The list of the toughest animals on earth might surprise you. The list includes the Emperor penguin, which breeds in the winter and stands in temperatures way below zero for 65 days. Also making the list is wood frog, which freezes and thaws as temperature vary throughout the winter. The the winner in the toughest animal competition is the Tardigrade. It is a little longer than a grain of salt and can survive boiling water, extreme cold, radiation, the vacuum of space and pressures six times greater than that which is found in the deepest ocean.