By Neil And Craig Dougherty
Morning and evening “thermals” create their own special kind of air movement. They’re called thermals because the air movement is caused by changes in air temperature and air weight. Morning thermals in our area kick in about 2 hours after first light, or just when you’re starting to take the first nap of the day.
The sun warms the ground and the warm air starts to rise. Up and up it travels, weaving its way in a relatively smooth lift over the hills and mountains. Anything above you will catch your scent when the morning thermals start to lift. Once the lifting air currents hit you, every deer in your scent cone (above you) will know that you’re “in the house.” Sometimes, the warm, rising air is forced into swifter-moving “thermal chimneys” by converging topography. Deer travel up these chimneys in the morning so they can “watch their back” as they climb. A good time to check out rising thermals is on foggy mornings. It’s fascinating to watch a fog gradually lift as the sun warms the earth.
These morning chimneys turn into “thermal drains” in the evening as cooler and heavier air drains from high spots to lower areas. Big bucks on the prowl seek out these drains when looking for does and/or danger. We have mapped thermal drains that have collected air from 50-75 acres at a time. Big bucks love these areas as they can stand in one place and see everything “draining” into their location..
One spot on our property drains no fewer than four food plots, one 3-acre cornfield, and about 50 acres of brush and another 20 of hardwoods. Any deer standing in the drain will know everything they need to know about those locations from hundreds of yards away. We often cross this drain coming out of the woods after an evening hunt. You notice a marked decrease in temperature when entering the drain and the wind (even on dead-calm nights) will chill your soul. What do they say about ghosts crossing your path?
We often take Radar, our tracking dog, out for summer evening rides on a dirt road bisecting our property and running midway along a hillside. He stands on the electric cart seat looking (with eyes and nose) over the woods on either side of the road. We drive through at least three thermal drains that are carrying super-cooled evening air; you feel the temperature change as you drive through them and feel the breeze. Radar almost always starts whining and yipping as we drive through these narrow bands of cool evening air. He’s catching fresh deer (or some other animal) scent carried by the air draining from the hillsides above the road. He doesn’t calm down until we clear the drain. That is exactly what big old bucks are doing all fall—standing in the drains and checking out 50 or 100 acres of does (and hunters) from below.
Ever see a mature buck standing statue-still, head high on a calm evening? Chances are he’s standing in a wind drain or air funnel or some other wind concentrator catching the evening thermals. Mature bucks love to set up in wind drainage areas in the evening … that’s how they keep track of who is where.
Deer like to move down with thermal drains at their back for the same reason they move up in thermal chimneys: Their eyes warn them of danger ahead while their noses keep track of their rear flank. This adds a whole new meaning to “got your back.” Our evening thermals pretty much roll off of our hills and into our valleys like so much water in a stream. The thermals drain from the entire property and smart, old deer know they can smell everything on an entire side-hill by catching the right thermal.
Brothers Neil and Craig Dougherty are two of the most well-respected whitetail experts in North America. They are both authors, TV personalities, land managers and hunters who have spent the majority of their lifetimes teaching others the ways of the whitetail. This article is from their book, “Whitetails: From Ground To Gun.” You can purchase a paper or electronic version of the book right here.