Deer are a common sight across many landscapes, and their presence often sparks curiosity about their eating habits. Understanding what deer naturally consume is important for their well-being and the health of their ecosystems. Deer are herbivores, meaning their diet consists entirely of plant matter. Their digestive systems are specifically adapted to process the fibrous components of plants found in their natural habitats.
Natural Deer Diet
Deer primarily forage on a diverse range of plant materials, which can vary significantly with the seasons and available vegetation. Their diet largely includes browse, which refers to the leaves, twigs, and shoots of woody plants, along with forbs, which are herbaceous broad-leaved plants. Grasses and various forms of mast, such as acorns, nuts, and fruits, also constitute important parts of their diet. For instance, hard mast like acorns provides a high-energy source, particularly during autumn, while soft mast, including berries, is consumed in summer. Deer are selective eaters, often choosing nutrient-rich and easily digestible plants to meet their daily intake requirements, which can be 6% to 8% of their body weight in green foliage and browse.
Their digestive system is specialized, featuring a four-chambered stomach, similar to cattle and other ruminants. The first and largest chamber, the rumen, acts as a fermentation vat where a diverse community of bacteria, protozoa, and fungi break down plant cellulose into usable nutrients. This process requires deer to regurgitate and re-chew their food, known as “chewing cud,” to further break down tough plant fibers. Because their digestive system is adapted to process specific types of forage, sudden changes in their diet can disrupt the delicate balance of their stomach microbes, making it difficult for them to digest unfamiliar foods.
Almonds: An Unnatural Treat?
While deer might eat almonds if offered, these nuts are not a natural or beneficial part of their typical diet. Deer are opportunistic and may consume unusual items out of curiosity or hunger, but almonds do not align with their specialized nutritional needs. The nutritional profile of almonds includes high levels of fat and protein, with one ounce providing about 165 calories, 14 grams of fat, and 6 grams of protein. This composition differs significantly from the fibrous plant matter that deer are naturally equipped to digest.
Raw almonds, particularly bitter varieties, contain cyanogenic glycosides like amygdalin, which can release hydrogen cyanide when metabolized. While the sweet almonds commonly sold in stores contain much lower levels of these compounds, the presence of even small amounts of cyanide is concerning for deer. For deer, whose digestive systems are finely tuned to their natural forage and adapt slowly to dietary changes, such compounds could pose a risk, especially if consumed in quantity.
Why Feeding Deer Can Be Harmful
Providing human foods, including almonds, to deer can have several negative consequences for their health and behavior. Deer stomachs are not designed to handle processed or high-sugar/fat human foods, which can lead to severe digestive issues like rumen acidosis. This condition, caused by an overload of carbohydrates, disrupts the microbial balance in their rumen, potentially leading to bloating, diarrhea, dehydration, and even death, sometimes within 72 hours. Deer can starve with a full stomach if their gut microbes cannot properly digest the food provided.
Feeding deer also alters their natural behaviors. They can become habituated to human presence, losing their innate fear, which increases the risk of conflicts such as property damage or vehicle collisions. This dependency can also disrupt their natural foraging patterns and migration routes. Concentrating deer at feeding sites facilitates the rapid spread of diseases like Chronic Wasting Disease (CWD) and bovine tuberculosis through direct contact or contaminated food and soil. Such gatherings can also strain local vegetation and attract pests, further harming the environment and the deer population.