Peek-a-boo, where are you? How plants and animals use camouflage
Lizzie De Lusignan investigates how species use camouflage to survive and thrive in a changing world.
Article by: Lizzie De Lusignan
Artwork by: Leoni Fretwell
Lookdown fish have the ability to detect and manipulate polarised light for camouflage.
Animals and plants are able to hide themselves in a variety of different ways - blending in with their backgrounds, pretending to be a species they’re not… endless possibilities.
Camouflage is hugely important in the ecology of many species. In fact, it has been proven that the chance of an animal being killed and eaten is directly correlated to the level of camouflage.
Camouflage can be defined as blending in with the background and remaining undetected by potential receivers (for example predators or prey).
There are many different types of camouflage used in nature to enable species to avoid detection, some key examples have been outlined here as well as some of the challenges these species face in our changing world.
Types of camouflage:
1. Background matching
A widespread and simple form of camouflage is background matching, quite simply where an animal or plant blends in with the substrate where they’re usually found.
Examples include red deer, brown hares and nightjars, which all blend into the background of the undergrowth.
As well as matching the overall background, some species choose backgrounds which best match their colouration to improve their camouflage, for example, some moths improve their camouflage by repositioning themselves and nightjars choose nest sites which best match their plumage pattern, directly increasing the likelihood of survival of their eggs.
Whilst camouflage is well-researched and understood in animals, it is much more subjective in plants.
One example that has been tested is cryptic leaf colour in Corydalis hemidicentra, which has been shown to more closely match the background in their native habitat than other habitats in the eyes of butterflies, which appears to decrease feeding risk from the butterfly larvae.
Nightjars use background matching camouflage, choosing nest sites which best match their plumage pattern, directly increasing the likelihood of survival of their eggs.
2. Disruptive colouration
Another common form of camouflage is disruptive colouration, where an animal or plant has a ‘set of markings that creates the appearance of false edges…and hinders the detection or recognition of an object's…outline and shape.’
When Hugh Cott presented his ideas about disruptive colouration in 1940, he highlighted the vertically banded humbug damselfish which has both background matching and disruptive colouration in their coral habitats.
Some individuals of the same species also exhibit different colouration, known as polymorphism. For example, shore crabs found in mudflats are more likely to match the plain substrate. In contrast, those in rock pool environments were more likely to display disruptive colouration due to the more complex, multicoloured background.
3. Motion camouflage
Another consideration for camouflage is movement - nature is constantly moving and changing.
Zebra stripes may be a form of motion camouflage, where the striped patterns cause confusing visual illusions during movement, particularly when in herds. These stripes make it difficult for biting flies to land on the zebra, and potentially also help it to evade predators.
Stick insects may also display motion camouflage through behaviour as they appear to intentionally sway in the breeze to mimic vegetation.
In comparison, dragonflies use a very sophisticated form of active motion camouflage to appear stationary to their prey by moving in a way that mimics that of a stationary object.
4. Manipulating light
Camouflage also works differently in different light environments. For example, the natural illumination of the sun has led to countershading, a type of camouflage where animals are darker on the upper side of their bodies and lighter underneath.
This has been shown in sharks, as well as black-headed gulls, whose white belly is difficult to see when viewed from below against the bright sky and whose darker wings and upper body are difficult to see against the sea from above.
As well as adapting to light conditions, some species are able to manipulate it. Many fish have evolved the ability to detect polarised light and some, such as lookdown fish, have the ability to manipulate it for camouflage.
They use a layer of platelets within the skin to scatter polarised light in different directions making them seemingly invisible. It is most effective when at a 45-degree angle which is called a ‘chase angle’ as this is the direction from which a predator would chase a fish or a fish chase its prey.
In the deep sea, you can also find 'ultra black' fish which live in environments with very little light other than that caused by bioluminescent species. Avoiding detection by bioluminescent predators is key to survival, therefore these ultra-black fish have evolved scales that absorb and scatter the light rather than bounce it back, rendering them almost invisible.
Corydalis hemidicentra uses background matching camouflage to decrease feeding risk from butterfly larvae.
5. Changing colour
Some creatures go to even greater lengths to improve their camouflage, including changing colour and adaptive camouflage.
Colour change can occur very quickly in some species, such as cuttlefish which can change colour in a matter of seconds, over days in species such as some shrimp and crabs, and even over weeks in some species.
Over 20 mammal and bird species in the northern hemisphere have been shown to undergo complete seasonal colour change from brown in summer to white in winter, for example, mountain hares, ptarmigans and the arctic fox.
As well as seasonal triggers, predation risk can trigger colour change, for example, fiddler crabs can change colour within minutes and exhibit different colouration dependent on perceived risk.
Colonies with more predators nearby display cryptic (harder to see) colouration whilst colonies with fewer predators are more likely to have bright display colouration. If the perceived risk increases, then the bright crabs will change their colouration over a few days to become more cryptic.
Human influences on camouflage
As with many things in the natural world, humans have begun to influence camouflage, from altering environments to driving competition and even potentially inducing camouflage.
The Fritillaria devlavayi plant has been used in traditional Chinese medicines for over 2,000 years. It can be found in mountainous areas in southwestern China but there is considerable variation in colour between populations.
In areas that were more likely to be harvested by humans, the plants were more likely to be brown or grey to blend in with their habitat. As they have no natural predators, it's thought that this camouflage has evolved to avoid humans.
Other human-caused changes are also likely to impact the ability of some species to remain camouflaged in their changed environments.
Species that experience seasonal colour change are now at increased threat due to increased periods of camouflage mismatch where their colouration is obscure against the background as snowfall and snow cover duration have decreased and are predicted to continue to decrease.
For example, the snowshoe hare has experienced a drastic decline in survival due to their white winter coats being very obvious against the brown vegetation when there is reduced snow cover. However, it was shown that some habitats acted as a buffer for this mismatch by providing better cover.
Light pollution can also cause problems.
Many diurnal predators increase foraging at night in artificially lit conditions, meaning prey are under increased predation pressure. This has led to some prey showing increased vigilance when experiencing artificial light, for example, captive peahens.
It has also been proposed that some species that use colour change for camouflage may change colour more frequently under light pollution which may be energetically costly.
Fortunately, some species have shown themselves to be adaptable to changing environments.
A famous example of this can be found in peppered moths, which can be found in two colour morphs. During the Industrial Revolution, many trees in urban areas became covered in dark soot. As the dark colour variant of the moth was better camouflaged, they were more successful at evading predators and outlived the lighter colour morph.
Some species may also have the potential to adapt to changing conditions in response to the environment.
With camouflage so widespread throughout nature, it is both essential to ecosystems and an important area of focus for conservation efforts.
The impact of changing climates and environments cannot yet be fully predicted, but the variation in camouflage strategies and the presence of species able to adapt to these challenges should be a focus for research and conservation efforts as well as hope for the future.
This article was written as an online exclusive, as part of our Volume 4: Hidden Worlds series.
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