You Asked: How do squirrels remember where they buried their food? --- Aidan, Concord, Massachusetts
Marshall Answered: First let's lay a foundation - Not all squirrels bury nuts. Gray squirrels do bury things like acorns and walnuts, but red squirrels do not. Red squirrels horde their nuts in piles. As described in this article, these two different behaviors can have a big effect on a forest. Gray squirrels do not recover all of the nuts that they bury, and these nuts go on to become trees. Red squirrels horde their nuts above ground, and those nuts never germinate. From the forest's perspective, gray squirrels are better.
So how do gray squirrels find all the buried nuts? As described in the article, they don't find a lot of them. To be more specific, this article points out that gray squirrels only find 26% of their buried nuts. In other words, the majority of nuts that gray squirrels bury stay in the ground, and have the potential to sprout.
How do gray squirrels find the nuts that they bury? Obviously, in most cases, they do not find them. But they do find some. It is thought that they remember where they bury some of the nuts through landmarks, in sort of the same way you remember (or don't remember) where you left your car keys when you got home.