In this Tuesday, Sept. 11, 2018 photo a squirrel runs with an acorn in Portland, Maine. A bumper crop of acorns, pine cones and other staples last year led to a population boom of squirrels. (AP Photo/Robert F. Bukaty)

If you live in an area with plenty of trees, you may be used to seeing a gray streak out of the corner of your eye — a gray squirrel scurrying up a tree toward a nut or darting out of the way of danger.

You may see them as feisty but trifling creatures. For scientists, however, squirrels are objects of fascination and inspiration. “A Squirrel’s Guide to Success,” on PBS’s Nature at 8 p.m. Wednesday, shows why. It focuses on the breathtaking abilities of these tiny animals as they chatter, leap and problem-solve their way through life.

The documentary shows how and why scientists study squirrels – and reveals astonishing facts about the nearly 300 species. They may be small but they’re surprisingly brainy. Their intellects can coordinate complex physical feats, circumvent barriers to food and help them play hide-and-seek with predators (and nuts). Fox squirrels can remember the location of 9,000 nuts; tree squirrels’ brains grow and shrink depending on the time of year.

Scientists are fascinated by how the rodents pair body and mind to get what they want. A highlight of the documentary is an outdoor obstacle course in England that helps scientists observe gray squirrels. The determined animals quickly learn how to navigate the obstacles, using every skill in their arsenal to get to a pile of hazelnuts. Slow-motion shots of their leaps and learnings reveal just how gracefully they use their tiny bodies.

The story gets personal by following Billy, a red squirrel that had been fostered after being rescued from the wild. Will the wily rodent have what it takes to live outside again after growing up inside a human house? Find out Wednesday. The show will remind you of the animals’ amazing abilities every time you see that gray streak go by.