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Fall Deer Movement Influences

A Elk Hunting Article

Written by T.R. Michels


While sitting in my tree stand, freezing my tail off and not seeing any deer, I have often wondered where the deer were and what they were doing. Yeah, I used to be one of those crazy idiots who went out in subfreezing weather dressed like the Pillsbury Dough Boy (six layers of clothing and a white suit) and sat in my stand with the wind howling around me, questioning my own sanity, but not any more. Maybe I have gotten smarter over the years or maybe I have just gotten too old. Either way, when the temperatures drop, the dewpoint lowers and the wind picks up, I don't get up early to go sit in my tree stand. Oh, I still hunt, I just don't sit in my tree stand. I still-hunt, especially if I've previously patterned the deer and know where to find them.

I have always been fascinated by animal behavior, and went to college to become a wildlife biologist, then quit to become a professional hunting guide. After ten years I quit guiding so I could return to my first love, wildlife research. Since 1994 I have spent hundreds of hours correlating deer movement with weather conditions, so that I wouldn't have to sit in my deer stand looking like Frosty the Snowman.

During my study I noted the light conditions, time, sunrise, sunset, temperature, wind-chill, dewpoint, wind speed, wind direction, precipitation, and barometric pressure. I placed my data on a graph and kept notes on when and where the deer where, what sex, which deer they were, what direction they were traveling and what they were doing. Several other researchers have studied many of the individual factors that I did, including temperature and dewpoint. But, my study differs from theirs, because I considered all the known factors I could think of. The results of my study concur with most of the other researchers. I found that the factors that affect fall deer movement are: Comfort, Security, Predatory Behavior, Food, Breeding, Distance, and Lunar.

Comfort Factors
During my studies I found what I believe to be the predominant meteorological factor that determines daytime deer movement in the fall; wind-chill. Wind-chill factors can cause both a decrease and an increase in daytime deer movement because it affects their comfort. Comfort factors are so powerful that they override most of the other factors that influence fall daily deer movement, including lunar forces and the rut.

Temperature Factors
Deer feel temperature the same way humans do. When it's hot we feel uncomfortable, when it's hot and humid (making the dewpoint high) we feel even more uncomfortable. When it's hot or the dewpoint is high and there is a strong wind we don't feel as uncomfortable. When it's cold we feel uncomfortable, when it's cold and damp creating a low dewpoint we feel more uncomfortable, when it's cold, damp and windy (creating low wind-chills) we feel very uncomfortable.

Like humans deer have preferred temperature, dewpoint, wind-chill and wind speeds in which they move. These are the Comfort Factors which influence daily deer activity. Once deer grow their winter coats in the fall high temperatures keep them from traveling very far in daylight hours. They usually wait until the sun goes down and temperatures drop before moving. When temperatures are low deer often stay in areas providing protection from the wind, move to areas open to the sun or wait until the daytime temperatures rise, then move during daylight hours, especially when cloud cover is present.

My studies and those of Dr. Ken "Doc" Nordberg both took place in Minnesota and the flexible parameters given should apply to whitetails in the northern half of the United States and Canada. I stress the word flexible because deer in different areas have different tolerances. Data from Texas suggests that southern deer are more tolerant of high temperatures, and because they are not subjected to the extreme cold of the north they are probably less tolerant of low temperatures. During his rattling study in Texas Mickey Hellickson found that bucks responded best to rattling when temperatures were between 70 and 80 degrees. Deer in other areas may have different comfort range tolerances. Even individual deer have different tolerances. Bucks, especially during the rut, will move in almost any weather in search of estrous does.

Deer Activity Times
When I charted deer sightings according to temperature it became evident that the majority of the movement occurred between 10 and 55 degrees. Most of the deer sightings occurred between an hour before and an hour after dawn and dusk as expected. When the temperatures dropped the morning deer sightings occurred from sunrise to an hour and a half after sunrise, with minimal pre-sunrise movement. The evening deer sightings occurred from an hour and a half before sunset until an hour after, with several deer sighted after sunset. As the temperatures dropped below 20 degrees the deer continued to move later in the morning, but there were fewer sightings, while afternoon sightings actually increased.

Dew point
When deer movement was charted in relation to dewpoint it became obvious that high dew points restricted deer movement. Most movement was seen between dew points of 5 and 55 degrees. Less deer were seen in the upper Comfort Factor range, with more deer seen in the middle range. When dew points were below 20 degrees daily movement occurred later in the morning and earlier in the evening than normal, with more movement in the evening. When dew points dropped below 15 degrees twice as many deer were seen in the evening as in the morning. When dew points dropped below 10 degrees five times more deer were seen in the evening.

