Winter presents a significant challenge for deer, as snow blankets the landscape and many plants become dormant. These herbivores must adapt their feeding strategies to survive the colder months. This seasonal shift highlights their natural diet and the adaptations that allow them to endure periods of scarcity.
Natural Winter Diet
During winter, a deer’s diet shifts from lush forage to woody browse. This includes twigs, buds, and bark from various trees and shrubs. Common examples of preferred browse species include red maple, yellow birch, willow, sumac, aspen, dogwood, and white cedar. Evergreen foliage, like needles from conifers such as arborvitae and yew, also serves as a food source when accessible.
Deer also seek out leftover agricultural crops like corn and soybeans if fields are nearby and not covered by deep snow. Less available, they may paw through snow to find dried forbs and grasses. Acorns and nuts, if present from late autumn and not buried under heavy snow, provide an energy-rich supplement. The nutritional value of these winter foods is generally lower than their summer diet, posing a challenge for deer to meet their energy needs.
Adapting to Winter Scarcity
Deer adapt to limited winter food availability through physiological and behavioral changes. They slow their metabolism, reducing energy expenditure and allowing them to endure longer periods without substantial food intake. This means they need approximately half the food required during summer. They also build up fat reserves during warmer months, which serve as important energy sources throughout winter.
Their digestive system changes to process high-fiber woody browse more efficiently. Rumen microbes, in a specialized stomach chamber, adapt over several weeks to break down tough plant material. Behaviorally, deer reduce movement to conserve energy and often gather in “deer yards” or sheltered, forested areas that offer protection from wind and snow and access to browse. They also obtain water by consuming snow or moisture within their food.
Dangers of Human-Provided Food
Despite good intentions, providing food to deer can be detrimental to their health and survival. Foods like corn, hay, or processed items are often unsuitable for a deer’s digestive system. Rumen microbes, specialized for high-fiber browse, cannot properly digest large amounts of carbohydrates from human-provided foods. This can lead to acidosis, where excess lactic acid builds up in their stomach, causing bloating, diarrhea, dehydration, and potentially death, even with a full stomach.
Artificial feeding sites concentrate deer, facilitating the rapid spread of diseases like Chronic Wasting Disease (CWD), bovine tuberculosis, and other parasites. This close contact increases the risk of transmission through saliva, urine, and feces. Deer habituated to human feeding may also lose their natural wariness, making them more vulnerable to vehicle collisions and predation. Such dependency can also alter their natural foraging instincts and lead to aggressive behavior as they compete for food.