Managing for optimal autumn nutrition
Unlike domestic livestock, the whitetail’s behavior, digestive processes, physiology — and resultant nutritional needs — change seasonally. Individual requirements also vary according to the animal’s sex, age, reproductive state and environmental pressures, which tend to vary regionally. Hence, identifying specific nutritional deficiencies and determining corrective measures can be difficult — there are no “cookbook” solutions.
For whitetails, the autumn season is an especially critical period — a time of physiological change and shift in nutritional requirements in preparation for the approaching stressful winter season.
Young deer are especially vulnerable to nutritional shortage during autumn because they must simultaneously grow and fatten. As a result, deer populations nutritionally stressed during autumn may suffer a host of consequences that set the stage for long-term herd management problems. Some of these maladies can readily be identified and corrected with proper food and cover management.
White-tailed deer fawns have the inherent ability to grow rapidly and assume adult habits at a young age provided they live in favorable habitat and have good nutrition. Fawns don’t become functional ruminants until they are about 2 months old.
Prior to this they are dependent upon a good supply of their mother’s milk, which will vary in quantity (but not quality) according to the mother’s nutritional state.
By the time fawns weigh 30 to 35 pounds, at about 2 months of age, the rumen-reticulum portions of their stomachs achieve nearly adult proportions. They are considered to be in the “juvenile ruminant phase” when 50 to 100 days old.
At least on northern range, fawns are weaned during the late summer/early autumn period — generally in late August or early September. The quality and quantity of nutritious forage they receive immediately post-weaning will determine how well they develop physically, the amount of fat they store, and ultimately their chances of surviving winter.
Given a favorable supply of nutritious forage during autumn, fawns can double their body weight between weaning and the start of winter, but do not reach their maximum body size and fatness until early December. Some might even achieve puberty.
It’s important to note that fawns must simultaneously grow and fatten during the autumn period. The critical body weight for Northern fawns is between 77 and 88 pounds. Animals weighing less than this lose more body heat from cold exposure, have shorter legs making travel through deep snow difficult, and are more likely to die from malnutrition during long, cold winters(as experienced during 2013-14).
This is not to imply that autumn nutrition is not important for adult whitetails. The nutritional status of yearlings, in particular, during autumn will at least in part determine their adult stature, possibly even their survival prospects. For example, yearling does malnourished during autumn are less likely to breed and conceive young.
In autumn, whitetail’s show a strong preference for energy-rich foods high in carbohydrates. Acorns, beechnuts and other starchy mast crops — as well as apples, cherries, grapes, and other wild-growing and cultivated crops — are choice deer foods because they promote fattening. When available, a deer will eat about 1 ½ pounds of acorns per day, per 100 pounds of body weight.
Because fat reserves can be metabolized more readily than protein for energy needs when nutritious forage is scarce, storing fat in autumn is a mechanism that enhances deer survival during the food scarce winter months. Like other seasonal events in the whitetail’s life, accumulation of fat is cued to photoperiod and is hormonally controlled — it’s an obligatory process. That is, all deer are inclined to store some fat in autumn.
The importance of digestible energy versus protein in the autumn diet of fawns was demonstrated in our studies at the Cusino Wildlife Research Station located in Upper Michigan.
During a 10-week period (October through mid-December), fawns provided diets higher in energy (3000 kilocalories per gram of pelletized feed) exhibited better body growth and fatness as compared to those fed low (2700 kcal) energy diets, regardless of feed protein content (16.2 percent or 6.6 percent). This indicates that autumn food sources high in digestible energy are critically important for proper fawn development, whereas the amount of protein in the diet is not particularly important.
In other words, in autumn, deposition of fat reserves takes precedence over body growth among young deer. Fawns nutritionally stressed in autumn may be reasonably fat but stunted in size at the start of winter a consequence that can carry into adulthood.
What to Look For
Deer are classified as “concentrate selectors” — they carefully select the most nutritious and palatable forages. As a result, overly abundant deer tend to remove the most nutritious plants, leaving the less nutritious ones to flourish. Consequently, areas of over-grazed herbaceous growth may not give the devastated appearance one would expect.
Certainly, not all areas may need or benefit from intense autumn range deer management. The presence of pregnant doe fawns, yearling does that routinely conceive twins, buck fawns with infant antlers, yearling bucks with respectable multi-tined antlers, and a fawn to doe ratio approaching or exceeding one fawn per doe are a few signs of a socially well-balanced and healthy deer population.
However, some areas may suffer from chronic shortages of nutritious forage, especially during the spring, summer, and autumn seasons, because of infertile soils, old growth forests, lack of openings, deer overabundance, unfavorable climate and other factors.
Obviously, where they are overly abundant the first order of business would be to decrease deer numbers. Likewise, frequent late-breeding/late birthing, as more likely occurs in the South, probably signals a socially unbalanced and/or year-round nutritionally stressed deer herd requiring harvest management changes. Late-birthing is less likely to account for runty fawns and small yearling bucks sporting poor antlers in the North.
