Summer Whitetails

The easy season for deer… sometimes

By John J. Ozoga

Generally speaking, summer is a good time for deer. For most whitetails, it’s the easy season – the season of spotted frolicking fawns, sleek red-coated does and lethargic, well-mannered bucks with bulging, velvet antlers. But, unfortunately, there are many exceptions.

Summer is when adult whitetails exhibit sexual segregation and deer are most evenly distributed across their range. It is also when young deer are growing, does are nursing rapidly developing fawns, and bucks are putting the final touches to new antlers, replacing spent body tissues and already building fat stores in anticipation of the up-and-coming rut. The nutritional demands are great, and there are other basic requirements that are not always met in every corner of the whitetail’s range.

Summer Deer Range

Although food and cover are about as plentiful as they’ll be over most of the whitetail's range during summer, some areas and regions of the country are better than others.

Like other wild animals, whitetails have four basic needs that must be supplied by the area in which they live: food, cover, water, and space. Obviously, many factors interact to determine the availability of these necessities, which, in some environments, vary greatly with the seasons.

In the North, for example, deer must vacate vast areas of their summer range and migrate long distances to find areas of dense conifer cover during the harsh winter months. In effect, many northern deer have distinct summer ranges that are sometimes widely separated from their winter range.

Early summer food resources are normally adequate for northern deer that have separate winter and summer ranges because poor winter ranges tend to control deer population size. A massive loss of deer to starvation during tough northern winters is only part of the problem. Malnourished does also give birth to stunted fawns that more than likely die when only a few days old.

Hence, where whitetails have separate seasonal ranges, they tend to live at densities below nutritional carrying capacity on summer range. As a result, they tend to enjoy adequate nutritional resources during the summer season.

Wherever winter weather is not severe, deer more likely live year round on the same area. For them, some habitat types are better than others, while certain areas are consistently poor because of infertile soils.

The amount of acreage occupied by an individual deer during summer will be considerably smaller than is normally the case during other seasons. Except for yearling bucks, which sometimes wander quite extensively, most deer living in favorable habitat can probably satisfy their early summer needs within an areas less than 200 acres in size. Nursing does, however, may restrict their activities to an area less than 40 acres in size until their fawns are six to eight weeks old.

The best summer deer range will have great diversity in habitat characteristics and contain a wide variety of grasses, weeds, shrubs and trees. Food plots, such as Imperial Clover, Alfa-Rack, No-Plow and EXTREME planted for deer and agricultural crops will add to an area’s nutritional richness. Such diversity allows deer to select a variety of foods and change their feeding habits in response to changes in forage availability without greatly increasing their radius of travel.

In heavily forested regions, disturbances such as fire and logging lanes create habitat diversity – “patchiness” of food and cover – that improves summer habitat for deer. Fertile farmland interspersed with brushy swales and patches of timber also offer choice habitat for whitetails. By mid summer, even intensively farmed lands, with their “corn forests,” offer deer an excellent combination of food and cover that is unavailable during other seasons.

Drought

Although water is an important component in the whitetail’s diet, water requirements vary with climatic conditions, type of food, the whitetails’ physiological state (growth, maintenance, and lactation) and amount of activity. Generally, the amount of liquid water consumed by deer is inversely proportional to the concentration of water in the food – deer drink less free water when consuming succulent green vegetation during early summer but more during late summer when plants become fibrous.

Except for those deer living in the Southwest, water shortage is not normally a problem for whitetails over most of their range. However, South Texas is notorious for extended drought that seriously impacts deer health and population size. There, long dry periods can drastically reduce the abundance and nutrient value of plant growth, and have devastating effects on whitetails.

The resultant food shortage and malnutrition caused by drought slows the body growth among young deer, delays their onset of sexual maturity, results in low conception rates among does the next autumn, stunts antler growth and sets the stage for high deer mortality during the winter season. And without low hiding cover, young fawns become easy prey for predators.

