Observing deer movement when barometric pressure changes is not a foolproof way to predict when deer will move again.
QUESTION: I read a lot of articles and hear on many television shows that the best way to predict deer movement is to watch the barometer. But since atmospheric pressure always fluctuates up and down in very small increments, how much of a change in pressure is enough to get them moving? — Brad L.
ANSWER: If I knew the answer to that, I would probably be a lot more successful than I am. The relationship between barometric pressure and deer movement is still something of a mystery.
If you search the internet, you can find thousands of articles discussing it, all based on something other than hard, empirical data. Most is purely anecdotal, which is not to say it should be disregarded.
There is a selective advantage to being able to predict the arrival of bad weather and respond by feeding more actively before it arrives. And there’s a fair amount of research showing animals do just that, by sensing and reacting to changes in barometric pressure.
However, reacting to small and subtle changes that occur more often might not be an advantage.
If deer ran off every time they encountered another animal or heard a noise in the forest, they probably wouldn’t survive long. Over eons, they’ve learned to discriminate between dangerous and innocuous sounds and creatures.
It’s also likely deer react differently depending on the range and, possibly, the speed of changes in barometric pressure. Sudden or significant drops may cause them to move more. As to what the magic number is, we just don’t know.