Squirrels bury nuts, a common and observable behavior that scientists formally call “food caching.” This instinctual strategy allows squirrels to survive periods of scarcity, particularly during the cold months of winter. By gathering and concealing nuts, seeds, and other provisions during times of abundance, squirrels secure a decentralized food supply they can rely on. This preparation ensures they have energy reserves when active foraging becomes difficult.
Why Squirrels Practice Food Caching
The primary adaptive function of food caching is to prepare for seasons when food is naturally scarce, such as winter or drought. Tree squirrels, like the familiar gray squirrel, do not hibernate. They remain active throughout the winter, requiring a consistent food source to maintain their body temperature and metabolism. Caching allows the squirrel to manage a surplus of calories efficiently, converting abundant food into a reliable, long-term pantry.
Caching also serves as a defense against competition from other animals, including other squirrels who pilfer caches. Scattering food across a wide area ensures that if a competitor raids one stash, the entire supply is not lost. Squirrels are selective, assessing a nut’s quality by weight and smell, choosing only viable, energy-dense items to bury. They often consume perishable items immediately while caching less perishable ones for later retrieval.
Methods of Hiding: Scatter Hoarding and Larder Hoarding
Squirrels employ two distinct strategies for caching food: scatter hoarding and larder hoarding. Scatter hoarding involves burying individual or small groups of food items across a wide territory, creating hundreds of small, geographically dispersed caches. This method is favored by species like the Eastern gray squirrel and the fox squirrel.
The advantage of scatter hoarding is that it reduces the risk of total loss to theft or spoilage. Conversely, larder hoarding involves storing a large quantity of food in a single, central location, such as a nest or protected den. North American red squirrels are known for being larder hoarders, often aggressively defending their single stockpile. While larder hoarding is easier to manage, the entire food supply is vulnerable if the location is discovered or compromised.
How Squirrels Find Their Stash
Squirrels are remarkably good at relocating their buried provisions, relying on a combination of cognitive and sensory tools. Spatial memory is the primary mechanism, allowing the squirrel to create a mental map of its territory. They use landmarks like specific trees, rocks, or structures to pinpoint the general cache area. Studies show that the hippocampus, the brain area associated with spatial memory, can increase in volume during the peak autumn caching season.
Olfactory cues, or a powerful sense of smell, are then used to home in on the precise location of the nut. The scent of the nut, even through dirt or snow, acts as a final confirmation for digging. Researchers have found that squirrels can remember the type of nut they buried in a specific location, a technique called “spatial chunking,” which aids in efficient retrieval.
Seed Dispersal and Forest Regeneration
The squirrel’s caching behavior has a positive consequence for the environment that extends beyond its own survival. A certain percentage of buried nuts are forgotten, unrecovered, or their original owner does not survive the season. This failure rate is often cited as being between 5% and 25% for scatter hoarders, though some studies suggest higher percentages remain unrecovered.
These forgotten caches, often acorns and hickory nuts, are perfectly planted a few centimeters underground, providing ideal conditions for germination. This unintentional planting makes the squirrel a highly effective agent of seed dispersal, a process known as zoochory. By scattering seeds across a wide area, especially those of hardwood species, squirrels play a direct role in the regeneration and health of forest ecosystems.