Blood moving into the legs is cooled by blood returning to the body in a countercurrent heat exchange (CCHE), a highly efficient means of minimizing heat loss through the skin's surface.
According to thirty-year veteran, David Shackleton, University of British Columbia emeritus professor, who has published widely on ungulates and other large mammals, the clicking sound made by caribou as they walk is caused by small tendons slipping over bone protuberances (sesamoid bones) in their feet.