Simplify the following text for a Grade 4 native English-speaking person.
Original: According to the British comedy panel game QI , Rudolph the Red-Nosed Reindeer and all of Santa 's other reindeer must be either female or castrated , because male reindeer lose their antlers during winter .
Simplified: The antlers of female reindeer are smaller than the antlers of males . Reindeer also have big feet , which helps them walk on soft ground .