Twenty-five years ago, after nearly a quarter-century in the deer woods, I thought I had a pretty good handle on what influences deer movement. At the time I had read much of what the popular press and scientific community had to say on the subject and felt confident I knew what could or couldn’t be expected from whitetails. I should have known better.
The last twenty plus years of photographing and raising whitetails and being involved in some interesting research have caused me to rethink some of what I thought to be “gospel” regarding deer movement.
In the broadest sense, there are six things that cause whitetails to move or stay on their bellies—weather, hormones, sex ratios, predators (man and beast), food and light (both sun and moon). Though each can trigger or suppress deer activity on its own, it’s when they work in concert with one another that they are most noticeable.
Precipitation: It should be pointed out that unlike humans, whitetails and other wild creatures have built-in mechanisms to alert them of impending environmental changes. Whitetails can detect when the barometric pressure is falling, even if the sky is clear. They know when conditions are changing and their feeding habits can increase dramatically prior to the arrival of bad weather and after a front has passed.
Bedded buck in rain–illustrating a suppressor.
Through the years I’ve observed that whitetails typically move more when the barometer is moving either up or down, than when it is steady. During this time, you’ll usually find periods of high humidity with fog, haze, rain or wet snow making up the weather system. When this happens, whitetails become secretive, especially in periods of dense fog. The sudden drop in temperature that often accompanies these fronts doesn’t cause whitetails to head for thick cover. Rather, it is caused by the unsettled weather associated with the leading edge of low-pressure fronts. The greatest movement occurs if barometric pressure drops rapidly. With few exceptions, there will be little or no deer movement once the front arrives and the weather becomes nasty. Then as the front passes and weather returns to normal, whitetails and other wildlife start to move again.
RELATED: 3 Must Use Weather Tools for Hunters
When the storm ends and the barometer rises, deer activity often increases dramatically, provided that air temperatures match the whitetail’s comfort zone. Several studies have been completed regarding the effects of barometric pressure on whitetails activity. Illinois biologist Keith Thomas found that greatest whitetail feeding occurred with barometric pressure was between 29.80 and 30.29 inches. When the barometer is falling or rising through this range deer activity should be greatest.
Temperature: Unseasonably warm temperatures shut down deer activity in a heartbeat. Of all activity suppressors, air temperature is perhaps the most powerful influence on daytime deer activity. Other suppressors work with temperature and might sometimes override the influence of temperature on deer movement. However, unless temperature matches a whitetail’s comfort zone, movement will halt during daylight hours.
Bedded buck and doe–suppressor showing the impact of heat on deer.
The best way to determine when the temperature will shut down deer activity is to know what normal temperatures are for your area. The bottom line is that when air temperature rises above the seasonal norm for a region, deer activity will decrease in direct proportion to how warm it gets.
Wind velocity: Down through the years I’ve heard and read much concerning the impact of wind on deer movements. This coupled with personal observations has made me aware that there are certain times when wind definitely affects deer movement.
It’s my belief that the amount of wind velocity required to suppress deer activity has much to do with the region of the country. For example, in prairie states such as Kansas, Nebraska and the Dakotas, high winds are a common everyday occurrence, so whitetails in these states don’t seem to be as affected by moderate to high winds as they are in the Northeast, Great Lakes states, or the Heartland.
On several occasions, I’ve observed whitetails in Montana freely moving around throughout the day when wind gusts were well over 20 miles per hour. Outside of the hot-to-trot rut, when a buck is chasing other bucks away from his estrous doe, I’ve seldom seen such a sight in the part of the Northeast where I live.
RELATED: 4 Things that can Ruin the Rut
Having raised whitetails for twenty-five years I’ve seen firsthand that they rely on their sense of smell more than anything else. When there is too much wind, or wind gusting in irregular patterns, deer don’t feel comfortable moving around. Whitetails do one of two things when they are spooky. They either get away from what is making them uneasy or if they know they cannot escape they will hit the ground and wait for conditions to return to normal.
The key to knowing the suppressing effects of wind velocity is being aware of what deer in a given area will tolerate. Here, in western New York, the breaking point appears to be roughly twelve miles per hour. It’s a regional thing and one all hunters should become aware of.
Science has revealed how a whitetail buck’s hormone levels ebb and flow with changing amounts of daylight (photoperiod).
By the time winter manifests itself, a buck’s testosterone level has bottomed out. With hormonal levels at a low point, deer activity slows to a crawl during the winter months. Then as daylight increases and winter melts into spring, a buck’s testosterone level slowly increases and the antlers begin growing again. With warmer temperatures and an abundance of food, deer activity increases dramatically from what it was during the winter months.
Two bucks at a scrape–illustrating the impact that high testosterone has on movement–a trigger.
Testosterone levels continue to slowly rise throughout the antler-growing months. By September, a buck’s serum androgen levels trigger the velvet-peeling process and the rutting season technically begins. As the amount of daylight decreases, hormone levels in both bucks and does continue to rise. In the North, the testosterone level in an average buck nearly doubles between October 1 and November 1, before returning to its early October level by December.
