Most male reindeer tend to lose their antlers around December and since Dasher, Dancer and the rest of the crew still have their antlers, it's safe to assume that they're female.
9 Weird Reindeer Facts That Will Make You Look At Rudolph Completely Differently - StumbleUpon
9 Weird Reindeer Facts That Will Make You Look At Rudolph Completely Differently - StumbleUpon