Deer relish fresh water during hot weather, but can survive on dew, temporary water from rain puddles or by eating succulent vegetation. Most deer in the eastern United States have ready access to surface water of some type. However, those living in arid regions of the Southwest may concentrate closer to permanent water areas during periods of extended drought.

Texas biologist Bob Zaglin points out the consequences of drought for whitetails are complex: “The impact drought has on the plant community is obvious. However, it’s when standing water is reduced and sometimes eliminated that the problem is compounded because deer then concentrate on water holes. Forced concentrations of deer exert excessive pressure on the local vegetative community to the point that some preferred plants are eliminated.”

In addition, Zaglin notes, South Texas coyotes take advantage of drought by concentrating their hunting for deer in the vicinity of water holes.

Cover Needs

Whitetails are not creatures of the open plains, nor do they flourish in dense old-growth forests. Instead, they are an early successional species – an animal of the edges – where there are a variety of trees and shrubs well interspersed with openings.

The whitetail’s need for protective cover is obvious on northern ranges during harsh winter weather. However, they require escape and hiding cover during all seasons of the year.

Adult does with young fawns, in particular, adopt a solitary, secretive lifestyle, requiring hiding cover in the form of dense shrubs and trees, while they watch over their fawns from a safe distance. At the same time, their newborn fawns require dense ground cover for hiding.

The newborn whitetail is a “hider,” in contrast to “follower” young typical of moose and caribou. Hiding is its best protection from predators for its first few weeks of life until it becomes strong enough to flee should a predator approach.

Intensively farmed land, dense old-growth forests and areas heavily browsed by overly abundant deer generally yield poor deer fawning habitat, as also commonly occurs in the Southwest during periods of drought. Wherever ground level hiding cover is deficient – for whatever reason – excessive predation of newborn fawns can be expected.

A lack of adequate cover, for the doe and her newborn, can also lead to intense competition among does seeking suitable fawn-rearing habitat. In the intensively farmed land of the Midwest , for example, forested cover is extremely limited, causing young subordinate does to disperse considerable distances to find suitable fawning sites.

Deer living in the savannah grasslands of Texas reportedly behave differently than those living in forested habitat. In the open grasslands, does usually leave their newborn fawns in hiding while they themselves graze with other deer. The differing maternal-care strategies, which apparently evolved in response to sharply contrasting environmental circumstances, allow whitetails in forested and non-forested habitats to cope most effectively with the constant threat that predation pose to the survival of their vulnerable offspring.

The Importance of Nutrition

The whitetail’s summertime diet will vary greatly, from one area to the next, depending primarily on what foods are available. They’ve been known to eat just about anything at one time or another ranging from mushrooms and lichens to fish and insects. However, they have the remarkable ability to select the best, most nutritious foods available, switching to less palatable and less-nourishing items as the preferred ones decline. Green leafy browse becomes more important in the deer's late summer diet as forbs abundance decreases and grasses mature, dry and become more fibrous.

Whitetails, being ruminants, require fiber in their diet for normal rumen function. Unlike domestic livestock, however, deer have smaller stomachs and cannot digest highly fibrous or lignified foods. Highly fibrous foods stay in the stomach longer than usual, taking longer to digest and thereby limit the amount of food a deer can consume. Limited food consumption equates to poor growth and slow weight gain.

Deer overabundance can also adversely impact habitat quality. Because deer are selective feeders, an expanding deer herd can drastically reduce or even eliminate certain choice natural herbage that is readily digestible and rich in protein. At the same time, other plants may increase either because they’re less palatable, resistant to grazing or both. Consequently, ranges severely overgrazed by whitetails may not exhibit the stark overused appearance one would expect. Even so, the land’s nutritional base and capacity to naturally support healthy deer steadily declines with continued overuse.

The nursing doe, in particular, is under considerable nutritional stress while at peak lactation in early summer. Even those does that are well nourished might devote as much as 70 percent of their time to foraging.

