During the gray squirrel’s fall caching season, when the critters bury nuts and seeds in hundreds of scattered caches to serve as emergency winter larders, a typical squirrel shows a 15 percent increase in the size of its hippocampus—the memory and emotion center of the brain—compared to the rest of the year.

The hind legs of squirrels are double-jointed, which gives them the ability to run up and down trees very quickly.

A squirrel’s front teeth never stop growing.