Scientists in Australia say they’ve discovered a rodent whose menstrual cycle rivals that of humans for the first time. Unlike other rodents, the spiny mouse — a nocturnal mouse found in northern Africa — menstruates regularly, according to a study published in bioRxiv earlier this month. At first blush, this is a quirky finding that connects us to a species most people don’t normally think about. But the researchers say that this information could end up being quite useful for science because the rodents might be a good, cheap model for human menstruation.
Okay so let’s be clear: the spiny mouse’s menstrual cycle doesn’t actually follow that of humans. Female spiny mice have a 9-day cycle and they spend about three of those days bleeding, according to Nature News. The average cycle for humans, on the other hand, lasts about 28 days and bleeding can last about a week. So when scientists say that the rodent’s cycle is similar to that of humans, they’re actually referring to the proportion of days both mammals spend bleeding. The rodents spend about 20 to 40 percent of the cycle bleeding, whereas people who menstruate spend between 15 to 35 percent of the cycle bleeding.
The spend about the same proportion of time bleeding
Now that the team has figured this out, they'll continue the research to find out if the timing for when the uterus lining breaks and regrows is also similar to humans. They’re also doing some genetic research to see how genes regulate the various stages of the mouse’s cycle. If that research shows that these rodents really are similar to humans when they menstruate, that could be a big deal.
Right now, scientists can use drugs to induce menstruation in lab mice, but that’s not particularly useful for researchers who want to study a healthy, natural cycle. That’s why scientists tend to rely on primates instead to study things like endometriosis, a painful disorder in which tissue that normally lines the uterus grows outside of it. Unfortunately, primates can be expensive to keep, and the regulations surrounding their use in science are more strict. So even though rodents aren’t always the best model for human health, they're cheap and they reproduce quickly — and that could make studying menstrual function a lot easier.