Whitetail Security Factors by TR Michels
During my study of white-tailed deer I discovered that deer are affected by several meteorological conditions that I call Comfort Factors. Many of these same factors also affect the health of the deer and can be considered as Security Factors. Deer rely on their sense of smell, their hearing and their sight to warn them of danger. The conditions that affect the security of deer include scents, the amount of light, visibility, and wind speed.
Scents of various kinds can be left on the ground or vegetation and in the air. Pheromones, chemical signals left behind by deer, relay information to other deer, sometimes hours later. These pheromones may tell other deer the direction of travel, and the other deer’s sex, age, social status, sexual readiness, health, and may impart fear.
Abundant tarsal and metatarsal scent left behind when deer fight or are in flight will alert and often alarm other deer, causing them to avoid the area where the pheromone is left. Abundant interdigital scent, left when a deer stamps its foot after sensing danger, will alert other deer of possible danger up to an hour later. Scents of any possible predator; fox, coyote, wolf, dog, mountain lion, lynx, bobcat, bear or human will alarm deer and cause them to become alert and avoid the area where the scent is.
Unnatural scents and those associated with human behavior will cause deer to become alert and alarmed. This wide range of scents includes foods, chemicals and medicines from humans, fumes from vehicles, and the many products humans use in daily life that are not normally present in high concentrations in areas deer use. The higher the concentration of the scents the higher the state of alarm the deer will exhibit.
Two things cause lower concentrations of scent; dissipation and dispersal. Because scent molecules evaporate (dissipate) at different rates (based on the wind speed, temperature and humidity) the longer it has been from the time the scent was left the less there is, and consequently the less alarmed the animals are. Scent left in the air and carried in the wind is spread out (dispersed) by the action of the wind. The farther scent is blown from its source the less there is, and the less alarmed the animals are.
Deer depend to a great extent on their sight to alert them of danger. Their sight allows them to move at night and during the low light conditions of dawn and dusk when they feel most secure. While most hunters know this they have a hard time translating it into whitetail terms because we don’t think in terms of light factors, we think in terms of time of day or hours.
Humans rely heavily on that piece of technology worn on the wrist called a watch, but deer don’t have watches or clocks. So, what tells a deer what time to get up in the evening and begin feeding and what time to head back to bed in the morning? Deer do have a circadian clock in their brains. The amount of chemicals in a particular portion of their brain allows them to know approximately what time it is. But, although this clock may tell them it is time to move, the urge to move is overridden by the need for security. And one of the primary factors that affect the deer’s security is light. Older deer, bucks in particular, usually wait until the light factor is right before moving. I don’t know exactly what the light factor (or lack of light) is that tells deer when it is safe to move and feed. But, it is definitely low light conditions resembling the conditions at sundown and sunrise.
Anything that causes the light factor to resemble twilight or darkness can cause deer to begin moving. This includes clouds, fog, rain, sleet, snow and leaves. Yes, leaves. Remember that deer often bed in heavy timber where the leaves on trees and shrubs provide shade which makes it darker in wooded areas than it is in open areas. When there are leaves on the trees deer feel secure in wooded areas and begin moving and feeding a couple of hours before sundown. But, they don’t usually move into low brushy areas or open fields until the light factor there resembles twilight.
Because leaves have the ability to alter the light factor there is a shift in deer movement that occurs every fall that most hunters fail to recognize. Once the leaves fall, wooded areas no longer provide as much shade as they did earlier in the season. Consequently the deer begin to move in wooded areas and along travel lanes about a half hour later than they did while the leaves were on the trees. The hunter who has been watching deer appear at 6:30 along a wooded trail for a week and then plans to hunt the trail a week or two later can be in for a big surprise. If the leaves have fallen the deer probably won’t show up until about 7:00, which may be after legal hunting hours.
As I mentioned earlier, anything that creates a reduction in the current light factor, making it resemble twilight conditions, may cause deer to begin moving earlier in the evening, and staying later in the morning than normal. These low light factors can cause bucks to make the mistake that hunter’s dream of. Clouds, fog, mist, light rain or light snow often cause deer to move into open areas up to a half hour earlier in the evening and a half hour later in the morning than normal, which means they may move during legal shooting hours. While the light conditions affect all deer they may be different for individual deer. I have kept a detailed record of individual deer movement times, including the subdominant and dominant bucks in my area. The data shows that bucks in general begin to move later in the evening and leave open areas earlier in the morning than the does.
Travel Route Changes
Because vegetation causes a change in the light factor, leaves, or the lack of leaves, cause other changes in deer movement patterns. The travel route of a deer is governed by two major factors, the path of least resistance and the need for security. Just like humans a deer doesn’t normally plow through hip deep mud, brush too thick to get through, or up extremely steep inclines. But, this desire to travel in the area of least resistance is overridden by the need for security. Deer normally travel in areas where they are not easily seen. This security need is also different for each deer. Bucks wear headgear and are more noticeable than does, which makes them more susceptible to being killed and eaten by predators and man. Because of this bucks usually travel, not on the doe highways, but on their own routes, often paralleling the doe trails. These buck trails often wind through heavy cover in gullies, creek bottoms, overgrown roads, or where they are out of sight of the top or bottom of the hill.
Early in the year when leaves are still on brush and trees the deer feel secure moving in vegetation paralleling open areas. But, once the leaves fall deer can easily see the open area and they feel insecure. This causes them to move farther into cover. After the leaves fall deer often move later than they did when the leaves were on the trees. This really hit home with me while hunting a trail that paralleled a road. Early in the season the deer used a trail about seventy-five yards from the road. During the week the leaves fell, the deer moved to a trail twenty yards from the road, farther into the woods. I couldn’t understand why the deer stopped using the original trail until I got down from my stand and stood on the first trail where I could see the cars driving past. When I stood on the second trail I could no longer see the cars. With the leaves gone the deer felt more secure on the second trail, which was farther into the woods.
Strong winds can carry scents to a deer and cause alarm. Strong winds can also cause scent to bounce of trees in thick woods, making it difficult for deer to determine which direction the scent came from. In either case strong winds make deer uneasy and hard to hunt. Winds between 10 and 15 miles per hour cause deer to seek shelter in areas with less wind. They stay in low areas, heavy cover or the downwind sides of hills and woods, where they can smell and determine scent direction better while moving and feeding. They may not leave their bedding areas during high winds
With their large rotating ears deer hear better than humans, and they probably hear every sound around them. But, when high winds rattle tree branches and leaves it makes it difficult for deer to distinguish one sound from another, and they become nervous. The point is that a deer’s survivability depends on its ability to smell and hear. When high winds make it difficult for deer to hear or smell properly they do not move far from secure areas. When they do move it is usually in areas where there is less wind and less noise.
Thermals, air currents that move up and down the contours of the land, affect deer movement because they also carry scent. Thermal currents usually move uphill as the temperature warms during the morning and move downhill as temperatures fall during the evening. Deer take advantage of this by bedding on hillsides during the day where they catch scents on the uphill currents. When the deer begin to move toward feeding areas in the late afternoon they often move downhill, which allows them to detect scent on the currents that are still moving uphill. During the night deer often bed in low areas where they can detect any scents on downhill thermals currents. As the deer move uphill toward their daytime bedding areas at sunrise they detect scents on the thermals which are moving downhill.