Favorable food conditions are essential for the doe if she is to achieve maximum milk production as well as to maintain her own physical vigor. If nutrition is inadequate, the doe’s milk yield declines, even though the milk quality in terms of chemical composition remains fairly constant. Reduced milk yield results in poor growth among young fawns, and on occasion their starvation has been reported from arid regions of deer overabundance where summer drought limits forage availability.

When only a few days old, fawns begin to nibble vegetation, although they do not start to ruminate until they are about two weeks old. By five weeks of age fawns are dependent upon rumination, but they still rely on their mother's milk for sustenance. Although some fawns may nurse well into autumn, they’re functionally weaned when 10 to 12 weeks old.

Fawns must have access to an abundance of nutritious forage during summer if they are to achieve maximum growth before the onset of winter. Fawns require forage that has from 14 to 22 percent protein content, with male fawns having higher requirements than females, for proper growth. This is where nutritious food plots like those provided by the Whitetail Institute are vital for deer to reach their potential. These products are high in protein when whitetails need good nutrition.

Mature whitetails require a diet that has from 16 to 18 percent protein for maximum health, but the sexes exhibit subtle differences in physiology and food preferences during the summer season. Bucks, for example, have a lower whole-body metabolic requirement per unit gut capacity, which permits them to subsist on lower quality foods, and they commence laying down fat sooner than does.

Soils in some regions are inherently infertile, and produce forage that is low in protein. If the whitetail’s summer diet contains less than six percent protein, their rumen function is seriously impaired. As a result, young deer then tend to grow poorly and exhibit delayed sexual maturity, adult does have poor reproductive success and bucks will be smaller than normal with stunted antlers.

Crowding Effects

Does with newborn fawns demonstrate a form of territorial defense for four to six weeks. Each doe defends an exclusive area – typically between 10 to 20 acres – from which she drives away all other deer. Such behavior socially isolates newborns and ensures they will imprint upon their mothers. This also reduces deer activity and deer odors near the newborn, which minimizes predation but limits the number of fawn-rearing does per unit area, even when food is unlimited.

Older does have an advantage when deer numbers are excessively high. Not only are they more aggressive, they tend to occupy the best habitat and breed and give birth before younger does. Therefore, younger does must occupy whatever space is available, which is often poor-quality habitat. As a result, younger does give birth to fawns that are less likely to survive.

When deer density reached 100 deer per square mile in Upper Michigan 's Cusino enclosure, first-time whitetail mothers lost 63 percent of their fawns, but prime-age does lost only 6 percent. Most fawns died shortly after birth, either because of imprinting failure or outright abandonment. As in the case of nutritional stress, abandonment often arises because of insufficient production of prolactin, a hormone that induces milk secretion and promotes maternal instinct.

When deer are crowded on summer range, resultant social stress can lead to other consequences even when nutrition is favorable. For example, behaviorally stressed young does generally exhibit delayed breeding, as well as increased newborn fawn mortality. Likewise, crowding can contribute to a decrease in antler quality, initially among young bucks, but inevitably even among mature individuals.

Mature bucks are especially sensitive to increasing herd density, even when deer numbers are below nutritional carrying capacity of the range. That is, as herd density increases, mature buck body weights and antler size tend to decline, even when nutrition is not a limiting factor.

So, in the long run, when whitetails live at high density, psychological stress due to crowding – even with adequate food – can lead to many of the same problems resulting from poor nutrition. In either case, herd health and productivity decline.

Normally, however, social stress and nutritional stress go together: as deer numbers increase, crowding causes psychological stress and too many deer eventually lead to range deterioration, poor nutrition, and declining deer physical condition.

Conclusions

On the surface, summer appears to be an easy, almost tranquil time for whitetails. In reality, it is a demanding period, when all deer require high-quality habitat – one that provides plenty of food, cover, water and space.

All too often, in certain parts of the country, a shortage of one or more of these basic necessities of life during the summer months can set the stage for nasty consequences later on. Wherever these life essentials are in short supply, whitetail populations will not prosper – and there will be few, if any, bucks of Boone and Crocket stature.