Maybe only Santa’s reindeer can fly—but regular reindeer come pretty close.

They can fly over the tundra at 50 miles an hour, covering more than 20 miles a day.

Their annual migrations span 3,000 miles, the longest of any land animal.

And they’re spectacularly adapted for that life:

Their eyes change color depending on the season. In their summer above the Arctic Circle, with nearly 24 hours of sun, their eyes turn gold, to reflect the harsh light.

In the dark months of winter, their eyes turn blue, to let in as much light as possible.

Their eyes also can see ultraviolet light.

This makes the snow even brighter, but against it, some important things appear black: The fur of predators, who might otherwise be camouflaged. And lichen, the reindeer’s primary winter food.

What their eyes can’t see is red. Like many mammals, they’re red–green colorblind; both colors appear brown.

While this would have made it hard to follow Rudolph’s nose, their noses are pretty amazing in their own right. They’re lined with capillaries, to warm the frigid air before it enters their lungs.

They’re also the only deer species where both males and females grow full antlers. The males’ drop off after mating season ends in November. But the females’ stay on through winter, into the spring calving season.

This means that if Santa’s reindeer do, in fact, have antlers on Christmas Eve, they’re all females.