Dasher and Dancer, Prancer and Vixen, even Donner and Rudolph — in all likelihood, they’re all female. The key piece of information is the antlers. Unlike other deer species, both male and female reindeer grow antlers. However, males shed theirs after the mating season, in early December. Meanwhile, females keep theirs; and that’s not the only hint.

Antlers and fat

Rudolph, the red-nosed reindeer, holds a special place in Christmas lore. While the original stories don’t really emphasize Rudolph’s gender, the reindeer is typically portrayed as a male. Science says that’s almost definitely not true.

Males only start recovering their antlers in the spring, and as Santa’s reindeer all have antlers, that kind of points towards females.

Beyond antler retention, female reindeer are better equipped for the demanding task of pulling Santa’s sleigh. In preparation for winter, female reindeer accumulate up to 50% body fat, providing insulation against extreme cold and serving as an energy reserve. This adaptation enables them to endure harsh Arctic conditions, maintaining strength and stamina during long, frigid nights. Meanwhile, males spend most of their energy reserves in the mating season.

Furthermore, reindeer herds often exhibit matriarchal structures, with females leading group movements and making decisions crucial for survival. During the reindeer migration (one of the most impressive migrations in the animal world), it’s the experienced females that guide the herd. This leadership role and ability also hints that Santa’s reindeer are females. After all, if you want to deliver gifts worldwide in a single night, you’d better be really good at navigating.

Despite these biological facts, cultural portrayals have traditionally assigned male identities to Santa’s reindeer. This may come from the historical gender roles and the tendency to attribute strength and endurance to males. But biology doesn’t always follow social norms. In fact, reindeer biology strongly contradicts these stereotypes, highlighting the strength and endurance of female reindeer.

The biology of reindeer shows us how nature equips these incredible animals — especially females — with the strength, endurance, and adaptability to thrive in the harshest conditions. Of course, the reindeer need a good amount of Christmas magic as well to be able to deliver all the gifts. But ultimately, this is a reminder that even in our most beloved stories, science can still play a role. Sometimes, a rather unexpected role.