It's true, that can be used as an explanation. There's nothing in the account about the animals being active during their time inside the Ark.
If all of the animals were hibernating, how could Noah send out birds to see if there was any dry land?
First of all, all species would not fit, even if you brought infants. Not to mention the precarious position any species would be in with only 2 members to repopulate.
Not all species are built to hibernate. Bears and other animals are built to bulk up and have food for their body to survive on because there is still a beating heart and that requires energy.
So, lots of miracles. If the animals were conscious, the job of caring for them and feeding them is WAY beyond the capabilites of 8 people. Just divide the millions of species by 8 people and calculate how many species would have to be tended to every minute.
And not only did miracles have to happen inside the ark, but also outside. Noah didn't bring fish. And what happened when fresh and salt water mixed? Many salt water fish die when the saline soution is even a little off. Many freshwater fish die in saltwater.
And what about the plants? Keeping them alive and able to reproduce after a year under saltwater. Not to mention that afterwards, there must have been a lot of salt residue above and soaked into the ground. How is anything supposed to grow?
Which comes to the entire point. God would have had to perform so many miracles to make this happen. Any intelligent person would have just zapped the bad people. There's an account of one angel killing over 100,000 in one night (forget the exact count). With thousands or millions of angels at his disposal, wouldn't it have been quick work to kill all the people? That's what an intelligent creator would do. Wouldn't he have to dispatch even more angels to preserve all the fish, animals, etc. To help with the ton of miracles needed to do the ark?
If I get mice in my garage and attic, I put out poison and/or traps. I don't grab what I want to save and demolish the house.