RELATED: 2017 Rut Predictions
Maxed-out on hormones, many bucks will go through the autumn months with a disposition that resembles that of a hyperactive child. Bucks are consumed with the thought of breeding by the time late October and early November arrive in the North and few things will slow them down. Raging hormones are the driving force behind a buck increasing its range in the autumn months. Throughout the summer, a buck will cover about 600 to 1,000 acres of land. However, during the rut it’s not uncommon for a buck to increase his range to over 3,000 acres.
A buck lip curling–showing the impact of the rut on movement–a trigger.
Hormones are also a primary trigger of the different types of rutting behavior exhibited by a buck. Their stimulating effect can be seen in rubbing, scraping and breeding behaviors. Simply put, bucks will go ballistic when hormone levels are high, and activity will be at a minimum when hormone levels are low.
Much has been made of the influence the adult-doe-to-antlered-buck ratio can have on the rut. If you hunt an area that has more than three adult does for every antlered buck, rutting behavior will be light, with little chasing and decreased amounts of rubbing and scraping taking place. If you hunt an area where the ratio is two to three adult does to every antlered buck, there should be a good amount of visible rutting activity. If the ratio is one-to-one, rutting activity—in the form of chasing, fighting, rubbing, and scraping—should be outstanding. And yes, a few places in North America do have more antlered bucks than adult does. In these areas, the rut tends to be unbelievably intense.
A buck pursuing a doe during the rut–a trigger.
Through the years, I’ve photographed and hunted areas that have the adult-doe-to-antlered buck ratios I’ve described. It’s been quite an education, and I’ve learned that a tighter adult-doe-to-antlered-buck ratio almost always creates a more intense rut.
Without competition, there is no need for bucks to go crazy. For this reason, poor ratios suppress rutting activity, night or day, especially in areas where 70% to 90% of the antlered buck harvest is composed of yearlings (1 ½-year-old bucks). This is particularly evident in states where the doe population has been protected at the expense of antlered bucks. When too much pressure is put on bucks, all aspects of the whitetail world suffer, especially rutting behavior.
A buck with numerous does–illustrating skewed buck to doe ratio–a suppressor.
Another thing that lessens the intensity of rutting activity is the absence of mature bucks. In areas where a deer population has adequate numbers of mature bucks, the rut’s intensity is greater in every aspect, from scraping to breeding.
The effect of human pressure on whitetail movement is of great interest to the deer hunter. In most parts of the country, the whitetail rut occurs during archery season, so human pressure is not as great as during firearms season. However, in more populated areas, human pressure can pose a significant problem. Whitetails quickly learn that darkness is quieter, less threatening, and has fewer people.
A group of gun hunters–illustrating the impact predators have on deer–a suppressor.
Location and the amount of human pressure can affect daytime deer sightings tremendously. Many urban areas have high deer populations, but unless landowners are feeding deer, the deer are seldom seen. Human noises, whether from automobiles, sirens, or children playing, keep deer under cover and out of sight until nightfall. This is especially true with mature bucks.
The accompanying graph is from a research project on the Crab Orchard National Wildlife Refuge in Illinois and shows what can happen when hunters invade the whitetail’s domain. Remember that it’s not just hunters that suppress daytime activity. The presence of any human puts whitetails on red alert. This can mean hikers, bird watchers, or hunters.
Graph showing the Thomas research done in Illinois illustrating how human pressure shuts down deer movement.
When you think about the various factors that stimulate or suppress whitetail movement, food probably isn’t the first thing that comes to mind. It doesn’t have the same frenzied effect that weather or hormones have on whitetails, but its influence on deer activity cannot be denied. The availability, quality, and location of a food source can dictate how far deer move and where they bed.
Due to the cyclical nature of mast crops, deer tend to adopt different travel patters from year to year. Also, changes in the location and types of farm crops can alter whitetail movement. Whitetails are basically nomads—they gravitate to the best food source available within their home range. If drought conditions hit an area, they may even shift their home range.
Two bucks during late season in a cornfield–illustrating the impact late season food sources have on movement–a trigger.
When an exceptional mast crop is present (e.g., apples, acorns, beechnuts) whitetails move very little because they typically bed right in the food source. In such years, deer that frequent agricultural crops during the summer months shift their attention to the mast when it begins to fall and make little effort to return to the crops before they are harvested. Deer sightings can be hard to come by when this type of scenario exists.
If you want to see the rut’s chemistry change, look no further than food sources. The rutting sequence will occur, but you won’t see it unless you have prime feeding areas to lure does.
In addition to identifying the food sources whitetails are gravitating to, it’s critical to know where they are bedding. Once the bedding area is defined, it becomes much easier to unravel how both bucks and does are moving to and from the most attractive feeding areas.