[Kalimac]

To be slightly more serious, maybe the Orcs *do* eat each other - they're certainly happy enough to kill each other (there are what, about fifty Orcs killed in the tower between the time Frodo is picked up by the Patrol and the time Sam gets past the Watchers?) And there's a hint in TTT (Pippin not wanting the eat the Orc-food, the flesh of "he dared not guess what creature") that whatever it is the Orcs eat, it's not something you'd want to showcase on the cover of Cook's.

There's not much else in the vicinity except thorns, and not everything would travel well from the southern countries they dominated. Maybe they could take some grain and make hardtack, and dry a few vegetables and fruits (though Orcs don't really seem like the vegetarian types) besides that they'd probably steal animals and use them for food - you can imagine that not all the horses stolen from the Rohirrim went for Nazgul steeds, unfortunately - a lot of them probably ended up in Ugluk's and his compatriots' ration tins. Besides, in "The Hobbit" isn't it mentioned that the goblins eat ponies and pretty much everything else? So probably hardtack, dried fruit and horsemeat for choice, fellow Orc when hard up - and in the last days of war, stuck in a land where nothing grew, they probably were.