Do Animals Menstruate?

Yes, many animals do menstruate, but only a handful menstruate overtly like humans dogorrilla (where there is blood flow from the uterus through the vagina). Other animals menstruate covertly (by simply reabsorbing the uterine lining into the body). Female animals with overt menstruation are generally sexually active throughout their cycle. In comparison, females with covert menstruation are only ‘in heat’ mid-cycle.

Overt menstruation occurs in humans; most primates (including chimpanzees, organutans, gorillas & rhesus monkeys); some types of fruit bats; and elephant shrews. The average cycle length in orangutans and opossums is the closest to that of humans, 28 days, while the cycle for chimpanzees is 35 days. Menstrual bleeding in non-human primates is minimal.

Covert menstruation (or the estrous cycle) occurs in all other placental mammals (including dogs, cats, horses, elephants, rats, pigs). Dogs have their cycle twice a year, cats have it about once a month, horses have it every three weeks, and rats go through their cycle rapidly – every 5 days. Some of these animals (eg. dogs) display a bloodily discharge from the vagina due to declining estrogen levels. This is different from menstruation because it occurs when the animal is ‘in heat’ during mid-cycle (at the time of ovulation) and the blood comes from the vaginal walls, not the uterus.

Egg-laying animals do not menstruate. This includes some reptiles, some amphibians, some fish, and all birds. Egg-laying animals do not need a uterus therefore they do not have a menstrual cycle.

See below for some photos of animals (other than humans) that have overt menstruation. From top-left, clockwise: gorilla mother and baby, chimpanzee, short-tailed fruit bat, elephant shrews, opossum, three opossums hanging from branch.

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13 Responses to Do Animals Menstruate?

  1. Surii says:

    I remember when my dog was going through her first menstruation. It was such a mess at first, but we soon discovered that we could put toddler undies on her (with a hole cut for her tail, of course) and just use a pad. It was perfect! She seemed much happier, too, and of course I was.

    • atozinco says:

      Wow! Very messy. I’ve never noticed my dog bleeding when she’s ovulating – she seems to do it without too much mess I guess. It helps that we have dark coloured carpet!

  2. jk says:

    Don’t gibbons and bonobos also have overt menstruation?

  3. Jazme says:

    I hav researched nd dis z wht i got.abt elephants menstruatng.

  4. matthew pillay says:

    Wow!! Very informative, theres alot that I didn’t know. Thank you :)

  5. Zorganoth says:

    thanks I’ve been wondering about this. btw to the main admin of this blog, this is an awesome topic to blog about and i was wondering if you have heard of or posted about the japanese menstration machine for men. its very strange but its worth looking it up either on youtube or google

    • atozinco says:

      Thanks Zorganoth. Yes, I have heard about the menstruation machine for men – I’m keen to see a video of it actually being used! There is a music video that shows the menstruation machine on youtube, but it doesn’t really explain anything or demonstrate what it’s actually like for users. I did a blog post about the menstruation machine here: http://myperiodblog.com/?p=261

  6. Oyelese sunday says:

    Wonders shal never ends
    one love’

  7. Bala madiu says:

    Cnt believe this, so animals do menstruate..

  8. Magamy says:

    I will now be tender to my pet, because I know what he goes through. We can grow stronger together through the struggles of life…and flow

  9. MISINDE OTHUMAN says:

    What about fish? Thanx

  10. happyquails says:

    My African Pygmy Hedgehog would overtly menstruate.

    • atozinco says:

      Hi happyquails, Hedgehogs don’t overtly menstruate. Some animals (such as dogs) bleed mid-cycle, when they are in heat/ovulating, however I haven’t heard about hedgehogs doing this (I’ve read that hedgehogs have triggered-ovulation, ovulating only when they are around males instead of on a regular schedule). If a hedgehog is bleeding from the genital area it might be due to a uterine tumour or a urinary tract infection.

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