Concealing Coloration in Animals

Concealing Coloration in Animals by Judy Diamond and Alan B. Bond was a short scientific analysis of camouflage. It was divided into four parts: concealment, perception, isolation and detection. I found the chapter on mimics, referring to species which evolved a camouflaged identity that copies others in order to take advantage of their life experience, to be the most interesting. The authors also covered evolutionary islands, whether surrounded by water or not, in describing how species adapted to their environments based on their limited areas. Thus they came to the conclusion:

“The association between the degree of genetic isolation and the occurrence of local forms that closely match the hue of their backgrounds is one of the strongest indications of the role of natural selection in the evolution of concealing coloration.”

One of my favourite birds is the kakapo, the largest species of parrot. It is flightless and camouflaged in the low-lying New Zealand greenery. However it has no native predators–at least none that predated European settlement. Why then would it be both flightless and camouflaged? Didn’t birds lose their ability to fly because of the absence of predation? And on the other hand, wouldn’t the presence of predators lead natural selection to develop camouflage in those birds that are preyed upon? The fact is that up until the mid-fourteenth century, the kakapo did have a native predator: Haast’s eagle. It was the largest eagle that ever existed. Thus “[t]he kakapo’s mossy coloration might be a kind of fossil camouflage, an adaptation to a predatory interaction that no longer exists.” This piece of history illustrates the concept of “time travel” below:

“Coloration is influenced by physical and chemical properties, the behavior and development of the animal, the structure and complexity of the environment, and the visual systems and cognitive abilities of predators and prey. Studying animal coloration is an exercise in time travel, illuminating the conditions of the past that have produced the diversity of the present.”

The book was illustrated with beautiful colour photos of the animals it describes, which is a must in any book about camouflage. If you have ever wondered how some animals developed such eerie resemblances to their environments, Concealing Coloration will help the reader grasp the concept of natural selection. A brief book but highly enlightening.

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