Why do reindeer legs make a clicking sound?

During the winter, there is a clicking sound that comes from the joints of a reindeer. The voice comes from the bones. The sound tells to the nearby reindeer about the movements of others. It is a warning signal if others start to move quickly and restlessly.

Reindeer have several signs to keep connection to others. They have a gland in the leg that leaves a smell on the ground. This also works when giving information about dangerous situations.

When reindeer escape, they lift their tails and show the white side of it. The other reindeer coming behind follow and the herd stays together.