I was waiting for the first report

- Something I was aware could happen , theoretically (and in practise) the fix to animal numbers meant that animals native to adjoining terrain types could cross migrate - Eventually over time they will migrate back to their natural habitats - this will only happen between areas bordering different terrain .
In the short term they may even breed and increase in numbers but over time they will migrate back home .
Treasure it , nuture it, but don't get too attached to the cow ... or the desert tortoise ...or ... mountain goat ...or ...
EDIT: Actually it's not the one-way vs two-way travel issue... its the picking of animal type for those who were hiding issue