I'm reposting this, not only because it's #frogfriday, but I also miss the internship I had up in Northern Michigan last summer. Here is a newly metamorphosed wood frog (Lithobates sylvaticus) I found in a road rut. Although they come in a variety of colors, this species can easily be recognized by its masked face. Wood frogs are highly tolerant of the cold and have been known to freeze over the winter while hibernating. Their heart and internal organs actually stop functioning and they don't need any oxygen during this time. They produce both urea and glucose that work like a cryoprotectant, which protects the frog's body tissues from dehydrating/shrinking during low temperatures. Wood frogs are able to survive several freezing and thawing events, if no more than 70% of the water in their body freezes. When warm temperatures arrive, their heart starts beating again and a repair process starts on the cold damaged body tissue.