Fox squirrels organize their nuts by quality, quantity and preference

Sept. 13 (UPI) — Like a child sorting Halloween candy, fox squirrels organize their loot using what’s known as “chunking.” Chunking describes the process of dividing a large number of items or information into smaller groups.

A new study — published this week in the journal Royal Society Open Science — offers the first evidence that squirrels use chunking to divvy up their nuts.

A single eastern fox squirrel collects between 3,000 to 10,000 nuts each year. The nuts aren’t lobbed haphazardly into a hole. Instead, they’re organized by type.

“This is the first demonstration of chunking in a scatter-hoarding animal, and also suggests that squirrels use flexible strategies to store food depending on how they acquire food,” Mikel Delgado, a post-doctoral researcher at the University of California, Berkeley, said in a news release.

Delgado hypothesizes that chunking helps squirrels recall what they hid and where.

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

For two years, Delgado and Jacobs tracked the nut-stashing patterns of 45 male and female fox squirrels. Every day, researchers gave each squirrel 16 nuts — a combination of almonds, pecans, hazelnuts and walnuts. Researchers varied the order of the distributed nuts and location at which the nuts were distributed. GPS devices helped the scientists track where the squirrels carried and buried each nut.

Squirrels who foraged in a single location tended to organize their caches, or groups, by nut type, while squirrels who foraged a several locations tended to prioritized spatial separation among their caches, never burying nuts close to the place where they retrieved them.

“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,” researchers concluded.