All animals have evolved to solve specific problems that affect their survival. One of squirrels’ big challenges is storing the supply of food they gather in the fall so it will last through the winter.
To study how they do that, we gave 45 fox squirrels in Berkeley, California, different kinds of nuts: almonds, hazelnuts, pecans, and walnuts. Then we followed the animals with a handheld GPS tracker—a device that uses satellites to provide positioning data on Earth—to see where they buried them. We found that the squirrels didn’t bury nuts randomly. Instead they clustered them by type. For example, they would put almonds in one place and walnuts in another.
Next, we put microchips in nuts so we could scan the ground with a detector and identify where squirrels had buried their caches. We discovered that a lot of squirrels moved their collections of nuts around. We’re not sure why. Maybe squirrels moved them to more secure areas. Or maybe reburying nuts refreshes their memory of where they’re hidden.