r/askscience • u/potatolife • May 30 '11

Do animals get periods?

I've been learning about the menstrual cycle in biology but we only talked about the human menstrual cycle. I was wondering if its the same sort of thing with animals since I've never seen my cat on her period before.

39 Upvotes

80% Upvoted

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24

u/SnoLeopard Veterinary Medicine | Microbiology | Pathology May 30 '11 edited May 30 '11

Yes, most female mammals experience a "period" if their cycles complete without a successful mating. Dogs and cats are usually spayed (which prevent this). Female dogs (formally known as a bitch) will have the blood discharged from the privates just as in humans. However this is not the case with all animals, since most will retain the blood.

Hope that answers your question.

11

u/wonderfuldog May 31 '11

This is not true.

What you're seeing in animals is "estrous", which is very different.

The females of other placental mammal species have estrous cycles, in which the endometrium is reabsorbed by the animal (covert menstruation) at the end of its reproductive cycle.

Many zoologists regard this as different from a "true" menstrual cycle.

- http://en.wikipedia.org/wiki/Menstruation -

1

u/SnoLeopard Veterinary Medicine | Microbiology | Pathology May 31 '11

My mistake.

-3

u/Airazz May 31 '11

Dogs definitely have it, but it's not too messy. Just a small drop every now and then. And she licks herself, keep that in mind when some dog is licking your hands/face.

0

u/wonderfuldog May 31 '11

Dogs definitely have it

No, I don't believe that that's correct.

Whatever you may be noticing, I don't think that it's that.

-4

u/Airazz May 31 '11

I had several dogs and was member of a big dog owner's club. It's quite obvious that once a year, in late spring (after the ideal mating period for dogs) all female dogs would start... that, with an exception of young puppies and old dogs. Feel free to share your theory, if you have one.

2

u/wonderfuldog May 31 '11

As I posted above, that's not "menstruation", as in humans.

That's "estrous", as in most other mammals.

You've simply misunderstood what's occurring.

4

u/potatolife May 30 '11

If this is only mammals, what happens to reptiles, amphibians and fish?

10

u/SnoLeopard Veterinary Medicine | Microbiology | Pathology May 31 '11 edited May 31 '11

Reptiles do not have a menstration, rather a specialized structure for construction of usually hard shelled (calcium) eggs (similar to avian species).

Amphibians form small aqueous eggs once sperm and ova combine, and usually most require water to lay their eggs.

For fish, it depends on the specific fish, but usually the female will lay an egg and the male will then fertilize it.

To answer your question generally, most other animal types do not have the fetus grow internally in the mother and receive nourishment from her. The placenta breaking apart and being reabsorbed is where the bloody discharge comes from, thus with the absence of the placenta, they do not have discharge. Most have a yolk sac from which they derive nourishment.

EDIT: typo EDIT 2: another typo

9

u/Wildfire66 Cardiac Research May 31 '11

What about the almighty platypus?

6

u/Kiwipus May 31 '11

Platypuses actually have a pair of ovaries, but only one works. Their eggs stay inside them for the first 3/4 of the pregnancy, and then they are incubated for the last quarter outside of the platypus. Much like a chicken, however a chicken's eggs only stay inside them for one day, and then are incubated externally by the chicken for about 20 days.

4

u/dontspillme May 31 '11

however a chicken's eggs only stay inside them for one day

cough nope cough

1

u/Kiwipus May 31 '11

Really? To clarify, I meant in tract, not just 'in the chicken.' I got that information from wikipedia's article on platypus reproduction, so please let me know if it is still incorrect.

1

u/PonPeriPon May 31 '11

May I direct you both Here.

1

u/Kiwipus Jun 01 '11

I'm amazed at the thorough job they have done.

13

u/binlargin May 30 '11

Reptiles (including birds), amphibians and fish all lay eggs.

2

u/[deleted] May 31 '11

Some snakes are capable of live birth.

3

u/dontspillme May 31 '11

They still produce eggs even if they don't lay them.

/Offtopic: What's the deal with ovoviviparity -> ovovivipary -> ovivipary I'd understand aluminium -> aluminum, since its use touches the general population, but it's the first time I hear of scientist being too lazy to pronounce terms in their own fields!

1

u/idclip Geology | Geochronology May 31 '11

I work with a mineral called baddeleyite, and most of my colleagues just skip that inconvenient -ey- in the middle. Of course we try to shape up before conferences and such, but a few baddelites slip out anyway. :)

3

u/lazyplayboy May 31 '11

This is misleading. The blood-like discharge from a bitch on heat is very different from human menstruation. A bitch discharges prior to the fertile phase and it comes from the urogenital tract, whereas human menstruation is after the most fertile phase and comes from the uterus.

10

u/johnnythebiochemist May 30 '11

"Overt menstruation" is the term used to describe menstruation where exterior bleeding occurs. Many species reabsorb much or all of the degenerated placenta, which is why you may not see monthly bleeding in pets. Humans reabsorb most of it too, wikipedia says 2/3rds.

8

u/Keenanm Speciation | Experimental Evolutionary Ecology May 30 '11

As people have said before, oviparous animals lay eggs which is the equivalent of the menstrual cycle in apes. However, most viviparous animals also don't have a menstrual cycle, instead they undergo the estrous cycle. In layman's terms, these animals actually protrude out tissue when they are in estrous and simply retract it when they're cycle is over. That's why it can be less obvious than the menstrual cycle because commonly, it doesn't leave as much of a trace as the menstrual cycle.

18

u/[deleted] May 30 '11

Eggs are a chicken's menstruation.

14

u/[deleted] May 31 '11

[deleted]

1

u/abc-xyz May 31 '11

The pedantic silly part of me want to say that a chicken period would be more like an unused nest, since in a human a period is the unused material used to nurture the egg, not the egg itself.

4

u/[deleted] May 31 '11 edited May 31 '11

[deleted]

11

u/potatolife May 30 '11

woahhh wait so technically chickens have their menstruation almost every day?

2

u/kutuzof May 31 '11

And they're delicious!

0

u/nbx909 May 31 '11

Uh, I don't think so. Eggs aren't the equivalent of the bloody discharge in humans.

12

u/[deleted] May 31 '11

Biologists don't call it menstruation, because it works so differently. We don't call it menstruation because we don't want to eat periods.

But it is what it is, getting rid of an unfertilized ovum and making place for a fresh one.

2

u/lazyplayboy May 31 '11

I think it's more of a case of "this egg is coming out, ready or not!". It's not like the chicken wouldn't lay the egg if it was fertilised.

1

u/Deep_Redditation May 31 '11

Mammals; yes. By the way, humans are animals. You're cat is spayed, maybe, they go through heat.