We all know camouflage when we see it, or when we don’t, as the case may be. But what does that actually mean?
“Qualitatively, it’s pretty easy for people to say ‘that’s camouflaged’ or ‘it’s not,’” says Roger Hanlon, a senior scientist at MBL, whose research focuses on camouflage in marine animals. “But to grade camouflage or to quantify it somehow, really has hardly ever been attempted until very recently.”
Camouflage is everywhere in the natural world – every branch of animal life, every habitat. It’s understood to be a critical survival tactic. And yet, when Hanlon first looked for studies probing how camouflage works, he came up empty handed.
“Camouflage is the least studied subject in biology that we think we already know about,” says Hanlon. “People think they know what it is, but as you dig a little deeper you get into visual perception. And now it gets a lot more interesting, but a lot more complicated.”
Hanlon’s research group has been attempting to nail down camouflage for ten years, and they’ve learned a few things. First and foremost, quantifying camouflage is difficult. Second, contrary to popular opinion, camouflage is not about matching the background.
Rather, Hanlon’s lab has identified just three types of patterns that make it difficult to distinguish an animal from its surroundings. On a simple background, uniform coloration may do the trick. In more complicated settings, a mottled, or splotchy, pattern may do the trick (think military camo). But the most underhanded – and scientifically contentious – trick is something called disruptive coloration, in which bold lines or patterns create the optical illusion of edges and obscure the true outline of the animal.
Those three strategies turned up early in Hanlon’s efforts to categorize camouflage patterns. He sat down with around a hundred photographs of camouflaged cuttlefish and sorted them into piles that – purely instinctively – looked similar to him.
“I was expecting, with the hundred-some pictures I began with, to get - who knows – five, ten, fifteen piles of look-alike pictures,” says Hanlon. “But I didn’t. I was very surprised. I only got three or four little piles.”
Hanlon’s first thought was that he was missing something, and needed more pictures to find it. But, after nearly a decade of study and more than 100,000 photographs (of a wide array of animals, not just cuttlefish), it’s still just three or four piles. Those same patterns explain every case of camouflage Hanlon has examined to date.
The question now is, why? Hanlon thinks it’s an indication of a widely conserved weakness in animal’s visual perception that prey species have evolved, time and again, to exploit. Much of the focus in Hanlon’s laboratory has shifted to understanding how predators see their world. If quantifying camouflage was hard, this new challenge promises to be even harder. For Hanlon, that’s part of the fun.