Animals That Change Color: Chameleons, Octopuses and More

How do animals change color?

Animals use three main tricks, often in combination:

• Pigment cells. Many fish, frogs, reptiles and cephalopods have chromatophores, skin cells or organs that hold pigments such as black melanin, red and yellow. Spreading the pigment out makes that color show; bunching it into a tiny dot hides it. In fish and frogs, nerves and hormones control these cells, and changes take seconds to hours.
• Structural color. Some colors are made not by pigment but by tiny structures that reflect certain wavelengths of light, the same way a soap bubble shimmers. If an animal changes the spacing of these structures, its color shifts.
• Molting. Mammals and birds cannot change the color of existing fur or feathers. Instead they shed their old coat and grow a new one of a different color, usually twice a year.

1. Chameleons

Chameleons are the most famous color changers, though their reasons are often misunderstood. A chameleon’s skin has layers of pigment cells over layers of cells called iridophores, which contain tiny crystals of guanine arranged in a regular lattice. A 2015 study of panther chameleons at the University of Geneva showed that the lizards change color by actively tuning the spacing of these nanocrystals. Tightly packed crystals reflect blue light, which mixes with yellow pigment above to look green; when the crystals spread apart, they reflect longer wavelengths and the skin shifts toward yellow, orange or red.

Male panther chameleons from Madagascar can turn from a resting green or blue to vivid red and orange within minutes when they meet a rival or court a female. Chameleons also darken to absorb heat on cool mornings and turn paler to stay cool. See why do chameleons change color? for more.

2. Common cuttlefish

The common cuttlefish of the eastern Atlantic and Mediterranean is perhaps the most skilled color changer on Earth. Its skin is packed with chromatophores, each a small elastic sac of yellow, red or brown pigment surrounded by tiny muscles. Nerves from the brain tell the muscles to pull the sac open or let it close, so a cuttlefish can switch its whole pattern in well under a second.

Beneath the chromatophores lie reflective iridophores and white leucophores, and the cuttlefish can also raise small bumps on its skin to copy the texture of rock or seaweed. It uses these skills to hide, to startle predators and to court: breeding males show a bold black-and-white zebra pattern. Young cuttlefish can already work their color cells inside the egg. More in how do cuttlefish change color?

3. Octopuses

Octopuses share the same muscle-controlled color organs. The common octopus can turn from sandy beige to mottled brown or flash dark red in an instant, and it often pales suddenly when alarmed. Octopuses tend to darken when acting aggressively toward each other and to change color as they move across different surfaces.

The mimic octopus of the Indo-Pacific goes further. It changes both its color and its body posture to impersonate other animals, including venomous lionfish, sea snakes and flatfish. It is one of only two octopuses known to imitate several different species.

A curious fact about cephalopods is that most of them appear to be colorblind, with only one type of light-sensitive cell in their eyes. Scientists are still working out exactly how they manage to match colors they may not be able to see.

4. Flounders

Flounders are flatfish that lie on the seafloor with both eyes on the upper side of the head. Species such as the peacock flounder of the Caribbean and western Atlantic can adjust the pattern of their pigment cells to match sand, gravel or rubble within seconds. In experiments, tropical flounders placed on artificial backgrounds such as checkerboards changed their patterns to suit each one within seconds. The change is driven by what the fish sees around it.

5. Green anole

The green anole of the southeastern United States is often nicknamed the “American chameleon,” although it is not a true chameleon. It can shift from bright green to dark brown and back, a change linked to temperature, stress and encounters with other anoles more than to the color of its perch. Males also flash a pink throat fan, called a dewlap, to defend territory and attract females.

6. Arctic fox

The Arctic fox molts twice a year. In autumn it grows a thick white winter coat that hides it against the snow, and in spring it sheds it for a thin brown or gray-brown summer coat that matches the bare tundra. A rarer “blue” form stays dark gray or brown all year and is most common on rocky coasts and islands such as Iceland. Read more in why do Arctic foxes change color?

7. Snowshoe hare

The snowshoe hare of Canada, Alaska and the northern United States is brown in summer and almost entirely white in winter, apart from black-tipped ears. Its molt takes several weeks and is timed mainly by day length. As winters warm and snow arrives later or melts earlier, more hares end up white on brown ground. Studies in Montana found that hares can shift the timing of their molt only a little and that these mismatched hares are more likely to be caught by predators.

8. Stoat

The stoat, known as the ermine in its white winter coat, turns white in snowy regions of Europe, Asia and North America but keeps the black tip of its tail all year. In places with mild winters, such as much of southern Britain, many stoats stay brown or turn only partly white. White ermine fur, with its black tail tips, was long used to trim royal and ceremonial robes in Europe.

9. Ptarmigans

Ptarmigans are grouse of the Arctic and high mountains, and they change their plumage with the seasons. The rock ptarmigan, found from the Alps and the Scottish Highlands to the Arctic tundra, is mottled brown and gray in summer and turns white in winter, except for black outer tail feathers. The willow ptarmigan, the state bird of Alaska, keeps white wing feathers all year. Ptarmigans also grow feathers on their feet in winter that act like snowshoes.

10. Golden tortoise beetle

The golden tortoise beetle of North and South America is only 5–7 mm (0.2–0.3 in) long but looks like a drop of polished gold. When it is disturbed or during mating, it can turn a dull reddish-brown with black spots. In a closely related species, the change works by moving moisture in and out of thin layers in the wing cases, which alters the way they reflect light.

11. Goldenrod crab spider

Female goldenrod crab spiders sit on flowers waiting to ambush visiting insects. They can be white or yellow and can change from one to the other to match the flower they are hunting on. The change is slow, taking up to about 25 days, because the spider has to produce or remove yellow pigment.

Myth: do chameleons change color to match their background?

This is the most popular myth about color-changing animals. A chameleon placed on a red cloth does not turn red, and one on a checkerboard does not become checkered. Chameleons’ everyday greens and browns already blend with leaves and bark, but their color changes are mostly about communication and temperature: a calm, cool chameleon is often dull, while an excited or warm one may become bright.

There are exceptions. Some dwarf chameleons from South Africa adjust their colors depending on whether a bird or a snake is threatening them, matching the different ways those predators see. The animals that truly copy their surroundings in real time are cuttlefish, octopuses and flounders.

Other animals that change color with the seasons

Many birds swap colors through molting. The male American goldfinch is bright yellow in summer and olive-brown in winter; see why do goldfinches change color? Some insects change with the weather: the Hercules beetle’s wing cases are olive-green or yellow in dry air and darken to black when the air is humid. Color change takes many forms, but it always helps an animal survive, whether by hiding, warning or attracting a mate.