I have two tortoise turtles in my backyard,have had them all summer. found them on the highway. winter is coming and I need to find out how to keep them through winter outdoors. they have been getting under a small bushy plant and I have hay on top of it, a small layer of it. what do i need to do? I live in southwest texas and it does get cold. thank you, and will be anxiously waitint to hear from you.