Did you know that a groundhog is really a type of squirrel? That squirrels control their body temperature with their tails? That most squirrels have yellow-tinted eye lenses that work like sunglasses to reduce glare? That tree squirrels can turn their hind feet completely around when climbing down a tree head-first? In Squirrels: The Animal Answer Guide, Richard W. Thorington Jr. and Katie Ferrell unveil the fascinating world of one of the -most watched- mammals on the planet.

The diversity of squirrels is astounding. There are 278 species that inhabit all continents except...