Deer and elk, both large herbivorous mammals belonging to the Cervidae family, have distinct diets reflecting different evolutionary strategies for extracting nutrition from diverse plant life. Understanding the specific feeding habits of species like white-tailed deer, mule deer, and elk is important for wildlife management and ecosystem health. Though all are ruminants with four-chambered stomachs, their preferred forage and digestive anatomy differ significantly, influencing where they thrive.
The Diet of Deer: Preferred Browse and Forage
Deer are classified as “concentrate selectors,” preferring highly digestible, nutrient-dense plant parts over bulky, fibrous forage. Their relatively small rumen limits the volume of food they can process, necessitating a diet rich in protein and energy. This constraint means deer must be selective, choosing the most tender leaves, buds, and new growth tips from woody plants, collectively known as browse.
Forbs, such as clover and ragweed, are a major component of their diet, especially during spring and summer when they are succulent and high in protein. This high-quality forage is necessary for does raising fawns and bucks growing their antlers, which require 13% to 16% crude protein for development. In the fall, mast—hard and soft fruits and nuts like acorns and berries—becomes a sought-after food source due to its concentration of fats and carbohydrates. These lipid-rich foods are stored as fat reserves, providing the energy needed to survive the breeding season and the lean winter months.
The Diet of Elk: Grazing and Grassland Staples
Elk are often described as “mixed feeders,” but they lean heavily toward a diet dominated by grasses and grass-like sedges. Their larger body size and larger rumen capacity allow them to process greater volumes of bulkier, lower-quality forage. This anatomical difference means elk can efficiently digest the structural carbohydrates found in coarse grasses, which would provide insufficient energy for the more selective deer.
During spring and summer, elk seek out new-growth grasses and forbs, such as dandelions and clovers, which are high in protein and moisture. Forbs provide the concentrated nutrition required for the metabolic demands of lactation and antler growth. As the growing season progresses, elk shift to consuming more shrubs or woody browse, though grasses and sedges may still account for over 70% of their fall and winter intake. This ability to utilize large quantities of lower-quality forage makes elk successful inhabitants of open grasslands and meadow environments.
Navigating the Seasons: Nutritional Shifts for Survival
The nutritional quality of available forage fluctuates with the seasons, forcing both deer and elk to make dietary and physiological adjustments to survive. During the growing season of spring and summer, both species focus on consuming succulent, protein-rich forbs and new browse tips to meet their highest annual energy and protein demands. This period is used to build up fat reserves, which are the primary source of energy for the breeding season and winter.
As winter approaches, high-protein summer forage dies back, and both deer and elk transition to a low-nutrient diet of dormant grasses, woody twigs, and tree bark. This switch to fibrous, lignified winter forage is accompanied by a change in their digestive physiology, as rumen microbes must adapt to break down the material. Deer, as concentrate selectors, enter a state of reduced metabolism and rely heavily on fall fat reserves, while elk rely more on processing large quantities of dormant grasses. A sudden change in diet, such as consuming high-starch grains, can disrupt the specialized rumen microbes and lead to fatal digestive issues.
Beyond Food: Water and Mineral Requirements
Beyond caloric food sources, deer and elk have requirements for water and specific minerals that are met through various means in their environment. Water is the most necessary nutrient for survival, and while they drink directly from streams and ponds, they also obtain significant moisture from the forage they consume. During winter, when open water sources may be frozen, both species can satisfy their hydration needs by consuming snow.
Minerals are particularly important for reproductive success and skeletal maintenance, with sodium, calcium, and phosphorus being of specific concern. Sodium is often scarce in natural forage, which leads both deer and elk to seek out natural salt licks, mineral springs, or brackish water sources. Calcium and phosphorus are important for bulls during the rapid growth of their antlers and for does during pregnancy and lactation. Forbs and specific shrubs are good sources of these minerals, and the ideal dietary ratio of calcium to phosphorus is maintained at around 1:1 or 2:1 for proper absorption.