If you saw a frozen frog that had ice crystals on it, that wasn’t breathing and didn’t have a heartbeat, you would probably think it was dead. If it was a wood frog, it would most likely be in hibernation. Wood frogs hibernate inside logs or burrows or under rocks or leaf piles. During the cold of winter, when in hibernation, they actually stop breathing, their heart stops and ice crystals form in their blood. When the weather warms, they defrost, and their lungs and heart go back into action. Pretty amazing!