The familiar sight of a squirrel burying a nut or darting up a tree often leads people to label it a simple forager. However, these common rodents, especially in urban environments, frequently exhibit behaviors that suggest a different classification. The confusion stems from their highly adaptable diet, which includes everything from natural seeds to discarded human food waste. To correctly understand a squirrel’s feeding habits, we must first establish the biological framework that differentiates active food acquisition from feeding on remnants.
Defining Scavenging and Foraging
In ecology, the term “foraging” describes the active search and exploitation of a food resource by an animal. A forager actively seeks out living or recently available food items, such as seeds, fruits, or insects. This action is the primary means by which most animals secure their sustenance.
Scavenging, in contrast, is defined as the consumption of dead and decaying organic matter, including carrion or refuse. Animals that rely on this method are known as scavengers and fill the ecological role of waste removal. While some species, like vultures, are obligate scavengers, many animals are facultative, meaning they will scavenge opportunistically only when necessary.
The Primary Diet of Squirrels
Squirrels are classified as opportunistic omnivores, meaning their diet consists of both plant and animal matter. Their primary food source is plant material, such as the nuts and seeds of deciduous and coniferous trees, which they actively search for and cache. They are well-known for scatter hoarding, a foraging strategy where food items are buried in many separate locations for later retrieval.
Depending on the season, their plant-based foraging extends to tree buds, flowers, fungi, and tree sap. This active searching for and harvesting of seasonally available natural items clearly places them within the biological definition of a forager. They possess powerful incisors and strong jaw muscles suited for gnawing and grinding the tough shells and husks of their preferred foods.
The omnivorous part of their diet involves animal protein, which is particularly important during periods of reproduction or limited plant availability. This animal matter can include insects, insect larvae, bird eggs, or even very young nestlings. The consumption of these items is a predatory or foraging act, not scavenging, as the squirrel is actively hunting or harvesting a live resource.
Examining Non-Standard Food Sources and Refuse Consumption
The popular perception of squirrels as scavengers arises from their behavior in human-dominated landscapes where they encounter non-standard food sources. In urban parks and city centers, squirrels frequently consume human refuse. This includes discarded items like leftover fast food, crumbs, and trash retrieved from bins.
Studies on urban populations, such as the Eastern Gray Squirrel, have shown that this refuse consumption is opportunistic and dictated by seasonal scarcity. Squirrels tend to raid trash bins and compost piles most frequently during winter, when natural food sources like nuts and seeds are depleted. The majority of the food retrieved from these urban sources consists of starchy foods like bread and French fries.
While squirrels will occasionally gnaw on discarded bones for calcium or consume small pieces of true carrion, this is not their primary feeding method. Their consumption of human refuse is a form of facultative scavenging—a behavior adopted out of necessity or convenience rather than a defining characteristic. Therefore, while a squirrel is an opportunistic omnivore and forager, its occasional reliance on discarded waste makes it a situational scavenger.