Great topic Alot of food for thought.
I've heard JW answers to this sort of topic as 'Jehovah has the power to create the flood, he has the power to sustain the animals during their migration' when the animals dispersed from the ark and moved all over the earth. Their reasoning is such that Jehovah could've filled their bellies long enough to settle somewhere (so they wouldn't eat each other, and the koalas would've survived without gum leaves). And if you believe in an almighty power, then I suppose this is reasonable.
But simple logic tells us this can't be right!