Biology

• The deer is a ruminant. This means that the deer has multiple chambers in its stomach for digesting food. In the first chambers, the food that a deer eats is mixed with bile to form cud, which is then regurgitated, chewed and re-swallowed. The cud passes through the first chambers and into the third, where water is removed and then to the final chamber where nutrients are absorbed. Deer are herbivores, which means they eat plants.
  
  

Function

• Ruminants, such as deer, are able to eat many plants that other animals can't digest. In particular, deer are able to eat woody plants because they can break them down into cud and then absorb any nutritional benefit. Other ruminants include cows, goats, llamas and giraffes.
  
  

Geography

• Deer populate the whole of the United States. White-tailed deer are less common in the western half of the U.S., but its relatives, the mule deer and black-tailed deer, can be found there. Deer diet will vary according to region and plant availability. Common food sources are legumes, grasses, acorns and corn.
  
  

Spring and Summer

• As deer have such a wide ranging diet, they will usually feed on the best available food source. In the spring deer tend to graze on grasses and other green plants. They will eat fruits and seeds as they come into season. These foods are typically referred to as "preferred" foods as deer will bypass other options at this time.
  
  

Fall

• "Marginal" foods are consumed by deer as the other food sources are depleted or become unavailable. Deer in farming areas will make corn a mainstay of their diets during the fall season. At this time, they will also eat hard mast foods such as acorns and other nuts as they build reserves for winter.
  
  

Winter

• Due to their ability to forage and their ruminant nature, deer seldom reach a starvation level during winter months unless the herd is severely overpopulated. During the winter, deer can exist on a diet of twigs and branches. Though these have little nutritional value, they can sustain the deer through the season.