Deer are widely perceived as peaceful herbivores, gracefully foraging on plants in forests and fields. However, a closer look at their dietary habits reveals a more complex picture, raising the question of whether these plant-eaters sometimes consume non-plant matter. This exploration delves into instances where deer deviate from their typical herbivorous diet.
The Deer’s Herbivorous Nature
Deer are ruminant animals, possessing a specialized four-chambered stomach designed to efficiently digest plant material. Their diet primarily consists of browse, including leafy parts of woody plants, forbs (herbaceous broad-leaved plants), and mast like fruits and nuts. This digestive system, particularly the rumen, houses microorganisms that break down tough plant cellulose, allowing deer to extract nutrients. Deer consume a wide variety of plant species, with some studies identifying over 600 different plants in their diet.
Instances of Non-Plant Consumption
Despite their primary herbivorous nature, deer have been observed consuming non-plant matter. One surprising behavior is scavenging on carrion. There are also instances where deer have been filmed eating bird eggs, particularly those of ground-nesting birds, and even young nestlings. This behavior provides a readily available source of protein and calcium.
Deer have also been observed gnawing on bones and shed antlers, a behavior known as osteophagia. This can include the bones of other animals. While less common, some reports and anecdotal evidence suggest deer might consume fish. Female deer have also been known to consume the placenta immediately following the birth of their fawns.
Why Deer Eat Non-Plant Matter
The primary motivation for deer consuming non-plant matter is to supplement nutritional deficiencies in their diet. Plant-based diets, while providing energy and fiber, can lack specific minerals and protein, especially during certain physiological periods. Calcium and phosphorus are important for deer, playing a role in bone health, milk production, and antler growth in males. Hardened antlers, for example, are composed of about 22% calcium and 11% phosphorus.
Protein requirements increase significantly for females during pregnancy and lactation, and for males during antler development. A diet of 13-16% protein is considered optimal for antler development, and lactation imposes the greatest protein demand on female deer. When plant forage is insufficient in these nutrients, deer opportunistically seek out alternative sources like bones, eggs, or carrion to meet their physiological needs. This behavior is observed during nutritionally stressful times, such as late winter or drought.
The Rarity of This Behavior
Despite these documented instances, consuming non-plant matter is an infrequent and opportunistic behavior for deer, not a regular part of their diet. Deer remain fundamentally herbivores, with their entire physiology adapted for processing plant material. Over 85% of their overall diet consists of browse, forbs, and mast.
These occasional forays into consuming animal matter are exceptions driven by specific needs, rather than a shift towards omnivory. The instances are observed when deer are experiencing nutritional stress or when non-plant food sources are readily available. Deer do not hunt or actively pursue animal prey, but rather scavenge what they find. Therefore, while surprising, these behaviors do not redefine deer as omnivores.