This question intrigued me a lot since if animals in the wild did have menstruation with blood flow, wouldn't all that blood be attracting every other predator in the vicinity?

  • $\begingroup$ Yes they do, most if not all mammals menstruate. Any dog owner can confirm this for example. Please research and try to answer your question before posting here. A 5 minute search for "mammal menstruation" for example would have answered it for you. If you want to know why that does not call in predators, edit your question accordingly. $\endgroup$ – terdon Feb 20 '14 at 16:53
  • $\begingroup$ Edited the question. I wasn't able to find why they would retain this trait. $\endgroup$ – S.Raaj Nishanth Feb 21 '14 at 5:07
  • $\begingroup$ I've always wondered the same thing about crying babies - would attract predators. $\endgroup$ – Alan Boyd Feb 21 '14 at 11:53

I would guess that the answer is something like this: ever since the development of the placenta enabled females to carry their offspring longer and to develop more fully. Upon birth they were stronger and/or their brains were more fully developed (in the case of humans). The increased gestation time, made possible by the structures of the womb and placenta is probably an adaptation whose advantages are much greater than the increased risk from menstruation once a month.

Some anthropological studies indicate that in preindustrial societies that women do not menstruate very much as adults though. If you subtract out the time that they are carrying infants and nursing, which both prevent menstrual cycles, females will miss years of menstruation with only a few months in between. I would assume this is a factor in the risk of menstruation for many animals.

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    $\begingroup$ Yeah! I guess in the wild most mammals will miss quite a lot of menstrual cycles. $\endgroup$ – S.Raaj Nishanth Feb 21 '14 at 7:03

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