“Squirrel proof” seems to be a temporary condition for bird feeders. To learn more about why this is the case, Karli and her family constructed a variety of “obstacle course” pathways that squirrels could cross to reach a box of nuts; Sylvia and an undergraduate research team helped Karli to record data on the squirrels’ progress. On average, squirrels required fewer than 5 trials to master a new pathway, and once they had learned how to cross it, they remembered. Squirrels seemed to learn by watching one another: once the first squirrel had mastered a pathway, others tended to have their first successful crossing within 6 minutes of another squirrel’s success. Errors that caused a squirrel to fall were extremely rare; instead, unsuccessful squirrels often simply turned around and left, to return later for another try.