There have been experiments where people were kept in domes to grow their own food over a period of time, with the goal of seeing if they could create a sealed, self-sustaining ecosystem by recycling their waste products back into nutrients and oxygen.
Let’s say I wanted to create a hands-off, sealed doggie paradise where former pets could leave freely without human support. If the same experiment were to be done again with a pack of dogs with no human intervention once it’s started, would it be easier or more difficult than with humans?
On the one hand the dogs would need fewer calories (maybe half a human’s? Google says 800 calories for a 30 lbs dog), perhaps less picky about a varied diet, less worry about proper hygiene and waste disposal, etc.
On the other hand they wouldn’t be able to identify or fix any problems, there might be social struggles in the pack (worse than humans?), they might overeat (or overhunt, if there are other small animals in there for them to feed on) right off the bat, etc.
Any kind of predator-prey dynamics will be tricky to balance. In natural systems, there tend to be cycles of growth and decline in both populations: successful predators grow in numbers, kill off too much of the prey, the predators starve, the prey population recovers, and the cycle starts again.
Simple systems, with just some sort of vegetation, a plant eater, and a predator, tend to be unstable. Humans might be able to manage it through careful planning, but it will be even trickier to maintain a sealed system with any kind of big predator let loose in it. It may be possible to design a more complicated and well-balance closed system, but nobody has any practical idea how to do it.