Being a reseaercher, who reads alot of research - here is my opinion.
1. I don't think it isw necessarily teh Barometric Pressure that causes a raction form deer, but rather the associated weather changes associated with Barometric Pressure changes. Why do I feel that wy - becuase they can actually feel those changes.
2. Here is an excerpt frrm my book The Complete Whitetail Addict's Manual.
Barometric Pressure
Because fish and birds have air sacs in their bodies they may have the ability to feel barometric pressure changes. Geese are known to feed and begin to flock two days prior to the arrival of a storm, then migrate with the advancing cold fronts. Many hunters claim deer also feed heavily prior to a storm. During my seven-year study I found that (approximately) 40 percent of the deer sightings occurred when the barometer was rising, 40 percent occurred when the barometer was falling, and 20 percent occurred when the barometer was steady.
I did find that more deer were seen when there were abrupt barometric changes than when the barometric pressure was steady. I found no evidence that deer began to feed prior to the arrival of a storm, suggesting that they knew or "felt" that a storm was approaching. However, deer were frequently seen feeding after storms let up, especially if the storm lasted a day or more.
In his study in Georgia, Kent Kammermeyer found that deer activity was correlated with barometric pressure changes in the morning and evening. But, he noted that this is when these barometric pressure changes normally occur in that area. 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. After several years of study, Dave Morris, the manager of a Georgia hunting preserve, concludedd that the deer in the study area were much more active when the barometric pressure was below 29.00 inches, and the temperature and the humidity were low.I suspect that deer may react to the weather changes associated with barometric pressure changes, such as wind speed, wind direction, temperature factor changes, cloud cover and precipitation; but not necessarily to minute changes in barometric pressure.
3. My current study, using 8 live feed cameras on a 3000+ acre gaem preserve in the Ozark Mountains of noethern Arkansas, should help me some more in determing if and when deer react to changes in Barometric Pressure. But, we may never know how much in advance the deer sense pressure changes.
As to why they react - probably becuse there is going to be a change in the weather. Which brings us back, not to Barometric Pressure, but to the Weather. This, I believe, strongly suggests it is the weather they react to.
3. Even if deer may not be able to sense Barometric Pressure, and therefore react to those changes, and react accordingly - WE can use the Barometer to predict deer movement, because we, through technology, know there is going to be a weather change, which MIGHT result in more deer activity tham normal.
God bless and good huntihng,
T.R.