Are humans the only animals that menstruate?

I know this is kind of a weird questions, but the girl that I was with hit her “cycle” the other day and didn’t want to have sex (which is another weird thing. Do women just feel uncomfortable and not sexy at this time, some more than others, or is it more likely a “shy” thing? Cause I’ve had girlfriends who are totally down whenever, and girlfriends who refuse completely at that time) anyway, so I was lying there and I got to thinking (usually not a good sign :wink: )

Are humans the only animals that go through a menstrual cycle? Does it have something to do with the fact that we don’t really have a mating “season” or ever go into heat? I mean, I’m obviously no biology expert, but I’m quite curious to know. Maybe you dopers (or even Cecil?) could help sate my curiosity on this one.

Dogs menstrate.

No, all mammals have a ‘season’. They just don’t do it every thirty days or so like humans.
The domestic dog, for instance, comes on twice a year. Outside of that, she’s not interested in sex.
Reeves’s Muntjac comes into season and mates again a few days after giving birth, thus the does are nearly always pregnant.

dogs menstruate? There’s something I didn’t know. Guess I’ve really only been around spayed dogs, not breeders. Thanks for the info

No, they do not.

No, they don’t. And even it was correct it has absolutely no relevance whatsoever to the question asked.

To give a correct answer to the question asked: no. Most primates menstruate as do a handful of non primates. Humans are definitely not alone.

Nope, because the majority of other primates do have breeding seasons and do go into “heat” and they all still menstruate.

The most plausible explanation I’ve ever heard is that primates menstruate simply because it evolved as an “emergency” measure and there’s never been a compelling enough reason to modify.

A lot of the small carnivores must mate when they come into season, if they don’t there’s a good chance they will die simply because there is no mechanism to switch the reproductive cycle off or dispose of the uterine lining, The primate ancestors probably had the same mechanism. That’s great if you live in fairly large colonies or if individuals occupy closely adjoining territories. However if the species moves into environments where finding mates is more difficult it becomes a disadvantage. As a result primates evolved a mechanism to shed the uterine lining when they cycle and can’t find a mate. It’s not ideal but it’s better than death through pyometra. And because it works they’ve been stuck with it ever since.

Remember that under normal circumstances menstruation was fairly rare. It’s certainly rare for non-human primates outside captivity. Females become sexually active before they first ovulate and have a good chance of becoming pregnant every cycle. So menstruation itself isn’t a common event. It has probably only been since the invention of agriculture and the imposition of artificial delays between the onset of ovulation and the start of sexual activity that menstruation was more than an occasional event in a woman’s life.

Yup. The day we were scheduled to have our puppy spayed she went into heat, leaving little drops of blood around the house.

We had to wait. humph.

You didn’t knwo it because it simply isn’t true. Dogs do not menstruate. They can not menstruate and they and never have menstuated.

Don’t believe everything you read on the internet. As you are learning, vast amounts of it is patently false.

So what’s with the drops of blood Mrs. Plant’s dogs leave all over the house when they are in season?

Blake is correct, however, it probably would have been better if he had explained further.

Dogs have an Estrous cycle. The main difference being that the uterine lining is reabsorbed if no pregnancy occurs, while during menstruation, the lining is shed.

Wiki here: http://en.wikipedia.org/wiki/Estrous_cycle

The fact that she left these “little drops of blood around the house” when she “went into heat” should have been enough to realise that this is could not possibly be menstruation. Menstruation is the shedding of the uterine lining after ovulation and only occurs after fertilisation has failed. Obviously an animal can’t menstruate when they go into heat, ie before ovulation and before fertilisation has had a chance to take place.

I’ve also cleaned up after bitches (golden retrievers, if it matters), dark spots of liquid that look like my menstrual blood. What was that, if not shed uterine lining? Some sort of “come hither” urine or scent marker?

It’s just blood. Nothing whatsoever to do with menstruation. Basically the uterine lining grows so rapidly that it swells and cracks, which of course causes bleeding.

In contrast menstruation is the shedding of the menstrual lining itself after it has ceased growth. Most of what is lost is not blood at all.

Thanks, Jman.

As far as women who feel like they are shy or uncomfortable during that time of the month there are plenty out there who just don’t want to be touched. Then there are those of us who feel the intense need to fuck just about anything that can be fucked during our periods. There are those of us who fall in between somewhere. Every woman is different so it will depend on the woman in question.

Thanks for an explanation without attitude Jman. :smiley:

I know I’m especially sensitive during that time, and any sort of contact is unpleasant. A lot of girls are the same way. Others just don’t want to deal with the mess, or have bad cramps, etc.

Ok, I hate having to link Wiki, but I’m at work and not going to dig up countless journal articles nor search in my college text books… plus nobody will care for my words, they just want a cite right?

Check wikipedia’s entry on estrous cycle.

Animals other than primates (and thus humans) go through estrous cycles different from the humans.

The blood you see in female dogs? The discharge? Not uterine lining, not menstruation like in female humans. Something different, looks the same. Not all animals have little drops of blood either. Different animals have slightly different cycles and reproductive behaviors. A few, off the top of my mind:

Cats are induced ovulators, meaning they won’t ovulate until they mate. If they don’t, they go through a phase called interestrus.

Dogs are more seasonal ovulators. I don’t want to kill my mind with math right now, so I’m not going to deal with the days of the cycle and numbers and etc.

Cows are also seasonal ovulators. Their heat period is much shorter than dogs (days vs 24 hrs). They cycle every 21-23 days, unlike dogs. They exhibit behavior that is useful for those that do AI (for example, the cow that is mounted by other cows is in heat).

Pigs are also polyestrous. Sows in heat exhibit lordosis. Means that you put your hand in their back and they arch and remain immobile. Kind of cool…

Mares are long day ovulators… Means they don’t start cycling until the days become longer, and their cycle stops when the days become shorter. BTW, cats are also long day ovulators.

Goats are the opposite! They’re short day ovulators.

Shouldn’t that be lardosis?

:smiley:
(I am **such **a biology dork.)

Heeeh… nah, it’s still lordosis. And like the person who told me said the class… “Could you imagine if women just became completely immobile if you touch them and they’re ‘in heat’?”

Personally, I would be immobile the whole day, every day. :wink:

you’ve never been to Japan :wink:

seriously though, the women here aren’t THAT bad, though some of them do exhibit Dead Fish Syndrome :smiley: