In the winter of 1979, I had the privilege of spending time with Bill Severinghaus, New York’s legendary deer research biologist. He had come to my part of New York to study the impact wintering whitetails were having on forest regeneration.

For two days, I watched Severinghaus as he scoured the woods checking for browse damage. He and his assistant took copious notes and every so often he would take the time to explain what he was observing, which gave me an opportunity to ask questions. Although I was a passionate deer hunter, I knew little of the whitetail’s nutritional needs.

The experience was a true eye-opener. In hindsight, it is safe to say I learned more about the whitetail’s feeding habits and nutritional needs in those two days than I had learned in all the years leading up to them.

Severinghaus taught me how critical it was for whitetails to get enough food to sustain them throughout the year. He mentioned several times that a white-tailed deer requires approximately 1½ tons of food per year to survive. At the time, I was impressed that a single deer could actually consume that much palatable food in 12 months. It wasn’t until years later when I actually began raising deer that I truly understood some of the struggles deer go through to find enough food to survive.

Constant Seekers

Fast forward to 1994. While preparing to shoot the photos for my book, Whitetail: Behavior through the Seasons, I made it a point to drastically increase the amount of time I spent in the woods. Throughout that year, I literally lived with whitetails, with much of my work taking place on the Avery Estate in the heart of New York’s Adirondack Mountains. That experience caused me to become more passionate about the study of deer behavior, which led to the building of a behavioral study facility on our farm the following year.

One of the more fascinating things I learned about whitetails during this time and the years that followed has dealt with their feeding habits. Although their overall behavior is quite similar, no two deer are the same, especially when it comes to food. The volume of food each deer consumes can vary greatly, even under the best of conditions. In fact, except for a few weeks during the rut, whitetails are almost always looking for food.

How it Works

White-tailed deer are ruminants, meaning they have a four-compartment stomach to process food. Being ruminants allows deer to eat and utilize foods man cannot. Their stomach’s four compartments (in order of flow) are; rumen, reticulum, omasum and abomasum.

When a deer bites off forage or browse, the food mixes with saliva before being swallowed to the rumen, where it mixes with bacteria, protozoa and other rumen contents. As the food begins to digest, it moves to the second stomach compartment, the reticulum. Once in the reticulum, boluses of food are regurgitated back up the esophagus for cud chewing. A whitetail chews its cud to further break down the food so microorganisms can better absorb it. The more thoroughly a deer chews its cud, the less time the food has to remain in the rumen.

My journal entries indicate that, on average, a whitetail will chew its cud 40 to 55 times before re-swallowing the food. In the spring and early summer months, when their natural foods are tender and low in fiber, they chew their cud 40 to 45 times before re-swallowing it. From late summer through winter, preferred foods get progressively more fibrous, forcing a deer to have to chew its cud 45 to 55 times before re-swallowing it.

From the reticulum, the food particles go to the third compartment, the omasum, where water absorption takes place. From here, the fermented stomach contents go to the stomach’s last compartment, the abomasum. In the abomasum, the food particles are mixed with digestive enzymes before moving on to the small intestine, where the nutrients from the food are absorbed into the bloodstream.

Seasonal Needs

Raising whitetails has provided me an opportunity to study their seasonal food needs. It has been 31 years since my first conversation with Severinghaus, and I will still say he was absolutely spot-on in his assessment that each whitetail consumes approximately 1½ tons of food per year, which breaks down to an average of about 8 pounds of dry matter per day.

However, the average doesn’t tell the whole story, because during winter a deer in the North might not eat for several days. In late summer and early autumn (when mast is everywhere), it might consume twice the daily average. Although the thought of finding 8 pounds of food a day might sound rather easy, it is not, because whitetails are very picky eaters and their preferred foods are not always available.

Spring Requirements

When a whitetail exits a Northern winter, its fat deposits are depleted. In some locations, their life teeters in the balance and they are seemingly ready to give up the ghost before spring green-up arrives. Unlike winter, when whitetails bed up to 90 percent of the time and eat very little, deer in spring are very active and feed more than five times a day.

Spring’s new growth is highly palatable, with most plants offering their highest protein and nutritional values of the year. Protein makes up the building blocks of animal tissue, so it is critical that high-protein food sources are available to ensure bucks obtain maximum antler growth and does get enough nutrition for lactation. On average, a whitetail should have an overall average protein level of 14 percent to 16 percent. Unfortunately, this is not possible in the natural habitats of many free-ranging deer herds.

In our research facility, we supplement the forage our 15 whitetails get from the 11 food plots inside the enclosure with a custom mixed feed, fed once a day. The protein level in the feed varies from 17 percent in winter to 22 percent during the antler-growing and lactation months. In addition to the 25 percent-plus protein levels our food plots offer in spring, we provide our deer with freshly cut browse. This combination gives our deer the balance of nutrients they need to flourish.

The protein levels of natural habitat in spring range from 5 percent to 13 percent, which are low compared to farm crops like clover and alfalfa, which can easily top 25 percent in spring. However, what the natural habitat lacks in protein it makes up for in other nutrients. From green-up to the end of May, whitetails might consume 16 pounds of highly nutritious dry matter each day in the form of buds, tender new-growth leaves and newly sprouted farm crops.

Summer

As spring fades to summer, plants and leaves begin to mature, making them less palatable. Lignin (the substance that allows plants to stand upright) increases and the fiber content rises along with it, lowering the protein levels of most plants as summer progresses. Summer’s heat and high insect populations place a tremendous amount of stress on deer, causing them to be less active during daylight hours. The stress causes deer to change their feeding habits during summer and feed heavily at the end of the day and throughout the night when conditions are cooler.

Despite being less active during daylight, a whitetail will still eat as much food as it will in the spring. During the summer, does will have a difficult time maintaining body weights — despite how much they eat — due to the stress of nursing and raising fawns.

Autumn

The amount of food available to whitetails from late August to the end of October can be impressive. I live in New York State’s dairy and wine country, which provides an incredible amount of natural and agricultural foods deer prefer. Consequently, our wild free-ranging whitetails have a lot of high-octane foods at their disposal.

For example, in autumn our enclosure whitetails will often gain more than 20 percent of their body weight in a 60-day period spanning from late August to late October.

Based on fat content analysis of the free-ranging deer harvested in our area, I believe the weight gain for wild deer is very similar to the animals in our enclosure.

Although I have never seen an exact figure given to the amount of food a wild deer consumes during the autumn months, my enclosure deer each consume 16 to 18 pounds per day. It is almost like they know they’ll need the extra fat to get them through the rut and coming winter.

Winter

Winter technically arrives Dec. 21, but in some parts of North America it settles in by mid-November. When snow piles up and temperatures drop to frigid levels, whitetails shut down and drastically reduce their eating habits. If conditions are extreme, a whitetail might go days between feeding sessions.

From mid-December through early April, deer get the nutrients they need for survival from the fat deposits they built up during autumn. What I’ve found especially interesting in photographing and raising deer is that even if food is available, they will not eat during harsh conditions. Rather, they bed extensively to conserve body heat and energy. About the only time they will consume any amount of food is when the air temperature reaches or rises above the seasonal norm. Even when good feed is available, most snowbound deer will not eat more than a pound of food per day in winter.

Conclusion

A whitetail’s life can be best summed up as a roller-coaster event, made up of many peaks and valleys as it strives to survive in the environments nature throws at it. In some ways, deer seem to be going with the flow. This is never more apparent than how they act and react to the food that sustains them. Their world is one of feast and famine — always dependent on food.

— Charles Alsheimer was D&DH’s contributing editor of deer behavior. He passed away in 2017.