July 26, 2021

I, Science

The science magazine of Imperial College

Hide and seek goes on just about everywhere. It’s a simple case of looking hard enough. Camouflage allows organisms of all shapes and sizes to remain unnoticed by their predators or prey. Obvious examples include a tiger’s stripes or a leopard’s spots, but let’s take a closer look at some more unusual cases of visual trickery.

Poisoned Pebbles

Stonefish (Synanceia verrucosa) lurk in the waters of the Indo-Pacific oceans and disguise themselves as harmless stones. In fact, they’re quite the opposite; stonefish are the most venomous fish in the world. They feed on small fish and take no more than 0.015 seconds to attack. Stonefish are preyed on by sharks and defend themselves with 13 lethal spines. When touched the spines release venomous neurotoxins, which cause paralysis and, in some cases, death. These feisty fish have acquired quite a reputation for themselves, to the point that Australian Aborigines even have a dance to warn against stepping on these hidden monsters.

Getting dressed up

The dresser crab manages to avoid predation with some serious style. This fashionista of a crustacean decorates its shell by attaching accessories from the sea bed to Velcro-like patches on its exoskeleton shell. Common outfit accessories include sponges, seaweed and even pearls, which allow the crab to blend perfectly into any sea-floor scene. Other animals are slightly more dynamic, such as chameleons, which are well known for their vibrant colour changes. Although their colour changing is important for camouflage, it originally evolved for social signalling purposes. When chameleons are angered or attempting an attack they appear darker, and take on multi-coloured patterns when courting prospective mates. Chameleons are able to change their colour due to specialised pigment cells called chromatophores under their transparent skin. Chromatophores are found in many organisms, including the illustrious golden tortoise beetle. These beetles dampen their golden gleam to an orange-brown colour and develop dark spots to don a ladybird disguise. Many birds find beetles an extremely nutritious treat, but ladybirds don’t taste so good and, therefore, offer a safe disguise.

Humans do it to

Although animals are the camouflage experts, it isn’t just in nature where we find this kind of visual subterfuge. Throughout history, humans have mimicked natural camouflage in military operations and artistic masterpieces. During the First World War, hiding from aeroplane surveillance became a top priority and prompted the French to create an artistic military division – aptly named the Camoufleurs. The Camoufleurs experimented with contrast and shape to invent the most elective military camouflage. Particularly e!ective was the ‘Dazzle’ pattern, which used bold geometric patterns to trick the mind of opponents and alter their perception of size and shape. Dazzle-emblazoned submarines confused the enemy, who couldn’t work out the size, speed or direction the submarines were heading in.

Invisibility Cloak

Camouflage is still a major focus for research today. Scientists here at Imperial are currently developing an invisibility cloak. The cloaking device is a metamaterial, which is an artificial structure capable of bending light, so a cloaked object is hidden from view. Scientists are aiming to eventually make the invisibility ‘cloak’ functional and sensitive to movement. The invisibility technology has many powerful applications, such as being able to peer through rubble after an earthquake and allowing doctors to see through skin and bone at damaged organs. It would, therefore, seem that camouflage is a survival tool, not just for tigers and leopards, but for all of us humans.