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Are sharks really attracted to menstrual blood?

Are sharks really attracted to menstrual blood?

Shark Week just wrapped — we’re referring, of course, not to the period euphemism, but to the eight-day shark-filled TV marathon on the Discovery channel. But some think there really is a link between our periods and sharks — a deadly one. Even professional surfer Laird Hamilton recently told TMZ, “The biggest, most common reason to be bitten is a woman with her period, which people don’t even think about that. Obviously, if a woman has her period, then there’s a certain amount of blood in the water.” So, is there any truth to Hamilton’s claim?

Simply put? No. The common misconception is just that — a misconception. One that seems to stem at least somewhat from a misunderstanding of how much blood we lose during an average period and of how strong a shark’s sense of smell really is.

It’s true that sharks have a great sense of smell, which is possibly how this myth got started in the first place. According to the American Museum of Natural History, sharks have a super sensitive olfactory system — their nostrils are used only for smelling, not breathing, and they’re lined with specialized cells that are extremely sensitive. The olfactory bulb in their brains are enlarged, too. Some species can detect tuna oil at one part per 25 million, aka about 10 drops of tuna oil in an average-sized home swimming pool. Other species of sharks can detect prey at one part per 10 billion — basically one drop of blood in an Olympic-sized swimming pool.

When you put it like that, it’s easy to make the jump to myths about sharks picking up on the scent of human blood and making a beeline for it. But the average woman loses 30-40 milliliters of blood during each cycle — that’s 30-40 milliliters over the course of days, not a single dip in the ocean. Hardly exciting enough to get a shark’s attention — and if it were enough, everyone who’s ever splashed around in the ocean with a scrape or cut would have to be worried, too. Not to mention, more than 90 percent of shark attacks have occurred on males, according to George H. Burgess, Director of the International Shark Attack File at the Florida Museum of Natural History.

Sharks don’t even find our blood all that tasty. “Our blood is different from a sea otter’s blood or cetacean blood,” shark behavior expert and head of nonprofit research and conservation group Shark Research Committee Ralph S. Jones tells Mother Jones. “Our blood is from a terrestrial environment.” Translation: sharks are not all that interested in human blood.

Bottom line? There’s no evidence you should cut your beach day or surfing lesson short on account of sharks if you happen to get your period.

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