Deer are a common sight across many landscapes. A common question arises regarding their diet: are these animals carnivores, herbivores, or omnivores? Despite some observations that might cause confusion, deer are primarily classified as herbivores.
Deer Primarily Consume Plants
The diet of deer overwhelmingly consists of plant matter, fitting their classification as herbivores. They consume a wide array of vegetation, adapting their intake based on season and geographic location. This plant-based diet includes leaves, tender twigs, and bark from woody plants, as well as buds, fruits, and nuts. They also eat forbs, which are broad-leaved herbaceous plants, along with fungi such as mushrooms. Forbs are often a preferred food choice due to their higher digestibility and nutrient content.
Browse, which refers to the leaves and twigs of woody plants, serves as a consistent and important food source for deer, particularly during colder months when other vegetation may be scarce. Deer are considered browsers rather than grazers, meaning they tend to eat parts of woody vegetation that are off the ground. Their ability to adapt their diet to various plant species demonstrates their flexibility in utilizing available resources for sustenance.
Digestive Adaptations for a Plant-Based Diet
Deer possess a specialized digestive system that enables them to efficiently process their plant-based diet. Like cattle and other ruminants, they have a four-chambered stomach: the rumen, reticulum, omasum, and abomasum. The process begins as deer consume plant material, which is then partially chewed and swallowed, entering the rumen, the largest chamber. Here, microorganisms ferment the food, initiating the breakdown of tough plant cellulose.
Following initial fermentation, deer engage in rumination, often referred to as “chewing cud.” They regurgitate partially digested plant matter back into their mouths for further mechanical breakdown. This re-chewing increases the surface area for microbial action and promotes saliva production, which helps buffer the rumen’s acidity. The food then passes to the reticulum, which works closely with the rumen, and subsequently to the omasum, where water and some minerals are absorbed. The final chamber, the abomasum, functions as the “true” stomach, secreting gastric juices for chemical digestion before nutrients are absorbed in the intestines. These adaptations allow deer to extract maximum nutrition from fibrous plant material, even from lower-quality forage.
Instances of Non-Plant Consumption
Despite their primary herbivorous classification, deer have occasionally been observed consuming non-plant matter. Such instances are rare and typically opportunistic. These unusual dietary behaviors include eating small birds, such as nestlings or eggs, which have been documented by trail cameras. Deer have also been seen consuming fish, particularly those washed ashore. Incidences of deer eating carrion, including dead animals or gut piles left by hunters, have been recorded.
Deer also chew on bones, shed antlers, and their own antler velvet. They may eat small mammals like rabbits or squirrels if they encounter them. Female deer have been observed consuming afterbirth following parturition, a common behavior among many mammals. These observations highlight a broader dietary flexibility than typically associated with herbivores.
Understanding These Dietary Exceptions
The occasional consumption of non-plant matter by deer is attributed to specific physiological needs rather than a shift in their fundamental dietary classification. A primary reason for these deviations is the supplementation of essential minerals, such as calcium, phosphorus, and sodium, which may be lacking in their herbivorous diet, especially during certain seasons. For instance, chewing bones or shed antlers provides a source of these minerals, which are important for antler growth in males and for lactation and reproductive success in females.
These behaviors also arise from opportunistic feeding, especially during periods of food scarcity like harsh winters, when alternative food sources are limited. While deer may consume meat or other animal products when the opportunity arises, their digestive system and physiology are not adapted for a carnivorous or omnivorous lifestyle. They lack the sharp teeth and predatory instincts to hunt prey, and their multi-chambered stomach is optimized for breaking down plant cellulose. These dietary exceptions do not reclassify deer; they remain herbivores that occasionally supplement their diet to meet specific nutritional demands.