A Question to need and drinking zones.

A while ago (when I started playing) I was so unlucky (stupid) to destroy a couple of need and drinking zones. Most of them came back some didn't. I didn't knew at that time that you could des destroy them permanently. My question would be, what is happening to the animals. Are they migrating to other need/drinking zones? Because they aren't around the area anymore. They migrated between the lake a need zone (for eating) and one for sleeping. But after the drinking zones vanished I barley can find them on their usual "route".