Hi Lois, Thank you for this Interesting article. For further reading, I would like to suggest one of my favorite books, "Winter World - The Ingenuity of Animal Survival" by Bernd Heinrich. This book is very readable yet is a scientific study of the subject. Professor Heinrich has written many books based on his scientific studies. All of his books contain his beautiful illustrations. Treat yourself and read his "Trees in My Forrest", "One Man's Owl", "A Year in the Maine Woods" or "Winter World". I promise that you will be amazed and delighted.