Do cougars hunt just for practice and leave the prey uneaten?
Predators (including domestic cats) don’t hunt just for practice. They hunt to eat. However, that being said, certain domesticated predators (dogs and cats) need to Learn how to hunt from their mothers, or at least need to actually be hungry so they will eat what they hunt and catch. Predators may need to reach a certain ‘threshold’ during the chase in order that instinct will take over and they ‘finish’ the hunt, i.e., either eat or hide their prey. I doubt that cougars hunt just for practice. As a very large wild cat, and hunting in competition with wolves, coyotes and perhaps even bobcats and vultures, it would not be beneficial for this cat to go through the effort of hunting prey simply Just Because.