Last year I let my daughter watch this SciShow Kids video about reindeer. 4 Facts to Know About Reindeer explains why reindeer are called caribou in North America. The lesson also teaches students how reindeer have adapted to find food and stay warm in cold weather. The video concludes with an explanation of why reindeer migrate.
Older kids and adults who want to learn a bit more about reindeer should watch this clip from BBC Earth. The video explains how reindeer stay warm in the coldest of conditions.
Another part of the same BBC series about reindeer is this Magical Finland Sleigh Ride.