This year marks the 10th anniversary of National Geographic’s Sharkfest, and the NatGeo channel is marking the occasion with an interesting new documentary that explores whether great white sharks can change their color to hunt more effectively. Huh. camo shark Ryan Johnson and graduate student Gibbs Kuguru, a marine biologist and research coordinator for the Blue Wilderness Research Unit, in the field as they attempt to gather evidence to support the hypothesis that these marine predators make dermal cells in their skin. Can change as a means of changing color. camouflage
A New Zealand native, Johnson grew up in a beachside town, absorbing the conventional wisdom that dolphins were the “good guys” and sharks were the “bad guys.” When he decided to become a marine biologist, he wanted to work with dolphins. When he was 20, he had the opportunity to do some research on great white sharks in South Africa, which were facing extreme fishing pressure at the time, leading to an increase in shark attacks.
“They had become very popular just as a delicacy,” Johnson told Ars. “The shark fin soup business went crazy, and [sharks] Mass killings were taking place. It was a wake-up call for me. I realized that it needed attention, at least from my point of view, much more than the dolphins.”
Since then, Johnson has studied questions such as whether the great white shark cage-diving industry makes sharks increasingly dangerous to humans and has conducted satellite and acoustic tracking of great whites. They have also studied the impact of eco-tourism on sharks, investigated the bite strength of great whites, and studied predator-prey games between great whites and the seals they hunt.
Based on his field experience, Johnson had long thought that great white sharks might be able to change their color. Shark scientists identify specific animals by their dorsal fins, markings, and other distinctive markings. Often, he recalls, he and his team would see one light-colored shark in the morning and another dark-colored shark in the afternoon and assume they were two different animals. “But then you’ll go back and look at the pictures and think, ‘Ah, this isn’t a new shark. That’s it. The dorsal fin marking is the same,'” Johnson said.
Then he met Gibbs Kuguru, who was doing his PhD work on color change in blacktip sharks in the Maldives. “I said, ‘Hey, man, what if I told you that great blondes change their color too? Johnson remembered. Kuguru thought the idea sounded appealing, and the pair began researching the topic. For example, they found cases of sunbathing from hammerhead sharks and some rays that could change their colour.
Other previous studies have found that zebra sharks change color as they age, and rainbow sharks can sometimes lose color due to stress and aging. And as we reported in 2019, a new family of small-molecule metabolites in the lighter parts of the swell shark’s skin (cephalosilium-bellied) and chain cat shark (scyliorrhinus retifer) enables them to absorb blue light in the ocean and essentially turn pale green, making them appear to glow. (The phenomenon is known as biofluorescence, not to be confused with a related phenomenon, bioluminescence.)