How Whitetail Deer Respond and React to Hunting Pressure

PRESSURE Nov17 LEAD GettyImages 114840591 1 How Whitetail Deer Respond and React to Hunting Pressure
All whitetails react differently to pressure from humans, especially during hunting season, but research shows some clues into what they do and where they go during these months of intrusion into their areas. (Photo: Getty Images)

Recent biological studies demonstrate very clearly that white-tailed deer not only perceive their environment in fine detail, but are able to respond immediately to risks and pressure.

Legal light ends in just a few minutes, but you dare not move. You’ve heard a few deer staging around you for the past half hour, and not long ago you heard the bark of your brother’s rifle from a stand not a quarter mile away.

By Dr. Stephen Ditchkoff and Jeff Sullivan

Yet, like many nights before, you’ve been left with nothing but an aching back and a dream of what might have been, while the deer that so patiently waited for darkness to fall feast upon the food plot you leave behind. This spot used to be packed with deer, but as the season comes to a close it seems that what was once your secret honey hole has lost its magic. Now you can do nothing but wonder what gave you away, and what to change for next season.

Not surprisingly, though deer hunters across the country come from a myriad of backgrounds they all seem able to relate to one issue — sometimes it feels like the deer know where you will be before you get there. While this is an often perplexing and frustrating phenomenon for hunters, biologists have been studying the reactions of wildlife to predators for decades and have developed a theory that appears to explain the activities of whitetails during the hunting season.

LANDSCAPE OF FEAR THEORY The landscape of fear theory suggests that animals are consistently at risk from predators, which in this case would be human hunters, and that the level of risk changes based upon two main factors. First is the animal’s location: While wild predators such as wolves might be more dangerous along grassy meadows, human hunters often concentrate near roadways and open areas, and often hunt repeatedly from the same location.

The second major factor influencing risk is the time of day. For instance, human hunters are limited by legal hunting times, and most often sit only during the periods around sunrise and sunset, abandoning their stands during the midday hours. This theory can be visualized as a mountain range where mountain peaks are areas of greatest risk and valleys are areas of greatest safety. Throughout the course of a day, each area’s height changes as the risk levels associated with that area change. The objective for prey species is to stay at the lowest possible elevation while still accessing all of the resources they need to survive and reproduce.

Previous studies have long confirmed what hunters already know; deer can recognize changes in risk and react as one would expect under the landscape of fear theory. Studies ranging as far back as the 1960s have demonstrated that when hunting pressure is sufficiently high, deer increase their use of dense cover areas such as thickets or hardwood drains and then use risky areas such as bait piles only during safe periods, such as nocturnal hours. Similarly, studies have found that activity patterns of deer are such that they are more active when hunters are not in the woods and less active when they are.

A fellow researcher, Kevyn Wiskirchen, with Auburn University, recently wrote an article (in the September 2016 issue of Deer & Deer Hunting) documenting just such a pattern. He detailed how white-tailed deer suppress movement during the weekend to minimize exposure to humans. But when hunters are absent from the woods during the week, the deer become much more active.

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While these studies have provided great insight into larger behavioral trends, they have all examined hunt- ing pressure in relation to an entire property or large landscape, leaving the question of how deer respond to risk at specific locations unanswered. Essentially, until now scientists have not been able to account for the potential that deer could recognize risk at a spatial scale as fine as individual hunting locations and respond accordingly. It is quite possible that the responses seen at the landscape scale are completely different from what is seen in relation to actual locations of risk, especially when hunting pressure is kept very low across a property. Fortunately, advances in technology now enable scientists to investigate such detailed behaviors.

With each additional hunting event at a given stand, deer became increasingly less likely to use the vulnerability zone around that stand during mornings and evenings (Figure 1).

RESPONSE TO LOCALIZED RISK Due to the general lack of data, and thus, understanding of how white- tailed deer respond to localized risk, we, with financial support from the South Carolina Department of Natural Resources, set out to examine this aspect of deer biology and determine the movement patterns of adult does during the hunting season with respect to hunting stands.

To accomplish our goal we darted adult female white-tailed deer and fit each with a GPS collar programmed to collect locational data every 30 minutes, allowing us to gather highly detailed information on deer movement relative to hunting pressure. Hunting on the property was strictly managed, with hunters taken to and picked up from permanent stands by guides.

We determined the GPS coordinates of every hunting stand, food plot and automatic feeder on the property, and determined the area around each stand in which a deer would be visible to a hunter (which we called the vulnerability zone). We then combined all of this information with the movement data collected by the GPS collars, and imported it into a data visualization tool known as ArcMap. This software enabled us to actually see how deer moved each day, and where they were located on the property.

We were interested in understanding how deer moved during three specific periods: Morning/Evening (from legal light to 8 a.m. and 3 p.m. to legal light), Midday (from 8 a.m. until 3 p.m.), and Night (from end of legal light to beginning of legal light the next morning). These periods were based upon changes in risk, as hunters were present only during the Morning/Evening period, a scenario likely to be true for most regions of the country where hunters choose not to sit throughout the midday hours.

Traditional knowledge, and the landscape of fear theory, would suggest that repeated hunting events at the same location would force deer to recognize that area as being of greater risk, and subsequently deer would reduce their usage of that area during times when hunters would be present, namely surrounding sunrise and sunset. This is precisely what we observed. With each additional hunting event at a given stand, deer became increasingly less likely to use the vulnerability zone around that stand during mornings and evenings (Figure 1).

Similarly, following the day that a stand was hunted, deer use of the vulnerability zone around that stand during the Morning/Evening period was at its least. But deer use of that area progressively increased with each passing day. This result was also expected, because the fear response of an animal should decrease over time, especially in hunting environments where most stands are associated with a food source such as a food plot or corn feeder. When the areas of risk are associated with a food reward, the animal must balance the trade-off of avoiding risk with miss- ing out on the nutritional benefits of visiting that location.

