Polar latitudes have among the harshest of climates on earth, and those ill prepared for these extremes sometimes pay with their lives. Witness those who were bent on finding the northwest passage in the early 1800s. Explorers such as Parry and Franklin, among others, lost ships, supplies, men, and in some cases their own lives in their quest for a route to the orient. They simply weren’t well enough prepared. Surprisingly, some vertebrates prepare for such extreme conditions in a manner many would consider wholly inconsistent with life. These creatures allow up to 65% of their body water, including their eyes, to freeze over winter!

Rana sylvatica, the North American wood frog, pictured on the front cover, is found across most of the northern tier of North America. While the range of this frog does extend south of Canada into the northeast United States and even further south into northern Georgia, its stronghold is the Canadian shield, extending northwest to include Alaska. It is the only frog found north of the Arctic Circle. This ectothermic anuran survives there—a feat that …