From the video owner:
This has been his favorite treat since he was a baby. And because marshmallows are almost entirely made out of sugar- he doesn't get it too often! I gave him the entire bag here, because it's fun and enriching for him to get excess food that triggers the instinct to hide the rest for later. Watch how he scrambles to stuff a few into his mouth before caching the rest.
Disclaimer: Foxes don't always make the best pets. This fox was saved from a fur farm after being injured as a kit and is part of a wildlife rehab program where he is lovingly cared for by responsible people that understand wild fox behavior. Foxes aren't domesticated and just because they're cute doesn't mean they're easy to take care of or in any way similar to a dog. If you want a fox as a pet, please do a lot of research and understand that they can bite, they smell, and make a mess. I have experience working with foxes and if you would like advice, please contact me.