Friday Weird Science: Sssssnakes can ssssmelll your menstrual ssssecretions

Feb 10 2012 Published by under Friday Weird Science

After last week's post on whether the bears can smell the menstruation (hehe, I can't get over that quote), I was inundated with questions and tips for papers. People asked if menstruation attracted sharks (answer: no one has tested it, right now shark attacks are 9.2:1 male:female, but that's probably due to differences in being in the right place at the right time, rather than being on your period. But I think I need to dangle some bloody tampons in shark infested waters...for science), if dogs were attracted to the smell of menstruation (I've been looking and looking for studies, but apparently that hasn't been done either), all sorts of things. But the vast majority of these studies...haven't been done. From all the stories I've heard of animals being attracted to menstrual blood, you'd have thought every female Homo sapiens on the planet would be ripped apart by wolves the instant she started menstruating.

But we're all still HERE. So I have to think that, until there are studies proving otherwise, most other mammals, and hopefully sharks, don't really care if you're seeping a little bit of endometrium from your nether regions.

But there IS one species, apparently that DOES care.

The brown tree snake.

Chiszar et al. "Response of brown tree snakes (Boiga irregularis) to human blood" Journal of Chemical Ecology, 1993.

The brown tree snake is native to the South Pacific, but is apparently a major pest in Guam, where it was introduced accidentally after World War II. It's nocturnal, lives generally in trees, has a wide variety of teeth (two of which inject venom, but the venom is not dangerous to adult humans), eats almost anything, and is generally between three and six feet long. In Guam it's been a major problem for causing power outages, apparently by weighing down powerlines.

From the descriptions of the brown tree snake, I'm now getting the terrifying idea of a bigass snake that will cut the power, sneak up on you through the trees, and DROP ON YOUR HEAD FROM ABOVE AND ENVENOM YOU TO DEATH. Though apparently it's not that bad, just annoying (at least in Guam, where they use dogs to keep it from spreading to other islands and try to keep it away from people's pets and small children).

But there is this threat...ladies, this snake likes your menstrual blood.

So apparently the idea for this experiment came from Brown tree snake attacks on babies in Guam. The authors inferred that the snakes were attempting to eat the babies (mmmm, delicious babies), and wanted to know why. They hypothesized that, since snakes are attracted to the smell of blood, the snakes were finding the babies because they were smelled the discarded feminine products of the mothers which were in the trash. Because apparently all of these babies had menstruating mothers who kept their used tampons in the trash in the baby's room? I'm a little skeptical of the logic of this train of thought, but that's how they told it.

So in order to test this hypothesis, the authors took 10 captive snakes. They presented the snakes with used or unused tampons (moistened with water), and watched to see what the snakes did. They measured how often the snakes flicked their tongues at the tampons (evidence that they were chemosensing), and advanced toward the tampons. However, the snakes were not allowed to STRIKE at the tampons (though apparently they had this problem anyway) due to inability to retrieve said tampon from a very ornery snake.

And then they got their results. The pictures are, predictably, kind of awesome.

I happen to loathe when people put all their data in tables, so I'm going to graph this for you.

It's pretty obvious that them snakes really like some menstrual blood!

The authors concluded that human blood (in this case menstrual blood) attracts brown tree snakes. But we don't know if it's human blood, or menstrual blood specifically. In order to prove that, we'd need more tampons, this time with regular blood (apparently none of the authors were willing to make that particular sacrifice for this paper).

They also talked about not leaving your post-partum blood and menstrual blood around your baby, as it might be unduly attractive to snakes. I'm not so sure about this. I mean, even IF the bloody items were in the same room as the baby, I'm sure the snake could tell which was which. Snakes not only have chemosensing, they can sense HEAT. So if forced to choose between the cold bloody tampon in the trash and the warm delicious baby...well let's just say I don't think the snake cares about the tampon in comparison. You'd have to have bloody items right up ON the baby to really say it was making a difference. Brown tree snakes eat small mammals all the time, I think it's not too much to assume that a baby on its own is plenty attractive to them regardless of whether or not there's blood around (mmmm, delicious babies).

But the moral of the story is that, if there's any animal out there that likes your used tampons, it's the brown tree snake. Oh well, at least it's not bears.

Chiszar, D., Dunn, T., & Smith, H. (1993). Response of brown tree snakes (Boiga irregularis) to human blood Journal of Chemical Ecology, 19 (1), 91-96 DOI: 10.1007/BF00987474

8 responses so far

  • Lyndell says:

    Fantastic! What an odd little study, although very interesting. I actually lived in Guam, where I am happy to report that I never once ran into a brown tree snake, nor did I find tampons missing from my trash. 🙂

    I will say that I lived on Andersen AFB, and they were very active in controlling their numbers. The brown tree snake situation was much worse in the past, and is well controlled on parts of the island with jack russell terriers. I'm sure it's still bad in areas that are mostly boonies (bush/jungle). The military patrols the base boundaries with terriers, keeps brush from getting too overgrown, and uses terriers to inspect containers entering and leaving the island. I hope the bird populations are's been 10 years since I've been there...because that's been the biggest problem with the introduction of the brown tree snake.

  • Connie says:

    While I don't have any experience with snakes and their intentions towards my menstrual blood, I do have anecdotal evidence for dogs.... (of which I own three, another dog died a few years ago). The female dogs (n=2) don't care whether I am menstruating or not (I use tampons), and they ignore tampons left in the trash. The male dogs (n=2) did not care about me menstruating either (at least they did not sniff my crotch more often), but they were inclined to ransack the trash and eat the tampons. It might just be, however, that they are a little less well-behaved than the ladies....

  • Tara says:

    There *must* be something about dogs. Every guy I've talked to from the U.S. military who told me they've done time there has told me that women shouldn't be allowed to do front line fighting with men because dogs can smell the menstruation from miles away. They do get vague though when you ask if the dogs can tell the difference between menstrual blood and blood from wounds.

    * Note: For me, this amounts to about 7 people. Small sample size, but I'd hope with an excuse that consistent, the information comes from somewhere.

  • Attached is a classic article in Physiological Psychology demonstrating that snakes may detect certain steroids. Probably there are other studies showing which non-human animals respond to chemical components of menstrual blood...then one could perform tests on those taxa such as the neat study you describe...David Crews (UT-Austin?, formerly @Cornell) could probably address a lot of the questions you raise...

  • janvones says:

    Doesn't the Book of Genesis cover the eternal enmity of woman and snake?

  • Ron says:

    Years ago I worked in the Arctic and occasionally we would have women scientists and staff. They had to tell the base security if when they were menstruating and the Polar Bears scould smell it miles away and would come over to the camp.

    If a menstruating woman wanted to do an experiment outside she needed an armed guard, to protect from the bears.

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