to spend days as defenceless caterpillars waiting to be eaten. Many masquerade as something that's actually dangerous. Some, when faced with a predator, retract their heads backward into themselves, causing a bulge that looks like the head of a snake. The snake "eyes" are just spots on the caterpillar's sides. Some even extend appendages from the top of their head to mimic a forked snake tongue.

The Oscar goes to the king of all mimics: the mimic Octopus, Thaumoctopus mimicus, an eight tentacled creature that can look like anything it wants to : a seasnake, a foul tasting flatfish, a shrimp, a seahorse, stingray, anemone, starfish, lionfish, crab. Inhabiting the coast of Indonesia, this creature is so good at not being an octopus that it eluded human discovery until 1998. In any other civilization it would be preserved as a being of magic. In this world it is killed in the millions and eaten. 

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