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Tapping Into What a Deer Sees, and Doesn’t
By JOHN TIERNEY, NY Times, September 23, 2008
Approximately 30,000 years after hunters took to adorning cave walls with their image of a deer, it occurred to them it might be more productive to consider the deer’s image of a hunter.
This was not an easy task. Deer have not left cave paintings of any humans, much less of hunters in camouflage. Those manly overalls and caps splotched with green leaves and brown branches may have looked invisible in the catalogue and impressed the other humans back at the lodge, but what did the deer think of it? Were they just rolling their eyes at each other?
Eventually, though, a few deer were bribed to reveal their secrets. They were given food pellets in return for taking vision tests. The results were not good news for the camo-clad hunters — but ultimately not really good news for the deer either.
For now, thanks to decades of research into ungulate vision combined with the latest in military concealment technology, hunters can don a computer-generated camouflage with fractal designs that look nothing like a shrub or a tree, at least not to the human eye. Named Optifade, it’s being introduced this fall by W.L. Gore (the makers of the breathable Gore-Tex rain gear) and promoted as the first camouflage scientifically designed to make hunters invisible to deer.
The deer, as usual, are not available for comment, so these claims of invisibility cannot be directly verified. But the psychologists who worked with Gore to develop it — Jay Neitz, an animal-vision expert at the Medical College of Wisconsin, and Timothy O’Neill, who pioneered the United States Army’s digital camouflage as a researcher at West Point — say they’re confident the deer will be fooled.
“A camouflage that makes a person look like a tree can work if you’re in a place where other trees look like that,” Dr. Neitz says. “But what if you’re somewhere else, or if the deer sees you move? This new camouflage is a totally different approach. It fools the deer’s vision system at its roots, so that it doesn’t recognize the person as anything.”
At Dr. Neitz’s laboratory, he tests some animals’ vision by training them to press touch screens, but the deer weren’t quite ready for the computer age. He and researchers at the University of Georgia showed them three cards at a time and rewarded them with food pellets when they picked out the right pattern by pushing a button with their noses.
“We can measure in animals anything you can measure in a human being and every bit as accurate,” Dr. Neitz says. “The difference is that a vision test that might take 10 minutes in a human can take six months.” The research revealed that deer vision is a little blurrier than human vision — about 20/40 — and that deer see the world roughly like a human with red-green colorblindness. Their eyes have only two color receptors (unlike the three in the human eye). Fortunately for hunters, they have a hard time seeing blaze orange.
But they’re more sensitive than humans to light at the blue end of the spectrum. And thanks to the eyes on either side of the head, they can see a field of vision covering 270 degrees.
Once they had assessed the deer’s visual strengths and weaknesses, Dr. Neitz and Dr. O’Neill worked out colors, textures and shapes with Guy Cramer of HyperStealth Biotechnology, a company that designs military camouflage. Mr. Cramer’s computer algorithms create fractal patterns that exploit a couple of ancient tricks used by animal predators.
The first and most obvious trick is to fade into the background, as a leopard’s spots enable it to do while it’s patiently waiting to ambush a prey. The spots aren’t shaped like leaves or branches, but they form an overall “micropattern” matching the colors and overall texture of the woodland background.
That trick, though, won’t work for a predator on the move, which is why a tiger doesn’t have spots. It has a “macropattern” of stripes that break up the shape of its body as it’s stalking or running.
“The prey can detect the tiger’s movement,” Dr. Neitz says, “but if the shape isn’t recognized as the outline of a tiger, nothing registers in the higher center of the prey’s brain.”
After 19th-century naturalists and 20th-century psychologists analyzed these camouflage techniques, military researchers worked out formulas for the optimum patterns. Before he retired from the engineering psychology department at the United States Military Academy, Dr. O’Neill developed the type of pixelated digital camouflage — made up of tiny colored squares — adopted in the past decade by many armies.
“The essence of digital camouflage goes back to the old question: Is the purpose of camouflage to match the background or to break up the shape of the target?” Dr. O’Neill says. “The answer is yes — you do both. You create a micropattern that matches the ‘busyness’ of the background and makes it harder to detect the target, and you overlay it with a macropattern that makes it harder to recognize the shape of the target once you’ve detected it.” (For a look at these patterns, go to TierneyLab.)
But no matter how carefully the patterns have been computed, no matter how precisely the new hunter’s digital camouflage is calibrated to deer’s vision, there remains one large uncertainty: Will hunters wear overalls covered with pixelated squares that look like computer-generated abstract art? Or will they stick with their traditional preference (see cave paintings) for representational art?
Getting soldiers, at least the male ones, to switch to digital camouflage wasn’t easy, Dr. O’Neill says, because for many men camouflage is less about invisibility than fashion. Some soldiers hung on to the old-fashioned designs because of what Dr. O’Neill called the C.D.I. factor: Chicks Dig It.
If male hunters feel that way about their old overalls, there may still be lots of shrubs and trees toting guns and bows during hunting season. These guys may or may not be right about women going for this look. But the deer probably appreciate it.
