While the red fox builds dens it rarely uses them. It prefers to sleep outside, even in our cold northern Ontario winters, curled up in a ball with his tail covering his nose. When the fox does build a den it is for the young to be born and raised in. There is often more than one den built in case the primary den is disturbed. Then the kits can be moved to safety if necessary. For his size the red fox can perform some pretty amazing physical feats. He is an excellent swimmer. He has also been known to run 30 mph. His disproportionately long hind legs allow him to leap up to 2 meters straight up when he needs to. The red fox's eyes are almost catlike. They are almond shaped rather than round and it's pupils constrict in bright light, much like a cat's. He can see very well at night as he stalks his prey.