Uniquely adapted for life in the treetops, tree squirrels are a common sight throughout North America, often entertaining to watch yet sometimes judged as nuisances by their human neighbors. Their sharp incisors, ideal for opening hard seed casings, never stop growing, and their hind feet can rotate 180 degrees, allowing them to scamper head first down tree trunks. They belong to an ancient mammal family of rodents, and their form and structure have been so unchanged over the past five million years that biologists call them living fossils, yet they remain one of the least understood groups of wild mammals. North American Tree Squirrels illuminates the everyday lives of gray and fox squirrels, the two most dominant types of tree squirrels of the eastern United States. Drawing on more than twenty years of research, Michael A. Steele and John L. Koprowski detail the behavior, reproduction, diet, physiology, and habitat use of these engaging rodents, as well as their complex interdependent relationships with seed-producing trees. The authors compare and contrast tree squirrels with other members of their family, including ground squirrels, chipmunks, marmots, and prairie dogs. In addition to scientific revelations, the authors describe their fieldwork, from the pitfalls of patrolling forests at night in order to check nest boxes to the challenges of fitting squirrels with radio-tracking collars. Both professional biologists and curious amateur naturalists will find North American Tree Squirrels entertaining, useful, and informative.