Surprise! Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Donner, Blitzen, and yes, even Rudolph, are ladies.

Clearing up this misconception is important, at least to one pro-woman Twitter user, who wanted to make sure everybody on social media knew the truth. Two years ago, Cat Reynolds tweeted the following message, which has racked up endless likes and retweets to date.

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Turns out she’s right.

The original eight — first introduced in the 1823 poem “A Visit from St. Nicholas” (a.k.a. “The Night Before Christmas”) — as well as the infamous red-nosed celebrity of song and screen, Rudolph, are commonly thought of and referred to as males in pop culture. But according to science, Christmas carolers and holiday hangers-on have had it all wrong all along.

Edinburgh University professors Gerald Lincoln and David Baird tell the U.K.’s Telegraph that Santa’s reindeer can’t be male for one simple reason: Only female reindeer still have antlers at Christmas; the males of the species shed their headgear before mid-December.

“Male reindeer actually cast their antlers before Christmas, so they don’t have any antlers at Christmastime,” says Lincoln. “They have their mating season in autumn when they use their antlers to fight, but once it finishes they cast them … I just wanted to remind people that it is never quite so straightforward, and even females develop weapons when it comes to the real world of seasonal breeding.”

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Besides, of the 40 various species of deer on Earth, only the reindeer species features females with antlers. Not only that, females have an edge over males in another important way. According to LiveScience, in preparation for winter, female reindeer build up to nearly 50 percent body fat. The additional weight gives them a couple extra inches of thick fat on their hindquarters, which helps keep them warm in temperatures as low as -45 degrees Fahrenheit. Meanwhile, their male counterparts typically weigh in around 5 percent body fat, as they deplete the majority of their energy reserves during the previous mating season.

This is all to say that if in fact reindeer did fly from the North Pole all around the world at Christmas, most likely only the gals would even be prepared for the journey.

However, Prof. Lincoln did make one interesting discovery while researching how female reindeer grow and cast their antlers. Apparently, if a male reindeer is castrated, it stops the process of casting the antlers, thus he becomes more like a female.

“Rudolph could be a castrated male, or a female. I think it’s nicest to think that Rudolph was a female!” says Lincoln.