Deer movement in relation to wind-chill showed even more dramatic results. Very few deer were seen during normal movement times when there were either high or low wind-chill factors. This was to be expected because deer don't move in high winds. But, light winds can actually increase deer movement when the temperature is high, because the wind provides a cooling effect. When temperatures were above 55 degrees, low wind speeds, which created wind-chills below 45 degrees, caused increased daytime deer movement. The data suggests that low wind-chills increase deer movement. However, when the number of deer sightings during normal movement times are considered in relation to low wind-chill factors it becomes evident that deer movement actually decreased. As with low temperatures and low dewpoints, low wind-chills caused deer to move later in the morning and earlier in the evening than normal. These findings indicate that cold, windy weather is more of a deterrent to deer movement than cold, damp weather; and that hot, humid weather is more of a deterrent than hot weather with mild winds.

Heavy precipitation of any kind causes deer to lose body heat. Heavy rain causes the most heat loss, with light rain and heavy snow next. Both conditions generally reduce daytime deer activity. During heavy precipitation, especially hail, deer seek cover in wooded areas or thick undergrowth. If heavy precipitation persists through one or more normal feeding periods the deer feed heavily shortly after the precipitation lets up or when the temperature warms.
Precipitation (rain, snow, drizzle, fog, mist) also diminishes the available amount of light, causing reduced visibility and ability of deer to see, which reduces daytime deer activity. Deer often travel and feed during light precipitation because they feel secure in the resulting low light conditions while there is not enough precipitation to make them uncomfortable. Most deer will not move during heavy precipitation because they not only feel uncomfortable but they can't see well. Exceptions to deer moving in heavy precipitation are usually older bucks, during the rut, in search of does that remain in their bedding areas, which makes them easy to locate. Many of these older bucks have also learned that few hunters are out during heavy rain or snow.

Knowing when and where to expect deer under the current weather conditions helps you choose when, where and how to hunt them. If the Comfort Factors aren't right deer can usually be found in or near bedding or comfort areas that protect them from the elements. When the temperature or dewpoint is high deer seek relief in shaded areas or cool microclimates in low lying or damp areas. When the temperature or dewpoint is high, and there are cooling winds, deer move to open wooded areas where shade and wind offer relief from the heat. In both cases they often wait until after sundown, when the temperatures cool before moving into open areas to feed.

When the temperature or dewpoint is low, deer stay in heavy cover, or move to the downwind side of hills and woods. When the temperature and dewpoint is low with high winds deer stay in heavy cover, seek relief in low-lying areas where there is less wind, or move to the downwind side of hills and woods. Under these conditions they may move later in the morning and earlier in the evening than normal, especially when cloud cover is present.
After storms deer often move and feed for a couple of hours, between late morning and early evening or during the warmer part of the day. Illinois biologist Keith Thomas found that the highest amount of white-tailed deer movement and feeding activity occurred when the barometric pressure was between 29.80 and 30.39.

During my study I found no correlation with rising or falling barometric pressure. I did find that more deer were seen when there were abrupt barometric changes. Deer were frequently seen feeding after storms let up, especially if the storm lasted a day or more. I found no evidence that deer began to feed prior to the arrival of a storm, suggesting that they knew a storm was approaching. I suspect that at least some of the increased deer movement associated with barometric pressure changes is a result of the changing of the weather conditions that accompany barometric changes, such as increasing clouds, temperature changes and changes in wind speed and direction.

Security Factors
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 it's 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 it's 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 affects 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.

Available Light
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 hunters 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 area 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 it's 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.

Thermal Currents
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.

Predatory Behavior Factors
Deer are accustomed to predatory behavior all year long from traditional predators like wolves, coyotes, mountain lion and lynx, which must hunt all year in order to survive. Unlike natural predation human predation, or hunting as we call it, occurs primarily in the fall. This invasion of hunters causes another change in fall deer movement.

