When the pressure drops it means a low front is moving in, which in turn means a chance for precipitation. Game animals can feel this pressure change in the inner ear and they know to eat because bad weather is approaching. When the storm hits they usually hunker down and ride it out. When the pressure begins to rise, animals once again feel the pressure change, and this signals that the storm is passing and high pressure is moving in(good weather). This was explained to me by a game biologist and is a shortened version of how and why the barometer affects deer. I try to hunt as much as possble but I definately try to be out when fronts are approaching. I have seen lots of deer during these times.