A difficult one,I would take the easy option and not give chews!
Maybe not giving Henry the chance to bury his. As soon as he finishes or leaves it take it away and give it to him another time and praise him for letting you take it away. Have a fun game after the chew has been given up.
Sit with Henry when has his chew & praise him if he is quiet when Oscar walks by. Only my suggestions
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Be careful, taking bones/food/treats/valuable items from a dog can cause food aggression with people. Make sure you always trade (give him something more valuable than what he has) then pick up the item you dont want the dog to have. I dont play the mess in the food dish game, or take then hand back bones. I need my dogs to trust me. Dogs live in the moment, and they dont correlate between you taking the bone away then giving it back.
I dont have any issues with food aggression with my dogs, but then, I have never messed around with my dogs' food. Especially when dealing with rescues that have been starved, they need to know they'll get their food. But they do have to work for their food, I make them sit, wait, lay down, high five... whatever i feel like before they get the sign to go eat, or get their treats.
I honestly would seperate the dogs to chew on their treats. and when they're done with them (either finished or bored) pick up the leftover's.
Another idea is using a spray bottle, if one tries to take the other's treat, spray the theif. when they walk away from their treats, pick them up.
I also never correct a dog for growling. growling is an early warning system. If you train the growl out of your dog, then you get "unprovoked attacks" If my dog is growling, it's for a reason, and we all better respect that.