Are Most Shark Attacks Caused by Women on Their Periods?

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Since I started surfing a few years ago, I’ve become very interested in the lives of professional surfers. I follow them on social media so I can see awesome videos of them surfing waves, but unfortunately that means that I’m also often exposed to their personal opinions, which sucks because a lot of them are gigantic morons.

I don’t mean to single out surfers, here, because I’m sure all sports have their share of morons. But today I want to talk about Laird Hamilton, one of the best big-wave surfers in the world. And when I say “big wave” I mean “big fucking wave,” like this dude bombs down 50-foot waves like nobody’s business. It’s really impressive.

That might qualify him as a gigantic moron to some people, but for me he didn’t actually reach that status until this week, when he told TMZ that in regards to shark attacks, the “most common reason to be bitten is a woman with her period, which people don’t even think about that. If a woman has her period there’s blood in the water.”

As a woman, I’ve been blamed for lots of things, like earthquakes in Iran, rape epidemics, and the ultimate destruction of the atheist movement as we know it, but this is a new one. Let’s take a look at Laird’s factoid and see what may be wrong with it.

First of all, I was curious about the statistics. If menstruating women are the primary reason for most shark attacks, it stands to reason that they’d be bitten more often than men. Unfortunately (or fortunately if you’re a woman, I guess), of all the shark attacks we have on record spanning several centuries, nearly every one has had a male victim. Only about 6% have involved women. The number of women is growing, because sharks don’t actually think men taste better — it’s just that men are more likely to be in the water doing things that make them look like delicious seals and other things that are actually on sharks’ menus.

So only 6 out of 100 shark attacks involve women, and of those we have no data to tell us whether or not those women were menstruating at the time of the bite. But even if we assume that 100% of them were, there’s still absolutely no way that that could be, and I quote, “the most common reason to be bitten.”

All this got me wondering, though, are sharks more likely to attack a woman who is menstruating?

That’s a lie, actually. It’s something I wondered two years ago when I started surfing. I mean come on, I’m in San Francisco, where we have more Great Whites than Republicans. I’m not going in the water if there are a few days a year that make me tastier.

So I looked into it, and it turns out the answer is “probably not.” There haven’t been any double-blinded studies on this, which is pretty unfortunate and I for one would like to volunteer to hang out in a shark cage while on or off my period for the good of science. But there was a small study done in the late ‘60s that found sharks in the open ocean weren’t interested in menstrual blood (and in fact were only interested in human gut liquid, of all things). And there are loads of female divers and surfers who report being in the ocean around sharks on their period and experiencing no problems.

Women only menstruate an average of one to six tablespoons of blood over the entirety of their cycle, which means at max we’re talking about a tablespoon per day. Even if you’re in the ocean for six hours, that still only works out to less than a teaspoon of blood which, by the way, you’re probably still keeping inside your body with a menstrual cup or a tampon or a wetsuit. Sharks may be good at smelling blood, but if they’re close enough to smell less than a teaspoon of it contained inside your wetsuit, they’re close enough to already see and hear you splashing around.

To sum up, no, Laird Hamilton, menstruating women are not the primary cause of shark attacks, by any stretch of the imagination. Stick to big waves, and leave biology to the scientists.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor. Twitter @rebeccawatson Mastodon Instagram @actuallyrebeccawatson TikTok @actuallyrebeccawatson YouTube @rebeccawatson BlueSky

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