Hunting Pressure
Once deer begin seeing, smelling and hearing humans in the woods they become alarmed and begin to move into open feeding areas later in the evening and leaving them earlier in the morning, than normal. They also begin using areas farther away from increased activity in their effort to avoid humans. There are times during the hunting season when deer activity actually increases during the day. Predatory behavior decreases as hunters leave the woods in the morning. Deer often begin to move again in the late morning and early afternoon. Bucks, in particular, will move in any weather during the rut as they search for does, especially when there are high winds and cold weather that keep hunters out of the woods and sitting by a warm fire.
The combination of low light, low wind and less hunting pressure often results in deer activity. Unfortunately this is often after dusk and before daylight, when hunting is not allowed. But, if you know how Security Factors cause changes in Fall deer movement, and know when and how deer react to the current conditions you have a better chance of seeing and finding deer, even when the conditions aren't right.

Forage Factors
During the fall deer are influenced by the need to find foods containing enough fat to get them through the winter. The availability and abundance of preferred food changes over the course of the fall and the hunting season, and deer move accordingly. During late summer deer search out forbes, grasses, sedges, clovers and agricultural crops that are still green. When these food sources are abundant deer have the luxury of feeding throughout the day and night, and they are seldom forced to look for food in open areas during the day. When these food sources become dry, or when they lack nourishment deer search for other types of forage, and consequently they may move farther and more often during the day in their search for food. As fruits, nuts and grains containing carbohydrates mature in late summer and early fall deer begin to feed heavily on them.
Freezing temperatures in the fall and winter cause most plants to die or become dormant, and they are no longer adequate food sources for deer. Because of the limited number of food sources in late fall and winter deer are forced to browse on twigs, leaves of some trees, needles of junipers and pine, and feed on agricultural crops (corn, barley, soybeans, oats, wheat, alfalfa, clover, pumpkins, squash, sweet potatoes, sugar beets). When these foods are abundant deer can feed primarily at night. But, when these food supplies are limited, and widely scattered, it forces deer to move more during the day.

Breeding Behavior Factors
Deer are greatly influenced by the drive to breed in the fall. In some instances, especially with dominant breeding bucks, the breeding urge can override all other factors. Breeding Factors are one of the most powerful influences on fall deer movement and the change from summer to fall activity.

The Rut
Most hunters know that whitetails act differently during the rut, but after spending time with and talking to a number of different hunters, most of them experienced and some of them quite knowledgeable, I realized many of them did not understand the progression of the rut. Most of them knew that rubbing in northern regions usually begins in September, scraping in October and the "peak of the rut" occurs in mid- November. I don't know how they interpreted the phrase "peak of the rut". Did they think all the breeding activity would occur that one week? Many seemed to think that once the peak had passed no more breeding activity would occur. They resigned themselves to the thought that if they did not get a buck by the "peak" there was no reason to hunt as hard as they had because there was less activity.

Well hold on, I'm going to try to explain the rut and make it clearer. At the same time I am l hoping you will hunt harder in your quest for a big buck. Then again maybe not, if you don't hunt hard it leaves me with more deer. First, let's examine the phrase "peak of the rut." Actually this term refers to the peak, on a curve, of the rut related activity. This activity includes rubbing, scraping and breeding. Each of these activities has it's own curve.

Rubbing and Scraping
In the upper Midwest bucks often begin rubbing in September. Peak rubbing activity usually occurs between mid and late September and generally decreases once the bucks begin scraping. But, rubbing often continues as long as there are does in estrus, which may be as late as the end of December in the northern states. Scraping activity may start shortly after rubbing begins, but without much activity until the rubbing activity peaks in September. Scrape activity often ceases when nighttime temperatures rise above 45 and this may be the reason for little scraping activity in September. As the nights get colder in October scraping activity begins to rise, and usually peaks in late October or early November, just before breeding peaks. Breeding activity increases along with the scraping activity in mid-October, with peak breeding occurring shortly after peak scraping in November. But what was that about breeding activity starting in mid- October?

My own observations, those of noted wildlife photographer Bill Kinney and the studies of Dr. Larry
Marchinton and his colleagues in Georgia all show that does have been observed breeding as early as September 24 near the Canadian border in Minnesota, October 15 in southern Minnesota, October 17 in Georgia, and October 24 in central Wisconsin. Thanks to Marchinton's study we can actually pinpoint estrus cycles in deer. The study was conducted to determine how many estrus cycles unbred does would experience. In the eight does observed recurrent estrus ranged from 2 to 7 times, with the first estrus on October 17 and the last on April 7. This shows that if does go unbred hunters can expect a second "breeding period" in December, after the "peak of the rut." The study also shows that there is a much longer "breeding period" than many hunters realize. I will use the term "breeding period" from now on when referring to the actual time frame when does are receptive and when breeding occurs. It clearly states the time frame hunters are interested in when they refer to the "peak of the rut."