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Next, we looked at movements during the Midday period. Interestingly, previous studies at the landscape scale had reported conflicting results. Some studies suggested that deer increase activity during midday hours as a way to make up for lost opportunities when they avoid moving during crepuscular periods, while others have claimed that deer remain cryptic during all daylight hours, thus reducing usage of risky areas.

We found that deer followed the same trends during the Midday period as they did during the Morning/Evening period. That is to say that they decreased usage of vulnerability zones around hunting stands following each additional hunting event, but increased usage as time passed. Surprisingly, we observed that deer were far less likely to utilize the vulnerability zone around a stand during the Midday period than during the Morning/Evening period.

PRESSURE Nov17 Figure 4 2 How Whitetail Deer Respond and React to Hunting Pressure
After a fourth hunting event at a given location, deer became less likely to use the vulnerability zone immediately following a hunting event and slowly increased usage with each passing day (Figure 2).

This might seem surprising at first, because deer could safely use these areas during the midday without the risk of being exposed to hunters. We believe that this response is due to the natural feeding behavior of deer being focused on crepuscular periods and the fact that vehicle traffic through the property might have been sufficient during the Midday period to make the vulnerability zones appear risky even if they were not.

While the responses we observed during the Morning/Evening and Midday periods were much as one would expect, a very interesting trend emerged during the Night period. We have all heard a hunter complain that “all of the deer have gone nocturnal” and you might very well be that hunter yourself. If so, it probably wouldn’t surprise you to hear that deer initially increased their usage of a vulnerability zone around a stand following the first few hunting events at that location and decreased usage with each passing night since hunting had occurred. Yet this trend changed with additional continued hunting pressure at that stand. After a fourth hunting event at a given location, deer became less likely to use the vulnerability zone immediately following a hunting event and slowly increased usage with each passing day (Figure 2).

Essentially, after continued hunting pressure at a particular stand, deer changed their behavioral response at night to the same avoidance we observed during the Morning/ Evening period. This suggests that deer respond to initial hunting events by simply accessing the area during a safe time and their fear decreases as time passes. But as hunters use the area more, deer respond by avoiding the area altogether. Perhaps the deer decide, in essence, to move on to safer pastures where they may be able to feed during Morning/Evening hours instead of confining themselves to nocturnal hours only.

BEHAVIOR MODIFICATION Our findings provide us with unique insight into the behavior of white-tailed deer in response to pressure from human hunters. While hunters have long known that white- tails have the ability to modify their behavior and space use in response to hunting pressure, this study has allowed us to document exactly how deer respond to spatially explicit risk and how that response differs from responses visible at the landscape level.

While one could look at the landscape level response of this population and assume that hunting pressure was not sufficiently strong enough to force deer to alter their behavior, a more thorough investigation reveals that deer are in fact recognizing and responding to the risks posed by hunters: They are merely doing so at a small enough spatial scale to reduce the impacts on their regular activities.

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It’s this minor variation in their movement and activity patterns that make it seem as though there aren’t any deer in the woods. Some might view deer as creatures randomly moving through the woods from one field to the next, but this study demonstrates that white-tailed deer not only perceive their environment in fine detail, but are able to respond to risks immediately and use infor- mation about past risk at a location to make informed future decisions about using or avoiding that location.

BUCKS Buck skylined snow How Whitetail Deer Respond and React to Hunting Pressure
No matter how little you are hunting an area you are influencing the likelihood of a deer using that area again, at least for a few days. Even if you never fire the gun, there is a strong likelihood that you were still detected by at least a few deer.

TAKEAWAYS FROM THE STUDY So what does this mean for you as a hunter? Well, there are a few clear takeaways from this study that you can use to aid your quest this fall. First, no matter how little you are hunting an area you are influencing the likelihood of a deer using that area again, at least for a few days. Even if you never fire the gun, there is a strong likelihood that you were still detected by at least a few deer.

While you might have still had plenty of deer come and go blissfully unaware of your presence, others might have been spooked off as they approached from downwind, or smelled the disturbance along the path you used to reach your stand. Therefore, after hunting a location try and give that stand a few days off so that the fear response can decrease before your next hunt.

Secondly, understand how the length of your season might impact deer behavior. If you live in a New England state with shorter seasons you can expect deer to have a much stronger reaction across the landscape to hunting pressure than in Southern states with more prolonged seasons. When the season is shorter, deer can afford to avoid high value areas (food plots and feeders) for the brief season and return when it’s safer, but such avoidance might be nutritionally prohibitive in states with longer hunting seasons.

Finally, consider moving your hunting stands between seasons, while this study did not investigate if the number of hunting events at a stand the year prior caused deer to avoid an area more quickly the next season, it is a good idea to reduce your predict- ability as much as possible.

We as hunters attempt to pattern deer almost every way imaginable, from extensive scouting and note taking from years on a property to a network of game cameras trying to locate that trophy buck. Yet, with all of the effort we direct toward patterning them, it can become all too easy to forget that deer are also capable of patterning us. So this coming season, as the days grow shorter and your heart gets restless, yearning for an all too brief escape into the peaceful hunting grounds, do your best to be aware of your own patterns and embrace the opportunity to outwit your prey — not by attempting to understand their predictability, but by limiting your own.

— Jeff Sullivan completed his M.S. degree in 2016 at Auburn University studying white-tailed deer under the supervision of Dr. Steve Ditchkoff. He is currently employed by USGS at the Patuxent Wildlife Research Center.

— Dr. Steve Ditchkoff is a professor in the School of Forestry and Wild- life Sciences at Auburn University. He manages the deer research program at Auburn and has been conducting research on white-tailed deer for 25 years.