The art of camouflage

Different kinds of animals use different kinds of biology to change their colouration: in some cases it is gradual and in keeping with the seasons, whilst other animals have evolved to change their colour in a split second and without a moment's hesitation. I find this absolutely fascinating and often marvel at the art of what is essentially camouflage.

Many mammals and birds alter their colour to adapt to changes in their environment; such as, weather and temperature. They usually alter the colour of their fur by moulting – this is a gradual process that takes place with the changes of the seasons. For example, in the summer the mountain hare has a brown coat: then, as the days get shorter and colder, the colour of its coat slowly turns to white.

The winter coat is usually thicker, softer and more densely-packed than the summer coat; this helps the mountain hare to keep them warm. They have no choice whether to change colour or not as the process is activated through the pineal gland in their brain, a gland that senses seasonal changes and daylight length.

Other animals change their colour far more quickly and likewise reverse this process quickly too. Amphibians, fish, insects and cephalopods don't have fur or feathers so do not need time to grow a new coat: they are also not bound to seasonal changes.

Cephalopods are very adaptive when it comes to changing their colour. Cephalopods (cuttlefish, octopuses and squid) can change their colour using their specialised chromatophore cells. These cells are located just underneath their skin and contain a stretchy sac of pigment which is attached to muscle fibres. When the muscle fibres contract, the pigment cells cover a larger area; when they relax, the area covered becomes smaller.

In some species, there are also some cells called iridophores cells - these are found beneath the chromatophores and are either protein based or made of chitin. Rather than producing pigment, the iridophores reflect light like a mirror which helps the animals blend in with their environment. Iridophores are thought to respond to a change in hormone levels. As they are in a deeper layer of skin, they can either be covered up or revealed by the action of the chromatophores above them.

These specialist cells are what give chameleons their famous technicolour coats. It is a common misconception that chameleons change their colours to blend into their environment. This is actually not true; instead, they use their colours to communicate their moods and to regulate their body temperature. Male chameleons use bold colours to show dominance and turn dark when they are angry. Females change to show they are interested in mating.

As a cold blooded animal that is unable to regulate its own heat, the chameleon can use colour to regulate their body temperature. This is seriously clever stuff! A chameleon will literally turn pale to stay cool on a hot day and turn dark to absorb more sun on a cold day – amazing!

Reversible colour changes are extremely rare in the insect world but the golden tortoise beetle is the first known insect species to demonstrate rapid and controlled colour change. The golden tortoise beetle is a member of the leaf beetle family; and I can't wait to be able to learn more about this special rarity.