In contrast, some areas suffer the consequences of more sporadic autumn nutritional stress. As an example, periodic drought, especially in the South, or unusually early snow cover in the North can negatively impact young deer development and survival, as can widespread nut-crop failure.
In the North, a mere 3 or 4 inches of snow cover can cause deer to shift from foraging on succulent herbaceous forage to eating energy deficient woody browse too early. Or, persistent early cold weather and heavy snow cover can cause unusually early deer migration to wintering habitat, which is sometimes devastating to local deer herds.
Fawns of small stature, a high incidence of non-pregnant yearling does, low conception rates among adult does, delayed autumn coat molt, yearling bucks sporting short-spike antlers, and high winter deer mortality rates are just a few things that might indicate serious autumn range deficiencies and a need to re-evaluate autumn deer range management practices.
Obviously, monitoring the autumn health status of young deer (fawns and yearlings) is the best way to detect autumn range shortages and to evaluate the success of changes in management efforts designed to rectify the situation.
What To Do About It
The best deer habitat is diverse. It contains a mix of food and cover in the form of trees, shrubs, and small openings that provide a plentiful supply of nutritious forage year-round. Food plots are not a substitute for proper forest and deer herd management, but they add valuable diversity to the landscape. Most importantly, when carefully planned, food plots can target specific seasonal needs and provide forage much higher in digestible energy, protein, minerals and vitamins than typically is available naturally. In some cases, even diet supplementation might be employed to improve autumn nutrition for deer.
Habitat Management: The goal of deer habitat management is to provide favorable interspersion of food, water, shelter, and escape cover. Generally speaking, deer do best in early successional stages of forest cover with plenty of “edge.”
Given the regional complexity of managing forest cover for deer, employing a forest consultant to devise a forest management plan is essential. Such a plan will use a variety clearcuts, select cuts, and shelter cuts best suited to the timber species and conditions involved. However, the plan should emphasize the importance of deer, including the development and maintenance of favorable autumn habitat for them. Such planning should also involve the interaction of burning, planting, as well as opening creation in order to achieve optimal habitat for deer.
There probably is no other natural food more attractive and valuable to white-tailed deer during autumn and early winter than oak acorns — and they grow just about anywhere. Although generally low in protein content, few other natural forages provide more metabolizable energy or fattening power than oak acorns.
Acorn production can be increased through wise forest management, sometimes involving planting of new trees. Protection of large oaks and selective thinning is recommended, because acorn production is directly related to tree diameter and crown size. It is wise to identify good producers and mark them as “save” trees. Because of the acorn’s value as a deer food source, it is best that both the white oak and black oak groups be left within managed forests to ensure some mast production each year.
Early successional forests dominated by aspen are considered good summer and fall habitat for deer across the northern region. However, their value for deer is influenced by the mix of plant species, tree age and stocking level, stand size, site productivity, and location relative to other stands. Moderately stocked stands with their inherently thin canopies, allow sunlight to penetrate and thereby provide favorable growth of herbaceous plants.
Aspen management for deer consists of cutting and removal of all trees in a stand (clear-cutting) to allow sunlight onto the forest floor, which stimulates sprouting from the parent root system. The economic rotation for aspen is usually between 40 and 60 years.
Forest openings are grassy fields or meadows comprised of grasses, legumes such as clovers, and numerous other herbaceous plants. Most existing relict openings are the result of historical logging, fires, or failed agricultural development. They are especially valuable to deer throughout the snow-free period.
A general goal is to have 5 to 10 percent of the available upland habitat maintained as permanent natural openings. For best results, openings created for deer should be 1 to 3 acres in size and irregularly shaped to provide maximum edge. A general rule is to have 1 or 2 openings for every 40 acres of forested land. Although the nutrient content and palatability of plants grown in openings for deer varies between various soil types, the diversity and abundance of herbaceous plant species preferred by deer is best on the more fertile soils.
Since natural openings tend to be invaded and filled by trees, due to succession, some maintenance may be required. Application of chemical herbicides, machine mowing, cutting with hand tools, or burning can control invading tree species.
Forest openings can also be created with minimum work and expense by clear-cutting on sites not particularly well-suited to food plot management. The best sites are pole-sized hardwood stands less than 50 years old, where there is little or no advanced reproduction. Select sites that are poorly or somewhat poorly drained, or spots that are excessively well-drained. Frost pockets are also good choices.
Simply clear-cut all hardwood trees on areas 1 to 10 acres in size. Sites dominated by good stump sprouters like red maple, basswood, or aspen should be cut during summer. Then spray the stumps with herbicide to minimize sprouting.
Food Plots: The role of agricultural food plots in deer management is a relatively new science. Originally viewed with skepticism by most dyed-in-the-wool wildlife habitat managers, the use of food plots to target spring and fall food stress for whitetails is now well accepted as sound scientific management.
There are no “cookbook” formulas for creating and maintaining food plots for deer, because environmental factors are so highly variable from one region to the next.
