Vagina MuseumOLD THREAD REPOST
As Halloween approaches, let's talk about spooky animals. 🦇 And blood. 🩸
Here's a run-down on the very unusual menstrual cycles of bats...
The first unusual thing about bats having periods is that menstrual cycles are unusual in nature. Most mammals do not menstruate at all. Even if you notice your pet bleeding, it's not a period (it's oestrus, AKA "heat")
Menstruation is limited to a handful of species. Us, obviously, and more closely-related primates, as well as elephant shrews, spiny mice and some bats. It probably evolved a few times over, since not all the species that have periods are related.
Here's a lovely fact to brighten your day: bats are split into two main groups, know as microbats and megabats. As implied by the name, the microbats are the little squeaky ones, and the megabats are the big ones.
The first few research studies into bat menstruation focused on some microbat species, such as the gloriously grumpy-looking C. perspicillata. Of the species that have been studied, their menstrual cycles look a little different to ours.
There's two key differences between a microbat menstrual cycle and a human menstrual cycle. Firstly, the endometrium builds up after ovulation (in a human menstrual cycle this happens before), and secondly they only menstruate after they've had sex and not got pregnant. This questions about whether we can call this true menstruation, because they don't have a cycle; and the build-up of the endometrium happens at a different point to how it does in other menstruating animals.
Then, a 2007 study examined a megabat species: the fulvous fruit bat. Here's a gratuitous cute bat picture, because we all need to look at cute animals sometimes.
This study looked at captured wild bats, and captive bats and found some remarkable characteristics of the fruit bats' menstrual cycles: they were really, really similar to human menstrual cycles.
A fulvous fruit bat cycle has a follicular phase, where hormones encourage eggs to mature, and the endometrium thickens. The bat then ovulates. If pregnancy doesn't happen, the bat enters the luteal phase, which ultimately triggers menstruation.
For a full explanation of the menstrual cycle, Tara Costello explains the ins and outs in our podcast episode "Welcome To Your Period". The hormones secreted and the order of events is exactly the same in fulvous fruit bats https://www.vaginamuseum.co.uk/podcasts/welcome-to-your-period
A fulvous fruit bat menstrual cycle lasts about 33 days, which is very similar to human cycles, which are usually around 21-40 days. The bat will ovulate on average at around day 18 of the cycle - in humans it's usually more likely to be slightly earlier, at around 10-16 days. But one of the biggest differences between fulvous fruit bats and humans is that the bats only bleed for one day when they have their period. In humans, the average is about 3-7 days.
Here's a picture of a (somewhat miffed) fulvous fruit bat during its period.
Because menstruation in bats hasn't been studied for every single species, we don't know how common it is, and how many of them are menstruating in the way we do. What we do know though, is some are just like us.
Maggie Maybe@vagina_museum I wouldn’t even complain about the bleeding if it only lasted one day. I would be delighted if I could get the pain to last only one day.
Eve, Go Listen to Dead Channel Sky@vagina_museum Astrozoologists have been searching for intermediate-mass bat holes for some time
SPICY EVIL CAET🍬🍭🎄
@vagina_museum and rats! They get in heat every few days