Deer are commonly perceived as animals that exclusively consume plants, a classification generally accurate given their biological makeup. While often observed grazing or browsing, their dietary flexibility occasionally includes non-plant items.
Deer’s Primary Diet: Herbivores by Nature
Deer are classified as ruminants, possessing a specialized four-chambered stomach that efficiently processes fibrous plant material. This adaptation allows them to break down cellulose and extract nutrients from tough vegetation. Their diet predominantly consists of browse like leaves, twigs, and buds, often over 80% of their intake. They also consume forbs (broad-leaved herbaceous plants) and various forms of mast, including acorns and berries, depending on seasonal availability.
Deer are selective feeders, using their narrow snouts and long tongues to pick out nutritious plant parts. While they eat some grasses, especially new growth, these are less preferred due to lower digestibility and nutrient content. Their nutritional needs fluctuate, with higher protein demands during growth and reproduction. This consistent reliance on plant matter underscores their primary role as herbivores.
The Unexpected Truth: Occasional Consumption of Animal Matter
Despite their herbivorous classification, deer have been documented consuming animal matter on rare occasions, indicating an opportunistic omnivorous tendency. This behavior is typically driven by specific nutritional deficiencies, particularly a need for minerals like calcium, phosphorus, sodium, and protein not adequately met by their plant-based diet. Male deer, for instance, require substantial calcium for antler development, and pregnant or lactating does have increased mineral needs. When these demands are high and plant sources are insufficient, deer may seek alternative sources.
Observations have recorded deer eating various animal products, including bird eggs and nestlings. Documented instances include deer consuming small rodents like mice, squirrels, or rabbits, especially if found deceased. Deer also scavenge on carrion, such as dead fish or animal remains, including gut piles left by hunters. Furthermore, deer gnaw on shed antlers and bones (osteophagia) to obtain calcium and phosphorus. This dietary flexibility highlights their adaptability in obtaining essential nutrients.
How Common is This Behavior?
Instances of deer consuming animal matter are uncommon, representing an opportunistic feeding strategy rather than a regular part of their diet. Deer are not predators and do not actively hunt; their physical adaptations are designed for processing plant material, not for hunting or tearing flesh. This behavior typically occurs under specific environmental pressures, such as severe food shortages or heightened physiological demands like antler growth or pregnancy.
This occasional consumption primarily supplements dietary gaps, particularly for minerals or protein. While documented, these occurrences do not alter their fundamental classification as herbivores. Their overwhelming diet consists of leaves, twigs, fruits, nuts, and grasses. It remains an infrequent and need-driven behavior, not a shift in their core dietary nature.