Texas A&M University scientist David Hewitt notes the following: “There is a bewildering array of forages that have been planted in food plots (at least 60 species).” For this reason, those considering establishment of food plots for deer should consult an expert in their area for advice.
Even so, if you are considering food plot management for deer, I would recommend reading the books cited here by the QDMA and Ed Spinazzola to gain a basic understanding of what is involved. Remember, although there may be regional similarities in autumn deer nutrition requirements, as well as associated problems and likely solutions, what works in the South might not in the North, and vice versa.
In the North, Spinazzola recommends that food plots be 3 to 5 acres in size. In late-spring, summer or late-fall, he suggests planting perennial forages such as forage chicory, legumes (including red, kura, white, alsike, and ladino clover), alfalfa, and birdsfoot trefoil. High energy brassicas like forage rape, kale, canola and turnips, which stay green under the snow all winter long, are good late-fall/winter choices, as are fields of standing corn, soybeans, and sugar beets.
Georgia scientist Karl Miller notes the following: “Obviously, winter stress is greater for deer in northern regions compared to many areas in the South that have a milder climate and a greater abundance of natural forages during winter. However, even in southern regions winter nutrition can be a significant concern. Targeting supplemental plantings…to provide high energy nutrition during fall to allow deer to maximize fat reserves before winter, can provide significant benefits to a deer herd.”
In the South, Miller indicates food plot management should target the late summer/early autumn period, when natural herbaceous forage has matured (i.e., is less nutritious) but oak mast is not yet available. He considers corn and grain sorghum the best to fill that void when digestible energy supplies for deer may be in short supply. However, planting must be timed so that the crops mature in a timely fashion when needed most. Also, if left standing into fall and winter, corn can provide critically needed energy during years of poor acorn production.
Supplemental Feeding: Jokingly, Miller says, “Or just pour the stuff on the ground.” Actually, hunters in many areas do just that annually, as they dump out thousands of tons of energy-rich apples, sugar beets, and corn for hunting purposes. While baiting is essentially a form of diet supplementation for deer during a nutritionally critical period, to my knowledge, the biological impact of baiting has not been determined.
Providing nutritional supplements to enhance the diet of deer has increased sharply in recent years. In the North, it is frequently used in emergency situations to reduce over winter malnutrition related losses during severe winters. In the South, diet supplementation on private lands is routinely employed to increase productivity and survival of deer in areas of inherently poor habitat.
Studies we conducted in Upper Michigan showed that supplementing autumn nutrition for deer with commercial pelleted feed increased survival, body mass, antler size, and productivity (conception rates among yearling does doubled).
Commercially available pelletized rations, formulated to meet the whitetail’s basic nutritional requirements, are recommended for supplemental feeding of deer. However, high energy feeds such as corn probably serve equally well during autumn. The strong case against widespread supplemental feeding of wild deer rests on economics, practicality, and on the potential spread of disease and damage to the associated habitat.
Deer also readily use mineral supplements, available in pelletized or block form, during the spring and summer period, but their use during autumn seems minimal. Their value to deer has not been well-documented.
Autumn for whitetails is a time of physiological change, a shift in nutritional requirements, increased need for high-energy food sources, and fattening among all deer in preparation for winter. Since these changes are hormonally driven and cued to changing photoperiod, autumn fattening among deer is obligatory and takes precedence over body growth among young deer.
Unfortunately, fawns (and even yearlings} must simultaneously grow and fatten during autumn, requiring a high energy diet. Young deer subsisting upon an energy-deficient diet may become reasonably fat prior to winter, but stunted in body growth - signaling the need for range management focused on increasing the amount of high-energy food sources in their autumn diet.
Autumn can be a nutritionally precarious a time of year for whitetails, especially at northern and southern reaches of their geographic range. Limitations in nutritious autumn forage sometimes may be due to over-grazing by too many deer, which can be remedied simply by herd reduction. In other instances autumn nutritional shortages may be chronic in nature due to infertile soil, adverse climate, or otherwise unfavorable habitat. In contrast, deer in some areas only experience periodic autumn nutritional failure caused by drought, early snow cover, nut-crop failure, or poor habitat management.
There are a variety of habitat
manipulations that will increase
the amount of high-energy foods available to deer during autumn. Although routine forest
management (i.e., cutting, burning, planting, etc.) can improve autumn habitat for deer, intense oak management, opening creation, and food-plot management will produce the best results — but all will require careful planning and often professional assistance.
Left unchecked, poorly managed autumn habitat will continue to produce poor quality young deer that grow to be inferior adults.
Literature Cited: Biology and Management of White-tailed Deer, Hewitt, 2011. Quality Food Plots, Quality Deer Management Association, Kammermeyer, Miller and Thomas Jr. (Eds.) 2006. Physical and reproductive characteristics of a supplementally fed white-tailed deer herd, Journal of Wildlife Management, Ozoga and Verme,1982. Ultimate Food Plots, Mid-Michigan Branch QDMA, Spinazzola, 2006.