Nature: The sophisticated way squirrels bury nuts

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Have you ever watched squirrels scurry around to bury a nut? If you’ve stayed in more than a few campgrounds, you’ve likely seen them do it many times. You may have wondered how those squirrels know where to bury the nuts, then return to find them. It turns out, they have a pretty sophisticated method.

Fox squirrel

Fox squirrels, for example, apparently organize their stashes of nuts by variety, quality and possibly even preference, according to new UC Berkeley research.


The study, published in the Royal Society Open Science journal, is the first to show evidence of squirrels arranging their bounty using “chunking,” a cognitive strategy in which humans and other animals organize spatial, linguistic, numeric or other information into smaller, more manageable collections, such as subfolders on a computer.

Fox squirrels stockpile at least 3,000 to 10,000 nuts a year and, under certain conditions, separate each cache into quasi “subfolders,” one for each type of nut, researchers said.

Presumably, sophisticated caching techniques maximize the squirrels’ ability to remember where they’ve stored their most prized treats while at the same time hiding them from potential pilferers, the researchers said.

“Squirrels may use chunking the same way you put away your groceries. You might put fruit on one shelf and vegetables on another. Then, when you’re looking for an onion, you only have to look in one place, not every shelf in the kitchen,” said study senior author Lucia Jacobs.

Over a two-year period, the research team tracked the caching patterns of 45 male and female fox squirrels as the reddish gray, bushy-tailed rodents buried almonds, pecans, hazelnuts and walnuts in various wooded locations on the UC Berkeley campus.

The study used combinations of locations and nut sequences on various groups of fox squirrels. In one experiment, for example, each of the squirrels were fed 16 nuts, one after another, under two separate conditions: Some were fed at the locale where they had cached the previous nut fed to them while others were fed at one central location, to which they would need to return if they wanted another nut.

Researchers gave some squirrels 16 nuts in rows of four, say, almonds followed by pecans, followed by hazelnuts and then walnuts, while others received 16 nuts in random order.

Using hand-held GPS navigators, researchers tracked the squirrels from their starting location to their caching location, then mapped the distribution of nut types and caching locations to detect patterns.

They found that the squirrels who foraged at a single location frequently organized their caches by nut species, returning to, say, the almond area, if that was the type of nut they were gathering, and keeping each category of nut that they buried separate. Meanwhile, the squirrels foraging in multiple locations deliberately avoided caching in areas where they had already buried nuts, rather than organizing nuts by type.

“These observations suggest that when lacking the cognitive anchor of a central food source, fox squirrels utilize a different and perhaps simpler heuristic (problem-solving approach) to simply avoid the areas where they had previously cached,” the study concludes.

Watch the video to watch a fox squirrel in action.

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Mark and Vickie

I’ve heard that squirrels only remember a 1/3 of the places they bury their stash. Not sure if that’s true or not.

Pamela

We will all have different ideas on how our hard-earned money should be spent.

We humans have done a lot of damage to our environment and the creatures sharing our world. I believe a greater understanding of animals and the natural balance of nature will improve our environment for all users.

wndopdlr

I’m with Nuts and Tommy. My first thoughts when reading this is “how many millions did this cost us?”

Lisa

Interesting! I’ll look at squirrels in a different light!

Nuts

How much did taxpayers “shell out” for this study?