# Why do female dogs bleed when they're fertile but human females bleed when they're not?

**URL:** https://boards.straightdope.com/t/why-do-female-dogs-bleed-when-theyre-fertile-but-human-females-bleed-when-theyre-not/561428
**Category:** Factual Questions
**Created:** [November 21, 2010, 1:14pm UTC](https://boards.straightdope.com/t/why-do-female-dogs-bleed-when-theyre-fertile-but-human-females-bleed-when-theyre-not/561428 "2010-11-21T13:14:29Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)
#### Post date: [November 21, 2010, 1:14pm UTC](https://boards.straightdope.com/t/why-do-female-dogs-bleed-when-theyre-fertile-but-human-females-bleed-when-theyre-not/561428/1 "2010-11-21T13:14:29Z")

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Answer that, bitches…

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### Author: ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)
#### Post date: [November 21, 2010, 1:43pm UTC](https://boards.straightdope.com/t/why-do-female-dogs-bleed-when-theyre-fertile-but-human-females-bleed-when-theyre-not/561428/2 "2010-11-21T13:43:35Z")

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(last bit said in jest, pls don’t get mad)

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### Author: ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)
#### Post date: [November 21, 2010, 2:10pm UTC](https://boards.straightdope.com/t/why-do-female-dogs-bleed-when-theyre-fertile-but-human-females-bleed-when-theyre-not/561428/3 "2010-11-21T14:10:24Z")

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Primates go through a menstrual cycle. They can have sex at any time but go through frequent bleeding. Non-primates have an [estrous cycle](http://en.wikipedia.org/wiki/Estrous_cycle) and only have sex during periods of heat.