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Sunday, August 01, 2021

Catch me if you can

How creatures deceive us in plain sight

Written by Ranjit Lal |
July 11, 2021 6:10:58 am
eye 2021, ranjit lal, camouflagingShape-Shifter: Tawny Rajah butterfly posing as a dried leaf (Photo Credit: Ranjit Lal)

One of Mother Nature’s most astonishing (and equitable) adaptations, by both prey and predator, is to avoid being eaten, or assist in hunting. Usually, the process takes thousands of years, but can happen even within decades — further proof to Charles Darwin’s theory of evolution.

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To avoid becoming lunch, or to help them get lunch, animals have been camouflaging themselves in myriad ways. I’ve spent hours staring into a verdant neem or peepul tree, trying my damnedest to winkle out the brown-faced barbet that I know is on it because it’s been calling away, but I’ve not been able to spot it. Yellow-footed green pigeons (apparently tasty) are even worse!

You can evade the enemy in various ways, or crouch unseen and poised to ambush. One method is to wear the colours of your environment and melt into it — the Arctic fox is pure white against the winter snow, and cannily, changes into brown in summer. The potoo or frogmouth and nightjar birds perfectly resemble the end of dead logs or tree trunks. Spotting a bittern among reed beds drives even experienced birders nuts; the bird not only blends into its background, but also sways like a reed in a breeze.

Zebras live in herds and when they move, the many moving stripes make the lions (their chief predators) cross-eyed because they need to focus on a single individual. Lions see in black and white, so the zebras merge into the background. Conversely, the black flames on a tiger against its fiery coat blends beautifully with the light and shadows of its jungle habitat. As do the spots on a leopard.

Among the small creatures, how many times have you been surprised by invisible grasshoppers leaping away as you walk through a shaggy lawn or by an ostensibly dead leaf on the ground suddenly fluttering past as you pass by?

The caterpillar and pupa of the lime butterfly takes blending to another level. When the eggs hatch, they resemble bird droppings. Now, which self-respecting bird would be caught alive eating bird-droppings? As the caterpillar grows, it seeks a more dignified disguise. And so, turns leaf green and arranges itself along the midrib of the leaf — again virtually invisible. If disturbed, it rears up, extending two red protrusions from its head, pretending to be a snake. The subterfuge continues when the caterpillar turns into a pupa. During the rains, they turn verdant green, in post-monsoon, they are brown, to match dried-up foliage!

Some butterflies are poisonous — having gorged on the poisonous leaves when they were caterpillars. They retain the poison. So, when a bird takes a peck at the now-butterflies, it gags and vomits — and won’t go near them ever again. Some butterflies advertise that they’re not to be tangled with by being brightly patterned, others simply mimic the genuine articles (called Batesian mimicry).

The beautiful pink “orchid mantis” resembles an orchid (on which it resides) and sways alluringly in the breeze, inveigling flies over — which are snapped up and devoured. This is called “aggressive mimicry”.

Many creatures use “counter-shading” to blend in. A shark is darker above and lighter below: if seen from above it blends into the darker depths of the ocean below it, and if seen from below it blends in with the lighter sky above! Black-and-white penguins are also counter-shaded — to escape predators.

Some creatures like a species of crab dresses up. If the sea bed is pebbly, they’ll place pebbles on their Velcro-like backs until they blend in perfectly. Put them in an aquarium with beads and pieces of coloured glass and they’ll deck themselves up!

Then there are shape-shifters, the classiest being cuttlefish and octopus. They change their camouflage depending on where they are — vanishing uncannily on the sea bed or among seaweed before ambushing (or escaping from) their prey or predators. The famous chameleon is another example, but uses its change in colour more to communicate its mood than as a form of defence.

You’d think that all this shape-shifting and imitating must take thousands of years because some disguises are perfect, but the famous peppered moth in the UK proved otherwise. These moths usually hung out on the trunks of trees, were light-coloured to blend with the tree trunks and, so, evaded being eaten. The Industrial Revolution deposited a whole lot of soot into the environment, darkening tree trunks — and also the moths. Generations later, only the slightly darker ones survived — and got darker. Once the environment cleaned up, and the tree trunks got lighter — so did the moths!

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