This Broadclub cuttle fish (Sepia latimanus) can go from camouflage tans and browns (top) to yellow with dark highlights (bottom) in less than a second.
An animal’s ability to blend into its environment and avoid detection, otherwise known as crypsis, can be a valuable, anti-predator, defence mechanism.
The best-known form of crypsis is camouflage, a technique found in a huge numbers of animals. Predators use it to sneak up on lunch, and prey attempt to blend into the background to avoid the hungry hunters.
Even colourblind animals can succeed in transforming the colour of their skin to imitate their surroundings. A recent study looked into what makes camouflage an effective tool in the defence against predators in octopi and squid (Coleoid cephalopods).
It is assumed that certain elements in the immediate surroundings of these animals, such as brightness and size of surrounding objects, are vital in extrapolating camouflage patterns.
The study assessed how cephalopods achieve a close colour match to their environment despite lacking colour vision. The scientists used an imaging technology, known as hyper spectral imaging, to precisely measure the colour similarity between the animal and the background it had intended to imitate. The imaging device uses a camera which detects 540 colours far beyond the simpler red, blue, green vision of the human eye.
These data enabled scientists to assemble an image from the perspective of a predator. Cross matching the colour vision of a potential predator of a cuttlefish with the colour that was actually present revealed that the contrast between the prey and the background lay in the brightness rather than colour. This means the predators have to spot the variation in brightness to help identify the camouflaged prey.
“So much is unknown about how predators actually see their prey. Using hyper spectral imagery tools is a huge advance in getting us the information we need to model predator vision,” says Kenneth Wickiser, an imagery specialist involved in the study.
“We hope our work takes us one step closer to understanding how a colour-blind animal adopts near-perfect camouflage in a variety of backgrounds.”
Image courtesy of: Nick Hobgood via Wikimedia Commons.
Chiao CC, Wickiser JK, Allen JJ, Genter B, & T Hanlon R (2011). Hyperspectral imaging of cuttlefish camouflage indicates good color match in the eyes of fish predators. Proceedings of the National Academy of Sciences of the United States of America PMID: 21576487
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