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

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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.

Could Gigantic Coconut Crabs Have Played a Part in Amelia Earhart’s Mysterious Disappearance? At Least One Scientist Thinks So

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Getty Images

Amelia Earhart's disappearance during her attempt to fly around the world has captivated historians and conspiracy theorists for more than 80 years. One organization is now suggesting that her fate may have been sealed by giant crabs.

The International Group for Historic Aircraft Recovery (TIGHAR) believes that Amelia Earhart and navigator Fred Noonan may have landed their plane on Nikumaroro Island when they couldn't find their target, Howland Island, and that Nikumaroro's endemic crustaceans may have played a part in the ensuing mystery.

According to National Geographic, there are several clues supporting TIGHAR's theory. The large reef that hugs Nikumaroro’s coast makes it conducive to emergency aircraft landings. In 1940—just three years after Earhart’s disappearance—British colonists found 13 human bones beneath a ren tree on the island and shipped them to Fiji, where they were lost. The colony's administrator, Gerald Gallagher, sent a telegram back to England positing that it was Earhart’s skeleton. Then, in 2001, researchers uncovered U.S.-made artifacts around the ren tree including a jackknife, a woman’s compact, a zipper, and glass jars. The plot thickened even further in 2017, when four forensic bone-sniffing dogs all indicated that a human had indeed died at the site, though excavators failed to dig up any more evidence.

If those 13 bones beneath the ren tree did belong to the unfortunate castaway, where are the rest of her remains? Tom King, TIGHAR’s former chief archaeologist, thinks that coconut crabs can answer that question.

Nikumaroro is home to thousands of the colossal creatures, which can grow to a terrifying 3 feet across and weigh 9 pounds. They’re sometimes called robber crabs because of their penchant for absconding with objects that smell like food, and they’ll eat practically anything—coconuts, fruit, birds, rodents, other crabs, their own discarded body parts, and carrion.

It’s not unreasonable, then, to think that coconut crabs may have feasted on Earhart’s corpse and then taken her bones home with them. In one experiment to test the theory, TIGHAR researchers deposited a pig carcass on the island and filmed the aftermath. With the help of small strawberry hermit crabs, coconut crabs stripped the pig down to the bone in two weeks. After a year, some of the bones had been dragged 60 feet from the carcass’s original location, and some were never recovered at all.

King believes Earhart’s missing 193 bones could be hidden in the burrows of various coconut crabs. As in the pig experiment, crabs may have scattered some of Earhart’s bones dozens of feet away, but maybe not all of them—after all, the forensic dogs smelled bones near the ren tree that haven’t yet been located. Right now, TIGHAR is working with the Canine Forensics Foundation to further explore the area.

While we wait for more answers, dive into these other theories about Earhart’s disappearance.

[h/t National Geographic]

The Cat Sanctuary That Sits Near the Ancient Roman Site Where Julius Caesar Was Murdered

ClaireLucia/iStock via Getty Images Plus
ClaireLucia/iStock via Getty Images Plus

Cats will sleep anywhere—even in ancient ruins. Located in Rome, Colonia Felina di Torre Argentina is a cat sanctuary on the site where conspirators stabbed Julius Caesar 22 times outside the Theatre of Pompey, on March 15 44 BCE. Centuries later, in 1929, Mussolini excavated the area to reveal four temples that are 20 feet below the street level. Today, it’s the oldest open-air spot in Rome.

Bystanders can view the temple complex known as Largo di Torre Argentina from the fenced-off street, but according to Conde Nast Traveler, after a $1.1 million restoration process, the sanctuary will open to tourists in the second half of 2021. For now, the only living things allowed in the sacred area (area sacra) are feral cats.

According to Colonia’s website, they are "the most famous cat sanctuary in Italy” and also the oldest in Rome. Many of the cats fall into the special needs category: Some are disabled, missing part of a paw, or are blind; the special needs and elderly cats live in a walled-off area. Volunteers—a.k.a. gattare, or cat ladies—take good care of them, and some cats are available for adoption.

Atlas Obscura reports that “since the mid-1990s, the population has grown from about 90 to a peak of 250” cats and notes that the sanctuary has a spay/neuter program. From the street, visitors can watch gatti like the three-legged Pioppo and Lladrò—known as “poisonous kitten” because of how angry he was when he got there—sunbathe and sleep under pillars.

It’s unclear if the cats are respecting Caesar or disrespecting the fallen leader. However, a gift shop is open to visitors, and people can donate money toward the cats and/or volunteer.

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