In Marchinton's study there were five 1.5 year old does, two 2.5 year olds, and one 5.5 year old. This is fairly representative of does in the wild and closely resembles the ages of the herd I watch on a daily basis. One 2.5 year old came into estrus October 17, another on October 24, three 1.5 year olds on November 11, one 2.5 year old on November 19, one 1.5 year old on November 21 and the 5.5 year old on December 1. This shows that the first estrus of a doe could occur anywhere from a month before the peak of the breeding period to almost a month after. Not all of the does came into estrus during the peak of the breeding period, which would have been November 9th. In fact, not a single doe was in estrus on that date. There was a doe in estrus on November 10th and three on the 11th. Less than half the does were in estrus the week of the peak of the breeding period. There were two does in estrus three to four weeks earlier and two does in estrus one week later. If recurrent estrus cycles are considered then there could have been three does in estrus the first week of December, two the second week, two the third and one the fourth. This is a fairly typical pattern that causes the breeding period in many areas to last 90 days or more, from mid-October to mid-December. Marchinton noted a breeding period of 96 days in South Carolina, that presumably lasted into January. The chances are most of the does in Marchinton's study would have been bred during their first estrus. A significant second "breeding period" could and often does occur in many deer populations.

As a result of Marchinton's study we know we cannot reliably predict when the second breeding period will occur. Even if the majority of the does come into estrus at the same time the research shows that recurrent estrus cycles are quite variable. Instead of occurring every 28 days as previously thought the cycles ranged from 21 to 30 days. This would make it difficult to pinpoint the second breeding period, especially when coupled with the knowledge that the first estrus may occur anywhere from mid-October to the first part of December. Another note of interest is that the does were in estrus from 24 to over 48 hours, not the 22 to 24 hours previously thought.

Moon Phase and The Rut
Some researchers and writers believe that the rut will occur during certain moon phases. But, there is no conclusive evidence that the moon phase does affect the rut of white-tailed deer. Although some of the does may be in estrus within a few days of one of one of the moon phases it does not mean all of them will be in estrus during any one phase. Even if moon phase affects the first estrus cycle of a doe it may not affect subsequent estrus cycles, because not all does have the same length of estrus. We know that the estrus cycles of individual deer do not occur every 28 days, but every 21-30 days. However, the moon phase does change every 29 days. Therefore, even if the first estrus of a doe fell on a certain moon phase the second estrus could be as much as a week before the next similar phase and two weeks before the following phase.

Buck To Doe Ratio
When the local deer population does not have equal numbers of bucks and does, and most hunted deer populations do not, it can cause the rut to be out of synchronization. When there are not enough bucks to leave priming pheromones for does to come in contact with, not all of the does will come into estrus or be bred during their first estrus. This will also cause some of the does to breed later than normal.

Buck Movement
Not all deer react in the same way during the rut, which makes it difficult to determine the peak of the rut. Does respond differently than bucks, and older breeding bucks respond differently than younger bucks. My research shows that during the rut, the movements of both subdominant and dominant bucks change as rut activity changes, but they do not change in the same way. During the study the dominant bucks were sighted more frequently than the subdominants in the morning during both October and December. Morning sightings of dominants increased only slightly in November (during the peak breeding period) and equaled about half the subdominant buck sightings, which increased dramatically. Young bucks during the rut act much like teenagers, they let their hormones control them and they do stupid things, like search for does during daylight hours. Older bucks, however, have learned that in order to survive they need to be wary and travel during darkness.

The subdominant bucks were seen more often in the evening than they were in the morning during October. But, in November, during the rut, they were seen only half as often in the evening as they were in the morning. In December they were seen more often during the evenings than they were in the mornings. This decrease in subdominant buck evening movement during the breeding period could be attributed to the fact that dominant bucks are quite aggressive during the rut and the subdominants avoided the dominants. There were twice as many dominant buck sightings in the evenings during October and December as there were morning sightings. However, during the November breeding period, while hunting pressure was the highest, the dominants were seen about the same number of times during the evening as they were in the morning. Both dominant and subdominant buck sightings were greater in the morning than in the evening during November, possibly because they were late returning to their bedding areas after chasing or searching for does.

Dominant and Subdominant Buck Movement Differences
Not only did dominant and subdominant bucks react differently to the progression of the rut they moved at different times than the does. During the morning in October the subdominant bucks were seen about a half-hour before the does, while the dominants were seen at the same time as the does. During the evening in October th