Scientists Can Tell If Great White Sharks Are Around by Testing DNA in Seawater

iStock
iStock

Love the beach but fear sharks? Your risk of dying in a shark attack is infinitesimal—roughly 1 in 3.7 million—but it’s still a risk nonetheless. Scientists say white sharks are becoming more prevalent along California’s coast thanks to federal protections, and on the opposite side of the country, Cape Cod recently saw its first fatal shark attack in more than 80 years.

A new proof-of-concept study, published in Frontiers in Marine Science, could shed new light on what's lurking beneath the surface. Researchers from UC Santa Barbara, the U.S. Geological Survey, and partner universities theorized that environmental DNA (eDNA)—an organism's cast-off bits of genetic material—could show the presence of white sharks in a particular part of the California coast.

White sharks forge distinctive trails by shedding skin and discharging mucus, feces, and other genetic markers in seawater. Researchers created a species-specific test for white shark eDNA, then rode stand-up paddleboards to four sites beyond the line of surf to collect water samples. After analyzing the samples in the lab, they found white shark eDNA in two samples from areas where the fish were known to gather, and no eDNA in the other two samples from sites where sharks hadn't been observed. The results from the preliminary experiment showed that the new test could accurately identify the sharks' eDNA—and that might save a surfer in the future.

"One of the goals of this research is for a lifeguard to be able to walk down to the shore, scoop up some water, shake it, and see if white sharks are around," Kevin Lafferty, lead author of the study, said in a statement.

The use of eDNA has some limitations. Ocean currents can cause eDNA to drift, and that genetic information can degrade quickly in the surrounding environment. “Another challenge is that eDNA might persist in the ocean environment for days, meaning a positive detection might indicate a species that is no longer locally present,” the researchers write in their paper. Still, they say the development is a step in the right direction for better shark monitoring and conservation efforts.

Friday’s Best Amazon Deals Include Digital Projectors, Ugly Christmas Sweaters, and Speakers

Amazon
Amazon
As a recurring feature, our team combs the web and shares some amazing Amazon deals we’ve turned up. Here’s what caught our eye today, December 4. Mental Floss has affiliate relationships with certain retailers, including Amazon, and may receive a small percentage of any sale. But we only get commission on items you buy and don’t return, so we’re only happy if you’re happy. Good luck deal hunting!

Can You Find the Doe Hiding Among the Stags?

Can you spot the doe?
Can you spot the doe?
Dudolf

Gergely "Dudolf" Dudás has a way of turning simple images into mind-numbing puzzles. Look closely at his amazing illustrations of squirrels, snails, and rabbits, and you'll find an object that doesn't belong in each one. This new image from the artist features a doe hiding in a crowd of stags, and it may be one of his toughest brainteasers yet.

Dudolf

Most of Dudolf's hidden image puzzles pair items that look similar. In the image above, the only difference between the doe and the stags surrounding it is the lack of antlers. You may have to study a lot of deer heads before finding the animal that's out of place. If you're feeling impatient, you can check the solution at the bottom of the page.

Dudolf has released many brain teasers inspired by the holidays. Pictures he's illustrated in the past include a sheep hidden among Santas, a snowman among snowflakes, and a panda among snowmen.

Looking for more ways to challenge your brain? See if you can beat these tricky puzzles.

 
 
 
 
 
 
 
 
 
 
 

Dudolf