# Cat menstruation
**URL:** https://boards.straightdope.com/t/cat-menstruation/9555
**Category:** Factual Questions
**Created:** [April 1, 2000, 12:14am UTC](https://boards.straightdope.com/t/cat-menstruation/9555 "2000-04-01T00:14:00Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@matt\_mcl](https://boards.straightdope.com/u/matt_mcl)
#### Post date: [April 1, 2000, 12:14am UTC](https://boards.straightdope.com/t/cat-menstruation/9555/1 "2000-04-01T00:14:00Z")
Don’t cats menstruate? If so, why don’t we ever see little red traces all over the place?
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### Author:  [@Gr8Kat](https://boards.straightdope.com/u/Gr8Kat)
#### Post date: [April 1, 2000, 12:19am UTC](https://boards.straightdope.com/t/cat-menstruation/9555/2 "2000-04-01T00:19:00Z")
Yes, it’s called “going into heat.” And I think it’s just because they’re so compulsive about cleanliness and licking themselves that you don’t normally find… residue.
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### Author:  [@matt\_mcl](https://boards.straightdope.com/u/matt_mcl)
#### Post date: [April 1, 2000, 3:15am UTC](https://boards.straightdope.com/t/cat-menstruation/9555/3 "2000-04-01T03:15:00Z")
All together now: Ewwwwww.
(glad his cat is spayed)
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### Author:  [@coosa](https://boards.straightdope.com/u/coosa)
#### Post date: [April 1, 2000, 2:59pm UTC](https://boards.straightdope.com/t/cat-menstruation/9555/4 "2000-04-01T14:59:00Z")
Actually, cats don’t menstruate. Menstruation seems to be confined to animals that are spontaneous ovulators. Cats belong to a small group of animals known as reflex, or induced, ovulators. (Also includes the mink, ferret, rabbit, and members of the camelloid family.)
In spontaneous ovulators, eggs mature in the ovaries and are automatically released at a certain stage. During this time, the uterus also develops a thick, enriched endometrial lining in preparation for implantation of the embryo. If implantation doesn’t occur, this lining must be either reabsorbed or discarded, hence menstruation.
In reflex/induced ovulators, mature eggs are not released from the ovaries unless copulation occurs. If copulation does not occur, the eggs regress and are reabsorbed. The endometrial lining doesn’t increase until ovulation occurs, so if there is no copulation, there is no ovulation, no excess endometrial lining to discard, hence no menstruation.
I’m not sure about menstruation in non-human species of spontaneous ovulators. I’ve been searching through a book called ‘Anatomy and Physiology of Farm Animals’ for mention of it, and have not found much about it. It seems that some types of menstruation may consist more of mucus than of blood and tissue. Also, different species have different types of placental attachments, which may affect the development of the endometrium.
Maybe funneefarmer can provide some information about cows?
Anyway, while unspayed female dogs will leave blood stains on your furniture, cats won’t.
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Some days you’re the dog, some days you’re the hydrant.