Great White Sharks Show Color-Changing Ability to Camouflage

Scientists stumbled upon the possibility that great white sharks can alter their skin tone to blend in, similar to the camouflage abilities of other animals.

Ryan Johnson, a shark biologist, and Gibbs Kuguru, a shark geneticist, collaborate on the new National Geographic Sharkfest film Camo Sharks to explore whether great white sharks can alter their color for camouflage and to blend into the environment, similar to other marine animals like squids or octopuses.

After years of working with white sharks, Johnson claims that he began to notice individuals who had slightly different skin tones from the norm. This led him to conclude that white sharks may be a species that can alter the color of their skin.

Shark Behavior

Possible Camouflage Ability of Great White Sharks Merit Nat Geo On-Show Research

(Photo : Photo: Oleksandr Sushko / Unsplash)

There needed to be a control to compare with to demonstrate that the sharks were indeed changing color. To photograph a grayscale color board alongside the sharks they were studying, Johnson and Kuguru devised a plan. They could then standardize the lighting using Photoshop. Sharks aren't the most cooperative models, so this proved to be difficult.

When the sharks breached, which is a hunting maneuver, as well as when they were swimming at the top and scavenging at the bottom of the water column, the researchers wanted to measure the color of the animals. They traveled to Seal Island, a shark hotspot off Cape Town, South Africa, and used a decoy seal as bait to entice the sharks to breach. The Sharkfest hosts used a drone and a remote-controlled boat with a color board attached to capture casual swimming behavior, and Johnson used a dive cage to capture footage of the sharks in deeper waters.

All in the Lighting?

The results of the color board tests appeared to show that, despite the color board's control for lighting conditions, individual sharks, distinguishable by scars and other distinctive characteristics, did indeed appear in different colors in various scenarios.

The scientists also needed to provide evidence that sharks can camouflage, so they looked for molecular evidence in the skin cells. Melanocytes, which produce melanin as the cell contracts, are found in the skin cells of species that have been observed to change color quickly.

The researchers intended to subject shark skin cells to a variety of hormones, including adrenaline, melanocyte-stimulating hormone (MSH), and melanin itself, to determine whether the sharks could physically change color. Using a dart gun, they collected the sharks' skin cells and transported them back to the lab.

To the researchers' surprise, the melanocytes in the shark cells dispersed when they were exposed to MSH, darkening the tissue. The tissue's color lightened when it was exposed to adrenaline. The tissue turned into a mixture of light and dark when melatonin was present.

These outcomes came from a remarkably small sample size of just three sharks, though. For the results to be statistically valid, more data must be gathered, Newsweek reports.

Even though the documentary's findings aren't yet ready for publication in a peer-reviewed journal, the researchers are thrilled to have the chance to make a movie that focuses on the research process rather than just the findings.