The working hypothesis here is that three basic types of camouflage might fool all visual systems. Meaning that every species deploys (at least) one of these three basic camo types, with species-specific elaborations on the chosen theme. But what is camouflage? We’ve pointed to a plausible evolutionary function: namely, the ability to fool other animals’ visual systems, making predation and evasion easier. While that might suggest what camouflage is for, it doesn’t tell us how that is accomplished in any particular animal. In order to answer that question, Hanlon and his team have extensively documented the camouflaging abilities of Cephalopoda, a class of the phylum Mollusca. Specifically these MBL scientists look at cuttlefish and octopuses, in the wild and in the lab.
Cuttlefish and octopuses are remarkably useful model organisms upon which to base studies of camouflage because of the remarkably dynamic nature of their camouflage abilities: they both change their camouflage depending on the background they’re against. This means that there must be a tight relationship between the visual system in these animals and their ability to manipulate their skin and body. Because of this fact, studying camouflage in these animals allows the scientist to study it as a visual phenomena from two directions: from the eye of the predator, whose visual system is fooled by this remarkable shifting, and from the eye of the prey, who has to extract relevant information from the environment and translate that into the complex body movements that alter the animal’s external appearance.
Hanlon and his lab’s extensive study of camouflaging animals suggests that most if not all camouflage is low-fidelity. That is, even in the most dynamic and skilled camouflaging animals, the task mostly isn’t achieved by becoming identical, or nearly so, to the background (hi-fidelity camo). Rather it appears as though good camouflage is an attempt to disguise the boundaries of a body by capitalizing on contrastive differences between patches of the coloration on the body and patches of coloration in the environment (low-fidelity camo). We’ve already seen how edge detection depends on the visual system’s exaggerating contrast between color fields (the Mach bands effect) in Hartline’s work. Camouflaging animals take advantage of this feature of visual perception by changing the color contrast of parts of their bodies against parts of the environment, thus hiding the location of the edges of their bodies. This can be seen in the first figure above, but perhaps the best way is to look at some of the videos produced about Hanlon’s lab. The New York Times’s science correspondent, Carl Zimmer, produced a video overview of Hanlon’s work that shows some of his best field and lab work. Additionally, Hanlon has a three part series of video web lectures with iBiology.org that explore all the details of this work and include man breathtaking filmed examples of dynamic camouflaging abilities.