We all know that weather affects whitetail movement, but even experts occasionally disagree on exactly how. Lively debates can ensue from simple questions like: Which is more important, wind or temperature? Do deer move best on a rising or falling barometer? Do atmospheric conditions (rain, cloud cover, fog) really matter?
In 1979, the opportunity to get the answers to these questions arose when I acquired a 1,900-acre tract of whitetail range in the famed South Texas "Brush Country" along the Mexican border. From the first day of the first hunting season I kept records of every whitetail we saw in the field, along with notes on wind velocity, wind direction, barometric movement, air temperature and sky conditions. I also noted the moon phase, month, week, date and number of hunters in the field each half-day. As a result, the database now reflects 1,113 days hunted; these days generated 9,104 antlerless and 4,337 antlered deer sightings for a grand total of 13,441 deer seen. (All of these sightings occurred on the same piece of property during hunting season.)
This massive log of observations has permitted me to calculate the total number of deer on the property, the deer observed per hunter-day, bucks seen per hunter-day, the observed sex ratio and totals of the above information for any given month, week or day of the season. It should be emphasized that this ranch was not enclosed by game-proof fences. Also, all ratios are derived from observed data, which is not necessarily identical to reality. Since the property actually supported fewer than 200 adult deer, rather than the 640 counted annually, obviously multiple sightings occurred. Experience suggests that because bucks are more secretive, does are more subject to multiple sightings. But how much more? We could not be sure. Several standard census methods were used (including helicopter counts) but no consistent correlation with reported numbers was ever discovered. These population figures, then, are only trend data, valid as such as long as the data-collection techniques were consistent from year to year, which they were.
The correlations between number of deer sighted and weather parameters are very reliable. However, because certain weather-related effects on deer movement will vary between "my" deer and those in your hunting grounds, the data shouldn't be taken unequivocally. One of the most obvious variables is temperature, which we will discuss shortly. Another is hunting pressure. We kept the hunting pressure on my land light by rotating stands, hunting only from stationary locations and never hunting over food plots. However, the hunting pressure where you hunt may be greater and that will certainly affect deer movement.
One pitfall that turned up during the analysis of this database was the interrelation of weather parameters. For example, winter weather fronts in our area come from the northwest. If you were to try to determine what wind direction whitetails prefer, you would find that a northwest wind is the optimum condition. It is, but further analysis of the data shows that deer actually don't care about wind direction. What they do love is a moving barometer, and a moving barometer is usually accompanied by a northwest wind.
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