Written by: Craig Glatthaar
I wasn’t planning on surfing, but with a light northwesterly wind cleaning the faces of corduroy lines I couldn’t help myself and paddled out from the beach at Muizenberg in Cape Town, like I had done a thousand times before. It wasn’t 15 minutes in and something rather larger splashed next to me.
I caught the eye of another surfer who was also now staring through the clear water and we both agreed it was probably a big seal, like we had seen, a thousand times before. Another few minutes passed as I chatted to another board rider. We were just on the verge of solving all the world’s problems but mid-sentence my fellow wave slider stopped. His eyes doubled in size and his mouth stayed open but no words came out. I glanced over my shoulder and there it was, a scarred, deathly grey fin cutting the surface of the water.
Your brain immediately tells you it’s not a dolphin, it’s not sickle shaped and is cutting cleanly through the water as opposed to porpoising up and down. You try to tell yourself it’s a sunfish or common mola, but it’s certainly neither floppy nor slow.
The grey bus gently cruised right under the front of my board. I was straining to see it, I could clearly make out my feet and legs dangling a few feet beneath me, but struggled to make out the outline of the great white shark. Then I saw it, the head was enormous, I could never have imagined such girth. The eye was about the size of a black billiard ball.
It’s funny how the brain works when adrenaline floods the mind. Instinctively I lifted my feet, the movement clearly scared the shark, for with a whip of its tail it was suddenly gone.
It only took a few seconds of me trying to steady myself in the turbulence from its tail and I immediately started to practice my walking on water skills. When I got to the beach, a fellow surfer came up and hugged me, “that was close” he said. I spent the evening reflecting on those words – that was close – an ominous warning that I had survived, but survived what? I didn’t feel the same way one does when walking away from a car accident, or after dodging a closely cancerous skin check, I felt rather privileged. So the next day I paddled straight back out there. I won’t lie, shark shadows plagued the brain, but for the first time I was more at ease with the outcome of meeting one of the giants of the deep than I had ever been before.
The most amazing element of my recent shark experience was the difficulty with which it took to see the shark that only passed a few feet in front of the nose of my surfboard. In perfectly clear water, I could easily see my feet, but struggled to see a ton or two of great white beneath me. It all has to do with the top-deck affect, or more scientifically called countershading. Thayer’s law is a simple yet visually complex concept that describes the way animal patterns or colouration helps them to remain well camouflaged. The simple rule is darker pigmentation on the upper side versus lighter pigmentation on the underside. It’s found in a delightful number of species, from insect to birds, mammals to reptiles, and clearly fish too.
When light falls on a uniformly coloured object such as a sphere from above, it makes the upper side appear lighter and the underside darker. This pattern and change in light and shading can make the object appear completely solid. This of course is counter productive if you’re trying to camouflage yourself either in defence or attack. Countershading by counterbalancing the effects of this self-shadowing helps reduces the ease of detection of predators and prey. You don’t have to go swimming with great white sharks to see this adaptation, your less toothy and friendlier impala is a perfect example of this trick.
Camouflage in the animal kingdom starts to get tricky when you consider the reverse of countershading, with the underside is pigmented darker than the top side, which enhances contrast and makes the animal a lot more conspicuous. This pattern is rather used to startle or in displays as a signal to warn away would be predators. It is therefore more commonly found in animals that can defend themselves, like honey badgers or striped polecats.
Abbott Handerson Thayer is often credited as the father of modern day military camouflage and it was his theory in 1892, where he proposed that all animals were cryptically camouflaged and often through forms of countershading. He was sadly vigorously attacked by Theodore Roosevelt on this theorem, but after experiencing this concept first-hand, I’m inclined to agree with Thayer’s Law.