Sharks and Periods.....

[Coogeeman]

I know that this is a sensitive subject but I need an oppinion.....

I led a class not that long ago to a cave where I knew there to be between 10 and 20 grey nurse sharks. Thats why we were doing the dive, to see the sharks.

Just before the dive, one of the women on the trip took me aside and said that she was having her period, and would this effect the behaviour of the sharks. I immediately said no, because I hadn't heard of anything like that altering the behaviour of sharks, and I've been diving for 16 years.

However during the dive I kep a close eye on here and her partner and sure enough I noticed that one of the larger sharks (10ft or so) started to act very agressive when it came near her. In fact at one stage as it went past her it whip cracked its tail which is a sure sign that soimething was annoying it. And you can hear the crack under the water. Its very distinctive.

At that point I went over to her and took her by the hand, she was shaking, and got her out of there. So..has anyone heard of this happening before and is it an issue that we should be thinking about before leading these sort of dives?

Coogeeman

 

[otter-cat]

The blood cells and tissue that are discharged during menstruation are essentially old & dead, and are generally of no interest to sharks, who can tell the difference between that and fresh, live blood cells from an injured organism.

There is some research to suggest that in cases where sharks have attacked divers who were carrying fish they had caught while spearfishing, the sharks were actually originally attracted by the electrical impulses given off by the agitated and struggling fish on the stringer, rather than by the scent of the fish's blood.

The shark may have been reacting to some actions and or postures being made by the woman (probably unconsciously) due to her heightened fear of the situation, despite your assurances to her.

Of course, I'm no shark behavioralist, so if I'm way off base, hopefully someone else can come along to enlighten us all.

 

[watersprite]

Coogeeman,

On this forum someone else asked the same question in this thread:

http://www.scubaboard.com/t26508/s.html

Hope that helps too...

Watersprite

 

[jbd]

if otter-cats first paragraph is true( and it has been mentioned several times) then why does chumming work to draw sharks in?

 

[DocVikingo]

IMHO, "otter-cats"' statement certainly is open to question, and, unless s/he desires to bring forth scientific reference or cogent argument, I'll suggest that my long post within the thread kindly provided by "watersprite" does refute it.

Best regards.

DocVikingo

 

[otter-cat]

The information about sharks from my earlier post in this thread was obtained a while back from another thread in the women's forum that was not specifically about sharks and menstruation, but the subject came up within the thread. I'll try and dig up the original one that I saw, and see if it references the source of the information.

Incidentally, I never said that sharks could not detect mentstrual blood. I just stated that they could tell the difference between it and other blood, and that they generally aren't interested in menstrual blood. After reading Doc Vikingo's post in the above referenced thread, it still seems that there is little if any evidence that menstruation poses an increased risk regarding diving with sharks.

Therefore, I still suggest that it seems more likely that some action or posture (conscious or unconscious) due to fear on the part of the diver in the situation described at the beginning of this thread was what the shark was reacting to, rather than the fact that she was menstruating. But of course, as I mentioned earlier, I don't know much about shark behavior patterns and could be wrong.

Hopefully, we can figure out the truth.

otter-cat

 

[otter-cat]

The place where I originally saw the information regarding sharks not being interested in (attracted by) menstrual blood was from a post dated July 2002, deep into (page 4) a thread entitled "Subtle sexism among instructors." Apparently that information came from a talk given at the Long Beach Scuba Expo by Ella Morgan, author of "When Women Dive" (co-authored by Erin O'Neill.)

I have never read the book, and do not know what the author's sources are. If anyone reading this thread has a copy, maybe you could see if it's mentioned in the book and fill us in.

Hope this helps a little in getting to the bottom of this question!

otter-cat

 

[jbichsel]

Just thought I would add this.

Growing up in western Montana, grizzly country, women were and are warned not to venture into grizzly territory during their period time. There have been numerous cases where women have been attacked, mauled and killed by bears when they have done so.

It would make sense to me that sharks being the "grizzly" of the sea, there would be potential for similar results.

 

[aquagirl]

I hope you don't mind if I give my two-cents worth.

DocVikingo's indepth data gathering provides some important facts.
1) sharks have a keen sense of smell - particularly for blood. DocVikingo states "one part of blood in 100 million parts of water"
2) sharks are attracted to fresh blood
3) "solid research findings" that sharks can detect "other human bodily fluids, including 'dead' ones" as DocVikingo states.

Add that to the number of anecdotal reports on sharks hassling menstruating divers and all I need to know is there. Sharks are VERY likely to detect menstrual blood. The question then is what, if anything, do they do when they detect the "old blood"? To me the answer to that question doesn't really matter because based on various unproven research, sharks MAY, in one way or another, react to it. Now whether the smell bothers them to get them agitated and hassle the diver, or whether they are attracted and attack the diver or whether they are repelled by the smell or do nothing is inconsiquential to me. As I see it, the facts coupled with various unproven research leads to a basic conclusion - Sharks are very likely to detect the menstruating blood, therefore they are very likely to notice you and they are likely to react (one way or another) to the smell. I would not want to personally learn how they react to it. But that's me. I would not want to dive on heavier mentruating days in areas known to have sharks. For all we know, perhaps most sharks are not interested but a few sharks may in fact be disturbed by it. As a woman, proven scientific evidence is not that important if there's the possibility that I may get first hand experience.

 

[MantaRey]

it's true that some sharks don't like dead flesh. but she said they were nurse sharks. they scavenge, and like most predators, they prefer to scavenge over wasting energy to kill. that's why when shark feedings are done, using chumsicles, the nurse sharks are almost always the first ones in, when others will investigate first. if it was a mako, or tiger, it would be a different story.